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Sample records for shrub larrea tridentata

  1. Ploidy race distributions since the Last Glacial Maximum in the North American desert shrub, Larrea tridentata

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    Hunter, K.L.; Betancourt, J.L.; Riddle, B.R.; Van Devender, T. R.; Cole, K.L.; Geoffrey, Spaulding W.

    2000-01-01

    1 A classic biogeographic pattern is the alignment of diploid, tetraploid and hexaploid races of creosote bush (Larrea tridentata) across the Chihuahuan, Sonoran and Mohave Deserts of western North America. We used statistically robust differences in guard cell size of modern plants and fossil leaves from packrat middens to map current and past distributions of these ploidy races since the Last Glacial Maximum (LGM). 2 Glacial/early Holocene (26-10 14C kyr BP or thousands of radiocarbon years before present) populations included diploids along the lower Rio Grande of west Texas, 650 km removed from sympatric diploids and tetraploids in the lower Colorado River Basin of south-eastern California/south-western Arizona. Diploids migrated slowly from lower Rio Grande refugia with expansion into the northern Chihuahuan Desert sites forestalled until after ???4.0 14C kyr BP. Tetraploids expanded from the lower Colorado River Basin into the northern limits of the Sonoran Desert in central Arizona by 6.4 14C kyr BP. Hexaploids appeared by 8.5 14C kyr BP in the lower Colorado River Basin, reaching their northernmost limits (???37??N) in the Mohave Desert between 5.6 and 3.9 14C kyr BP. 3 Modern diploid isolates may have resulted from both vicariant and dispersal events. In central Baja California and the lower Colorado River Basin, modern diploids probably originated from relict populations near glacial refugia. Founder events in the middle and late Holocene established diploid outposts on isolated limestone outcrops in areas of central and southern Arizona dominated by tetraploid populations. 4 Geographic alignment of the three ploidy races along the modern gradient of increasingly drier and hotter summers is clearly a postglacial phenomenon, but evolution of both higher ploidy races must have happened before the Holocene. The exact timing and mechanism of polyploidy evolution in creosote bush remains a matter of conjecture. ?? 2001 Blackwell Science Ltd.

  2. Volatile organic compound emissions from Larrea tridentata (creosotebush

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    A. Guenther

    2010-12-01

    Full Text Available We present results from the CREosote ATmosphere Interactions through Volatile Emissions (CREATIVE 2009 field study in southern Arizona aimed at quantifying emission rates of VOCs from creosotebush (Larrea tridentata during the summer 2009 monsoon season. This species was chosen because of its vast distribution in North and South American deserts and because its resins have been reported to contain a rich set of volatile organic compounds (VOC. While a variety of ecosystems have been investigated for VOC emissions, deserts remain essentially unstudied, partially because of their low biomass densities and water limitations. However, during the North American monsoon, a pronounced increase in rainfall from an extremely dry June (80 mm occurs over large areas of the Sonoran desert in the southwestern United States and northwestern Mexico. We observed a strong diurnal pattern of branch emissions and ambient concentrations of an extensive suite of VOCs with maxima in early afternoon. These include VOCs typically observed in forest sites (oxygenated VOCs and volatile isoprenoids as well as a large number of other compounds, some of which have not been previously described from any plant including 1-chloro-2-methoxy-benzene and isobutyronitrile. Although generally considered to be derived from anthropogenic sources, we observed emissions of aromatic compounds including benzene, and a broad range of phenolics. Dimethyl sulfide emissions from creosotebush were higher than reported from any previously studied plant suggesting that terrestrial ecosystems should be reconsidered as an important source of this climatically important gas. We also present direct, primary emission measurements of isoprene and its apparent oxidation products methyl vinyl ketone, methacrolein, and 3-methyl furan (the later three compounds are typically assumed to form from secondary reactions within the atmosphere, as well as a group of compounds considered to be fatty acid

  3. Identifying multiple timescale rainfall controls on Mojave Desert ecohydrology using an integrated data and modeling approach for Larrea tridentata

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    Ng, Gene-Hua Crystal; Bedford, David R.; Miller, David M.

    2015-01-01

    The perennial shrub Larrea tridentata is widely successful in North American warm deserts but is also susceptible to climatic perturbations. Understanding its response to rainfall variability requires consideration of multiple timescales. We examine intra-annual to multi-year relationships using model simulations of soil moisture and vegetation growth over 50 years in the Mojave National Preserve in southeastern California (USA). Ecohydrological model parameters are conditioned on field and remote sensing data using an ensemble Kalman filter. Although no specific periodicities were detected in the rainfall record, simulated leaf-area-index exhibits multi-year dynamics that are driven by multi-year (∼3-years) rains, but with up to a 1-year delay in peak response. Within a multi-year period, Larrea tridentata is more sensitive to winter rains than summer. In the most active part of the root zone (above ∼80 cm), >1-year average soil moisture drives vegetation growth, but monthly average soil moisture is controlled by root uptake. Moisture inputs reach the lower part of the root zone (below ∼80 cm) infrequently, but once there they can persist over a year to help sustain plant growth. Parameter estimates highlight efficient plant physiological properties facilitating persistent growth and high soil hydraulic conductivity allowing deep soil moisture stores. We show that soil moisture as an ecological indicator is complicated by bidirectional interactions with vegetation that depend on timescale and depth. Under changing climate, Larrea tridentata will likely be relatively resilient to shorter-term moisture variability but will exhibit higher sensitivity to shifts in seasonal to multi-year moisture inputs.

  4. Activity of Larrea tridentata (D.C. Coville L. extracts and chitosan against fungi that affect horticultural crops

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    R. H. Lira-Saldivar

    2006-01-01

    Full Text Available La actividad antifúngica de extracto de resina hidrosoluble de gobernadora [Larrea tridentata (D.C. Coville (L] y soluciones de quitosán (Ch, solos y combinados fueron investigados in vitro por su actividad antifúngica contra Botrytis cinerea, Colletotrichum coccodes y Fusarium oxysporum f. sp. lycopersici que fueron aislados de rosas de invernadero y de lotes comerciales de papa y tomate, respectivamente, mismos que posteriormente fueron purificados. Ambos bioproductos manifestaron su efecto funguicida a 1,000 y 2,000 ì l·litro-1, sin embargo, cuando fueron combinados mostraron una actividad fungicida sinérgica. Estos resultados preliminares indican que el extracto hidrosoluble de L. tridentata o la combinación L-Ch pudiesen ser considerados como agroquímicos potenciales de bajo impacto ambiental para ser usados como fungicidas orgánicos, pero se requiere más trabajo de investigación antes de que esto tenga una aplicación comercial. Hasta lo mejor de nuestro conocimiento esta es la primera vez que se reporta a la mezcla L. tridentata y quitosán actuando como un compuesto antifúngico

  5. Larrea tridentata: A novel source for anti-parasitic agents active against Entamoeba histolytica, Giardia lamblia and Naegleria fowleri.

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    Bharat Bashyal

    2017-08-01

    Full Text Available Protozoan parasites infect and kill millions of people worldwide every year, particularly in developing countries where access to clean fresh water is limited. Among the most common are intestinal parasites, including Giardia lamblia and Entamoeba histolytica. These parasites wreak havoc on the epithelium lining the small intestines (G. lamblia and colon (E. histolytica causing giardiasis and amebiasis, respectively. In addition, there are less common but far more deadly pathogens such as Naegleria fowleri that thrive in warm waters and infect the central nervous systems of their victims via the nasal passages. Despite their prevalence and associated high mortality rates, there remains an unmet need to identify more effective therapeutics for people infected with these opportunistic parasites. To address this unmet need, we have surveyed plants and traditional herbal medicines known throughout the world to identify novel antiparasitic agents with activity against G. lamblia, E. histolytica, and N. fowleri. Herein, we report Larrea tridentata, known as creosote bush, as a novel source for secondary metabolites that display antiparasitic activity against all three pathogens. This report also characterizes the lignan compound classes, nordihydroguairetic acid and demethoxyisoguaiacin, as novel antiparasitic lead agents to further develop more effective drug therapy options for millions of people worldwide.

  6. Larrea tridentata: A novel source for anti-parasitic agents active against Entamoeba histolytica, Giardia lamblia and Naegleria fowleri.

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    Bashyal, Bharat; Li, Linfeng; Bains, Trpta; Debnath, Anjan; LaBarbera, Daniel V

    2017-08-01

    Protozoan parasites infect and kill millions of people worldwide every year, particularly in developing countries where access to clean fresh water is limited. Among the most common are intestinal parasites, including Giardia lamblia and Entamoeba histolytica. These parasites wreak havoc on the epithelium lining the small intestines (G. lamblia) and colon (E. histolytica) causing giardiasis and amebiasis, respectively. In addition, there are less common but far more deadly pathogens such as Naegleria fowleri that thrive in warm waters and infect the central nervous systems of their victims via the nasal passages. Despite their prevalence and associated high mortality rates, there remains an unmet need to identify more effective therapeutics for people infected with these opportunistic parasites. To address this unmet need, we have surveyed plants and traditional herbal medicines known throughout the world to identify novel antiparasitic agents with activity against G. lamblia, E. histolytica, and N. fowleri. Herein, we report Larrea tridentata, known as creosote bush, as a novel source for secondary metabolites that display antiparasitic activity against all three pathogens. This report also characterizes the lignan compound classes, nordihydroguairetic acid and demethoxyisoguaiacin, as novel antiparasitic lead agents to further develop more effective drug therapy options for millions of people worldwide.

  7. Creosote bush (Larrea tridentata) resin increases water demands and reduces energy availability in desert woodrats (Neotoma lepida).

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    Mangione, Antonio M; Dearing, M Denise; Karasov, William H

    2004-07-01

    Although many plant secondary compounds are known to have serious consequences for herbivores, the costs of processing them are generally unknown. Two potential costs of ingestion and detoxification of secondary compounds are elevation of the minimum drinking water requirement and excretion of energetically expensive metabolites (i.e., glucuronides) in the urine. To address these impacts, we studied the costs of ingestion of resin from creosote bush (Larrea tridentata) on desert woodrats (Neotoma lepida). The following hypotheses were tested: ingestion of creosote resin by woodrats (1) increases minimum water requirement and (2) reduces energy available by increasing fecal and urinary energy losses. We tested the first hypothesis, by measuring the minimum water requirement of woodrats fed a control diet with and without creosote resin. Drinking water was given in decreasing amounts until woodrats could no longer maintain constant body mass. In two separate experiments, the minimum drinking water requirement of woodrats fed resin was higher than that of controls by 18-30% (about 1-1.7 ml/d). We tested several potential mechanisms of increased water loss associated with the increase in water requirement. The rate of fecal water loss was higher in woodrats consuming resin. Neither urinary water nor evaporative water loss was affected by ingestion of resin. Hypothesis 2 was tested by measuring energy fluxes of woodrats consuming control vs. resin-treated diets. Woodrats on a resin diet had higher urinary energy losses and, thus, metabolized a lower proportion of the dietary energy than did woodrats on control diet. Fecal energy excretion was not affected by resin. The excretion of glucuronic acid represented almost half of the energy lost as a consequence of resin ingestion. The increased water requirement and energy losses of woodrats consuming a diet with resin could have notable ecological consequences.

  8. [Temporal diversity dynamics of the arbuscular mycorrhizal fungi of Larrea tridentata (Sesse & Mocino ex DC) Coville in a semi-arid ecosystem].

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    Hernández-Zamudio, Genoveva; Sáenz-Mata, Jorge; Moreno-Reséndez, Alejandro; Castañeda-Gaytán, Gamaliel; Ogaz, Alfredo; Carballar-Hernández, Santos; Hernández-Cuevas, Laura

    2017-12-06

    Arbuscular mycorrhizal fungi (AMF) of arid and semiarid ecosystems are important for the development of plants that grow under biotic stress in wild or in agro-ecosystems. There is little information on the temporal diversity of these organisms in perennial plants from arid ecosystems in northern Mexico. On this study, the mycorrhizal colonization and the temporal diversity of AMF in the rhizosphere of Larrea tridentata, perennial plant abundant in the Chihuahuan Desert region were explored. Samples of the rhizosphere and roots of fifteen plants in each of the three sampling dates during the 2015 year were obtained. A total of 17 species of HMA belonging to 12 genera and 7 families within the phylum Glomeromycota in all three sampling dates were found. Funneliformis geosporum was the dominant species belonging to the family Glomeraceae which possess the highest genera number on L. tridentata. The highest mycorrhization percentage was in February with 83.22, followed by September and May with 75.27 and 65.27%, respectively. A maximum of 16 AM fungal species were isolated and identified from L. tridentata rhizosphere in February, 15 species in May and 12 species in September. Statistical analysis showed significant differences between sampling dates in the spores number. Copyright © 2017 Asociación Argentina de Microbiología. Publicado por Elsevier España, S.L.U. All rights reserved.

  9. Composición química y efecto antibacteriano in vitro de extractos de larrea tridentata, origanum vulgare, artemisa ludoviciana y ruta graveolens

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    Lucía Delgadillo Ruíz

    2017-01-01

    Full Text Available Introducción . Los extractos de algunas plantas han demostrado tener propiedades antimicr o bianas relacionadas a ciertos compuestos químicos como son el timol, carvacrol, limoneno, linalol y terpineno. El objetivo del presente trabajo fue determinar la concentración de estos compue s tos en los extractos de Larrea tridentata , Origanum vulgare , Artemisa ludoviciana y Ruta graveolens ; así como evaluar su efecto antimicrobiano en Escherichia coli , Acinetoba c ter baumanii , Pseudomona sp y Staphyloc o ccus aureus . Método . Los extractos se obtuvieron por destilación simple empleando alcohol etílico como solvente, la composición química se evaluó mediante cromatografía de gases. La actividad antimicrobia na de cada uno de los extractos de plantas se realizó por los métodos difusión en pozo y difusión en disco. Resultados . Las bacterias mostraron diferentes grados de sensibilidad a los extractos, prese n tando inhibición de crecimiento S. aureus con el extra cto de O. vulgare y R. graveolens , mientras que la bacteria Pseudomona sp. , con los extracto s de A. ludoviciana, L. tridentata y O. vulgare . Discusión . La mayor concentración de timol y carvacrol se encontró en los extractos de O. vulgare y L. tridentata . El compuesto linalol se encontró en una proporción mayor en O. vulgare y en menor proporción en A. ludoviciana . Limoneno se encontró en los extractos de O. vulgare y R. graveolens . De las cuatro plantas evaluadas, el extracto de L. tridentata fue mejor , de bido a que presenta la mayor inhibición en comparación con los otros extractos; y con un efecto similar a los aceites empleados como control. La técnica de dif u sión en disco, permitió observar mejor los efectos inhibitorios de los extra c tos y los aceites s obre cada una de las bacterias empleadas en comparación con el método de difusión en pozo.

  10. The infrared emissivities of soil and Artemisia tridentata and subsequent temperature corrections in a shrub-steppe ecosystem

    International Nuclear Information System (INIS)

    Hipps, L.E.

    1989-01-01

    The determination of plant and soil temperatures using remote sensing technology is examined in a shrub-steppe ecosystem. The emissivities of Artemisia tridentata L. shrubs and the soil surface were examined in such an ecosystem. The emissivity of A. tridentata plants was calculated to be 0.97, which is in the range of reported values for other green plants. The soil emissivity was 0.93. Temperature readings from an infrared thermometer (IRT) must be corrected for the emissivity value of the target and the reflected sky radiation. Although these two factors produce errors which are opposite in sign, they will not offset one another. An analysis is presented which quantifies the temperature error resulting from ignoring the corrections. The error is negligible only for emissivity values greater than 0.98. The error is proportional to temperature, and increases rapidly with decreases in emissivity. The true emissivities must be determined, and the above corrections must be calculated in order to obtain accurate temperatures in an ecosystem from remote sensing methods. (author)

  11. The infrared emissivities of soil and Artemisia tridentata and subsequent temperature corrections in a shrub-steppe ecosystem

    International Nuclear Information System (INIS)

    Hipps, L.E.

    1989-01-01

    The determination of plant and soil temperatures using remote sensing technology is examined in a shrub-steppe ecosystem. The emissivities of Artemisia tridentata L. shrubs and the soil surface were examined in such an ecosystem. The emissivity of A. tridentata plants was calculated to be 0.97, which is in the range of reported values for other green plants. The soil emissivity was 0.93. Temperature readings from an infrared thermometer (IRT) must be corrected for the emissivity value of the target and the reflected sky radiation. Although these two factors produce errors which are opposite in sign, they will not offset one another. An analysis is presented which quantifies the temperature error resulting from ignoring the corrections. The error is negligible only for emissivity values greater than 0.98. The error is proportional to temperature, and increases rapidly with decreases in emissivity. The true emissivities must be determined, and the above corrections must be calculated in order to obtain accurate temperatures in an ecosystem from remote sensing methods

  12. IN VITRO BIOACTIVITY OF CREOSOTE BUSH EXTRACTS (LARREA TRIDENTATA ON THE INHIBITION OF POSTHARVEST FUNGI: PENICILLIUM POLONICUM, ASPERGILLUS NIGER, RHIZOPUS ORYZAE Y ALTERNARIA TENUISSIMA

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    O. Peñuelas-Rubio

    2015-11-01

    Full Text Available En el presente estudio se evaluó la eficiencia de extractos vegetales deLarrea tridentataobtenidos con diclorometano, etanol, metanol y agua, sobre el crecimiento radial in vitro de cuatro hongos fitopatógenos, los cuales primeramente fueron identificados en género y especie empleando claves taxonómicas y técnicas moleculares. Para los bioensayosin vitrose aplicaron diseños completamente al azar con cuatro tratamientos y tres repeticiones en cada hongo, utilizando las concentraciones: 0, 250, 500 y 750 ppm paraAlternaria sp.; 0, 2000, 2500 y 3000 paraAspergillus sp.; 0, 1500, 1750 y 2000 paraPenicillium sp. y 0, 150, 200 y 250 ppm paraRhizopus sp. Cada tratamiento tuvo tres repeticiones. El análisis molecular determinó la especie tenuissima paraAlternaria,nigerparaApergillus,polonicumparaPenicilliumyoryzaeparaRhizopus. En cuanto a las pruebasin vitro, se determinaron inhibiciones del 100% para tres de los hongos en estudio:Alternaria tenuissimacon extracto EtOH a 750 ppm;Aspergillus nigercon extracto DCM a 3000 ppm yRhizopus oryzaea partir de 150 ppm y 250 ppm de los extractos DCM y EtOH respectivamente. Se presentó una inhibición del 82% a 2000 ppm paraPenicillium polonicum. Se concluye que a pesar de las diferencias en susceptibilidad entre las especies fúngicas, los extractos deLarrea tridentataobtenidos con etanol y dicloromentano son efectivos para el control de los hongos fitopatógenos bajo estudioin vitro.

  13. Spreaders, igniters, and burning shrubs: plant flammability explains novel fire dynamics in grass-invaded deserts.

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    Fuentes-Ramirez, Andres; Veldman, Joseph W; Holzapfel, Claus; Moloney, Kirk A

    2016-10-01

    Novel fire regimes are an important cause and consequence of global environmental change that involve interactions among biotic, climatic, and human components of ecosystems. Plant flammability is key to these interactions, yet few studies directly measure flammability or consider how multiple species with different flammabilities interact to produce novel fire regimes. Deserts of the southwestern United States are an ideal system for exploring how novel fire regimes can emerge when fire-promoting species invade ecosystems comprised of species that did not evolve with fire. In these deserts, exotic annual grasses provide fuel continuity across landscapes that did not historically burn. These fires often ignite a keystone desert shrub, the fire-intolerant creosote bush, Larrea tridentata (DC.) Coville. Ignition of Larrea is likely catalyzed by fuels produced by native plants that grow beneath the shrubs. We hypothesize that invasive and native species exhibit distinct flammability characteristics that in combination determine spatial patterns of fire spread and intensity. We measured flammability metrics of Larrea, two invasive grasses, Schismus arabicus and Bromus madritensis, and two native plants, the sub-shrub Ambrosia dumosa and the annual herb Amsinckia menziesii. Results of laboratory experiments show that the grasses carry fire quickly (1.32 cm/s), but burn for short duration (0.5 min) at low temperatures. In contrast, native plants spread fire slowly (0.12 cm/s), but burn up to eight times longer (4 min) and produced hotter fires. Additional experiments on the ignition requirements of Larrea suggest that native plants burn with sufficient temperature and duration to ignite dead Larrea branches (time to ignition, 2 min; temperature at ignition 692°C). Once burning, these dead branches ignite living branches in the upper portions of the shrub. Our study provides support for a conceptual model in which exotic grasses are "spreaders" of fire and native

  14. Maintenance of C sinks sustains enhanced C assimilation during long-term exposure to elevated [CO2] in Mojave Desert shrubs.

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    Aranjuelo, Iker; Ebbets, Allison L; Evans, R Dave; Tissue, David T; Nogués, Salvador; van Gestel, Natasja; Payton, Paxton; Ebbert, Volker; Adams, Williams W; Nowak, Robert S; Smith, Stanley D

    2011-10-01

    During the first few years of elevated atmospheric [CO(2)] treatment at the Nevada Desert FACE Facility, photosynthetic downregulation was observed in desert shrubs grown under elevated [CO(2)], especially under relatively wet environmental conditions. Nonetheless, those plants maintained increased A (sat) (photosynthetic performance at saturating light and treatment [CO(2)]) under wet conditions, but to a much lesser extent under dry conditions. To determine if plants continued to downregulate during long-term exposure to elevated [CO(2)], responses of photosynthesis to elevated [CO(2)] were examined in two dominant Mojave Desert shrubs, the evergreen Larrea tridentata and the drought-deciduous Ambrosia dumosa, during the eighth full growing season of elevated [CO(2)] treatment at the NDFF. A comprehensive suite of physiological processes were collected. Furthermore, we used C labeling of air to assess carbon allocation and partitioning as measures of C sink activity. Results show that elevated [CO(2)] enhanced photosynthetic performance and plant water status in Larrea, especially during periods of environmental stress, but not in Ambrosia. δ(13)C analyses indicate that Larrea under elevated [CO(2)] allocated a greater proportion of newly assimilated C to C sinks than Ambrosia. Maintenance by Larrea of C sinks during the dry season partially explained the reduced [CO(2)] effect on leaf carbohydrate content during summer, which in turn lessened carbohydrate build-up and feedback inhibition of photosynthesis. δ(13)C results also showed that in a year when plant growth reached the highest rates in 5 years, 4% (Larrea) and 7% (Ambrosia) of C in newly emerging organs were remobilized from C that was assimilated and stored for at least 2 years prior to the current study. Thus, after 8 years of continuous exposure to elevated [CO(2)], both desert perennials maintained their photosynthetic capacities under elevated [CO(2)]. We conclude that C storage, remobilization

  15. Bidirectional recovery patterns of Mojave Desert vegetation in an aqueduct pipeline corridor after 36 years: I. Perennial shrubs and grasses

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    Berry, Kristin H.; Weigand, James F.; Gowan, Timothy A.; Mack, Jeremy S.

    2015-01-01

    We studied recovery of 21 perennial plant species along a severely disturbed aqueduct corridor in a Larrea tridentata-Ambrosia dumosa plant alliance in the Mojave Desert 36 years after construction. The 97-m wide corridor contained a central dirt road and buried aqueduct pipeline. We established transects at 0 m (road verge), 20 m and 40 m into the disturbance corridor, and at 100 m in undisturbed habitat (the control). Although total numbers of shrubs per transect did not vary significantly with distance from the verge, canopy cover of shrubs, species richness, and species diversity were higher in the control than at the verge and other distances. Canopy cover of common shrubs (Ericameria nauseosa, Ambrosia salsola, A. dumosa, L. tridentata, Grayia spinosa) and perennial grasses (Elymus elymoides, Poa secunda) also varied significantly by location. Discriminant analysis clearly separated the four distances based on plant composition. Patterns of recovery were bidirectional: secondary succession from the control into the disturbance corridor and inhibition from the verge in the direction of the control. Time estimated for species composition to resemble the control is dependent on location within the disturbance corridor and could be centuries at the road verge. Our findings have applications to other deserts.

  16. Effects of drought on shrub survival and longevity in the northern Sonoran Desert

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    Bowers, Janice E.

    2005-01-01

    Permanent vegetation plots in the northern Sonoran Desert, USA, provided an opportunity to assess the effects of recent drought on desert shrubs and to examine survival in relation to rainfall variability during the past 76 years. Survival and maximum longevity of six species were determined for eight intercensus periods between 1928 and 2004. Average annual survival was Ambrosia deltoidea, 0.9167 ?? 0.0415; Encelia farinosa, 0.7952 ?? 0.0926; Janusia gracilis, 0.9334 ?? 0.0247; Krameria grayi, 0.9702 ?? 0.0270; Larrea tridentata, 0.9861 ?? 0.0174; and Lycium berlandieri, 0.9910 ?? 0.0077. The longest-lived species were Larrea, Lycium, and Krameria, with average maximum life spans of 330, 211, and 184 years. Janusia, Ambrosia, and Encelia were much shorter lived, with average maximum longevity of 53, 40, and 16 years. Winter rain equalled or exceeded 90% of the long-term average accumulation except during 1948 to 1959 (65% of average) and from 2001 to 2003 (49% of average). Summer rain did not drop below 90% of the average accumulation in any period. The 1950s drought caused modest declines in survival of Ambrosia, Encelia, Janusia, Krameria, and Lycium. The effects of the recent drought were much more pronounced, resulting in sharp declines in survival and maximum longevity of Ambrosia, Encelia, Krameria, and Larrea, and modest declines for Lycium. Despite heightened mortality during the recent severe drought, 72% of the deaths observed between 1928 and 2004 occurred during periods of average or better-than-average rain, providing support for the idea that demography of shrubs in arid regions is influenced by continuous as well as episodic processes.

  17. Attempting to restore mountain big sagebrush (Artemisia tridentata ssp. vaseyana) four years after fire

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    Restoration of shrubs is increasingly needed throughout the world because of altered fire regimes, anthropogenic disturbance, and over-utilization. The native shrub mountain big sagebrush (Artemisia tridentata Nutt. ssp. vaseyana (Rydb.) Beetle) is a restoration priority in western North America be...

  18. Larrea interspecific hybrids revisited (Zygophyllaceae

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    Juan H. Hunziker

    2002-01-01

    Full Text Available Estudios moleculares recientes nos han inducido a realizar una reinterpretación de las relaciones genómicas entre Larrea ameghinoi y las otras especies sudamericanas del género. Se hicieron nuevos intentos para estudiar el apareamiento de los cromosomas del híbrido L. ameghinoi x L. cuneifolia (2n = 3x = 39. El promedio de bivalentes y univalentes fue de 9.8 y 19.4, respectivamente. Dado que el número básico x es 13 la interpretación más razonable es que L. ameghinoi (2n = 2x = 26 (AA y L. cuneifolia (2n = 4x = 52 (DDCC comparten genomas parcialmente homeólogos (A y C que forman la mayoría de los bivalentes y eso explicaría la producción de semillas (15-19.4 % de estos híbridos triploides. El genoma de L. ameghinoi (A podría haber retenido varias partes de un genoma ancestral que hace posible algún apareamiento con aquellos de las otras especies y que lo capacitaría para funcionar como un genoma pivote que permite alguna fertilidad (desde parcial a completa en todas las posibles combinaciones híbridas con sus tres congéneres sudamericanos. Se incluye un apéndice con las leyendas completas del capítulo 2 del libro de Mabry et al. (1977 que fueran omitidas por error en el proceso editorial y de impresión

  19. Cytogeography of Larrea tridentata at the Chihuahuan-Sonoran Desert ecotone

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    Robert G. Laport; Robert L.. Minckley

    2013-01-01

    The long separation of the Chihuahuan and Sonoran Deserts is reflected in the high species richness and endemism of their floras. Although many endemic species from both deserts reach their distributional limits where the Sierra Madre Occidental massif fragments into smaller mountain complexes in northern Mexico and adjoining areas of the United States, indicator...

  20. Genes encoding chavicol/eugenol synthase from the creosote bush Larrea tridentata

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    Lewis, Norman G.; Davin, Laurence B.; Kim, Sung -Jin; Vassao, Daniel Giddings; Patten, Ann M.; Eichinger, Dietmar

    2015-09-15

    Particular aspects provide novel methods for redirecting carbon allocation in plants or cell culture from lignification to inherently more useful and tractable materials, and to facilitate the generation of, e.g., biofuels from the remaining plant ro culture biomass. Particular aspects provided novel methods for converting monolignols into allyl/propenyl phenols, and for chavicol/eugenol formation or production. Additional aspects relate to the discovery of novel chavicol/eugenol synthases that convert p-coumaryl/coniferyl alcohol esters into chavicol/eugenol, and to novel compositions (e.g., novel proteins and nucleic acids encoding same), and novel methods using same for producing or forming chavicol/eugenol and other derivatives in cell culture and/or genetically modified plants, and for re-engineering the composition of plant biomass. Particular aspects provide novel methods for generation in culture or in planta of liquid/combustible allyl/propenyl phenols, and these phenolic products are utilized for (non-ethanol) biofuel/bioenergy purposes, while the remaining plant biomass facilitates the generation of other biofuels.

  1. Burial increases seed longevity of two Artemisia tridentata (Asteraceae) subspecies

    Science.gov (United States)

    Wijayratne, Upekala C.; Pyke, David A.

    2012-01-01

    Premise of the study: Seed longevity and persistence in soil seed banks may be especially important for population persistence in ecosystems where opportunities for seedling establishment and disturbance are unpredictable. The fire regime, an important driver of population dynamics in sagebrush steppe ecosystems, has been altered by exotic annual grass invasion. Soil seed banks may play an active role in postfire recovery of the foundation shrub Artemisia tridentata, yet conditions under which seeds persist are largely unknown. Methods: We investigated seed longevity of two Artemisia tridentata subspecies in situ by retrieving seed bags that were placed at varying depths over a 2 yr period. We also sampled naturally dispersed seeds in litter and soil immediately after seed dispersal and before flowering in subsequent seasons to estimate seed persistence. Key results: After 24 mo, seeds buried at least 3 cm below the soil surface retained 30–40% viability whereas viability of seeds on the surface and under litter declined to 0 and Artemisia tridentata has the potential to form a short-term soil seed bank that persists longer than has been commonly assumed, and that burial is necessary for seed longevity. Use of seeding techniques that promote burial of some seeds to aid in formation of a soil seed bank may increase restoration potential.

  2. Common and distinguishing features of the bacterial and fungal communities in biological soil crusts and shrub root zone soils

    Science.gov (United States)

    Steven, Blaire; Gallegos-Graves, La Verne; Yeager, Chris; Belnap, Jayne; Kuske, Cheryl R.

    2013-01-01

    Soil microbial communities in dryland ecosystems play important roles as root associates of the widely spaced plants and as the dominant members of biological soil crusts (biocrusts) colonizing the plant interspaces. We employed rRNA gene sequencing (bacterial 16S/fungal large subunit) and shotgun metagenomic sequencing to compare the microbial communities inhabiting the root zones of the dominant shrub, Larrea tridentata (creosote bush), and the interspace biocrusts in a Mojave desert shrubland within the Nevada Free Air CO2 Enrichment (FACE) experiment. Most of the numerically abundant bacteria and fungi were present in both the biocrusts and root zones, although the proportional abundance of those members differed significantly between habitats. Biocrust bacteria were predominantly Cyanobacteria while root zones harbored significantly more Actinobacteria and Proteobacteria. Pezizomycetes fungi dominated the biocrusts while Dothideomycetes were highest in root zones. Functional gene abundances in metagenome sequence datasets reflected the taxonomic differences noted in the 16S rRNA datasets. For example, functional categories related to photosynthesis, circadian clock proteins, and heterocyst-associated genes were enriched in the biocrusts, where populations of Cyanobacteria were larger. Genes related to potassium metabolism were also more abundant in the biocrusts, suggesting differences in nutrient cycling between biocrusts and root zones. Finally, ten years of elevated atmospheric CO2 did not result in large shifts in taxonomic composition of the bacterial or fungal communities or the functional gene inventories in the shotgun metagenomes.

  3. Pruning Shrubs

    OpenAIRE

    French, Sue (Sue C.); Appleton, Bonnie Lee, 1948-2012

    2009-01-01

    Understanding the "natural habit" or "shape" of shrubs will help you determine how to prune them. This publication explores how and when to prune, maintenance and rejuvenation pruning, and the growth habit of shrubs.

  4. Establishing Artemisia tridentata ssp wyomingensis on mined lands: Science and economics

    Energy Technology Data Exchange (ETDEWEB)

    Schuman, G.E.; Vicklund, L.E.; Belden, S.E. [ARS, Cheyenne, WY (United States). High Plains Grasslands Research Station

    2005-12-01

    In 1996, the Wyoming Department of Environmental Quality enacted regulations governing the reestablishment of woody shrubs on mined lands. The regulation required that an average density of one shrub m{sup -2} be reestablished on at least 20% of the disturbed land area and that the shrub composition must include dominant premine species. In Wyoming, and much of the Northern Great Plains, that meant that Artemisia tridentata Nutt. ssp. wyomingensis (Beetle and Young) (Wyoming big sagebrush) had to be reestablished on mined lands. Artemisia tridentata Nutt. ssp. wyomingensis had proven difficult to reestablish on mined lands because of poor quality seed, seed dormancy and a poor understanding of the seedbed ecology of this species. Research in the last two decades has produced significant knowledge in the area of direct-seed establishment of Artemisia tridentata Nutt. ssp. wyomingensis on mined lands. Our research has shown that reducing grass seeding rates will reduce competition and result in larger sagebrush plants that are more likely to survive and provide greater structural diversity to the plant community. Economic analyses demonstrated that big sagebrush can be established at a cost of $0.01-0.05 per seedling using direct seeding methods compared to transplanting nursery grown seedlings, estimated to cost $0.72-$1.65 per seedling (depending on size) to grow and from $1.30-$2.40 to plant (flat land to 2:1 slopes). An adequate level of precipitation will be necessary to ensure successful establishment of this species no matter what method of propagation is selected and direct seeding gives greater opportunity for success because of the demonstrated longevity of the seed to germinate 3-5 years after the initial seeding.

  5. Characterization of a sagebrush (Artemisia tridentata ssp. wyomingensis) die-off on the Handford Site

    International Nuclear Information System (INIS)

    Cardenas, A.; Lewinsohn, J.; Auger, C.; Downs, J.L.; Cadwell, L.L.; Burrows, R.

    1997-09-01

    The Hanford Site contains one of the few remaining contiguous areas of shrub-steppe habitat left in Washington State. This habitat is home to many native plant and wildlife species, some of which are threatened with extinction or are unique to the Site. The importance of the Hanford Site increases as other lands surrounding the Site are developed, and these native species and habitats are lost. Stands of Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) on the Site are a particularly important component of shrub-steppe habitat, because a number of wildlife require big sagebrush for food and cover. Since 1993, researchers and field biologists have made anecdotal observations of dying and declining sagebrush in stands of shrubs near the 100 Areas. This study was initiated to delineate and document the general boundary where sagebrush stands appear to be declining. We mapped the areal extent of the die-off using a global positioning system and found that the central portion of the die-off encompasses 280 hectares. Shrub stand defoliation was estimated to be near or greater than 80% in this area. The remainder of the die-off area exhibits varying mixtures of completely defoliated, partially defoliated, and healthy-looking stands. Declining sagebrush stands comprise a total of 1776 hectares

  6. Characterization of a sagebrush (Artemisia tridentata ssp. wyomingensis) die-off on the Handford Site

    Energy Technology Data Exchange (ETDEWEB)

    Cardenas, A.; Lewinsohn, J.; Auger, C.; Downs, J.L.; Cadwell, L.L.; Burrows, R.

    1997-09-01

    The Hanford Site contains one of the few remaining contiguous areas of shrub-steppe habitat left in Washington State. This habitat is home to many native plant and wildlife species, some of which are threatened with extinction or are unique to the Site. The importance of the Hanford Site increases as other lands surrounding the Site are developed, and these native species and habitats are lost. Stands of Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) on the Site are a particularly important component of shrub-steppe habitat, because a number of wildlife require big sagebrush for food and cover. Since 1993, researchers and field biologists have made anecdotal observations of dying and declining sagebrush in stands of shrubs near the 100 Areas. This study was initiated to delineate and document the general boundary where sagebrush stands appear to be declining. We mapped the areal extent of the die-off using a global positioning system and found that the central portion of the die-off encompasses 280 hectares. Shrub stand defoliation was estimated to be near or greater than 80% in this area. The remainder of the die-off area exhibits varying mixtures of completely defoliated, partially defoliated, and healthy-looking stands. Declining sagebrush stands comprise a total of 1776 hectares.

  7. Flowering branches cause injuries to second-year main stems of Artemisia tridentata nutt. subspecies tridentata

    Science.gov (United States)

    Lance S. Evans; Angela Citta; Stewart C. Sanderson

    2012-01-01

    Eccentricity of stems of Artemisia tridentata Nutt. (big sagebrush) has been reported previously. Analysis of samples observed over 2 years documented that each stem terminal produces about 8-10 branches each year, and during second-year growth, 3-8 of these develop into short, flowering, determinate branches. Each flowering branch produces hundreds of seeds and then...

  8. Cytogeography and chromosome evolution of subgenus Tridentatae of Artemisia (Asteraceae)

    Science.gov (United States)

    E. Durant McArthur; Stewart C. Sanderson

    1999-01-01

    The subgenus Tridentatae of Artemisia (Asteraceae: Anthemideae) is composed of 11 species of various taxonomic and geographic complexities. It is centered on Artemisia tridentata with its three widespread common subspecies and two more geographically confined ones. Meiotic chromosome counts on pollen mother cells...

  9. Investigation of Artemisia tridentata as a biogeochemical uranium indicator

    Energy Technology Data Exchange (ETDEWEB)

    Diebold, F E; McGrath, S [Montana Coll. of Mineral Science and Technology, Butte (USA)

    1985-01-01

    Hydroponic experiments were conducted with seedlings of Artemisia tridentata subsp. tridentata (big sagebrush) to test the effect of the phosphate speciation of uranium in solution on its uptake by big sagebrush. No single complex could be identified as being preferentially taken up by the plant, but the varying aqueous phosphate concentrations did affect uranium uptake by the plants at the higher uranium concentrations in solution. The data also substantiate the tendency for uranium to behave as an essential element in this plant species. The implications for the use of Artemisia tridentata as a biogeochemical uranium indicator are discussed.

  10. Spectrophotometry of Artemisia tridentata to quantitatively determine subspecies

    Science.gov (United States)

    Richardson, Bryce; Boyd, Alicia; Tobiasson, Tanner; Germino, Matthew

    2018-01-01

    Ecological restoration is predicated on our abilities to discern plant taxa. Taxonomic identification is a first step in ensuring that plants are appropriately adapted to the site. An example of the need to identify taxonomic differences comes from big sagebrush (Artemisia tridentata). This species is composed of three predominant subspecies occupying distinct environmental niches, but overlap and hybridization are common in ecotones. Restoration of A. tridentata largely occurs using wildland collected seed, but there is uncertainty in the identification of subspecies or mix of subspecies from seed collections. Laboratory techniques that can determine subspecies composition would be desirable to ensure that subspecies match the restoration site environment. In this study, we use spectrophotometry to quantify chemical differences in the water-soluble compound, coumarin. Ultraviolet (UV) absorbance of A. tridentata subsp. vaseyana showed distinct differences among A.t. tridentata and wyomingensis. No UV absorbance differences were detected between A.t. tridentata and wyomingensis. Analyses of samples from > 600 plants growing in two common gardens showed that UV absorbance was unaffected by environment. Moreover, plant tissues (leaves and seed chaff) explained only a small amount of the variance. UV fluorescence of water-eluted plant tissue has been used for many years to indicate A.t. vaseyana; however, interpretation has been subjective. Use of spectrophotometry to acquire UV absorbance provides empirical results that can be used in seed testing laboratories using the seed chaff present with the seed to certify A. tridentata subspecies composition. On the basis of our methods, UV absorbance values 3.1 would indicate either A.t. tridentata or wyomingensis. UV absorbance values between 2.7 and 3.1 would indicate a mixture of A.t. vaseyana and the other two subspecies.

  11. Water relations and photosynthesis along an elevation gradient for Artemisia tridentata during an historic drought.

    Science.gov (United States)

    Reed, Charlotte C; Loik, Michael E

    2016-05-01

    Quantifying the variation in plant-water relations and photosynthesis over environmental gradients and during unique events can provide a better understanding of vegetation patterns in a future climate. We evaluated the hypotheses that photosynthesis and plant water potential would correspond to gradients in precipitation and soil moisture during a lengthy drought, and that experimental water additions would increase photosynthesis for the widespread evergreen shrub Artemisia tridentata ssp. vaseyana. We quantified abiotic conditions and physiological characteristics for control and watered plants at 2135, 2315, and 2835 m near Mammoth Lakes, CA, USA, at the ecotone of the Sierra Nevada and Great Basin ecoregions. Snowfall, total precipitation, and soil moisture increased with elevation, but air temperature and soil N content did not. Plant water potential (Ψ), stomatal conductance (g s), maximum photosynthetic rate (A max), carboxylation rate (V cmax), and electron transport rate (J max) all significantly increased with elevations. Addition of water increased Ψ, g s, J max, and A max only at the lowest elevation; g s contributed about 30 % of the constraints on photosynthesis at the lowest elevation and 23 % at the other two elevations. The physiology of this foundational shrub species was quite resilient to this 1-in-1200 year drought. However, plant water potential and photosynthesis corresponded to differences in soil moisture across the gradient. Soil re-wetting in early summer increased water potential and photosynthesis at the lowest elevation. Effects on water relations and photosynthesis of this widespread, cold desert shrub species may be disproportionate at lower elevations as drought length increases in a future climate.

  12. Chapter 22. Rosaceous shrubs

    Science.gov (United States)

    Nancy L. Shaw; Stephen B. Monsen; Richard Stevens

    2004-01-01

    Important shrubs of the Rose Family (Rosaceae) in the Intermountain region are distributed from blackbrush and salt desert shrub communities through high elevation forests and meadows. Growth habits of this group vary from trailing brambles to upright shrubs and small trees. Some species are evergreen while others are deciduous. Many of these species are highly valued...

  13. Studies of a new hybrid taxon in the Artemisia tridentata (Asteraceae: Anthemideae) complex

    Science.gov (United States)

    Heather D. Garrison; Leila M. Shultz; E. Durant McArthur

    2013-01-01

    Members of the Artemisia tridentata complex (ASTERACEAE: Anthemideae: Artemisia subgen. Tridentatae) have adapted to changing environmental conditions through geographic migration, introgression, and hybridization. These processes have resulted in morphologic and genetic variation. A presumed hybrid ("Bonneville" big sagebrush) of the complex occurs in the...

  14. Taxonomic and nomenclatural rearrangements in Artemisia subgen. Tridentatae, including a redefinition of Sphaeromeria (Asteraceae, Anthemideae)

    Science.gov (United States)

    Sonia Garcia; Teresa Garnatje; E. Durant McArthur; Jaume Pellicer; Stewart C. Sanderson; Joan Valles

    2011-01-01

    A recent molecular phylogenetic study of all members of Artemisia subgenus Tridentatae, as well as most of the other New World endemic Artemisia and the allied genera Sphaeromeria and Picrothamnus, raised the necessity of revising the taxonomic framework of the North American endemic Artemisia. Composition of the subgenus Tridentatae is enlarged to accommodate other...

  15. Juan Larrea Holguín y su visión de la universidad

    OpenAIRE

    Juan Carlos Riofrío Martínez-Villalba

    2015-01-01

    La investigación muestra la visión teórica y práctica que Larrea te- nía de la universidad. Para ello revisa tanto sus escritos, como varias anécdotas de su vida, bajo una metodología histórico-deductiva que compara la teoría con la práctica. El estudio inicia con la visión genérica de la labor académica, para luego abordar el tema vivencial. Como con- clusión se obtienen varios valores universitarios que Larrea supo vivir: el amor y confianza en la verdad, la actitud magnánima ante l...

  16. Use of UV absorption for identifying subspecies of Artemisia tridentata

    International Nuclear Information System (INIS)

    Spomer, G.G.; Henderson, D.M.

    1988-01-01

    Use of UV absorption spectra for identifying subspecies of Artemisia tridentata Nutt. was investigated by analyzing the relative optical densities of alcohol extracts from herbarium and fresh plant material at 240 nm, 250 nm, and 265 nm. In all but 1 comparison, mean relative optical densities were significantly different (p=0.95) between subspecies, but intraplant and intrasubspecies variation and overlap was found to be too large to permit use of UV absorbance alone for identifying individual specimens. These results held whether dry or fresh leaves were extracted, or whether methanol or ethanol was used as the extracting solvent. (author)

  17. The response of big sagebrush (Artemisia tridentata) to interannual climate variation changes across its range.

    Science.gov (United States)

    Kleinhesselink, Andrew R; Adler, Peter B

    2018-05-01

    Understanding how annual climate variation affects population growth rates across a species' range may help us anticipate the effects of climate change on species distribution and abundance. We predict that populations in warmer or wetter parts of a species' range should respond negatively to periods of above average temperature or precipitation, respectively, whereas populations in colder or drier areas should respond positively to periods of above average temperature or precipitation. To test this, we estimated the population sensitivity of a common shrub species, big sagebrush (Artemisia tridentata), to annual climate variation across its range. Our analysis includes 8,175 observations of year-to-year change in sagebrush cover or production from 131 monitoring sites in western North America. We coupled these observations with seasonal weather data for each site and analyzed the effects of spring through fall temperatures and fall through spring accumulated precipitation on annual changes in sagebrush abundance. Sensitivity to annual temperature variation supported our hypothesis: years with above average temperatures were beneficial to sagebrush in colder locations and detrimental to sagebrush in hotter locations. In contrast, sensitivity to precipitation did not change significantly across the distribution of sagebrush. This pattern of responses suggests that regional abundance of this species may be more limited by temperature than by precipitation. We also found important differences in how the ecologically distinct subspecies of sagebrush responded to the effects of precipitation and temperature. Our model predicts that a short-term temperature increase could produce an increase in sagebrush cover at the cold edge of its range and a decrease in cover at the warm edge of its range. This prediction is qualitatively consistent with predictions from species distribution models for sagebrush based on spatial occurrence data, but it provides new mechanistic

  18. Pre-treating Seed to Enhance Germination of Desert Shrubs

    Energy Technology Data Exchange (ETDEWEB)

    W. K. Ostler; D. C. Anderson; D. J. Hansen

    2002-06-01

    Creosotebush [Larrea tridentata (D.C.) Cav.] and white bursage [Ambrosia dumosa (A. Gray) W.W. Payne] seeds were subjected to pre-treatments of rinsing and soaking in water and thiourea to enhance germination in laboratory experiments. The effects of darkness, temperature, seed source, and soil moisture were also evaluated in the laboratory. The best pre-treatment from the laboratory experiments, rinsing with water for 36 hours followed by drying, was field-tested at Fort Irwin, California. Two sites and two seeding dates (early March and mid April) were determined for each site. Five mulch treatments (no mulch, straw, gravel, chemical stabilizer, and plastic) were evaluated in combination with the seed pre-treatments. Field emergence was greatly enhanced with the seed pre-treatment for white bursage during the March (18-42% increase in germination) and April seedings (16-23% increase in germination). Creosotebush showed poor germination during March (2-5%) when soil temperatures averaged 15 C, but germination increased during the April trials (6-43%) when soil temperatures averaged 23 C. The seed pre-treatment during the April trials increased germination from 16-23%. The plastic mulch treatment increased germination dramatically during both the March and April trials. The plastic mulch increased soil temperatures (8-10 C)and maintained high humidity during germination. Both the chemical stabilizer and the gravel mulches improved germination over the control while the straw mulch decreased germination. These results suggest that seed pre-treatments combined with irrigation and mulch are effective techniques to establish these two dominant Mojave Desert species from seed.

  19. Impact of intra- versus inter-annual snow depth variation on water relations and photosynthesis for two Great Basin Desert shrubs.

    Science.gov (United States)

    Loik, Michael E; Griffith, Alden B; Alpert, Holly; Concilio, Amy L; Wade, Catherine E; Martinson, Sharon J

    2015-06-01

    Snowfall provides the majority of soil water in certain ecosystems of North America. We tested the hypothesis that snow depth variation affects soil water content, which in turn drives water potential (Ψ) and photosynthesis, over 10 years for two widespread shrubs of the western USA. Stem Ψ (Ψ stem) and photosynthetic gas exchange [stomatal conductance to water vapor (g s), and CO2 assimilation (A)] were measured in mid-June each year from 2004 to 2013 for Artemisia tridentata var. vaseyana (Asteraceae) and Purshia tridentata (Rosaceae). Snow fences were used to create increased or decreased snow depth plots. Snow depth on +snow plots was about twice that of ambient plots in most years, and 20 % lower on -snow plots, consistent with several down-scaled climate model projections. Maximal soil water content at 40- and 100-cm depths was correlated with February snow depth. For both species, multivariate ANOVA (MANOVA) showed that Ψ stem, g s, and A were significantly affected by intra-annual variation in snow depth. Within years, MANOVA showed that only A was significantly affected by spatial snow depth treatments for A. tridentata, and Ψ stem was significantly affected by snow depth for P. tridentata. Results show that stem water relations and photosynthetic gas exchange for these two cold desert shrub species in mid-June were more affected by inter-annual variation in snow depth by comparison to within-year spatial variation in snow depth. The results highlight the potential importance of changes in inter-annual variation in snowfall for future shrub photosynthesis in the western Great Basin Desert.

  20. Measuring carbon in shrubs. Chapter 5

    Science.gov (United States)

    David C. Chojnacky; Mikaila Milton

    2008-01-01

    Although shrubs are a small component of the overall carbon budget, shrub lands and shrub cover within forested lands warrant monitoring with consistent procedures to account for carbon in shrubs and to track carbon accumulation as communities change from shrubs to trees and vice versa. Many different procedures have been used to sample and measure shrubs (Bonham 1989...

  1. Investigation into seed collection practices and shrub manipulations to improve sustainable seed yield in wildland stands of bitterbrush (Purshia tridentata)

    Science.gov (United States)

    F. Leland Roberts

    2007-01-01

    The Great Basin is a series of unique ecosystems. Starting at the western edge of the Sierra Nevada mountain range in California it stretches east to the Wasatch Mountains of Utah. In the north it starts in central Oregon and Idaho and stretches south through out most of Nevada. In all the Great Basin is found in five states of the western U.S. The Great Basin supports...

  2. Deep sequencing of amplicons reveals widespread intraspecific hybridization and multiple origins of polyploidy in big sagebrush (Artemisia tridentata, Asteraceae)

    Science.gov (United States)

    Bryce A. Richardson; Justin T. Page; Prabin Bajgain; Stewart C. Sanderson; Joshua A. Udall

    2012-01-01

    Premise of the study: Hybridization has played an important role in the evolution and ecological adaptation of diploid and polyploid plants. Artemisia tridentata (Asteraceae) tetraploids are extremely widespread and of great ecological importance. These tetraploids are often taxonomically identified as A. tridentata subsp. wyomingensis or as autotetraploids of diploid...

  3. Natural regeneration processes in big sagebrush (Artemisia tridentata)

    Science.gov (United States)

    Schlaepfer, Daniel R.; Lauenroth, William K.; Bradford, John B.

    2014-01-01

    Big sagebrush, Artemisia tridentata Nuttall (Asteraceae), is the dominant plant species of large portions of semiarid western North America. However, much of historical big sagebrush vegetation has been removed or modified. Thus, regeneration is recognized as an important component for land management. Limited knowledge about key regeneration processes, however, represents an obstacle to identifying successful management practices and to gaining greater insight into the consequences of increasing disturbance frequency and global change. Therefore, our objective is to synthesize knowledge about natural big sagebrush regeneration. We identified and characterized the controls of big sagebrush seed production, germination, and establishment. The largest knowledge gaps and associated research needs include quiescence and dormancy of embryos and seedlings; variation in seed production and germination percentages; wet-thermal time model of germination; responses to frost events (including freezing/thawing of soils), CO2 concentration, and nutrients in combination with water availability; suitability of microsite vs. site conditions; competitive ability as well as seedling growth responses; and differences among subspecies and ecoregions. Potential impacts of climate change on big sagebrush regeneration could include that temperature increases may not have a large direct influence on regeneration due to the broad temperature optimum for regeneration, whereas indirect effects could include selection for populations with less stringent seed dormancy. Drier conditions will have direct negative effects on germination and seedling survival and could also lead to lighter seeds, which lowers germination success further. The short seed dispersal distance of big sagebrush may limit its tracking of suitable climate; whereas, the low competitive ability of big sagebrush seedlings may limit successful competition with species that track climate. An improved understanding of the

  4. Influence of Mowing Artemisia tridentata ssp. wyomingensis on Winter Habitat for Wildlife

    Science.gov (United States)

    Davies, Kirk W.; Bates, Jonathan D.; Johnson, Dustin D.; Nafus, Aleta M.

    2009-07-01

    Mowing is commonly implemented to Artemisia tridentata ssp. wyomingensis (Beetle & A. Young) S.L. Welsh (Wyoming big sagebrush) plant communities to improve wildlife habitat, increase forage production for livestock, and create fuel breaks for fire suppression. However, information detailing the influence of mowing on winter habitat for wildlife is lacking. This information is crucial because many wildlife species depended on A. tridentata spp. wyomingensis plant communities for winter habitat and consume significant quantities of Artemisia during this time . Furthermore, information is generally limited describing the recovery of A. tridentata spp. wyomingensis to mowing and the impacts of mowing on stand structure. Stand characteristics and Artemisia leaf tissue crude protein (CP), acid detergent fiber (ADF), and neutral detergent fiber (NDF) concentrations were measured in midwinter on 0-, 2-, 4-, and 6-year-old fall-applied mechanical (mowed at 20 cm height) treatments and compared to adjacent untreated (control) areas. Mowing compared to the control decreased Artemisia cover, density, canopy volume, canopy elliptical area, and height ( P < 0.05), but all characteristics were recovering ( P < 0.05). Mowing A. tridentata spp. wyomingensis plant communities slightly increases the nutritional quality of Artemisia leaves ( P < 0.05), but it simultaneously results in up to 20 years of decrease in Artemisia structural characteristics. Because of the large reduction in A. tridentata spp. wyomingensis for potentially 20 years following mowing, mowing should not be applied in Artemisia facultative and obligate wildlife winter habitat. Considering the decline in A. tridentata spp. wyomingensis-dominated landscapes, we caution against mowing these communities.

  5. Nitrogen limitation, 15N tracer retention, and growth response in intact and Bromus tectorum-invaded Artemisia tridentata ssp. wyomingensis communities

    Science.gov (United States)

    Witwicki, Dana L.; Doescher, Paul S.; Pyke, David A.; DeCrappeo, Nicole M.; Perakis, Steven S.

    2012-01-01

    Annual grass invasion into shrub-dominated ecosystems is associated with changes in nutrient cycling that may alter nitrogen (N) limitation and retention. Carbon (C) applications that reduce plant-available N have been suggested to give native perennial vegetation a competitive advantage over exotic annual grasses, but plant community and N retention responses to C addition remain poorly understood in these ecosystems. The main objectives of this study were to (1) evaluate the degree of N limitation of plant biomass in intact versus B. tectorum-invaded sagebrush communities, (2) determine if plant N limitation patterns are reflected in the strength of tracer 15N retention over two growing seasons, and (3) assess if the strength of plant N limitation predicts the efficacy of carbon additions intended to reduce soil N availability and plant growth. Labile C additions reduced biomass of exotic annual species; however, growth of native A. tridentata shrubs also declined. Exotic annual and native perennial plant communities had divergent responses to added N, with B. tectorum displaying greater ability to use added N to rapidly increase aboveground biomass, and native perennials increasing their tissue N concentration but showing little growth response. Few differences in N pools between the annual and native communities were detected. In contrast to expectations, however, more 15N was retained over two growing seasons in the invaded annual grass than in the native shrub community. Our data suggest that N cycling in converted exotic annual grasslands of the northern Intermountain West, USA, may retain N more strongly than previously thought.

  6. Big sagebrush (Artemisia tridentata) in a shifting climate context: Assessment of seedling responses to climate

    Science.gov (United States)

    Martha A. Brabec

    2014-01-01

    The loss of big sagebrush (Artemisia tridentata) throughout the Great Basin Desert has motivated efforts to restore it because of fire and other disturbance effects on sagebrush-dependent wildlife and ecosystem function. Initial establishment is the first challenge to restoration, and appropriateness of seeds, climate, and weather variability are factors that may...

  7. Abiotic and biotic influences on Bromus tectoreum invasion and Artemisia tridentata recovery after fire

    Science.gov (United States)

    Lea Condon; Peter J. Weisberg; Jeanne C. Chambers

    2011-01-01

    Native sagebrush ecosystems in the Great Basin (western USA) are often invaded following fire by exotic Bromus tectorum (cheatgrass), a highly flammable annual grass. Once B. tectorum is established, higher fire frequencies can lead to local extirpation of Artemisia tridentata ssp. vaseyana (mountain big sagebrush) and have cascading effects on sagebrush ecosystems and...

  8. The draft genome sequence and annotation of the desert woodrat Neotoma lepida

    Directory of Open Access Journals (Sweden)

    Michael Campbell

    2016-09-01

    Full Text Available We present the de novo draft genome sequence for a vertebrate mammalian herbivore, the desert woodrat (Neotoma lepida. This species is of ecological and evolutionary interest with respect to ingestion, microbial detoxification and hepatic metabolism of toxic plant secondary compounds from the highly toxic creosote bush (Larrea tridentata and the juniper shrub (Juniperus monosperma. The draft genome sequence and annotation have been deposited at GenBank under the accession LZPO01000000.

  9. Investigating Seed Longevity of Big Sagebrush (Artemisia tridentata)

    Science.gov (United States)

    Wijayratne, Upekala C.; Pyke, David A.

    2009-01-01

    The Intermountain West is dominated by big sagebrush communities (Artemisia tridentata subspecies) that provide habitat and forage for wildlife, prevent erosion, and are economically important to recreation and livestock industries. The two most prominent subspecies of big sagebrush in this region are Wyoming big sagebrush (A. t. ssp. wyomingensis) and mountain big sagebrush (A. t. ssp. vaseyana). Increased understanding of seed bank dynamics will assist with sustainable management and persistence of sagebrush communities. For example, mountain big sagebrush may be subjected to shorter fire return intervals and prescribed fire is a tool used often to rejuvenate stands and reduce tree (Juniperus sp. or Pinus sp.) encroachment into these communities. A persistent seed bank for mountain big sagebrush would be advantageous under these circumstances. Laboratory germination trials indicate that seed dormancy in big sagebrush may be habitat-specific, with collections from colder sites being more dormant. Our objective was to investigate seed longevity of both subspecies by evaluating viability of seeds in the field with a seed retrieval experiment and sampling for seeds in situ. We chose six study sites for each subspecies. These sites were dispersed across eastern Oregon, southern Idaho, northwestern Utah, and eastern Nevada. Ninety-six polyester mesh bags, each containing 100 seeds of a subspecies, were placed at each site during November 2006. Seed bags were placed in three locations: (1) at the soil surface above litter, (2) on the soil surface beneath litter, and (3) 3 cm below the soil surface to determine whether dormancy is affected by continued darkness or environmental conditions. Subsets of seeds were examined in April and November in both 2007 and 2008 to determine seed viability dynamics. Seed bank samples were taken at each site, separated into litter and soil fractions, and assessed for number of germinable seeds in a greenhouse. Community composition data

  10. Determinismo, analogia e preveggenza in Pierre Mabille. Basi per un raffronto con Juan Larrea

    Directory of Open Access Journals (Sweden)

    A. D’Urso

    2012-08-01

    Full Text Available ENThis text is a brief commentary on Pierre Mabille’s Del nuevo mundo, published in Mexico in 1943 and that we give here in our translation, which is perhaps absolutely the first in Italy concerning one of the writings of this important Surrealist, who is little studied by the French criticism even.Within the limits of the themes of this article and of the space granted here, we preferred to illustrate the implicit – and yet so evident – relations between Mabille’s thought and Dialectical Materialism, particularly by showing those passages of his text which seem to refer to some (even minor Marx and Engels’ works, rather than delay in a bio-bibliographical reconstruction and examine thoroughly the influence of materialist Monism, alchemical Hermetism and revolutionary Freemasonry on the “stylistic” construction of this brief essay.Around the themes of determinism, analogy and clairvoyance, Mabille’s original reading of fundamental thesis of Hegelian Dialectics and Marxist Materialism in their possible synthesis with the principles of cosmic Monism will be put in relief. This is an interpretation which permits to face such matters from inside a fully Surrealist point of view, rather than from outside it (and a little more metaphysically as Juan Larrea pretended to, thus allowing to put the basis for a possible comparison between him and his friend Mabille, who both never failed to influence each other.Keywords: Monism; Surrealism; Materialism; Engels; Marxism.ITQuesto testo è un breve commento dell’articolo Del nuevo mundo di Pierre Mabille, apparso in Messico nel 1943 e che qui forniamo nella nostra traduzione, probabilmente la prima in assoluto in Italia di uno scritto di quest’importante surrealista, poco studiato anche dalla critica francese.Nei limiti dello spazio disponibile e delle tematiche del testo in questione abbiamo preferito esporre le rela¬zioni implicite – eppure così evidenti – del pensiero di Mabille

  11. Seasonal soil CO2 flux under big sagebrush (Artemisia tridentata Nutt.)

    Science.gov (United States)

    Michael C. Amacher; Cheryl L. Mackowiak

    2011-01-01

    Soil respiration is a major contributor to atmospheric CO2, but accurate landscape-scale estimates of soil CO2 flux for many ecosystems including shrublands have yet to be established. We began a project to measure, with high spatial and temporal resolution, soil CO2 flux in a stand (11 x 25 m area) of big sagebrush (Artemisia tridentata Nutt.) at the Logan, Utah,...

  12. Shrub expansion in SW Greenland

    DEFF Research Database (Denmark)

    Jørgensen, Rasmus Halfdan

    Arctic regions have experienced higher temperatures in recent decades, and the warming trend is projected to continue in the coming years. Arctic ecosystems are considered to be particularly vulnerable to climate change. Expansion of shrubs has been observed widely in tundra areas across the Arctic......, and has a range of ecosystem effects where it occurs. Shrub expansion has to a large extend been attributed to increasing temperatures over the past century, while grazing and human disturbance have received less attention. Alnus viridis ssp. crispa is a common arctic species that contributes...... to increasing shrub cover. Despite this, there is only limited experimental evidence that growth of the species responds to warming. Plant populations in fragmented and isolated locations could face problems adapting to a warming climate due to limited genetic variation and restricted migration from southern...

  13. Root systems of chaparral shrubs.

    Science.gov (United States)

    Kummerow, Jochen; Krause, David; Jow, William

    1977-06-01

    Root systems of chaparral shrubs were excavated from a 70 m 2 plot of a mixed chaparral stand located on a north-facing slope in San Diego County (32°54' N; 900 m above sea level). The main shrub species present were Adenostoma fasciculatum, Arctostaphylos pungens, Ceanothus greggii, Erigonum fasciculatum, and Haplopappus pinifolius. Shrubs were wired into their positions, and the soil was washed out beneath them down to a depth of approximately 60 cm, where impenetrable granite impeded further washing and root growth was severely restricted. Spacing and interweaving of root systems were recorded by an in-scale drawing. The roots were harvested in accordance to their depths, separated into diameter size classes for each species, and their dry weights measured. Roots of shrubs were largely confined to the upper soil levels. The roots of Eriogonum fasciculatum were concentrated in the upper soil layer. Roots of Adenostoma fasciculatum tended to be more superficial than those from Ceanothus greggii. It is hypothesized that the shallow soil at the excavation site impeded a clear depth zonation of the different root systems. The average dry weight root:shoot ratio was 0.6, ranging for the individual shrubs from 0.8 to 0.4. The root area always exceeded the shoot area, with the corresponding ratios ranging from 6 for Arctostaphylos pungens to 40 for Haplopappus pinifolius. The fine root density of 64 g dry weight per m 2 under the canopy was significantly higher than in the unshaded area. However, the corresponding value of 45 g dry weight per m 2 for the open ground is still high enough to make the establishment of other shrubs difficult.

  14. Chapter 23. Shrubs of other families

    Science.gov (United States)

    Stephen B. Monsen; Richard Stevens; Nancy L. Shaw

    2004-01-01

    Numerous genera and species of shrubs occur throughout the Intermountain region in addition to those included in the Asteraceae, Chenopodiaceae, and Rosaceae families. Although shrubs are widespread throughout this region and dominate many areas, species richness is low compared to the shrub flora of the Pacific United States, Chile, western Australia, and South Africa...

  15. Narrow hybrid zone between two subspecies of big sagebrush (Artemisia tridentata: Asteraceae): XI. Plant-insect interactions in reciprocal transplant gardens

    Science.gov (United States)

    John H. Graham; E. Durant McArthur; D. Carl Freeman

    2001-01-01

    Basin big sagebrush (Artemisia tridentata ssp. tridentata) and mountain big sagebrush (A. t. ssp. vaseyana) hybridize in a narrow zone near Salt Creek, Utah. Reciprocal transplant experiments in this hybrid zone demonstrate that hybrids are more fit than either parental subspecies, but only in the hybrid zone. Do hybrids experience greater, or lesser, use by...

  16. Legume Shrubs Are More Nitrogen-Homeostatic than Non-legume Shrubs.

    Science.gov (United States)

    Guo, Yanpei; Yang, Xian; Schöb, Christian; Jiang, Youxu; Tang, Zhiyao

    2017-01-01

    Legumes are characterized as keeping stable nutrient supply under nutrient-limited conditions. However, few studies examined the legumes' stoichiometric advantages over other plants across various taxa in natural ecosystems. We explored differences in nitrogen (N) and phosphorus (P) stoichiometry of different tissue types (leaf, stem, and root) between N 2 -fixing legume shrubs and non-N 2 -fixing shrubs from 299 broadleaved deciduous shrubland sites in northern China. After excluding effects of taxonomy and environmental variables, these two functional groups differed considerably in nutrient regulation. N concentrations and N:P ratios were higher in legume shrubs than in non-N 2 -fixing shrubs. N concentrations were positively correlated between the plants and soil for non-N 2 -fixing shrubs, but not for legume shrubs, indicating a stronger stoichiometric homeostasis in legume shrubs than in non-N 2 -fixing shrubs. N concentrations were positively correlated among three tissue types for non-N 2 -fixing shrubs, but not between leaves and non-leaf tissues for legume shrubs, demonstrating that N concentrations were more dependent among tissues for non-N 2 -fixing shrubs than for legume shrubs. N and P concentrations were correlated within all tissues for both functional groups, but the regression slopes were flatter for legume shrubs than non-N 2 -fixing shrubs, implying that legume shrubs were more P limited than non-N 2 -fixing shrubs. These results address significant differences in stoichiometry between legume shrubs and non-N 2 -fixing shrubs, and indicate the influence of symbiotic nitrogen fixation (SNF) on plant stoichiometry. Overall, N 2 -fixing legume shrubs are higher and more stoichiometrically homeostatic in N concentrations. However, due to excess uptake of N, legumes may suffer from potential P limitation. With their N advantage, legume shrubs could be good nurse plants in restoration sites with degraded soil, but their P supply should be taken care

  17. Status report of the Pacific lamprey (Lampetra tridentata) in the Columbia River Basin

    International Nuclear Information System (INIS)

    Close, D.A.; Fitzpatrick, M.; Li, H.; James, G.

    1995-07-01

    The widespread decline of Pacific lamprey (Lampetra tridentata) in the Pacific Northwest, especially in the Columbia River system has led to concerns and questions from a number of regional agencies, Native American tribes, and the public. To address these concerns, new research efforts must focus on specific problems associated with this understudied species. The preservation and restoration of this species is critical for a number of reasons, including its importance to the tribes and its importance as an indicator of ecosystem health. Historically lamprey have been labeled a pest species due to the problems associated with the exotic sea lamprey, (Petromyzon marinus), invading the Great Lakes

  18. Phenolic compounds as indicators of drought resistance in shrubs from Patagonian shrublands (Argentina).

    Science.gov (United States)

    Varela, M Celeste; Arslan, Idris; Reginato, Mariana A; Cenzano, Ana M; Luna, M Virginia

    2016-07-01

    Plants exposed to drought stress, as usually occurs in Patagonian shrublands, have developed different strategies to avoid or tolerate the lack of water during their development. Production of phenolic compounds (or polyphenols) is one of the strategies used by some native species of adverse environments to avoid the oxidative damage caused by drought. In the present study the relationship between phenolic compounds content, water availability and oxidative damage were evaluated in two native shrubs: Larrea divaricata (evergreen) and Lycium chilense (deciduous) of Patagonian shrublands by their means and/or by multivariate analysis. Samples of both species were collected during the 4 seasons for the term of 1 year. Soil water content, relative water content, total phenols, flavonoids, flavonols, tartaric acid esters, flavan-3-ols, proanthocyanidins, antioxidant capacity and lipid peroxidation were measured. According to statistical univariate analysis, L. divaricata showed high production of polyphenols along the year, with a phenolic compound synthesis enhanced during autumn (season of greatest drought), while L. chilense has lower production of these compounds without variation between seasons. The variation in total phenols along the seasons is proportional to the antioxidant capacity and inversely proportional to lipid peroxidation. Multivariate analysis showed that, regardless their mechanism to face drought (avoidance or tolerance), both shrubs are well adapted to semi-arid regions and the phenolic compounds production is a strategy used by these species living in extreme environments. The identification of polyphenol compounds showed that L. divaricata produces different types of flavonoids, particularly bond with sugars, while L. chilense produces high amount of non-flavonoids compounds. These results suggest that flavonoid production and accumulation could be a useful indicator of drought tolerance in native species. Copyright © 2016 Elsevier Masson

  19. Development of pH-responsive biopolymer-silica composites loaded with Larrea divaricata Cav. extract with antioxidant activity.

    Science.gov (United States)

    Alvarez Echazú, María Inés; Olivetti, Christian Ezequiel; Peralta, Ignacio; Alonso, Maria Rosario; Anesini, Claudia; Perez, Claudio Javier; Alvarez, Gisela Solange; Desimone, Martin Federico

    2018-05-07

    A detailed study of biomaterials is mandatory to comprehend their feasible biomedical applications in terms of drug delivery and tissue regeneration. Particularly, mucoadhesive biopolymers such as chitosan (chi) and carboxymethylcellulose (CMC) have become interesting biomaterials regards to their biocompatibility and non-toxicity for oral mucosal drug delivery. In this work, pH-responsive biopolymer-silica composites (Chi-SiO 2 , Chi-CMC-SiO 2 ) were developed. These two types of composites presented a different swelling behavior due to the environmental pH. Moreover, the nanocomposites were loaded with aqueous Larrea divaricata Cav. extract (Ld), a South American plant which presents antioxidant properties suitable for the treatment of gingivoperiodontal diseases. Chi-CMC-SiO 2 composites showed the highest incorporation and reached the 100% of extract release in almost 4 days while they preserved their antioxidant properties. In this study, thermal and swelling behavior were pointed out to show the distinct water-composite interaction and therefore to evaluate their mucoadhesivity. Furthermore, a cytotoxicity test with 3T3 fibroblasts was assessed, showing that in both composites the addition of Larrea divaricata Cav. extract increased fibroblast proliferation. Lastly, preliminary in vitro studies were performed with simulated body fluids. Indeed, SEM-EDS analysis indicated that only chi-SiO 2 composite may provide an environment for possible biomineralization while the addition of CMC to the composites discouraged calcium accumulation. In conclusion, the development of bioactive composites could promote the regeneration of periodontal tissue damaged throughout periodontal disease and the presence of silica nanoparticles could provide an environment for biomineralization. Copyright © 2018 Elsevier B.V. All rights reserved.

  20. Chemicals from trees and shrubs

    Energy Technology Data Exchange (ETDEWEB)

    Halloran, G M

    1978-01-01

    The need for finding economically viable alternatives to crude oil is discussed in the context of Australia's uncertain reserves of black coal, from which crude oil derivatives may have to be obtained when oil supplies become depleted. A table is presented showing the major fractions of crude oil and the likely sources (in general terms) of equivalent substances from forest trees, shrubs and agricultural species.

  1. Plants and ventifacts delineate late Holocene wind vectors in the Coachella Valley, USA

    Science.gov (United States)

    Griffiths, P.G.; Webb, R.H.; Fisher, M.; Muth, Allan

    2009-01-01

    Strong westerly winds that emanate from San Gorgonio Pass, the lowest point between Palm Springs and Los Angeles, California, dominate aeolian transport in the Coachella Valley of the western Sonoran Desert. These winds deposit sand in coppice dunes that are critical habitat for several species, including the state and federally listed threatened species Uma inornata, a lizard. Although wind directions are generally defined in this valley, the wind field has complex interactions with local topography and becomes more variable with distance from the pass. Local, dominant wind directions are preserved by growth patterns of Larrea tridentata (creosote bush), a shrub characteristic of the hot North American deserts, and ventifacts. Exceptionally long-lived, Larrea has the potential to preserve wind direction over centuries to millennia, shaped by the abrasive pruning of windward branches and the persistent training of leeward branches. Wind direction preserved in Larrea individuals and clones was mapped at 192 locations. Compared with wind data from three weather stations, Larrea vectors effectively reflect annual prevailing winds. Ventifacts measured at 24 locations record winds 10° more westerly than Larrea and appear to reflect the direction of the most erosive winds. Based on detailed mapping of local wind directions as preserved in Larrea, only the northern half of the Mission-Morongo Creek floodplain is likely to supply sand to protected U. inornata habitat in the Willow Hole ecological reserve.

  2. Simulating the productivity of desert woody shrubs in southwestern Texas

    Science.gov (United States)

    In the southwestern U.S., many rangelands have converted from native grasslands to woody shrublands dominated by creosotebush (Larrea tridentate) and honey mesquite (Prosopis glandulosa), threatening ecosystem health. Both creosotebush and mesquite have well-developed long root systems that allow t...

  3. Composition of the essential oils from Rocky Mountain juniper (Juniperus scopulorum), Big sagebrush (Artemisia tridentata), and White Sage (Salvia apiana).

    Energy Technology Data Exchange (ETDEWEB)

    Hochrein, James Michael; Irwin, Adriane Nadine; Borek, Theodore Thaddeus III

    2003-09-01

    The essential oils of Juniperus scopulorum, Artemisia tridentata, and Salvia apiana obtained by steam extraction were analyzed by GC-MS and GC-FID. For J. scopulorum, twenty-five compounds were identified which accounts for 92.43% of the oil. The primary constituents were sabinene (49.91%), {alpha}-terpinene (9.95%), and 4-terpineol (6.79%). For A. tridentata, twenty compounds were identified which accounts for 84.32% of the oil. The primary constituents were camphor (28.63%), camphene (16.88%), and 1,8-cineole (13.23%). For S. apiana, fourteen compounds were identified which accounts for 96.76% of the oil. The primary component was 1,8-cineole (60.65%).

  4. Stem secondary growth of tundra shrubs

    DEFF Research Database (Denmark)

    Campioli, Matteo; Leblans, Niki; Michelsen, Anders

    2012-01-01

    Our knowledge of stem secondary growth of arctic shrubs (a key component of tundra net primary production, NPP) is very limited. Here, we investigated the impact of the physical elements of the environment on shrub secondary growth by comparing annual growth rates of model species from similar...... growth (stem apical growth, stem length, and apical growth of stem plus leaves), in some cases even with opposite responses. Thus caution should be taken when estimating the impact of the environment on shrub growth from apical growth only. Integration of our data set with the (very limited) previously...

  5. Abiotic factors affect the recruitment and biomass of perennial grass and evergreen shrub seedlings in denuded areas of Patagonian Monte rangelands.

    Science.gov (United States)

    Bosco, Tomás; Bertiller, Mónica Beatriz; Carrera, Analía Lorena

    2018-07-15

    Assessing the ability of key species to cope with environmental stresses in disturbed areas is an important issue for recovery of degraded arid ecosystem. Our objective was to evaluate the effect of soil moisture, exposure to UV radiation, and presence/absence of litter with different chemistry on soil N, recruitment and biomass of seedlings of perennial grass (Poa ligularis and Nassella tenuis) and evergreen shrub species (Atriplex lampa and Larrea divaricata) in denuded areas. We carried out a microcosm experiment with soil blocks (28 cm depth) sowed with seeds of the target species, subjected to different levels of litter type (perennial grass-evergreen shrub mixture, evergreen shrub mixture, and no litter), UV radiation (near ambient and reduced UV), and soil water (high: 15-25% and low 5-15%). Periodically, during 6 months, we assessed soil-N (total and inorganic) at two depths and species seedling recruitment at microcosms. Additionally, emerged seedlings of each species were transplanted to individual pots containing soil and subjected to the same previous factors during 12 months. Then, all plants were harvested and biomass assessed. Only inorganic soil-N at the upper soil varied among treatments increasing with the presence of evergreen shrub litter, exposure to ambient UV, and high soil water. Inorganic soil-N, promoted by near ambient UV and high soil water, had a positive effect on recruitment of perennial grasses and A. lampa. Both litter types promoted the recruitment of perennial grasses. Evergreen shrub litter and high soil water promoted the recruitment of L. divaricata. Seedling biomass of perennial grasses increased with high soil water and reduced UV. Ambient UV had positive or null effects on biomass of evergreen shrub seedlings. High soil water increased biomass of L. divaricata seedlings. We concluded that soil water appeared as the most limiting factor for seedling recruitment of all species whereas inorganic soil N limited the

  6. Grass-Shrub Associations over a Precipitation Gradient and Their Implications for Restoration in the Great Basin, USA.

    Directory of Open Access Journals (Sweden)

    Maike F Holthuijzen

    Full Text Available As environmental stress increases positive (facilitative plant interactions often predominate. Plant-plant associations (or lack thereof can indicate whether certain plant species favor particular types of microsites (e.g., shrub canopies or plant-free interspaces and can provide valuable insights into whether "nurse plants" will contribute to seeding or planting success during ecological restoration. It can be difficult, however, to anticipate how relationships between nurse plants and plants used for restoration may change over large-ranging, regional stress gradients. We investigated associations between the shrub, Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis, and three common native grasses (Poa secunda, Elymus elymoides, and Pseudoroegneria spicata, representing short-, medium-, and deep-rooted growth forms, respectively, across an annual rainfall gradient (220-350 mm in the Great Basin, USA. We hypothesized that positive shrub-grass relationships would become more frequent at lower rainfall levels, as indicated by greater cover of grasses in shrub canopies than vegetation-free interspaces. We sampled aerial cover, density, height, basal width, grazing status, and reproductive status of perennial grasses in canopies and interspaces of 25-33 sagebrush individuals at 32 sites along a rainfall gradient. We found that aerial cover of the shallow rooted grass, P. secunda, was higher in sagebrush canopy than interspace microsites at lower levels of rainfall. Cover and density of the medium-rooted grass, E. elymoides were higher in sagebrush canopies than interspaces at all but the highest rainfall levels. Neither annual rainfall nor sagebrush canopy microsite significantly affected P. spicata cover. E. elymoides and P. spicata plants were taller, narrower, and less likely to be grazed in shrub canopy microsites than interspaces. Our results suggest that exploring sagebrush canopy microsites for restoration of native perennial

  7. Seasonal changes in morphophysiological traits of two native Patagonian shrubs from Argentina with different drought resistance strategies.

    Science.gov (United States)

    Varela, M Celeste; Reinoso, Herminda; Luna, Virginia; Cenzano, Ana M

    2018-06-01

    In semi-arid regions, plants develop various biochemical and physiological strategies to adapt to dry periods. Understanding the resistance mechanisms to dry periods under field conditions is an important topic in ecology. Larrea divaricata and Lycium chilense provide various ecological services. The aim of this work is to elucidate new morpho-histological, biochemical and hormonal traits that contribute to the drought resistance strategies of two native shrubs. Green leaves and fine roots from L. divaricata and L. chilense were collected in each season for one year, and various traits were measured. The hormone (abscisic acid, ABA-glucose ester, gibberellins A 1 and A 3 , and indole acetic acid) contents were determined by liquid chromatography coupled to mass spectrometry. Rainfall data and the soil water content were also measured. A multivariate analysis showed that green leaves from L. divaricata showed high values for the leaf dry weight, blade leaf thickness and ABA content in the summer compared with those from L. chilense. Fine roots from L. divaricata had high RWC and high IAA levels during the autumn-dry period compared with those from L. chilense, but both had similar levels during the winter and spring. Our results support the notion that species with different drought resistance mechanisms (avoidance or tolerance) display different responses to dry periods throughout the year. Larrea divaricata, which exhibits more xerophytic traits, modified its morphology and maintained its physiological parameters (high RWC in leaves and roots, high ABA levels in leaves during summer, high GA 3 in leaves and high IAA in roots during autumn) to tolerate dry periods, whereas Lycium chilense, which displays more mesophytic traits, uses strategies to avoid dry periods (loss of leaves during autumn and winter, high RWC in leaves, high ABA-GE and GA 3 in leaves during summer, high GA 1 and GA 3 in roots during summer, and high IAA in roots during autumn and summer) and

  8. Average biomass of four Northwest shrubs by fuel size class and crown cover.

    Science.gov (United States)

    Robert E. Martin; David W. Frewing; James L. McClanahan

    1981-01-01

    The average biomass of big sagebrush (Artemisia tridentata Nutt.), antelope bitterbrush (Purshia tridentata (Pursh) DC.), snowbrush ceanothus (Ceanothus velutinus Dougl. ex Hook.), and greenleaf manzanita (Arctostaphylos patula Greene) was 6.1, 5.1, 10.7, and 16.2 tons per acre (13.9,...

  9. Divergent evapotranspiration partition dynamics between shrubs and grasses in a shrub-encroached steppe ecosystem.

    Science.gov (United States)

    Wang, Pei; Li, Xiao-Yan; Wang, Lixin; Wu, Xiuchen; Hu, Xia; Fan, Ying; Tong, Yaqin

    2018-06-04

    Previous evapotranspiration (ET) partitioning studies have usually neglected competitions and interactions between antagonistic plant functional types. This study investigated whether shrubs and grasses have divergent ET partition dynamics impacted by different water-use patterns, canopy structures, and physiological properties in a shrub-encroached steppe ecosystem in Inner Mongolia, China. The soil water-use patterns of shrubs and grasses have been quantified by an isotopic tracing approach and coupled into an improved multisource energy balance model to partition ET fluxes into soil evaporation, grass transpiration, and shrub transpiration. The mean fractional contributions to total ET were 24 ± 13%, 20 ± 4%, and 56 ± 16% for shrub transpiration, grass transpiration, and soil evaporation respectively during the growing season. Difference in ecohydrological connectivity and leaf development both contributed to divergent transpiration partitioning between shrubs and grasses. Shrub-encroachment processes result in larger changes in the ET components than in total ET flux, which could be well explained by changes in canopy resistance, an ecosystem function dominated by the interaction of soil water-use patterns and ecosystem structure. The analyses presented here highlight the crucial effects of vegetation structural changes on the processes of land-atmosphere interaction and climate feedback. © 2018 The Authors. New Phytologist © 2018 New Phytologist Trust.

  10. Shrubs and vines for northeastern wildlife

    Science.gov (United States)

    John D. Gill; William M. Healy

    1974-01-01

    A non-technical handbook in which 34 authors discuss management of 97 native and 3 naturalized shrubs or woody vines most important to wildlife in the Northeast,-Kentucky to Maryland to Newfoundland to Ontario. Topics include range, habitat, life history, uses, propagation, and management; but not identification.

  11. Modeling regeneration responses of big sagebrush (Artemisia tridentata) to abiotic conditions

    Science.gov (United States)

    Schlaepfer, Daniel R.; Lauenroth, William K.; Bradford, John B.

    2014-01-01

    Ecosystems dominated by big sagebrush, Artemisia tridentata Nuttall (Asteraceae), which are the most widespread ecosystems in semiarid western North America, have been affected by land use practices and invasive species. Loss of big sagebrush and the decline of associated species, such as greater sage-grouse, are a concern to land managers and conservationists. However, big sagebrush regeneration remains difficult to achieve by restoration and reclamation efforts and there is no regeneration simulation model available. We present here the first process-based, daily time-step, simulation model to predict yearly big sagebrush regeneration including relevant germination and seedling responses to abiotic factors. We estimated values, uncertainty, and importance of 27 model parameters using a total of 1435 site-years of observation. Our model explained 74% of variability of number of years with successful regeneration at 46 sites. It also achieved 60% overall accuracy predicting yearly regeneration success/failure. Our results identify specific future research needed to improve our understanding of big sagebrush regeneration, including data at the subspecies level and improved parameter estimates for start of seed dispersal, modified wet thermal-time model of germination, and soil water potential influences. We found that relationships between big sagebrush regeneration and climate conditions were site specific, varying across the distribution of big sagebrush. This indicates that statistical models based on climate are unsuitable for understanding range-wide regeneration patterns or for assessing the potential consequences of changing climate on sagebrush regeneration and underscores the value of this process-based model. We used our model to predict potential regeneration across the range of sagebrush ecosystems in the western United States, which confirmed that seedling survival is a limiting factor, whereas germination is not. Our results also suggested that modeled

  12. Legume Shrubs Are More Nitrogen-Homeostatic than Non-legume Shrubs

    OpenAIRE

    Guo, Yanpei; Yang, Xian; Schöb, Christian; Jiang, Youxu; Tang, Zhiyao

    2017-01-01

    Legumes are characterized as keeping stable nutrient supply under nutrient-limited conditions. However, few studies examined the legumes' stoichiometric advantages over other plants across various taxa in natural ecosystems. We explored differences in nitrogen (N) and phosphorus (P) stoichiometry of different tissue types (leaf, stem, and root) between N2-fixing legume shrubs and non-N2-fixing shrubs from 299 broadleaved deciduous shrubland sites in northern China. After excluding effects of ...

  13. Shrub water use dynamics in arctic Alaska

    Science.gov (United States)

    Clark, J.; Young-Robertson, J. M.; Tape, K. D.

    2016-12-01

    In the Arctic tundra, hydrologic processes influence the majority of ecosystem processes, from soil thermal dynamics to energy balance and trace gas exchange to vegetation community distributions. The tundra biome is experiencing a broad spectrum of ecosystem changes spurred by 20th century warming, including deciduous shrub expansion. Deciduous woody vegetation typically has high water use rates compared to evergreen and herbaceous species, and is projected to have a greater impact on energy balance than altered albedo from changes in snowpack. However, the impact of greater shrub cover on water balance has been overlooked. Shrubs have the potential to significantly dry the soil, accessing stored soil moisture in the organic layers, while increasing atmospheric moisture. The goal of this study is to quantify the water use dynamics (sap flux and stem water content) of three common arctic shrub species (Salix alexensis, S. pulchra, Betula nana) over two growing seasons. Stem water content was measured through a novel application of time domain reflectometry (TDR). Maximum sap flow rates varied by species: S. alexensis-600g/hr, S. pulchra-60g/hr, and B. nana-40g/hr. We found daily sap flow rates are highly correlated with atmospheric moisture demand (VPD) and not limited by soil moisture or antecedent precipitation. Stem water content varied between 20% and 60%, was correlated with soil moisture, and showed weak diurnal variation. This is one of the first studies to provide a detailed look at arctic tundra shrub water balance and explore the environmental controls on water flux. Planned future work will expand on these results for estimates of evapotranspiration over larger landscape areas.

  14. Consequences of pre-inoculation with native arbuscular mycorrhizae on root colonization and survival of Artemisia tridentata ssp. wyomingensis (Wyoming big sagebrush) seedlings after transplanting

    Science.gov (United States)

    Bill Eugene Davidson

    2015-01-01

    Inoculation of seedlings with arbuscular mycorrhizal fungi (AMF) is a common practice aimed at improving seedling establishment. The success of this practice largely depends on the ability of the inoculum to multiply and colonize the growing root system after transplanting. These events were investigated in Artemisia tridentata ssp. wyomingensis (Wyoming big sagebrush...

  15. Effects of sub-Arctic shrub canopies on snowmelt energetics

    Science.gov (United States)

    Bewley, D.; Essery, R.; Pomeroy, J.

    2006-12-01

    Much of the low Arctic is covered with shrub tundra, and there is increasing evidence that snowmelt rates are substantially different between shrub tundra and poorly vegetated sites. The cause of this remains uncertain, however, and extends beyond simple differences in albedo. Results are presented in this study from a detailed field investigation at Wolf Creek Research Basin in 2004 to determine the effect of two different shrub canopy structures on both melt rates and the partitioning of melt energy. The low shrub site (LSS) was essentially an unvegetated snowfield prior to melt (mean albedo ~0.85), and shrubs only became exposed during the last few days of melt reaching a mean height of 0.31 m and mean Plant Area Index (PAI) of 0.32. Shrubs at the tall shrub site (TSS) were partially buried initially (shrub fraction, mean height and PAI of 0.2, 0.9 m and 0.41) but dominated the landscape by the end of melt (corresponding values of 0.71, 1.6 m and 0.6). Melt rates were higher at TSS up until the exposure of shrubs and bare ground at LSS, after which the rates converged. A Shrub-Snow Canopy Model (SSCM) is developed to improve snowmelt simulations for shrub canopies by parameterizing the key shrub effects on surface fluxes, including the extinction of shortwave irradiance beneath shrubs and in canopy gaps, and the enhancement of snow surface fluxes of longwave radiation and sensible heat. SSCM was run for LSS assuming no shrubs were present above the variable snow and bare ground tiles, whereas for TSS an increasing shrub fraction above each tile was prescribed from observations. Results from both sites suggest that sensible heat fluxes contributed more melt energy than net radiation, and were greater during early melt at TSS due to the warming of exposed shrubs. SWE was accurately predicted against transect measurements at TSS (rms error 4 mm), but was overestimated at LSS (rms error 13 mm) since both air temperatures and turbulent transport were underestimated

  16. Estimating shrub biomass from basal stem diameters

    Energy Technology Data Exchange (ETDEWEB)

    Brown, J K

    1976-01-01

    Stem lengths and oven dry wt of stemwood and foilage were determined for shrubs in dia classes of 0 to 0.5 cm, 0.5 to 2 cm and 2 to 5 cm in various habitat types in Idaho and Montana. The logarithm of basal stem dia was closely correlated with the logarithm of wt. Regression components are presented for estimating leaf wt and total above-ground wt of 25 woody shrub species using a linear equation relating these 2 variables. Percentage stemwood wt is given for the 3 dia classes. Dia distributions for the smallest dia class were normal except for a few species with fine twigs; distributions for the other classes were positively skewed. Applications to forest fuel studies are briefly discussed.

  17. Estimating shrub biomass from basal stem diameters

    Energy Technology Data Exchange (ETDEWEB)

    Brown, J K

    1976-01-01

    Stem lengths and oven dry wt of stemwood and foilage were determined for shrubs in dia classes of 0 to 0.5 cm, 0.5 to 2 cm and 2 to 5 cm in various habitat types in Idaho and Montana. The logarithm of basal stem dia was closely correlated with the logarithm of wt. Regression components are presented for estimating leaf wt and total above-ground wt of 25 woody shrub species using a linear equation relating these 2 variables. Percentage stemwood wt is given for the 3 dia classes. Dia distributions for the smallest dia class were normal except for a few species with fine twigs: distributions for the other classes were positively skewed. Applications to forest fuel studies are briefly discussed.

  18. Contrasting shrub species respond to early summer temperatures leading to correspondence of shrub growth patterns

    Science.gov (United States)

    Weijers, Stef; Pape, Roland; Löffler, Jörg; Myers-Smith, Isla H.

    2018-03-01

    The Arctic-alpine biome is warming rapidly, resulting in a gradual replacement of low statured species by taller woody species in many tundra ecosystems. In northwest North America, the remotely sensed normalized difference vegetation index (NDVI), suggests an increase in productivity of the Arctic and alpine tundra and a decrease in productivity of boreal forests. However, the responses of contrasting shrub species growing at the same sites to climate drivers remain largely unexplored. Here, we test growth, climate, and NDVI relationships of two contrasting species: the expanding tall deciduous shrub Salix pulchra and the circumarctic evergreen dwarf shrub Cassiope tetragona from an alpine tundra site in the Pika valley in the Kluane Region, southwest Yukon Territories, Canada. We found that annual growth variability of both species at this site is strongly driven by early summer temperatures, despite their contrasting traits and habitats. Shrub growth chronologies for both species were correlated with the regional climate signal and showed spatial correspondence with interannual variation in NDVI in surrounding alpine and Arctic regions. Our results suggest that early summer warming represents a common driver of vegetation change for contrasting shrub species growing in different habitats in the same alpine environments.

  19. Expansion of deciduous tall shrubs but not evergreen dwarf shrubs inhibited by reindeer in Scandes mountain range.

    Science.gov (United States)

    Vowles, Tage; Gunnarsson, Bengt; Molau, Ulf; Hickler, Thomas; Klemedtsson, Leif; Björk, Robert G

    2017-11-01

    One of the most palpable effects of warming in Arctic ecosystems is shrub expansion above the tree line. However, previous studies have found that reindeer can influence plant community responses to warming and inhibit shrubification of the tundra.We revisited grazed (ambient) and ungrazed study plots (exclosures), at the southern as well as the northern limits of the Swedish alpine region, to study long-term grazing effects and vegetation changes in response to increasing temperatures between 1995 and 2011, in two vegetation types (shrub heath and mountain birch forest).In the field layer at the shrub heath sites, evergreen dwarf shrubs had increased in cover from 26% to 49% but were unaffected by grazing. Deciduous dwarf and tall shrubs also showed significant, though smaller, increases over time. At the birch forest sites, the increase was similar for evergreen dwarf shrubs (20-48%) but deciduous tall shrubs did not show the same consistent increase over time as in the shrub heath.The cover and height of the shrub layer were significantly greater in exclosures at the shrub heath sites, but no significant treatment effects were found on species richness or diversity.July soil temperatures and growing season thawing degree days (TDD) were higher in exclosures at all but one site, and there was a significant negative correlation between mean shrub layer height and soil TDD at the shrub heath sites. Synthesis . This study shows that shrub expansion is occurring rapidly in the Scandes mountain range, both above and below the tree line. Tall, deciduous shrubs had benefitted significantly from grazing exclosure, both in terms of cover and height, which in turn lowered summer soil temperatures. However, the overriding vegetation shift across our sites was the striking increase in evergreen dwarf shrubs, which were not influenced by grazing. As the effects of an increase in evergreen dwarf shrubs and more recalcitrant plant litter may to some degree counteract some of

  20. Climate sensitivity of shrub growth across the tundra biome

    DEFF Research Database (Denmark)

    Myers-Smith, Isla H.; Elmendorf, Sarah C.; Beck, Pieter S.A.

    2015-01-01

    Rapid climate warming in the tundra biome has been linked to increasing shrub dominance1–4. Shrub expansion can modify climate by altering surface albedo, energy and water balance, and permafrost2,5–8, yet the drivers of shrub growth remain poorly understood. Dendroecological data consisting...... of multi-decadal time series of annual shrub growth provide an underused resource to explore climate–growth relationships. Here, we analyse circumpolar data from 37 Arctic and alpine sites in 9 countries, including 25 species, and 42,000 annual growth records from 1,821 individuals. Our analyses...... demonstrate that the sensitivity of shrub growth to climate was: (1) heterogeneous, with European sites showing greater summer temperature sensitivity than North American sites, and (2) higher at sites with greater soil moisture and for taller shrubs (for example, alders and willows) growing at their northern...

  1. Shrubs of the Field Irradiator - Gamma area in eastern Manitoba

    International Nuclear Information System (INIS)

    Dugle, J.R.; Mayoh, K.R.; Barclay, P.J.

    1979-11-01

    Detailed descriptions and line drawings are given of over 100 shrub taxa (including semi-woody shrubs and vines) which are common in Manitoba; most of them are found within the Field Irradiator - Gamma (FIG) area or its immediate surroundings. Ecological and morphological notes are included along with a few general remarks on the effects of exposure to long-term gamma radiation. Keys are given for certain genera, small family groups or other critical species groups. This document is intended to facilitate identification of shrubs for experimental purposes in the FIG projects, and it should also be useful to those who are generally interested in the shrubs of Manitoba. (auth)

  2. Comparative wood anatomy of some shrubs native to the Northern Rocky Mountains

    Science.gov (United States)

    Arlene Dale

    1968-01-01

    This paper describes some xylem characteristics of the more important shrub species of the Northern Rockies and presents a key for identifying shrub-wood specimens by microscopic characters. The paper contains photomicrographs of 55 shrub woods.

  3. Patterns of seed production and shrub association in two palatable ...

    African Journals Online (AJOL)

    Seed production and shrub association patterns of the twopalatable shrubs. Tripteris sinuatum and Tetragoma froticosa were investigated on heavily grazed communal and lightly grazed commercial rangeland in the succulent karoo. Namaqualand. Seed production in both these species was substantially reduced on the ...

  4. Shrub expansion may reduce summer permafrost thaw in Siberian tundra

    NARCIS (Netherlands)

    Blok, D.; Heijmans, M.M.P.D.; Schaepman-Strub, G.; Kononov, A.V.; Maximov, T.C.; Berendse, F.

    2010-01-01

    Climate change is expected to cause extensive vegetation changes in the Arctic: deciduous shrubs are already expanding, in response to climate warming. The results from transect studies suggest that increasing shrub cover will impact significantly on the surface energy balance. However, little is

  5. Relationships between Arctic shrub dynamics and topographically derived hydrologic characteristics

    International Nuclear Information System (INIS)

    Naito, Adam T; Cairns, David M

    2011-01-01

    Shrub expansion is a global phenomenon that is gaining increased attention in the Arctic. Recent work employing the use of oblique aerial photographs suggested a consistent pattern of positive change in shrub cover across the North Slope of Alaska. The greatest amounts of change occurred in valley slopes and floodplains. We studied the association between shrub cover change and topographically derived hydrologic characteristics in five areas in northern Alaska between the 1970s and 2000s. Change in total shrub cover ranged from − 0.65% to 46.56%. Change in floodplain shrub cover ranged from 3.38% to 76.22%. Shrubs are preferentially expanding into areas of higher topographic wetness index (TWI) values where the potential for moisture accumulation or drainage is greater. In addition, we found that floodplain shrub development was strongly associated with high TWI values and a decreasing average distance between shrubs and the river bank. This suggests an interacting influence of substrate removal and stabilization as a consequence of increased vegetation cover.

  6. Methods for measuring arctic and alpine shrub growth: A review

    NARCIS (Netherlands)

    Myers-Smith, I.H.; Hallinger, M.; Blok, D.; Sass-Klaassen, U.G.W.; Rayback, S.A.

    2015-01-01

    Shrubs have increased in abundance and dominance in arctic and alpine regions in recent decades. This often dramatic change, likely due to climate warming, has the potential to alter both the structure and function of tundra ecosystems. The analysis of shrub growth is improving our understanding of

  7. The changing role of shrubs in rangeland-based livestock production systems: Can shrubs increase our forage supply?

    Science.gov (United States)

    Projected global increases in ruminant numbers and loss of native grasslands will present a number of challenges for livestock agriculture. Escalated demand for livestock products may stimulate interest in using shrubs on western rangelands. A paradigm shift is needed to change the role of shrubs in...

  8. Understanding the erosion of semi-arid landscapes subject to vegetation change: a combined approach using monitoring, isotope and {sup 1}4c analysis

    Energy Technology Data Exchange (ETDEWEB)

    Brazier, R. E.; Turbull, L.; Bol, R.; Dixon, L.; Wainwright, J.

    2009-07-01

    The degradation of grasslands is a common problem across semi-arid areas worldwide.over the last 150 years much of the south-Western USA has experienced significant land degradation, with desert grasslands becoming dominated by shrubs and concurrent changes in runoff and erosion which are thought to propagate further the process of degradation. Field-based experiments were carried out to determine how runoff and erosion vary at stages over a transition from a black grama (Bouteloua eriopoda) grassland to creosote bush (Larrea tridentata) shrub land at the Sevilleta NWR LTER site in New Mexico. {delta}{sup 1}3 C and {delta}{sup 1}5 N analyses were carried out to investigate the age and potential provenance of eroded sediment. (Author) 4 refs.

  9. Understanding the erosion of semi-arid landscapes subject to vegetation change: a combined approach using monitoring, isotope and 14c analysis

    International Nuclear Information System (INIS)

    Brazier, R. E.; Turbull, L.; Bol, R.; Dixon, L.; Wainwright, J.

    2009-01-01

    The degradation of grasslands is a common problem across semi-arid areas worldwide.over the last 150 years much of the south-Western USA has experienced significant land degradation, with desert grasslands becoming dominated by shrubs and concurrent changes in runoff and erosion which are thought to propagate further the process of degradation. Field-based experiments were carried out to determine how runoff and erosion vary at stages over a transition from a black grama (Bouteloua eriopoda) grassland to creosote bush (Larrea tridentata) shrub land at the Sevilleta NWR LTER site in New Mexico. δ 1 3 C and δ 1 5 N analyses were carried out to investigate the age and potential provenance of eroded sediment. (Author) 4 refs.

  10. Does browsing reduce shrub survival and vigor following summer fires?

    Science.gov (United States)

    Fulbright, Timothy E.; Dacy, Emily C.; Drawe, D. Lynn

    2011-01-01

    Periodic fire is widely hypothesized to limit woody plant encroachment in semiarid grasslands. In southern Texas, however, most of the woody plants that have invaded grasslands during the past two centuries are resistant to fire. We hypothesized that browsing by Odocoileus virginianus increases mortality of palatable shrubs and reduces vigor of shrubs following fire. We randomly selected ten pairs of each of three shrub species -Condalia hookeri, Acacia farnesiana, and Celtis ehrenbergiana - in each of three locations before prescribed burns during summer 2001. Following burns, we used a wire fence to protect one shrub of each pair from browsing. We estimated intensity of O. virginianus browsing and number and height of sprouts 4, 12, 20, 30, 38, and 47 weeks post-fire. We determined shrub height, survival, and biomass one year post-fire. Averaged across species, browsing intensity on unfenced shrubs was greater (LS Means, P 0.05) one year post-burn. Browsing by O. virginianus at the intensity in our study does not increase mortality or reduce vigor of C. hookeri, A. farnesiana, and Condalia ehrenbergiana producing new growth following destruction of aboveground tissues by a single fire compared to shrubs that are not browsed following fire.

  11. Spatial analysis of root hemiparasitic shrubs and their hosts

    DEFF Research Database (Denmark)

    Dueholm, Bjørn; Bruce, David; Weinstein, Philip

    2017-01-01

    to as spatial signatures of the root hemiparasites. In order to search for such spatial signatures, we investigated a population of a predominant Acacia species in Australia co-occurring with established root hemiparasitic shrubs, using intensity estimates of the Acacia and dead shrubs to be indicators...... of parasite populations. We find evidence that the root hemiparasitic shrubs, like herbaceous root hemiparasites, prefer growing at distances from neighbouring plants that fulfil resource requirements both below-ground and above-ground. Assuming that root hemiparasites are limited by their hosts, we present...

  12. Mean species cover: a harmonized indicator of shrub cover for forest inventories

    Science.gov (United States)

    Iciar Alberdi; Sonia Condés; Ronald E. Mcroberts; Susanne Winter

    2018-01-01

    Because shrub cover is related to many forest ecosystem functions, it is one of the most relevant variables for describing these communities. Nevertheless, a harmonized indicator of shrub cover for large-scale reporting is lacking. The aims of the study were threefold: to define a shrub indicator that can be used by European countries for harmonized shrub cover...

  13. Shrubs of California's chaparral, timberland, and wood land: area, ownership, and stand characteristics.

    Science.gov (United States)

    Charles L. Boisinger

    1988-01-01

    A statewide inventory of shrubs in chaparral and on timberland and woodland in California is presented, and the relevance of shrubs to resource management is discussed. Shrub types (excluding coastal sage and Great Basin and desert shrubs) cover about 10 million acres, 73 percent of which is chaparral. Chamise is the most widespread type in chaparral (51 percent of...

  14. IMPACTS ON FLOODPLAINS BY AN INVASIVE SHRUB, BUDDLEJA DAVIDII

    Science.gov (United States)

    Despite its popularity, the ornamental, Buddleja davidii, a woody shrub of Asian origin, is considered problematic because of its ability to rapidly colonize and dominate floodplain and riparian ecosystems. Dominance during early succession may influence community dynamics and ec...

  15. Methods for measuring arctic and alpine shrub growth

    DEFF Research Database (Denmark)

    Myers-Smith, Isla; Hallinger, Martin; Blok, Daan

    2015-01-01

    Shrubs have increased in abundance and dominance in arctic and alpine regions in recent decades. This often dramatic change, likely due to climate warming, has the potential to alter both the structure and function of tundra ecosystems. The analysis of shrub growth is improving our understanding...... of tundra vegetation dynamics and environmental changes. However, dendrochronological methods developed for trees, need to be adapted for the morphology and growth eccentricity of shrubs. Here, we review current and developing methods to measure radial and axial growth, estimate age, and assess growth...... dynamics in relation to environmental variables. Recent advances in sampling methods, analysis and applications have improved our ability to investigate growth and recruitment dynamics of shrubs. However, to extrapolate findings to the biome scale, future dendroecologicalwork will require improved...

  16. Shrub expansion in SW Greenland under modest regional warming

    DEFF Research Database (Denmark)

    Jørgensen, Rasmus Halfdan; Meilby, Henrik; Kollmann, Johannes

    2013-01-01

    Shrub expansion has been observed widely in tundra areas across the Arctic. This phenomenon has been partially attributed to increasing temperatures over the past century. However, relationships among shrub expansion, grazing, and human disturbance have been studied little. SW Greenland...... is a subarctic to low-arctic region with a long and complex land-use history and only modest temperature increases over the past 50 years (0.2 °C decade-1), but changes in shrub cover have not previously been studied in this region. We compiled historical photographs of vegetation in SW Greenland (1898......–1974) and repeated the photos in 2010 and 2011. Sixty-four photo pairs were cropped into 133 smaller units and classified by aspect, substrate stability, muskoxen grazing, and human disturbance. The photo material was evaluated by 22 experts with respect to changes in shrub cover, revealing a general increase across...

  17. Changes in Nitrogen Cycling in a Shrub-Encroached Dryland

    Science.gov (United States)

    Turpin-Jelfs, T. C.; Michaelides, K.; Biederman, J. A.; Evershed, R. P.; Anesio, A. M.

    2017-12-01

    Land degradation is estimated to have occurred in 10-20% of Earth's drylands, where the environmental and socioeconomic consequences have affected 250 million people. The prevailing form of land degradation in drylands over the past ca. 150 years has been the encroachment of woody plants into arid and semi-arid grasslands. The density of mesquite (Prosopis spp.), a significant nitrogen (N)-fixing woody encroacher, has increased within the arid and semi-arid grasslands of the southwestern US by >400% over the past 30 years to occupy an area of >38 Mha. However, the impacts of an increasing density of N-fixing shrubs on the cycling and spatial variability of N within these ecosystems remains poorly understood. Here, we quantify how concentrations of N (ammonium-N, nitrate-N, organic N), as well as carbon (C; total C and organic C) and phosphorous (P; loosely-bound P, iron- and aluminium-bound P, apatite P and calcite-bound P, and residual P), and the structure of the microbial community (phospholipid fatty acids), change in the soils underneath and between shrub canopies along a gradient of shrub-encroachment for a semiarid grassland in the Santa Rita Experimental Range (SRER) Arizona, US. This gradient of encroachment was comprised of five sites that ranged from a grass dominated state to a shrub-dominated state characterised by mosaics of shrub patches and bare-soil interspaces. Our results show that the organic C and total N content of soils between shrubs decreased by >50% between grass dominant and shrub dominant end-member sites. Conversely, the organic C and total N content of soils beneath shrub canopies remained relatively constant along the encroachment gradient.

  18. Enhanced precipitation variability decreases grass- and increases shrub-productivity

    Science.gov (United States)

    Gherardi, Laureano A.; Sala, Osvaldo E.

    2015-01-01

    Although projections of precipitation change indicate increases in variability, most studies of impacts of climate change on ecosystems focused on effects of changes in amount of precipitation, overlooking precipitation variability effects, especially at the interannual scale. Here, we present results from a 6-y field experiment, where we applied sequences of wet and dry years, increasing interannual precipitation coefficient of variation while maintaining a precipitation amount constant. Increased precipitation variability significantly reduced ecosystem primary production. Dominant plant-functional types showed opposite responses: perennial-grass productivity decreased by 81%, whereas shrub productivity increased by 67%. This pattern was explained by different nonlinear responses to precipitation. Grass productivity presented a saturating response to precipitation where dry years had a larger negative effect than the positive effects of wet years. In contrast, shrubs showed an increasing response to precipitation that resulted in an increase in average productivity with increasing precipitation variability. In addition, the effects of precipitation variation increased through time. We argue that the differential responses of grasses and shrubs to precipitation variability and the amplification of this phenomenon through time result from contrasting root distributions of grasses and shrubs and competitive interactions among plant types, confirmed by structural equation analysis. Under drought conditions, grasses reduce their abundance and their ability to absorb water that then is transferred to deep soil layers that are exclusively explored by shrubs. Our work addresses an understudied dimension of climate change that might lead to widespread shrub encroachment reducing the provisioning of ecosystem services to society. PMID:26417095

  19. Patterned-ground facilitates shrub expansion in Low Arctic tundra

    International Nuclear Information System (INIS)

    Frost, Gerald V; Epstein, Howard E; Walker, Donald A; Matyshak, Georgiy; Ermokhina, Ksenia

    2013-01-01

    Recent expansion of tall shrubs in Low Arctic tundra is widely seen as a response to climate warming, but shrubification is not occurring as a simple function of regional climate trends. We show that establishment of tall alder (Alnus) is strongly facilitated by small, widely distributed cryogenic disturbances associated with patterned-ground landscapes. We identified expanding and newly established shrub stands at two northwest Siberian sites and observed that virtually all new shrubs occurred on bare microsites (‘circles’) that were disturbed by frost-heave. Frost-heave associated with circles is a widespread, annual phenomenon that maintains mosaics of mineral seedbeds with warm soils and few competitors that are immediately available to shrubs during favorable climatic periods. Circle facilitation of alder recruitment also plausibly explains the development of shrublands in which alders are regularly spaced. We conclude that alder abundance and extent have increased rapidly in the northwest Siberian Low Arctic since at least the mid-20th century, despite a lack of summer warming in recent decades. Our results are consistent with findings in the North American Arctic which emphasize that the responsiveness of Low Arctic landscapes to climate change is largely determined by the frequency and extent of disturbance processes that create mineral-rich seedbeds favorable for tall shrub recruitment. Northwest Siberia has high potential for continued expansion of tall shrubs and concomitant changes to ecosystem function, due to the widespread distribution of patterned-ground landscapes. (letter)

  20. Do changes in grazing pressure and the degree of shrub encroachment alter the effects of individual shrubs on understorey plant communities and soil function?

    Science.gov (United States)

    Soliveres, Santiago; Eldridge, David J

    2014-04-01

    Shrub canopies in semi-arid environments often produce positive effects on soil fertility, and on the richness and biomass of understorey plant communities. However, both positive and negative effects of shrub encroachment on plant and soil attributes have been reported at the landscape-level. The contrasting results between patch- and landscape-level effects in shrublands could be caused by differences in the degree of shrub encroachment or grazing pressure, both of which are likely to reduce the ability of individual shrubs to ameliorate their understorey environment.We examined how grazing and shrub encroachment (measured as landscape-level shrub cover) influence patch-level effects of shrubs on plant density, biomass and similarity in species composition between shrub understories and open areas, and on soil stability, nutrient cycling, and infiltration in two semi-arid Australian woodlands.Individual shrubs had consistently positive effects on all plant and soil variables (average increase of 23% for all variables). These positive patch-level effects persisted with increasing shrub cover up to our maximum of 50% cover. Heavy grazing negatively affected most of the variables studied (average decline of 11%). It also altered, for some variables, how individual shrubs affected their sub-canopy environment with increasing shrub cover. Thus for species density, biomass and soil infiltration, the positive effect of individual shrubs with increasing shrub cover diminished under heavy grazing. Our study refines predictions of the effects of woody encroachment on ecosystem structure and functioning by showing that heavy grazing, rather than differences in shrub cover, explains the contrasting effects on ecosystem structure and function between individual shrubs and those in dense aggregations. We also discuss how species-specific traits of the encroaching species, such as their height or its ability to fix N, might influence the relationship between their patch

  1. Synergistic mutual potentiation of antifungal activity of Zuccagnia punctata Cav. and Larrea nitida Cav. extracts in clinical isolates of Candida albicans and Candida glabrata.

    Science.gov (United States)

    Butassi, Estefanía; Svetaz, Laura A; Ivancovich, Juan J; Feresin, Gabriela E; Tapia, Alejandro; Zacchino, Susana A

    2015-06-01

    Zuccagnia punctata Cav. (Fabaceae) and Larrea nitida Cav. (Zygophyllaceae) are indistinctly or jointly used in traditional medicine for the treatment of fungal-related infections. Although their dichloromethane (DCM) extract have demonstrated moderate antifungal activities when tested on their own, antifungal properties of combinations of both plants have not been assessed previously. The aim of this study was to establish with statistical rigor whether Z. punctata (ZpE) and L. nitida DCM extract (LnE) interact synergistically against the clinically important fungi Candida albicans and Candida glabrata and to characterize the most synergistic combinations. For synergism assessment, the statistical-based Boik's design was applied. Eight ZpE-LnE fixed-ratio mixtures were prepared from four different months of 1 year and tested against Candida strains. Lϕ (Loewe index) of each mixture at different fractions affected (ϕ) allowed for the finding of the most synergistic combinations, which were characterized by HPLC fingerprint and by the quantitation of the selected marker compounds. Lϕ and confidence intervals were determined in vitro with the MixLow method, once the estimated parameters from the dose-response curves of independent extracts and mixtures, were obtained. Markers (four flavonoids for ZpE and three lignans for LnE) were quantified in each extract and their combinations, with a valid HPLC-UV method. The 3D-HPLC profiles of the most synergistic mixtures were obtained by HPLC-DAD. Three over four IC50ZpE/IC50LnE fixed-ratio mixtures displayed synergistic interactions at effect levels ϕ > 0.5 against C. albicans. The dosis of the most synergistic (Lϕ = 0.62) mixture was 65.96 µg/ml (ZpE = 28%; LnE = 72%) containing 8 and 36% of flavonoids and lignans respectively. On the other hand, one over four IC50ZpE/IC50LnE mixtures displays synergistic interactions at ϕ > 0.5 against C. glabrata. The dosis of the most synergistic (Lϕ = 0.67) mixture was 168

  2. Permafrost response to increasing Arctic shrub abundance depends on the relative influence of shrubs on local soil cooling versus large-scale climate warming

    International Nuclear Information System (INIS)

    Lawrence, David M; Swenson, Sean C

    2011-01-01

    Deciduous shrub abundance is increasing across the Arctic in response to climatic warming. In a recent field manipulation experiment in which shrubs were removed from a plot and compared to a control plot with shrubs, Blok et al (2010 Glob. Change Biol. 16 1296–305) found that shrubs protect the ground through shading, resulting in a ∼ 9% shallower active layer thickness (ALT) under shrubs compared to grassy-tundra, which led them to argue that continued Arctic shrub expansion could mitigate future permafrost thaw. We utilize the Community Land Model (CLM4) coupled to the Community Atmosphere Model (CAM4) to evaluate this hypothesis. CLM4 simulates shallower ALT (∼− 11 cm) under shrubs, consistent with the field manipulation study. However, in an idealized pan-Arctic + 20% shrub area experiment, atmospheric heating, driven mainly by surface albedo changes related to protrusion of shrub stems above the spring snowpack, leads to soil warming and deeper ALT (∼+ 10 cm). Therefore, if climate feedbacks are considered, shrub expansion may actually increase rather than decrease permafrost vulnerability. When we account for blowing-snow redistribution from grassy-tundra to shrubs, shifts in snowpack distribution in low versus high shrub area simulations counter the climate warming impact, resulting in a grid cell mean ALT that is unchanged. These results reinforce the need to consider vegetation dynamics and blowing-snow processes in the permafrost thaw model projections.

  3. Water storage capacity, stemflow and water funneling in Mediterranean shrubs

    Science.gov (United States)

    Garcia-Estringana, P.; Alonso-Blázquez, N.; Alegre, J.

    2010-08-01

    SummaryTo predict water losses and other hydrological and ecological features of a given vegetation, its water storage capacity and stemflow need to be accurately determined. Vast areas of the Mediterranean region are occupied by shrublands yet there is scarce data available on their rainwater interception capacity. In this study, simulated rainfall tests were conducted in controlled conditions on nine Mediterranean shrubs of varying anatomic and morphological features to determine water storage capacity, stemflow and the funneling ratio. After assessing correlations between these hydrological variables and the biometric characteristics of the shrubs, we compared two methods of determining storage capacity: rainfall simulation and immersion. Mean water storage capacity was 1.02 mm (0.35-3.24 mm), stemflow was 16% (3.8-26.4%) and the funneling ratio was 104 (30-260). Per unit biomass, mean storage capacity was 0.66 ml g -1 and ranged from 0.23 ml g -1 for Cistus ladanifer to 2.26 ml g -1 for Lavandula latifolia. Despite their small size, shrubs may generate high water losses to the atmosphere when they form dense communities and this can have a significant impact in regions where water is scarce. When considered the whole shrubs in absolute terms (ml per plant), water storage capacity and stemflow were correlated to biomass and the dendrometric characteristics of the shrubs, yet in relative terms (expressed per surface area unit or as %), anatomic features such as pubescence, branch rigidity or leaf insertion angle emerged as determining factors. The use of a simple procedure to assess storage capacity was inefficient. The immersion method underestimated storage capacity to a different extent for each species. Some shrubs returned high stemflow values typical of their adaptation to the semiarid climate. In contrast, other shrubs seem to have structures that promote stemflow yet have developed other drought-adaptation mechanisms. In this report, we discuss the

  4. Facilitating the afforestation of Mediterranean polluted soils by nurse shrubs.

    Science.gov (United States)

    Domínguez, María T; Pérez-Ramos, Ignacio M; Murillo, José M; Marañón, Teodoro

    2015-09-15

    The revegetation of polluted sites and abandoned agricultural soils is critical to reduce soil losses and to control the spread of soil pollution in the Mediterranean region, which is currently exposed to the greatest soil erosion risk in Europe. However, events of massive plant mortality usually occur during the first years after planting, mainly due to the adverse conditions of high irradiance and drought stress. Here, we evaluated the usefulness of considering the positive plant-plant interactions (facilitation effect) in the afforestation of polluted agricultural sites, using pre-existing shrubs as nurse plants. We used nurse shrubs as planting microsites for acorns of Quercus ilex (Holm oak) along a gradient of soil pollution in southwestern Spain, and monitored seedling growth, survival, and chemical composition during three consecutive years. Seedling survival greatly increased (from 20% to more than 50%) when acorns were sown under shrub, in comparison to the open, unprotected matrix. Facilitation of seedling growth by shrubs increased along the gradient of soil pollution, in agreement with the stress gradient hypothesis that predicts higher intensity of the facilitation effects with increasing abiotic stress. Although the accumulation of trace elements in seedling leaves was higher underneath shrub, the shading conditions provided by the shrub canopy allowed seedlings to cope with the toxicity provoked by the concurrence of low pH and high trace element concentrations in the most polluted sites. Our results show that the use of shrubs as nurse plants is a promising tool for the cost-effective afforestation of polluted lands under Mediterranean conditions. Copyright © 2015 Elsevier Ltd. All rights reserved.

  5. Effects of Mediterranean shrub species on rainfall interception

    International Nuclear Information System (INIS)

    Garcia-Estringana, P.; Alonso-Blazquez, N.; Marques, M. J.; Bienes, R.; Alegre, J.

    2009-01-01

    Rainfall is intercepted by vegetation. Water intercepted could be evaporated, or it could drip from the leaves and stems to the soil or it could run down the stems to the base of the plant. In the Mediterranean, where water is a scant resource, interception loss could have an influence on hydrology. Water storage capacity depends on vegetation type. In the Mediterranean, there are many types of shrubs, and many of them are able to intercept large volumes of water depending on the shrub type. many lands of the Mediterranean basin of Europea Union have been abandoned in the last decades and consequently vegetation type changes too. This modifies hydrologic processes, changing the volume and the way in which the rainfall reaches the soil. The aim of this study was to characterize water storage capacity in 9 Mediterranean shrub species, working with the whole plant and comparing results obtained by two methods, rainfall simulation and submersion method in laboratory conditions. (Author) 12 refs.

  6. Can shrubs help to reconstruct historical glacier retreats?

    International Nuclear Information System (INIS)

    Buras, Allan; Hallinger, Martin; Wilmking, Martin

    2012-01-01

    In the 21st century, most of the world’s glaciers are expected to retreat due to further global warming. The range of this predicted retreat varies widely as a result of uncertainties in climate and glacier models. To calibrate and validate glacier models, past records of glacier mass balance are necessary, which often only span several decades. Long-term reconstructions of glacier mass balance could increase the precision of glacier models by providing the required calibration data. Here we show the possibility of applying shrub growth increments as an on-site proxy for glacier summer mass balance, exemplified by Salix shrubs in Finse, Norway. We further discuss the challenges which this method needs to meet and address the high potential of shrub growth increments for reconstructing glacier summer mass balance in remote areas. (letter)

  7. Environmental Limits of Tall Shrubs in Alaska's Arctic National Parks.

    Science.gov (United States)

    Swanson, David K

    2015-01-01

    We sampled shrub canopy volume (height times area) and environmental factors (soil wetness, soil depth of thaw, soil pH, mean July air temperature, and typical date of spring snow loss) on 471 plots across five National Park Service units in northern Alaska. Our goal was to determine the environments where tall shrubs thrive and use this information to predict the location of future shrub expansion. The study area covers over 80,000 km2 and has mostly tundra vegetation. Large canopy volumes were uncommon, with volumes over 0.5 m3/m2 present on just 8% of plots. Shrub canopy volumes were highest where mean July temperatures were above 10.5°C and on weakly acid to neutral soils (pH of 6 to 7) with deep summer thaw (>80 cm) and good drainage. On many sites, flooding helped maintain favorable soil conditions for shrub growth. Canopy volumes were highest where the typical snow loss date was near 20 May; these represent sites that are neither strongly wind-scoured in the winter nor late to melt from deep snowdrifts. Individual species varied widely in the canopy volumes they attained and their response to the environmental factors. Betula sp. shrubs were the most common and quite tolerant of soil acidity, cold July temperatures, and shallow thaw depths, but they did not form high-volume canopies under these conditions. Alnus viridis formed the largest canopies and was tolerant of soil acidity down to about pH 5, but required more summer warmth (over 12°C) than the other species. The Salix species varied widely from S. pulchra, tolerant of wet and moderately acid soils, to S. alaxensis, requiring well-drained soils with near neutral pH. Nearly half of the land area in ARCN has mean July temperatures of 10.5 to 12.5°C, where 2°C of warming would bring temperatures into the range needed for all of the potential tall shrub species to form large canopies. However, limitations in the other environmental factors would probably prevent the formation of large shrub canopies

  8. Environmental Limits of Tall Shrubs in Alaska's Arctic National Parks.

    Directory of Open Access Journals (Sweden)

    David K Swanson

    Full Text Available We sampled shrub canopy volume (height times area and environmental factors (soil wetness, soil depth of thaw, soil pH, mean July air temperature, and typical date of spring snow loss on 471 plots across five National Park Service units in northern Alaska. Our goal was to determine the environments where tall shrubs thrive and use this information to predict the location of future shrub expansion. The study area covers over 80,000 km2 and has mostly tundra vegetation. Large canopy volumes were uncommon, with volumes over 0.5 m3/m2 present on just 8% of plots. Shrub canopy volumes were highest where mean July temperatures were above 10.5°C and on weakly acid to neutral soils (pH of 6 to 7 with deep summer thaw (>80 cm and good drainage. On many sites, flooding helped maintain favorable soil conditions for shrub growth. Canopy volumes were highest where the typical snow loss date was near 20 May; these represent sites that are neither strongly wind-scoured in the winter nor late to melt from deep snowdrifts. Individual species varied widely in the canopy volumes they attained and their response to the environmental factors. Betula sp. shrubs were the most common and quite tolerant of soil acidity, cold July temperatures, and shallow thaw depths, but they did not form high-volume canopies under these conditions. Alnus viridis formed the largest canopies and was tolerant of soil acidity down to about pH 5, but required more summer warmth (over 12°C than the other species. The Salix species varied widely from S. pulchra, tolerant of wet and moderately acid soils, to S. alaxensis, requiring well-drained soils with near neutral pH. Nearly half of the land area in ARCN has mean July temperatures of 10.5 to 12.5°C, where 2°C of warming would bring temperatures into the range needed for all of the potential tall shrub species to form large canopies. However, limitations in the other environmental factors would probably prevent the formation of large

  9. Uptake of Radium by Grass and Shrubs Grown on Mineral Heaps: A Preliminary Study

    International Nuclear Information System (INIS)

    Laili, Z.; Omar, M.; Yusof, M.A. Wahab; Ibrahim, M.Z.

    2015-01-01

    A preliminary study of the uptake of 226 Ra and 228 Ra by grass and shrubs grown on mineral heaps was carried out. Activity concentrations of 226 Ra and 228 Ra in grass and shrubs were measured using gamma spectrometry. The result showed that grass and shrubs grown on mineral heaps contained elevated levels of radium compared to grass and shrubs grown on normal soils. Thus, these plants might be used for phytoremediation of radium contaminated soil. (author)

  10. GROWTH-RATES OF SHRUBS ON DIFFERENT SOILS IN TANZANIA

    NARCIS (Netherlands)

    PRINS, HHT; VANDERJEUGD, HP

    1992-01-01

    Because little is known of growth rates of shrubs in East Africa, the growth rates of Acalypha fructicosa, Gardenia jovis-tonantis, Justicia cordata, Maerua triphylla, and Ocimum suave were measured in Lake Manyara National Park, northern Tanzania. Branch diameter increments and branch length

  11. Growth rates of shrubs on different soils in Tanzania.

    NARCIS (Netherlands)

    Prins, H.H.T.; Jeugd, van der H.P.

    1992-01-01

    Because little is known of growth rates of shrubs in East Africa, the growth rates of Acalypha fructicosa, Gardenia jovis-tonantis, Justicia cordata, Maerua triphylla, and Ocimum suave were measured in Lake Manyara National Park, northern Tanzania. Branch diameter increments and branch length

  12. Micropropagation of the endangered shrub pondberry (Lindera melissifolia [Walt.] Blume)

    Science.gov (United States)

    Tracy S. Hawkins; Nathan M. Schiff; Emile s. Gardiner; Theodore Leininger; Margaret S. Devall; A. Dan Wilson; Paul Hamel; Deborah D. McCown; Kristina Connor

    2007-01-01

    A micropropagation protocol using shoot cultures is described for Lindera melissifolia, a federally listed endangered shrub endemic to the southeastern United States. Stock plants were harvested from native L. melissifolia populations growing in the lower Mississippi Alluvial Valley. In vitro proliferation was on woody plant medium...

  13. Experimental and numerical modeling of shrub crown fire initiation

    Science.gov (United States)

    Watcharapong Tachajapong; Jesse Lozano; Shakar Mahalingam; Xiangyang Zhou; David Weise

    2009-01-01

    The transition of fire from dry surface fuels to wet shrub crown fuels was studied using laboratory experiments and a simple physical model to gain a better understanding of the transition process. In the experiments, we investigated the effects of varying vertical distances between surface and crown fuels (crown base height), and of the wind speed on crown fire...

  14. Drought damage to bushveld trees and large shrubs | JJP | African ...

    African Journals Online (AJOL)

    An intensive survey was carried out in Sweet Bushveld (savanna) to study drought damage to the trees and large shrubs in a Combretum apiculatum community. In general, the severity of damage was less than was expected and its pattern differed markedly between the 21 different species encountered. Keywords: ...

  15. Seeds of Puerto Rican Trees and Shrubs: Second Installment

    Science.gov (United States)

    John K. Francis; Alberto Rodríguez

    1993-01-01

    Seed weights and germination information were obtained for 119 native Puerto Rican and naturalized exotic trees and shrubs. Fruit was collected from 34 of these species, and the weights were recorded. The data are presented in tables that list the species alphabetically by scientific names.

  16. Use and availability of tree and shrub resources on Maasai ...

    African Journals Online (AJOL)

    Twenty-four tree and shrub species were utilised for four main purposes: medicinal, fencing, firewood and shelter. These uses were mainly confined to four key species: Acacia mellifera, Acacia xanthophloea , Acacia tortilisand Balanites glabra. Ethno-medicine was the most common use and required smaller quantities of ...

  17. Recent emissions research in southwestern shrub and grassland fuels

    Science.gov (United States)

    David R. Weise; Wayne Miller; David R. Cocker; Heejung Jung; Seyedehsan Hosseini; Marko Princevac; Robert J. Yokelson; Ian Burling; Sheryl Akagi; Shawn Urbanski; WeiMin Hao

    2015-01-01

    While it is currently challenging to use prescribed burning in chaparral and other southwestern shrub fuel types due to many constraints, any such activities require smoke management planning. Information on fuels and emissions from chaparral were limited and based on older sampling systems. The DoD SERDP program funded a project to measure fuels and smoke emissions in...

  18. The Invasive Shrub, Buddleja davidii (Butterfl y Bush)

    Science.gov (United States)

    Buddleja davidii Franchet (Synonym. Buddleia davidii; common name Butterfly bush) is a perennial, semi-deciduous shrub or small multi-stemmed tree that is resident in gardens and disturbed areas in temperate locations worldwide. Since its introduction to the United Kingdom from c...

  19. Siliceous Shrubs in Yellowstone's Hot Springs: Implications for Exobiological Investigations

    Science.gov (United States)

    Guidry, S. A.; Chafetz, H. S.

    2003-01-01

    Potential relict hot springs have been identified on Mars and, using the Earth as an analog, Martian hot springs are postulated to be an optimal locality for recognizing preserved evidence of extraterrestrial life. Distinctive organic and inorganic biomarkers are necessary to recognize preserved evidence of life in terrestrial and extraterrestrial hot spring accumulations. Hot springs in Yellowstone National Park, Wyoming, U.S.A., contain a wealth of information about primitive microbial life and associated biosignatures that may be useful for future exobiological investigations. Numerous siliceous hot springs in Yellowstone contain abundant, centimeter-scale, spinose precipitates of opaline silica (opal-A). Although areally extensive in siliceous hot spring discharge channel facies, these spinose forms have largely escaped attention. These precipitates referred to as shrubs, consist of porous aggregates of spinose opaline silica that superficially resemble miniature woody plants, i.e., the term shrubs. Shrubs in carbonate precipitating systems have received considerable attention, and represent naturally occurring biotically induced precipitates. As such, shrubs have great potential as hot spring environmental indicators and, more importantly, proxies for pre-existing microbial life.

  20. Plant Identification Characteristics for Deciduous Trees & Shrubs. Lesson Plans.

    Science.gov (United States)

    Burkholder, Kathy

    This manual contains a group of lesson plans designed for use with a slide series (not included here). Its purpose is to introduce students to the basic concepts and terminology used in the identification of deciduous trees and shrubs. The manual is composed of 12 lesson plans. The first lesson is an introduction to plant identification. The…

  1. Environmental indices for common Michigan trees and shrubs.

    Science.gov (United States)

    Gary J. Brand

    1985-01-01

    Plants are indicators of environmental factors like moisture, nutrients, heat, and light. Semi-quantitative indices for these four factors were developed for 90 Michigan trees and shrubs. The indices and a tally of species present provide a simple evaluation of the environment of a forest stand and a useful management aid.

  2. Ecology and utilization of desert shrub rangelands in Iraq

    NARCIS (Netherlands)

    Thalen, Derk Catharinus Peter

    1979-01-01

    When grazing is the accepted land use, vegetation is the key resource. The present study deals with the desert shrub rangelands of lraq, which contain the major characteristics of such an area, having been under grazing for many centuries. Emphasis is given to the ecology and utilization of the

  3. tree and shrub species integration in the crop-livestock farming ...

    African Journals Online (AJOL)

    Prof. Adipala Ekwamu

    cash for investment in the required activities, easy land certification and market opportunity for tree and shrub products. The tree and shrub .... for its consistency, logical flow, coding and length were amended. .... TABLE 2. List of shrub species identified in the watershed of highlands of central Ethiopia. Scientific name.

  4. Assessing effect of rainfall on rate of alien shrub expansion in a southern African savanna

    NARCIS (Netherlands)

    Masocha, Mhosisi; Dube, Timothy; Skidmore, A.K.; Holmgren, Milena; Prins, Herbert

    2017-01-01

    Understanding the environmental factors governing the spread of alien shrubs is crucial for conserving biodiversity. In the semi-arid savannas of Africa, alien shrub invasion often occurs simultaneously with native shrub encroachment but climate-dependent differences in encroachments of native and

  5. Shrubs as ecosystem engineers across an environmental gradient: effects on species richness and exotic plant invasion.

    Science.gov (United States)

    Kleinhesselink, Andrew R; Magnoli, Susan M; Cushman, J Hall

    2014-08-01

    Ecosystem-engineering plants modify the physical environment and can increase species diversity and exotic species invasion. At the individual level, the effects of ecosystem engineers on other plants often become more positive in stressful environments. In this study, we investigated whether the community-level effects of ecosystem engineers also become stronger in more stressful environments. Using comparative and experimental approaches, we assessed the ability of a native shrub (Ericameria ericoides) to act as an ecosystem engineer across a stress gradient in a coastal dune in northern California, USA. We found increased coarse organic matter and lower wind speeds within shrub patches. Growth of a dominant invasive grass (Bromus diandrus) was facilitated both by aboveground shrub biomass and by growing in soil taken from shrub patches. Experimental removal of shrubs negatively affected species most associated with shrubs and positively affected species most often found outside of shrubs. Counter to the stress-gradient hypothesis, the effects of shrubs on the physical environment and individual plant growth did not increase across the established stress gradient at this site. At the community level, shrub patches increased beta diversity, and contained greater rarified richness and exotic plant cover than shrub-free patches. Shrub effects on rarified richness increased with environmental stress, but effects on exotic cover and beta diversity did not. Our study provides evidence for the community-level effects of shrubs as ecosystem engineers in this system, but shows that these effects do not necessarily become stronger in more stressful environments.

  6. Spatial patterns of grasses and shrubs in an arid grassland environment

    Science.gov (United States)

    In the Chihuahuan Desert of Mexico and New Mexico, shrub invasion is a common problem, and once-abundant grassland ecosystems are being replaced by shrub-dominated habitat. The spatial arrangement of grasses and shrubs in these arid grasslands can provide better insight into community dynamics and c...

  7. The effect of polyethylene glycol on intake of Mediterranean shrubs by sheep and goats.

    Science.gov (United States)

    Rogosic, J; Pfister, J A; Provenza, F D; Pavlicevic, J

    2008-12-01

    Poor nutritional quality and increased content of secondary compounds can reduce consumption of Mediterranean shrubs by herbivores. In 2 sequential trials, we examined the effect of polyethylene glycol (PEG) and number of shrub species offered on daily intake of Mediterranean shrubs by 12 sheep and 12 goats. The PEG (25 g) was fed to experimental animals with barley. In trial 1 (6 shrubs), goats ate more (P = 0.0008) daily total shrub biomass than did sheep (60.7 vs. 45.9 +/- 2.6 g/kg of BW). There was a trend (P = 0.08) toward a positive PEG effect on total shrub intake, with PEG-supplemented animals consuming more total shrubs than controls (56.7 vs. 50.0 +/- 2.6 g/kg of BW). Trial 2 (using 3 shrubs) was a continuation of trial 1, except that animals were given less barley and treatment animals were given more PEG (50 g). Both sheep and goats showed a numerical decrease in total shrub intake from trial 1 to trial 2. Sheep receiving PEG ate more (P = 0.002) total shrubs than did controls, but no PEG effect was found for goats. Thus, PEG had a greater influence on sheep than goats when only 3 shrubs were offered, a result that may be related to the fact that fewer shrubs with complementary secondary compounds were offered and that goats appear to have a greater ability to consume and detoxify secondary compounds from Mediterranean shrubs. Overall, as the number and diversity of shrubs offered increased, supplemental PEG had less effect on increasing intake for both goats and sheep.

  8. Role of species diversity and secondary compound complementarity on diet selection of Mediterranean shrubs by goats.

    Science.gov (United States)

    Rogosic, Jozo; Estell, Richard E; Skobic, Dragan; Martinovic, Anita; Maric, Stanislava

    2006-06-01

    Goats foraging on Mediterranean shrubs containing secondary compounds (toxins) may consume a variety of shrubs that contain different phytotoxins, thereby increasing shrub intake and avoiding toxicosis. We conducted eight experiments to examine whether goats offered different mixtures of shrubs containing different phytotoxins (tannins and saponins) would consume more shrub biomass than goats offered one shrub a single phytotoxin (tannin or saponin). In the first three experiments, goats fed a mixture of three tannin-rich shrubs (Quercus ilex, Arbutus unedo, and Pistacia lentiscus) ate more foliage than goats offered only one shrub (23.2 vs. 10.7 g/kg BW; 25.2 vs. 13.4 g/kg BW, and 27.9 vs. 7.9 g/kg BW), regardless of tannin concentration in individual shrub species. Goats also consumed more foliage when offered the same three tannin-rich shrubs than when offered the saponin-rich shrub Hedera helix (25.4 vs. 8.0 g/kg BW). However, goats offered a mixture of the same three tannin-rich shrubs consumed less foliage than goats offered a mixture of two shrubs containing tannins and saponins: Quercus and Hedera (21.6 vs. 27.1 g/kg BW), Arbutus and Hedera (21.8 vs. 27.1 g/kg BW), and Pistacia and Hedera (19.7 vs. 22.0 g/kg BW). Comparison of intake of shrubs containing only tannins or saponins to intake of shrubs containing both tannins and saponins indicated that goats consumed more total biomass when fed with shrubs with both classes of compounds than with either tannins or saponins alone. Our results suggest that goats can increase intake of Mediterranean shrubs high in secondary compounds by selecting those with different classes of phytotoxins. Simultaneous ingestion of shrubs containing tannins and saponins may promote chemical interactions that inhibit toxic effects of these phytotoxins in the intestinal tract. In addition to complementary interactions between tannins and saponins, biological diversity within Mediterranean maquis vegetation also plays a positive

  9. Generating new varieties of shrubs for landscapes in Malaysia

    International Nuclear Information System (INIS)

    Zaiton Ahmad; Affrida Abu Hassan; Shuhaimi Shamsudin; Norimah Yusof; Shakinah Salleh

    2012-01-01

    This project which was funded by National Landscape Department was aimed at generating new varieties of shrubs suitable for landscapes in Malaysia. Three species of shrubs commonly used in Malaysian landscapes (hibiscus, canna and turnera) were selected for generating new varieties through mutagenesis techniques using gamma rays and ion beams. The main objective was to produce new varieties with desired characters, such as longer bloom period, unique and prominent petal colors and larger flower size. Through this project, several potential mutants have been identified such as turnera with longer bloom period, canna with new flower colors and hibiscus with different flower form. These mutants are currently undergoing field screening at Serdang to analyze their genetic stability, and will be registered as new varieties with Department of Agriculture before being transferred to end-users. (author)

  10. Shrub Abundance Mapping in Arctic Tundra with Misr

    Science.gov (United States)

    Duchesne, R.; Chopping, M. J.; Wang, Z.; Schaaf, C.; Tape, K. D.

    2013-12-01

    Over the last 60 years an increase in shrub abundance has been observed in the Arctic tundra in connection with a rapid surface warming trend. Rapid shrub expansion may have consequences in terms of ecosystem structure and function, albedo, and feedbacks to climate; however, its rate is not yet known. The goal of this research effort is thus to map large scale changes in Arctic tundra vegetation by exploiting the structural signal in moderate resolution satellite remote sensing images from NASA's Multiangle Imaging SpectroRadiometer (MISR), mapped onto a 250m Albers Conic Equal Area grid. We present here large area shrub mapping supported by reference data collated using extensive field inventory data and high resolution panchromatic imagery. MISR Level 1B2 Terrain radiance scenes from the Terra satellite from 15 June-31 July, 2000 - 2010 were converted to surface bidirectional reflectance factors (BRF) using MISR Toolkit routines and the MISR 1 km LAND product BRFs. The red band data in all available cameras were used to invert the RossThick-LiSparse-Reciprocal BRDF model to retrieve kernel weights, model-fitting RMSE, and Weights of Determination. The reference database was constructed using aerial survey, three field campaigns (field inventory for shrub count, cover, mean radius and height), and high resolution imagery. Tall shrub number, mean crown radius, cover, and mean height estimates were obtained from QuickBird and GeoEye panchromatic image chips using the CANAPI algorithm, and calibrated using field-based estimates, thus extending the database to over eight hundred locations. Tall shrub fractional cover maps for the North Slope of Alaska were constructed using the bootstrap forest machine learning algorithm that exploits the surface information provided by MISR. The reference database was divided into two datasets for training and validation. The model derived used a set of 19 independent variables(the three kernel weights, ratios and interaction terms

  11. Técnicas De Comprensión Lectora En El Área De Lengua Y Literatura, Y Su Influencia En Los Procesos De Aprendizaje De Los Estudiantes De Educación Básica Elemental En La Escuela Dr. Oswaldo Hurtado Larrea Del Cantón Milagro

    OpenAIRE

    Astudillo Erazo, Patricia

    2015-01-01

    This research is a didactic-pedagogical compendium prepared to implement in the learning process of students SCHOOL DR. OSWALDO HURTADO LARREA CANTON MIRACLE, confident that the implementation of these strategies will develop significant learning basic skills specified in the Upgrading and Strengthening Curriculum of General Basic Education, and thinking that it is inscribed within the broader criterion of recreational endeavor Good Live. The methodological strategies are teaching guidel...

  12. Increased spring freezing vulnerability for alpine shrubs under early snowmelt.

    Science.gov (United States)

    Wheeler, J A; Hoch, G; Cortés, A J; Sedlacek, J; Wipf, S; Rixen, C

    2014-05-01

    Alpine dwarf shrub communities are phenologically linked with snowmelt timing, so early spring exposure may increase risk of freezing damage during early development, and consequently reduce seasonal growth. We examined whether environmental factors (duration of snow cover, elevation) influenced size and the vulnerability of shrubs to spring freezing along elevational gradients and snow microhabitats by modelling the past frequency of spring freezing events. We sampled biomass and measured the size of Salix herbacea, Vaccinium myrtillus, Vaccinium uliginosum and Loiseleuria procumbens in late spring. Leaves were exposed to freezing temperatures to determine the temperature at which 50% of specimens are killed for each species and sampling site. By linking site snowmelt and temperatures to long-term climate measurements, we extrapolated the frequency of spring freezing events at each elevation, snow microhabitat and per species over 37 years. Snowmelt timing was significantly driven by microhabitat effects, but was independent of elevation. Shrub growth was neither enhanced nor reduced by earlier snowmelt, but decreased with elevation. Freezing resistance was strongly species dependent, and did not differ along the elevation or snowmelt gradient. Microclimate extrapolation suggested that potentially lethal freezing events (in May and June) occurred for three of the four species examined. Freezing events never occurred on late snow beds, and increased in frequency with earlier snowmelt and higher elevation. Extrapolated freezing events showed a slight, non-significant increase over the 37-year record. We suggest that earlier snowmelt does not enhance growth in four dominant alpine shrubs, but increases the risk of lethal spring freezing exposure for less freezing-resistant species.

  13. Fire tolerance of a resprouting Artemisia (Asteraceae) shrub

    Science.gov (United States)

    Winter, S.L.; Fuhlendorf, S.D.; Goad, C.L.; Davis, C.A.; Hickman, K.R.; Leslie, David M.

    2011-01-01

    In North America, most Artemisia (Asteraceae) shrub species lack the ability to resprout after disturbances that remove aboveground biomass. We studied the response of one of the few resprouting Artemisia shrubs, Artemisia filifolia (sand sagebrush), to the effects of prescribed fires. We collected data on A. filifolia density and structural characteristics (height, canopy area, and canopy volume) in an A. filifolia shrubland in the southern Great Plains of North America. Our study sites included areas that had not been treated with prescribed fire, areas that had been treated with only one prescribed fire within the previous 5 years, and areas that had been treated with two prescribed fires within the previous 10 years. Our data were collected at time periods ranging from 1/2 to 5 years after the prescribed fires. Density of A. filifolia was not affected by one or two fires. Structural characteristics, although initially altered by prescribed fire, recovered to levels characteristic of unburned areas in 3-4 years after those fires. In contrast to most non-sprouting North American Artemisia shrub species, our research suggested that the resprouting A. filifolia is highly tolerant to the effects of fire. ?? 2011 Springer Science+Business Media B.V.

  14. Soil microbial diversity in the vicinity of desert shrubs.

    Science.gov (United States)

    Saul-Tcherkas, Vered; Unc, Adrian; Steinberger, Yosef

    2013-04-01

    Water and nutrient availability are the major limiting factors of biological activity in arid and semiarid ecosystems. Therefore, perennial plants have developed different ecophysiological adaptations to cope with harsh conditions. The chemical profile of the root exudates varies among plant species and this can induce variability in associated microbial populations. We examined the influence of two shrubs species, Artemisia sieberi and Noaea mucronata, on soil microbial diversity. Soil samples were collected monthly, from December 2006 to November 2007, near canopies of both shrubs (0-10-cm depth). Samples were used for abiotic tests and determination of soil bacterial diversity. No significant differences were found in the abiotic variables (soil moisture, total organic matter, and total soluble nitrogen (TSN)) between soil samples collected from under the two shrubs during the study period. No obvious differences in the Shannon-Weaver index, evenness values, or total phylogenetic distances were found for the soil microbial communities. However, detailed denaturing gradient gel electrophoresis (DGGE) clustering as well as taxonomic diversity analyses indicated clear shifts in the soil microbial community composition. These shifts were governed by seasonal variability in water availability and, significantly, by plant species type.

  15. The Influence of an Invasive Shrub, Buddleja Davidii on a Native Shrub, Griselinia Littoralis Transplanted into a New Zealand Floodplain Chronosequence

    Science.gov (United States)

    Griselinia littoralis, a native New Zealand shrub, was planted into a chronosequence (0 to 8 yrs since flooding) dominated by the non-indigenous shrub, Buddleja davidii in three New Zealand floodplains to determine to what extent facilitation and competitive inhibition may influe...

  16. Independent Effects of Invasive Shrubs and Deer Herbivory on Plant Community Dynamics

    Directory of Open Access Journals (Sweden)

    Jeffrey S. Ward

    2016-12-01

    Full Text Available Both invasive species and deer herbivory are recognized as locally important drivers of plant community dynamics. However, few studies have examined whether their effects are synergistic, additive, or antagonistic. At three study areas in southern New England, we examined the interaction of white-tailed deer (Odocoileus virginianus Zimmermann herbivory and three levels of invasive shrub control over seven growing seasons on the dynamics of nine herbaceous and shrub guilds. Although evidence of synergistic interactions was minimal, the separate effects of invasive shrub control and deer herbivory on plant community composition and dynamics were profound. Plant communities remained relatively unchanged where invasive shrubs were not treated, regardless if deer herbivory was excluded or not. With increasing intensity of invasive shrub control, native shrubs and forbs became more dominant where deer herbivory was excluded, and native graminoids became progressively more dominant where deer herbivory remained severe. While deer exclusion and intensive invasive shrub control increased native shrubs and forbs, it also increased invasive vines. Restoring native plant communities in areas with both established invasive shrub thickets and severe deer browsing will require an integrated management plan to eliminate recalcitrant invasive shrubs, reduce deer browsing intensity, and quickly treat other opportunistic invasive species.

  17. Spatio-temporal patterns of ptarmigan occupancy relative to shrub cover in the Arctic

    Science.gov (United States)

    Schmutz, Joel A.

    2014-01-01

    Rock and willow ptarmigan are abundant herbivores that require shrub habitats in arctic and alpine areas. Shrub expansion is likely to increase winter habitat availability for ptarmigan, which in turn influence shrub architecture and growth through browsing. Despite their ecological role in the Arctic, the distribution and movement patterns of ptarmigan are not well known, particularly in northern Alaska where shrub expansion is occurring. We used multi-season occupancy models to test whether ptarmigan occupancy varied within and among years, and the degree to which colonization and extinction probabilities were related to shrub cover and latitude. Aerial surveys were conducted from March to May in 2011 and April to May 2012 in a 21,230 km2 area in northeastern Alaska. In areas with at least 30 % shrub cover, the probability of colonization by ptarmigan was >0.90, indicating that moderate to extensive patches of shrubs (typically associated with riparian areas) had a high probability of becoming occupied by ptarmigan. Occupancy increased throughout the spring in both years, providing evidence that ptarmigan migrated from southern wintering areas to breeding areas north of the Brooks Range. Occupancy was higher in the moderate snow year than the high snow year, and this was likely due to higher shrub cover in the moderate snow year. Ptarmigan distribution and migration in the Arctic are linked to expanding shrub communities on a wide geographic scale, and these relationships may be shaping ptarmigan population dynamics, as well as rates and patterns of shrub expansion.

  18. SUPPLEMENTAL ACTIVATED CHARCOAL AND ENERGY INCREASE INTAKE OF MEDITERRANEAN SHRUBS BY SHEEP AND GOATS

    Directory of Open Access Journals (Sweden)

    Jozo Rogošić

    2008-07-01

    Full Text Available Utilization of the Mediterranean shrubby vegetation is often limited by secondary compounds, such as terpenes, which at too high concentrations can adversely affect forage intake and animal health. Ingesting compounds such as activated charcoal and energy can ameliorate the negative effects of secondary compounds and enable animals to eat more shrubs. Thus, our objectives were to determine if supplemental charcoal, energy and numbers of shrub species offered influenced intake of shrubs by sheep and goats. We conducted three experiments each with 12 lambs and 12 kids (6 activated charcoal vs. 6 controls. In the first experiment, we initially offered three shrubs (Juniperus phoenicea, Helichrysum italicum and Juniperus oxicedrus, then in the second one, two shrubs (Juniperus phoenicea and Helichrysum italicum, and finally one shrub (Juniperus phoenicea in the third experiment. In all three experiments (Exp. 1, P<0.001; Exp. 2, P < 0.0003 and Exp. 3, P < 0.03, supplemental charcoal and energy had a positive effect on total shrub intake for both lambs and kids. Kids ate more shrubs than lambs did in all three experiments (P<0.01. Regardless of experiment, both species of animals showed a numerical decrease in total shrub intake, with or without supplemental charcoal and energy, as the number of shrub species on offer decreased. Our findings support the hypothesis that biochemical diversity plays an important role in diet selection, thus enabling animals to better meet their nutritional needs and avoid toxicity.

  19. [Quality level assessment of lowly efficient Tamarix chinensis secondary shrubs in Laizhou Bay of Yellow River Delta].

    Science.gov (United States)

    Xia, Jiang-Bao; Liu, Yu-Ting; Zhu, Jin-Fang; Xu, Jing-Wei; Lu, Zhao-Hua; Liu, Jing-Tao; Liu, Qing

    2013-06-01

    Taking the Tamarix chinensis secondary shrubs in Laizhou Bay of Yellow River Delta as test objects, and by using synthetic factor method, this paper studied the main factors causing the lowly efficiency of T. chinensis secondary shrubs as well as the main parameters for the classification of lowly efficient T. chinensis secondary shrubs. A total of 24 indices including shrubs growth and soil physical and chemical properties were selected to determine the main affecting factors and parameters in evaluating and classifying the lowly efficient shrubs. There were no obvious correlations between the indices reflecting the shrubs growth and soil quality, and thus, only using shrub growth index to reflect the lowly efficiency level of T. chinensis was not enough, and it would be necessary to combine with soil quality factors to make a comprehensive evaluation. The principal factors reflecting the quality level of lowly efficient T. chinensis shrubs included soil salt content and moisture content, stand age, single tree's aboveground stem, leaf biomass, and basal diameter, followed by soil density, porosity, and soil nutrient status. The lowly efficient T. chinensis shrubs in the Bay could be classified into five types, namely, shrub with growth potential, slightly low quality shrub, moderately lowly efficient shrub, moderately low quality and lowly efficient shrub, and seriously low quality and lowly efficient shrub. The main features, low efficiency causes, and management measures of these shrubs were discussed based on the mean cluster value.

  20. Co-occurring nonnative woody shrubs have additive and non-additive soil legacies

    DEFF Research Database (Denmark)

    Kuebbing, Sara E.; Patterson, Courtney M.; Classen, Aimee Taylor

    2016-01-01

    shrubs, Lonicera maackii and Ligustrum sinense, in deciduous forests of the southeastern United States. We measured the performance of each nonnative shrub, a native herbaceous community, and a nonnative woody vine in soils conditioned by each shrub singly or together in polyculture. Soils conditioned...... by both nonnative shrubs had non-additive impacts on native and nonnative performance. Root mass of the native herbaceous community was 1.5 times lower and the root mass of the nonnative L. sinense was 1.8 times higher in soils conditioned by both L. maackii and L. sinense than expected based upon growth...... in soils conditioned by either shrub singly. This result indicates that when these two nonnative shrubs co-occur, their influence on soils disproportionally favors persistence of the nonnative L. sinense relative to this native herbaceous community, and could provide an explanation of why native species...

  1. Challenges of establishing big sgebrush (Artemisia tridentata) in rangeland restoration: effects of herbicide, mowing, whole-community seeding, and sagebrush seed sources

    Science.gov (United States)

    Brabec, Martha M.; Germino, Matthew J.; Shinneman, Douglas J.; Pilliod, David S.; McIlroy, Susan K.; Arkle, Robert S.

    2015-01-01

    The loss of big sagebrush (Artemisia tridentata Nutt.) on sites disturbed by fire has motivated restoration seeding and planting efforts. However, the resulting sagebrush establishment is often lower than desired, especially in dry areas. Sagebrush establishment may be increased by addressing factors such as seed source and condition or management of the plant community. We assessed initial establishment of seeded sagebrush and four populations of small outplants (from different geographies, climates, and cytotypes) and small sagebrush outplants in an early seral community where mowing, herbicide, and seeding of other native plants had been experimentally applied. No emergence of seeded sagebrush was detected. Mowing the site before planting seedlings led to greater initial survival probabilities for sagebrush outplants, except where seeding also occurred, and these effects were related to corresponding changes in bare soil exposure. Initial survival probabilities were > 30% greater for the local population of big sagebrush relative to populations imported to the site from typical seed transfer distances of ~320–800 km. Overcoming the high first-year mortality of outplanted or seeded sagebrush is one of the most challenging aspects of postfire restoration and rehabilitation, and further evaluation of the impacts of herb treatments and sagebrush seed sources across different site types and years is needed.

  2. Tundra plant above-ground biomass and shrub dominance mapped across the North Slope of Alaska

    Science.gov (United States)

    Berner, Logan T.; Jantz, Patrick; Tape, Ken D.; Goetz, Scott J.

    2018-03-01

    Arctic tundra is becoming greener and shrubbier due to recent warming. This is impacting climate feedbacks and wildlife, yet the spatial distribution of plant biomass in tundra ecosystems is uncertain. In this study, we mapped plant and shrub above-ground biomass (AGB; kg m-2) and shrub dominance (%; shrub AGB/plant AGB) across the North Slope of Alaska by linking biomass harvests at 28 field sites with 30 m resolution Landsat satellite imagery. We first developed regression models (p plant AGB (r 2 = 0.79) and shrub AGB (r 2 = 0.82) based on the normalized difference vegetation index (NDVI) derived from imagery acquired by Landsat 5 and 7. We then predicted regional plant and shrub AGB by combining these regression models with a regional Landsat NDVI mosaic built from 1721 summer scenes acquired between 2007 and 2016. Our approach employed a Monte Carlo uncertainty analysis that propagated sampling and sensor calibration errors. We estimated that plant AGB averaged 0.74 (0.60, 0.88) kg m-2 (95% CI) and totaled 112 (91, 135) Tg across the region, with shrub AGB accounting for ~43% of regional plant AGB. The new maps capture landscape variation in plant AGB visible in high resolution satellite and aerial imagery, notably shrubby riparian corridors. Modeled shrub AGB was strongly correlated with field measurements of shrub canopy height at 25 sites (rs  = 0.88) and with a regional map of shrub cover (rs  = 0.76). Modeled plant AGB and shrub dominance were higher in shrub tundra than graminoid tundra and increased between areas with the coldest and warmest summer air temperatures, underscoring the fact that future warming has the potential to greatly increase plant AGB and shrub dominance in this region. These new biomass maps provide a unique source of ecological information for a region undergoing rapid environmental change.

  3. Range Expansion of Moose in Arctic Alaska Linked to Warming and Increased Shrub Habitat.

    Directory of Open Access Journals (Sweden)

    Ken D Tape

    Full Text Available Twentieth century warming has increased vegetation productivity and shrub cover across northern tundra and treeline regions, but effects on terrestrial wildlife have not been demonstrated on a comparable scale. During this period, Alaskan moose (Alces alces gigas extended their range from the boreal forest into tundra riparian shrub habitat; similar extensions have been observed in Canada (A. a. andersoni and Eurasia (A. a. alces. Northern moose distribution is thought to be limited by forage availability above the snow in late winter, so the observed increase in shrub habitat could be causing the northward moose establishment, but a previous hypothesis suggested that hunting cessation triggered moose establishment. Here, we use recent changes in shrub cover and empirical relationships between shrub height and growing season temperature to estimate available moose habitat in Arctic Alaska c. 1860. We estimate that riparian shrubs were approximately 1.1 m tall c. 1860, greatly reducing the available forage above the snowpack, compared to 2 m tall in 2009. We believe that increases in riparian shrub habitat after 1860 allowed moose to colonize tundra regions of Alaska hundreds of kilometers north and west of previous distribution limits. The northern shift in the distribution of moose, like that of snowshoe hares, has been in response to the spread of their shrub habitat in the Arctic, but at the same time, herbivores have likely had pronounced impacts on the structure and function of these shrub communities. These northward range shifts are a bellwether for other boreal species and their associated predators.

  4. Hydraulic lift through transpiration suppression in shrubs from two arid ecosystems: patterns and control mechanisms.

    Science.gov (United States)

    Prieto, Iván; Martínez-Tillería, Karina; Martínez-Manchego, Luis; Montecinos, Sonia; Pugnaire, Francisco I; Squeo, Francisco A

    2010-08-01

    Hydraulic lift (HL) is the passive movement of water through the roots from deep wet to dry shallow soil layers when stomata are closed. HL has been shown in different ecosystems and species, and it depends on plant physiology and soil properties. In this study we explored HL patterns in several arid land shrubs, and developed a simple model to simulate the temporal evolution and magnitude of HL during a soil drying cycle under relatively stable climatic conditions. This model was then used to evaluate the influence of soil texture on the quantity of water lifted by shrubs in different soil types. We conducted transpiration suppression experiments during spring 2005 in Chile and spring 2008 in Spain on five shrub species that performed HL, Flourensia thurifera, Senna cumingii and Pleocarphus revolutus (Chile), Retama sphaerocarpa and Artemisia barrelieri (Spain). Shrubs were covered with a black, opaque plastic fabric for a period of 48-72 h, and soil water potential was recorded at different depths under the shrubs. While the shrubs remained covered, water potential continuously increased in shallow soil layers until the cover was removed. The model output indicated that the amount of water lifted by shrubs is heavily dependent on soil texture, as shrubs growing in loamy soils redistributed up to 3.6 times more water than shrubs growing on sandy soils. This could be an important consideration for species growing in soils with different textures, as their ability to perform HL would be context dependent.

  5. Disentangling the effects of shrubs and herbivores on tree regeneration in a dry Chaco forest (Argentina).

    Science.gov (United States)

    Tálamo, Andrés; Barchuk, Alicia H; Garibaldi, Lucas A; Trucco, Carlos E; Cardozo, Silvana; Mohr, Federico

    2015-07-01

    Successful persistence of dry forests depends on tree regeneration, which depends on a balance of complex biotic interactions. In particular, the relative importance and interactive effects of shrubs and herbivores on tree regeneration are unclear. In a manipulative study, we investigated if thornless shrubs have a direct net effect, an indirect positive effect mediated by livestock, and/or an indirect negative effect mediated by small vertebrates on tree regeneration of two key species of Chaco forest (Argentina). In a spatial association study, we also explored the existence of net positive interactions from thorny and thornless shrubs. The number of Schinopsis lorentzii seedlings was highest under artificial shade with native herbivores and livestock excluded. Even excluding livestock, no seedlings were found with natural conditions (native herbivores present with natural shade or direct sunlight) at the end of the experiment. Surprisingly, seedling recruitment was not enhanced under thornless shrubs, because there was a complementary positive effect of shade and interference. Moreover, thornless shrubs had neither positive nor negative effects on regeneration of S. lorentzii. Regeneration of Aspidosperma quebracho-blanco was minimal in all treatments. In agreement with the experiment, spatial distributions of saplings of both tree species were independent of thornless shrubs, but positively associated with thorny shrubs. Our results suggest that in general thornless shrubs may have a negligible effect and thorny shrubs a net positive effect on tree regeneration in dry forests. These findings provide a conceptual framework for testing the impact of biotic interactions on seedling recruitment in other dry forests.

  6. Polymorphic microsatellite markers in the invasive shrub Buddleja davidii (Scrophulariaceae).

    Science.gov (United States)

    Schreiter, Susanne; Ebeling, Susan K; Durka, Walter

    2011-02-01

    Microsatellite primers were developed for the invasive plant Buddleja davidii, a Chinese shrub that is an invader in most other continents. An invasive population was analyzed using eight di- and tetranucleotide microsatellite loci. The number of alleles per locus ranged from 5 to 14. Due to polyploidy, exact genotypes could not be determined. Progeny arrays were used to study the outcrossing rate using presence/absence data of alleles resulting in an estimate of multilocus outcrossing rate of 93%. The markers were successfully tested in five congeneric species. The results indicate the utility of these loci in future studies of population genetics and breeding systems in B. davidii and in congeneric species.

  7. Temperature-induced recruitment pulses of Arctic dwarf shrub communities

    Czech Academy of Sciences Publication Activity Database

    Büntgen, Ulf; Hellmann, L.; Tegel, W.; Normand, S.; Myers-Smith, I.; Kirdyanov, A. V.; Nievergelt, D.; Schweingruber, F. H.

    2015-01-01

    Roč. 103, č. 2 (2015), s. 489-501 ISSN 0022-0477 R&D Projects: GA MŠk(CZ) EE2.3.20.0248 Institutional support: RVO:67179843 Keywords : recent climate-change * tree-line * environmental-change * forest limit * northern siberia * pinus-sylvestris * kola-peninsula * carbon-cycle * picea-abies * polar urals * Arctic tundra * cambial activity * climate change * dendroecology * dwarf shrubs * East Greenland * plant longevity * plant population and community dynamics * vegetation dynamics * wood anatomy Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 6.180, year: 2015

  8. Deciduous shrubs for ozone bioindication: Hibiscus syriacus as an example

    Energy Technology Data Exchange (ETDEWEB)

    Paoletti, Elena [Institut Plant Protection (IPP), National Council Research (CNR), Via Madonna del Piano 10, 50019 Sesto Fiorentino, Florence (Italy)], E-mail: e.paoletti@ipp.cnr.it; Ferrara, Anna Maria [Istituto per le Piante da Legno e l' Ambiente (IPLA), Corso Casale 476, 10132 Turin (Italy); Calatayud, Vicent; Cervero, Julia [Fundacion C.E.A.M., Charles R. Darwin 14, Parc Tecnologic, 46980 Paterna, Valencia (Spain); Giannetti, Fabio [Istituto per le Piante da Legno e l' Ambiente (IPLA), Corso Casale 476, 10132 Turin (Italy); Sanz, Maria Jose [Fundacion C.E.A.M., Charles R. Darwin 14, Parc Tecnologic, 46980 Paterna, Valencia (Spain); Manning, William J. [Department of Plant, Soil and Insect Sciences, University of Massachusetts, Amherst, MA 01003-9320 (United States)

    2009-03-15

    Ozone-like visible injury was detected on Hibiscus syriacus plants used as ornamental hedges. Weekly spray of the antiozonant ethylenediurea (EDU, 300 ppm) confirmed that the injury was induced by ambient ozone. EDU induced a 75% reduction in visible injury. Injury was more severe on the western than on the eastern exposure of the hedge. This factor of variability should be considered in ozone biomonitoring programmes. Seeds were collected and seedlings were artificially exposed to ozone in filtered vs. not-filtered (+30 ppb) Open-Top Chambers. The level of exposure inducing visible injury in the OTC seedlings was lower than that in the ambient-grown hedge. The occurrence of visible injury in the OTC confirmed that the ozone sensitivity was heritable and suggested that symptomatic plants of this deciduous shrub population can be successfully used as ozone bioindicators. EDU is recommended as a simple tool for diagnosing ambient ozone visible injury on field vegetation. - An Italian population of the deciduous shrub Hibiscus syriacus, a common ornamental species in temperate zones, is recommended as ozone bioindicator.

  9. Deciduous shrubs for ozone bioindication: Hibiscus syriacus as an example

    International Nuclear Information System (INIS)

    Paoletti, Elena; Ferrara, Anna Maria; Calatayud, Vicent; Cervero, Julia; Giannetti, Fabio; Sanz, Maria Jose; Manning, William J.

    2009-01-01

    Ozone-like visible injury was detected on Hibiscus syriacus plants used as ornamental hedges. Weekly spray of the antiozonant ethylenediurea (EDU, 300 ppm) confirmed that the injury was induced by ambient ozone. EDU induced a 75% reduction in visible injury. Injury was more severe on the western than on the eastern exposure of the hedge. This factor of variability should be considered in ozone biomonitoring programmes. Seeds were collected and seedlings were artificially exposed to ozone in filtered vs. not-filtered (+30 ppb) Open-Top Chambers. The level of exposure inducing visible injury in the OTC seedlings was lower than that in the ambient-grown hedge. The occurrence of visible injury in the OTC confirmed that the ozone sensitivity was heritable and suggested that symptomatic plants of this deciduous shrub population can be successfully used as ozone bioindicators. EDU is recommended as a simple tool for diagnosing ambient ozone visible injury on field vegetation. - An Italian population of the deciduous shrub Hibiscus syriacus, a common ornamental species in temperate zones, is recommended as ozone bioindicator

  10. Does NDVI reflect variation in the structural attributes associated with increasing shrub dominance in arctic tundra?

    International Nuclear Information System (INIS)

    Boelman, Natalie T; Gough, Laura; McLaren, Jennie R; Greaves, Heather

    2011-01-01

    This study explores relationships between the normalized difference vegetation index (NDVI) and structural characteristics associated with deciduous shrub dominance in arctic tundra. Our structural measures of shrub dominance are stature, branch abundance, aerial per cent woody stem cover (deciduous and evergreen species), and per cent deciduous shrub canopy cover. All measurements were taken across a suite of transects that together represent a gradient of deciduous shrub height. The transects include tussock tundra shrub and riparian shrub tundra communities located in the northern foothills of the Brooks Range, in northern Alaska. Plot-level NDVI measurements were made in 2010 during the snow-free period prior to deciduous shrub leaf-out (early June, NDVI pre-leaf ), at the point in the growing season when canopy NDVI has reached half of its maximum growing season value (mid-June, NDVI demi-leaf ) and during the period of maximum leaf-out (late July, NDVI peak-leaf ). We found that: (1) NDVI pre-leaf is best suited to capturing variation in the per cent woody stem cover, maximum shrub height, and branch abundance, particularly between 10 and 50 cm height in the canopy; (2) NDVI peak-leaf is best suited to capturing variation in deciduous canopy cover; and (3) NDVI demi-leaf does not capture variability in any of our measures of shrub dominance. These findings suggest that in situ NDVI measurements made prior to deciduous canopy leaf-out could be used to identify small differences in maximum shrub height, woody stem cover, and branch abundance (particularly between 10 and 50 cm height in the canopy). Because shrubs are increasing in size and regional extent in several regions of the Arctic, investigation into spectrally based tools for monitoring these changes are worthwhile as they provide a first step towards development of remotely sensed techniques for quantifying associated changes in regional carbon cycling, albedo, radiative energy balance, and wildlife

  11. Tundra shrub effects on growing season energy and carbon dioxide exchange

    Science.gov (United States)

    Lafleur, Peter M.; Humphreys, Elyn R.

    2018-05-01

    Increased shrub cover on the Arctic tundra is expected to impact ecosystem-atmosphere exchanges of carbon and energy resulting in feedbacks to the climate system, yet few direct measurements of shrub tundra-atmosphere exchanges are available to corroborate expectations. Here we present energy and carbon dioxide (CO2) fluxes measured using the eddy covariance technique over six growing seasons at three closely located tundra sites in Canada’s Low Arctic. The sites are dominated by the tundra shrub Betula glandulosa, but percent cover varies from 17%–60% and average shrub height ranges from 18–59 cm among sites. The site with greatest percent cover and height had greater snow accumulation, but contrary to some expectations, it had similar late-winter albedo and snow melt dates compared to the other two sites. Immediately after snowmelt latent heat fluxes increased more slowly at this site compared to the others. Yet by the end of the growing season there was little difference in cumulative latent heat flux among the sites, suggesting evapotranspiration was not increased with greater shrub cover. In contrast, lower albedo and less soil thaw contributed to greater summer sensible heat flux at the site with greatest shrub cover, resulting in greater total atmospheric heating. Net ecosystem exchange of CO2 revealed the potential for enhanced carbon cycling rates under greater shrub cover. Spring CO2 emissions were greatest at the site with greatest percent cover of shrubs, as was summer net uptake of CO2. The seasonal net sink for CO2 was ~2 times larger at the site with the greatest shrub cover compared to the site with the least shrub cover. These results largely agree with expectations that the growing season feedback to the atmosphere arising from shrub expansion in the Arctic has the potential to be negative for CO2 fluxes but positive for turbulent energy fluxes.

  12. Gulf-Wide Information System, Environmental Sensitivity Index Scrub-Shrub and Wetlands, Geographic NAD83, LDWF (2001) [esi_scrub-shrub_wetland_LDWF_2001

    Data.gov (United States)

    Louisiana Geographic Information Center — This data set contains Environmental Sensitivity Index (ESI) scrub-shrub and wetlands data of coastal Louisiana. The ESI is a classification and ranking system,...

  13. The invasive shrub Piper aduncum in Papua New Guinea: a review

    NARCIS (Netherlands)

    Hartemink, A.E.

    2010-01-01

    HARTEMINK AE. 2010. The invasive shrub Piper aduneum in Papua New Guinea: a review. Piper aduncum is a shrub native to Central America. It is found in most Central and South American countries and also in the Caribbean and southern Florida (USA). In Asia and the Pacific, P aduncum occurs in

  14. Shrubs in the cold : interactions between vegetation, permafrost and climate in Siberian tundra

    NARCIS (Netherlands)

    Blok, D.

    2011-01-01

    The Arctic is experiencing strong increases in air temperature during the last decades. High-latitude tundra regions are very responsive to changes in temperature and may cause a shift in tundra vegetation composition towards greater dominance of deciduous shrubs. With increasing deciduous shrub

  15. Shrub encroachment alters sensitivity of soil respiration to temperature and moisture 2115

    Science.gov (United States)

    Shrub encroachment into grasslands creates a mosaic of different soil microsites ranging from open spaces to well-developed shrub canopies, and it is unclear how this affects the spatial variability in soil respiration characteristics, such as the sensitivity to soil temperature and moisture. This i...

  16. Food for early succession birds: relationships among arthropods, shrub vegetation, and soil

    Science.gov (United States)

    Richard N. Conner; Daniel Saenz; D. Brent Burt

    2006-01-01

    During spring and early summer, shrub- and herbaceous-level vegetation provides nesting and foraging habitat for many shrub-habitat birds. We examined relationships among arthropod biomass and abundance, foliage leaf surface area and weight, vegetation ground cover, soil characteristics, relative humidity, and temperature to evaluate what factors may influence...

  17. Degree of susceptibility of industrial gases of tree and shrub species

    Energy Technology Data Exchange (ETDEWEB)

    Dobrovoljskii, I A

    1952-01-01

    The trees and shrubs of the iron smelting region of Krivoi Rog, in the Ukraine, were surveyed to determine susceptibility to air pollution damage. Most of the observations were made in parks and green belts in industrial areas. A classification of tree and shrub species is presented; they are separated into three classes according to their susceptibility to air pollutant injury.

  18. First-order fire effects on herbs and Shrubs: present knowledge and process modeling needs

    Science.gov (United States)

    Kirsten Stephan; Melanie Miller; Matthew B. Dickinson

    2010-01-01

    Herbaceous plants and shrubs have received little attention in terms of fire effects modeling despite their critical role in ecosystem integrity and resilience after wildfires and prescribed burns. In this paper, we summarize current knowledge of direct effects of fire on herb and shrub (including cacti) vegetative tissues and seed banks, propose key components for...

  19. On the influence of shrub height and expansion on northern high latitude climate

    International Nuclear Information System (INIS)

    Bonfils, C J W; Phillips, T J; Cameron-Smith, P; Lawrence, D M; Riley, W J; Subin, Z M

    2012-01-01

    There is a growing body of empirical evidence documenting the expansion of shrub vegetation in the circumpolar Arctic in response to climate change. Here, we conduct a series of idealized experiments with the Community Climate System Model to analyze the potential impact on boreal climate of a large-scale tundra-to-shrub conversion. The model responds to an increase in shrub abundance with substantial atmospheric heating arising from two seasonal land–atmosphere feedbacks: a decrease in surface albedo and an evapotranspiration-induced increase in atmospheric moisture content. We demonstrate that the strength and timing of these feedbacks are sensitive to shrub height and the time at which branches and leaves protrude above the snow. Taller and aerodynamically rougher shrubs lower the albedo earlier in the spring and transpire more efficiently than shorter shrubs. These mechanisms increase, in turn, the strength of the indirect sea-ice albedo and ocean evaporation feedbacks contributing to additional regional warming. Finally, we find that an invasion of tall shrubs tends to systematically warm the soil, deepen the active layer, and destabilize the permafrost (with increased formation of taliks under a future scenario) more substantially than an invasion of short shrubs. (letter)

  20. Mapping snags and understory shrubs for LiDAR based assessment of wildlife habitat suitability

    Science.gov (United States)

    Sebastian Martinuzzi; Lee A. Vierling; William A. Gould; Michael J. Falkowski; Jeffrey S. Evans; Andrew T. Hudak; Kerri T. Vierling

    2009-01-01

    The lack of maps depicting forest three-dimensional structure, particularly as pertaining to snags and understory shrub species distribution, is a major limitation for managing wildlife habitat in forests. Developing new techniques to remotely map snags and understory shrubs is therefore an important need. To address this, we first evaluated the use of LiDAR data for...

  1. HIGH FOLIAR NITROGEN IN DESERT SHRUBS: AN IMPORTANT ECOSYSTEM TRAIT OR DEFECTIVE DESERT DOCTRINE?

    Science.gov (United States)

    Nitrogen concentrations in green and senesced leaves of perennial desert shrubs were compiled from a worldwide literature search to test the validity of the doctrine that desert shrubs produce foliage and leaf litter much richer in nitrogen than that in the foliage of plants from...

  2. Influence of shrubs on soil chemical properties in Alxa desert steppe, China

    Science.gov (United States)

    Hua Fu; Shifang Pei; Yaming Chen; Changgui Wan

    2007-01-01

    Alxa desert steppe is one of severely the degraded rangelands in the Northwest China. Shrubs, as the dominant life form in the desert steppe, play an important role in protecting this region from further desertification. Chemical properties of three soil layers (0 to 10, 10 to 20 and 20 to 30 cm) at three locations (the clump center [A], in the periphery of shrub...

  3. Effects of cattle and rabbit grazing on clonal expansion of spiny shrubs in wood-pastures

    NARCIS (Netherlands)

    Smit, Christian; Bakker, Elisabeth S.; Apol, M. Emile F.; Olff, Han

    2010-01-01

    Spiny shrubs protect non-defended plants against herbivores. Therefore, they play a role for the diversity in grazed ecosystems. While the importance of these keystone nurse shrubs is presently recognized, little is known about the factors controlling them. This knowledge is required to understand

  4. Resilience of arctic mycorrhizal fungal communities after wildfire facilitated by resprouting shrubs

    Science.gov (United States)

    Rebecca E. Hewitt; Elizabeth Bent; Teresa N. Hollingsworth; F. Stuart Chapin; D. Lee Taylor

    2013-01-01

    Climate-induced changes in the tundra fire regime are expected to alter shrub abundance and distribution across the Arctic. However, little is known about how fire may indirectly impact shrub performance by altering mycorrhizal symbionts. We used molecular tools, including ARISA and ITS sequencing, to characterize the mycorrhizal communities on resprouting ...

  5. Atlas of United States Trees, Volume 2: Alaska Trees and Common Shrubs.

    Science.gov (United States)

    Viereck, Leslie A.; Little, Elbert L., Jr.

    This volume is the second in a series of atlases describing the natural distribution or range of native tree species in the United States. The 82 species maps include 32 of trees in Alaska, 6 of shrubs rarely reaching tree size, and 44 more of common shrubs. More than 20 additional maps summarize environmental factors and furnish general…

  6. The Relationship between an Invasive Shrub and Soil Moisture: Seasonal Interactions and Spatially Covarying Relations

    Directory of Open Access Journals (Sweden)

    Yuhong He

    2014-09-01

    Full Text Available Recent studies indicate that positive relationships between invasive plants and soil can contribute to further plant invasions. However, it remains unclear whether these relations remain unchanged throughout the growing season. In this study, spatial sequences of field observations along a transect were used to reveal seasonal interactions and spatially covarying relations between one common invasive shrub (Tartarian Honeysuckle, Lonicera tatarica and soil moisture in a tall grassland habitat. Statistical analysis over the transect shows that the contrast between soil moisture in shrub and herbaceous patches vary with season and precipitation. Overall, a negatively covarying relationship between shrub and soil moisture (i.e., drier surface soils at shrub microsites exists during the very early growing period (e.g., May, while in summer a positively covarying phenomenon (i.e., wetter soils under shrubs is usually evident, but could be weakened or vanish during long precipitation-free periods. If there is sufficient rainfall, surface soil moisture and leaf area index (LAI often spatially covary with significant spatial oscillations at an invariant scale (which is governed by the shrub spatial pattern and is about 8 m, but their phase relation in space varies with season, consistent with the seasonal variability of the co-varying phenomena between shrub invasion and soil water content. The findings are important for establishing a more complete picture of how shrub invasion affects soil moisture.

  7. Phenotypic sex ratios of Atriplex canescens shrubs in relation to cattle browsing

    Science.gov (United States)

    Andres F. Cibils; David M. Swift; Richard H. Hart

    2001-01-01

    Previous studies conducted at our research site on the shortgrass steppe in Colorado showed that phenotypic sex ratios of tetraploid fourwing saltbush (Atriplex canescens Pursh [Nutt]) shrubs were less female biased in grazed pastures than in adjacent exclosures. The potential effects of cattle browsing on shrub sex ratios were studied both in the field and in a...

  8. High precipitation and seeded species competition reduce seeded shrub establishment during dryland restoration.

    Science.gov (United States)

    Rinella, Matthew J; Hammond, Darcy H; Bryant, Ana-Elisa M; Kozar, Brian J

    2015-06-01

    Drylands comprise 40% of Earth's land mass and are critical to food security, carbon sequestration, and threatened and endangered wildlife. Exotic weed invasions, overgrazing, energy extraction, and other factors have degraded many drylands, and this has placed an increased emphasis on dryland restoration. The increased restoration focus has generated a wealth of experience, innovations and empirical data, yet the goal of restoring diverse, native, dryland plant assemblages composed of grasses, forbs, and shrubs has generally proven beyond reach. Of particular concern are shrubs, which often fail to establish or establish at trivially low densities. We used data from two Great Plains, USA coal mines to explore factors regulating shrub establishment. Our predictor data related to weather and restoration (e.g., seed rates, rock cover) variables, and our response data described shrub abundances on fields of the mines. We found that seeded non-shrubs, especially grasses, formed an important competitive barrier to shrub establishment: With every one standard deviation increase in non-shrub seed rate, the probability shrubs were present decreased ~0.1 and shrub cover decreased ~35%. Since new fields were seeded almost every year for > 20 years, the data also provided a unique opportunity to explore effects of stochastic drivers (i.e., precipitation, year effects). With every one standard deviation increase in precipitation the first growing season following seeding, the probability shrubs were present decreased ~0.07 and shrub cover decreased ~47%. High precipitation appeared to harm shrubs by increasing grass growth/competition. Also, weak evidence suggested shrub establishment was better in rockier fields where grass abundance/competition was lower. Multiple lines of evidence suggest reducing grass seed rates below levels typically used in Great Plains restoration would benefit shrubs without substantially impacting grass stand development over the long term. We used

  9. Shrub expansion at the forest–tundra ecotone: spatial heterogeneity linked to local topography

    International Nuclear Information System (INIS)

    Ropars, P; Boudreau, S

    2012-01-01

    Recent densification of shrub cover is now documented in many Arctic regions. However, most studies focus on global scale responses, yielding very little information on the local patterns. This research aims to quantify shrub cover increase at northern treeline (Québec, Canada) in two important types of environment, sandy terraces and hilltops (which cover about 70% of the landscape), and to identify the species involved. The comparison of a mosaic of two aerial photographs from 1957 (137 km 2 ) and one satellite image taken in 2008 (151 km 2 ) revealed that both hilltops and terraces recorded an increase in shrub cover. However, the increase was significantly greater on terraces than on hilltops (21.6% versus 11.6%). According to ground truthing, the shrub cover densification is associated mainly with an increase of Betula glandulosa Michx. The numerous seedlings observed during the ground truthing suggest that shrub densification should continue in the future. (letter)

  10. Competition for phosphorus: differential uptake from dual-isotope-labeled soil interspaces between shrub and grass

    International Nuclear Information System (INIS)

    Caldwell, M.M.; Eissenstat, D.M.; Richards, J.H.; Allen, M.F.

    1985-01-01

    Two species of Agropyron grass differed strikingly in their capacity to compete for phosphate in soil interspaces shared with a common competitor, the sagebrush Artemisia tridentata. Of the total phosphorus-32 and -33 absorbed by Artemisia, 86% was from the interspace shared with Agropyron spicatum and only 14% from that shared with Agropyron desertorum. Actively absorbing mycorrhizal roots of Agropyron and Artemisia were present in both interspaces, where competition for the labeled phosphate occurred. The results have important implications about the way in which plants compete for resources below ground in both natural plant communities and agricultural intercropping systems

  11. Throughfall and its spatial variability beneath xerophytic shrub canopies within water-limited arid desert ecosystems

    Science.gov (United States)

    Zhang, Ya-feng; Wang, Xin-ping; Hu, Rui; Pan, Yan-xia

    2016-08-01

    Throughfall is known to be a critical component of the hydrological and biogeochemical cycles of forested ecosystems with inherently temporal and spatial variability. Yet little is understood concerning the throughfall variability of shrubs and the associated controlling factors in arid desert ecosystems. Here we systematically investigated the variability of throughfall of two morphological distinct xerophytic shrubs (Caragana korshinskii and Artemisia ordosica) within a re-vegetated arid desert ecosystem, and evaluated the effects of shrub structure and rainfall characteristics on throughfall based on heavily gauged throughfall measurements at the event scale. We found that morphological differences were not sufficient to generate significant difference (P < 0.05) in throughfall between two studied shrub species under the same rainfall and meteorological conditions in our study area, with a throughfall percentage of 69.7% for C. korshinskii and 64.3% for A. ordosica. We also observed a highly variable patchy pattern of throughfall beneath individual shrub canopies, but the spatial patterns appeared to be stable among rainfall events based on time stability analysis. Throughfall linearly increased with the increasing distance from the shrub base for both shrubs, and radial direction beneath shrub canopies had a pronounced impact on throughfall. Throughfall variability, expressed as the coefficient of variation (CV) of throughfall, tended to decline with the increase in rainfall amount, intensity and duration, and stabilized passing a certain threshold. Our findings highlight the great variability of throughfall beneath the canopies of xerophytic shrubs and the time stability of throughfall pattern among rainfall events. The spatially heterogeneous and temporally stable throughfall is expected to generate a dynamic patchy distribution of soil moisture beneath shrub canopies within arid desert ecosystems.

  12. H -Supermagic Labeling on Shrubs Graph and Lm ⨀ Pn

    International Nuclear Information System (INIS)

    Ulfatimah, Risala; Roswitha, Mania; Kusmayadi, Tri Atmojo

    2017-01-01

    A nite simple graph G admits an H -covering if every edge of E ( G ) belongs to a subgraph of G isomorphic to H . We said the graph G = ( V , E ) that admits H -covering to be H -magic if there exists a bijection function f : V ( G ) ∪ E ( G ) → {1, 2, …, | V ( G )| + | E ( G )|} such that for each subgraph H ′ of G isomorphic to H , f ( H ′) = ∑ υ ∈ V ′ f ( υ ) + ∑ e ∈ E ′ f ( e ) = m ( f ) is constant. Furthermore, if f ( V ) = 1, 2, …, | V ( G )| then G is called H -supermagic. In this research we de ned S 2,2 -supermagic labeling on shrub graph Š ( m 1 , m 2 , …, m n ) and fish-supermagic labeling on L m ⨀ P n for m , n ≥ 2. (paper)

  13. Volatile diterpene emission by two Mediterranean Cistaceae shrubs.

    Science.gov (United States)

    Yáñez-Serrano, A M; Fasbender, L; Kreuzwieser, J; Dubbert, D; Haberstroh, S; Lobo-do-Vale, R; Caldeira, M C; Werner, C

    2018-05-01

    Mediterranean vegetation emits a wide range of biogenic volatile organic compounds (BVOCs) among which isoprenoids present quantitatively the most important compound class. Here, we investigated the isoprenoid emission from two Mediterranean Cistaceae shrubs, Halimium halimifolium and Cistus ladanifer, under controlled and natural conditions, respectively. For the first time, diurnal emission patterns of the diterpene kaurene were detected in real-time by Proton-Transfer-Reaction-Time-of-Flight-Mass-Spectrometer. Kaurene emissions were strongly variable among H. halimifolium plants, ranging from 0.01 ± 0.003 to 0.06 ± 0.01 nmol m -2 s -1 in low and high emitting individuals, respectively. They were in the same order of magnitude as monoterpene (0.01 ± 0.01 to 0.11 ± 0.04 nmol m -2 s -1 ) and sesquiterpene (0.01 ± 0.01 to 0.52 nmol m -2 s -1 ) emission rates. Comparable range and variability was found for C. ladanifer under natural conditions. Labelling with 13 C-pyruvate suggested that emitted kaurene was not derived from de novo biosynthesis. The high kaurene content in leaves, the weak relationship with ecophysiological parameters and the tendency of higher emissions with increasing temperatures in the field indicate an emission from storage pools. This study highlights significant emissions of kaurene from two Mediterranean shrub species, indicating that the release of diterpenes into the atmosphere should probably deserve more attention in the future.

  14. Local biotic adaptation of trees and shrubs to plant neighbors

    Science.gov (United States)

    Grady, Kevin C.; Wood, Troy E.; Kolb, Thomas E.; Hersch-Green, Erika; Shuster, Stephen M.; Gehring, Catherine A.; Hart, Stephen C.; Allan, Gerard J.; Whitham, Thomas G.

    2017-01-01

    Natural selection as a result of plant–plant interactions can lead to local biotic adaptation. This may occur where species frequently interact and compete intensely for resources limiting growth, survival, and reproduction. Selection is demonstrated by comparing a genotype interacting with con- or hetero-specific sympatric neighbor genotypes with a shared site-level history (derived from the same source location), to the same genotype interacting with foreign neighbor genotypes (from different sources). Better genotype performance in sympatric than allopatric neighborhoods provides evidence of local biotic adaptation. This pattern might be explained by selection to avoid competition by shifting resource niches (differentiation) or by interactions benefitting one or more members (facilitation). We tested for local biotic adaptation among two riparian trees, Populus fremontii and Salix gooddingii, and the shrub Salix exigua by transplanting replicated genotypes from multiple source locations to a 17 000 tree common garden with sympatric and allopatric treatments along the Colorado River in California. Three major patterns were observed: 1) across species, 62 of 88 genotypes grew faster with sympatric neighbors than allopatric neighbors; 2) these growth rates, on an individual tree basis, were 44, 15 and 33% higher in sympatric than allopatric treatments for P. fremontii, S. exigua and S. gooddingii, respectively, and; 3) survivorship was higher in sympatric treatments for P. fremontiiand S. exigua. These results support the view that fitness of foundation species supporting diverse communities and dominating ecosystem processes is determined by adaptive interactions among multiple plant species with the outcome that performance depends on the genetic identity of plant neighbors. The occurrence of evolution in a plant-community context for trees and shrubs builds on ecological evolutionary research that has demonstrated co-evolution among herbaceous taxa, and

  15. Does fire severity influence shrub resprouting after spring prescribed burning?

    Science.gov (United States)

    Fernández, Cristina; Vega, José A.; Fonturbel, Teresa

    2013-04-01

    Prescribed burning is commonly used to reduce the risk of severe wildfire. However, further information about the associated environmental effects is required to help forest managers select the most appropriate treatment. To address this question, we evaluated if fire severity during spring prescribed burning significantly affects the resprouting ability of two common shrub species in shrubland under a Mediterranean climate in NW Spain. Fire behaviour and temperatures were recorded in tagged individuals of Erica australis and Pterospartum tridentatum during prescribed burning. The number and length of resprouted shoots were measured three times (6, 12 and 18 months) after the prescribed burning. The influence of a series of fire severity indicators on some plant resprouting vigour parameters was tested by canonical correlation analysis. Six months and one year after prescribed burning, soil burn severity (measured by the absolute reduction in depth of the organic soil layer, maximum temperatures in the organic soil layer and the mineral soil surface during burning and the post-fire depth of the organic soil layer) reduced the resprouting vigour of E. australis and P. tridentatum. In contrast, direct measurements of fire effects on plants (minimum branch diameter, duration of temperatures above 300 °C in the shrub crown and fireline intensity) did not affect the post-fire plant vigour. Soil burn severity during spring prescribed burning significantly affected the short-term resprouting vigour in a mixed heathland in Galicia. The lack of effects eighteen months after prescribed burning indicates the high resilience of these species and illustrates the need to conciliate fire prevention and conservation goals.

  16. Arctic Tundra Soils: A Microbial Feast That Shrubs Will Cease

    Science.gov (United States)

    Machmuller, M.; Calderon, F.; Cotrufo, M. F.; Lynch, L.; Paul, E. A.; Wallenstein, M. D.

    2016-12-01

    Rapid climate warming may already be driving rapid decomposition of the vast stocks of carbon in Arctic tundra soils. However, stimulated decomposition may also release nitrogen and support increased plant productivity, potentially counteracting soil carbon losses. At the same time, these two processes interact, with plant derived carbon potentially fueling soil microbes to attack soil organic matter (SOM) to acquire nitrogen- a process known as priming. Thus, differences in the physiology, stoichiometry and microbial interactions among plant species could affect climate-carbon feedbacks. To reconcile these interactive mechanisms, we examined how vegetation type (Betula nana and Eriophorum vaginatum) and fertilization (short-term and long-term) influenced the decomposition of native SOM after labile carbon and nutrient addition. We hypothesized that labile carbon inputs would stimulate the loss of native SOM, but the magnitude of this effect would be indirectly related to soil nitrogen concentrations (e.g. SOM priming would be highest in N-limited soils). We added isotopically enriched (13C) glucose and ammonium nitrate to soils under shrub (B. nana) and tussock (E. vaginatum) vegetation. We found that nitrogen additions stimulated priming only in tussock soils, characterized by lower nutrient concentrations and microbial biomass (p20yrs. Rather, we found that long-term fertilization shifted SOM chemistry towards a greater abundance of recalcitrant SOM, lower microbial biomass, and decreased SOM respiration (p<0.05). Our results suggest that, in the short-term, the magnitude of SOM priming is dependent on vegetation and soil nitrogen concentrations, but this effect may not persist if shrubs increase in abundance under climate warming. Therefore, including nitrogen as a control on SOM decomposition and priming is critical to accurately model the effects of climate change on arctic carbon storage.

  17. Shrub growth rate and bark responses to soil warming and nutrient addition – A dendroecological approach in a field experiment

    NARCIS (Netherlands)

    Iturrate-Garcia, Maitane; Heijmans, Monique M.P.D.; Schweingruber, Fritz H.; Maximov, Trofim C.; Niklaus, Pascal A.; Schaepman-Strub, Gabriela

    2017-01-01

    Tundra shrubs are slow-growing species limited by low air temperature and scarce nutrient availability. However, shrub expansion has been widely observed in the Arctic during the last decades and attributed to climate warming. Shift in shrub growth, wood structure and abundance affects the

  18. Arid oil-field restoration: native perennial grasses suppress weeds and erosion, but also suppress native shrubs

    Science.gov (United States)

    1. Long-lived, drought-tolerant shrubs are dominant components of many arid ecosystems, and shrubs provide multiple ecosystem services (e.g., soil stabilization, herbaceous plant facilitation, carbon storage and wildlife habitat). On denuded sites, shrub restoration is hindered by abiotic (erosion ...

  19. Changes in epiphyte communities as the shrub, Acer circinatum, develops and ages

    Science.gov (United States)

    Ruchty, A.M.; Rosso, A.L.

    2001-01-01

    The Pacific Northwest tall shrub Acer circinatum (vine maple) can host diverse and abundant epiphyte communities. A chronosequence approach revealed that these communities gradually shift in composition as the shrub progresses through its life cycle. Different epiphytic life forms occupy different spatial and temporal niches on shrub stems. These life forms generally shift upwards along the shrub stem as the stem ages and develops, in accordance with the similar gradient hypothesis. We postulate the following sequence of events. An initial wave of colonization occurs as new substrate is laid down. Over time, superior competitors gradually engulf and overgrow competitively inferior primary colonizers. Concurrently, shrub stem microclimate changes as shrub stems grow, age, and layer, causing the processes of competition and colonization to shift in favor of different epiphytic life forms during different life stages of the shrub stem. We define four separate shrub stem life stages: life classes 1a??4 describe, respectively, young upright a??whipsa??; vigorous, upright, mature stems; declining stems beginning to bend towards the forest floor; and horizontal, decadent stems. As space on the shrub stem is filled through growth and colonization, interspecific competition intensifies. Successful competitors persist and spread, while poor competitors are increasingly restricted to the stem tips, where interspecific competition is less intense. In these forests, Usnea, green-algal foliose lichens, and moss tufts excel as the primary colonizers and become common on the outer portions of shrub stems over time, as long as the overstory is not too dense. Moss mats are also good primary colonizers, but excel as secondary colonizers, often coming to dominate decadent shrub stems. Although all life forms can be primary colonizers, the remaining forms (cyanolichens, liverworts, and Antitrichia curtipendula) are effective secondary colonizers. Liverworts are also effective

  20. Response of dominant grass and shrub species to water manipulation: an ecophysiological basis for shrub invasion in a Chihuahuan Desert grassland.

    Science.gov (United States)

    Throop, Heather L; Reichmann, Lara G; Sala, Osvaldo E; Archer, Steven R

    2012-06-01

    Increases in woody vegetation and declines in grasses in arid and semi-arid ecosystems have occurred globally since the 1800s, but the mechanisms driving this major land-cover change remain uncertain and controversial. Working in a shrub-encroached grassland in the northern Chihuahuan Desert where grasses and shrubs typically differ in leaf-level nitrogen allocation, photosynthetic pathway, and root distribution, we asked if differences in leaf-level ecophysiology could help explain shrub proliferation. We predicted that the relative performance of grasses and shrubs would vary with soil moisture due to the different morphological and physiological characteristics of the two life-forms. In a 2-year experiment with ambient, reduced, and enhanced precipitation during the monsoon season, respectively, the encroaching C(3) shrub (honey mesquite Prosopis glandulosa) consistently and substantially outperformed the historically dominant C(4) grass (black grama Bouteloua eriopoda) in terms of photosynthetic rates while also maintaining a more favorable leaf water status. These differences persisted across a wide range of soil moisture conditions, across which mesquite photosynthesis was decoupled from leaf water status and moisture in the upper 50 cm of the soil profile. Mesquite's ability to maintain physiologically active leaves for a greater fraction of the growing season than black grama potentially amplifies and extends the importance of physiological differences. These physiological and phenological differences may help account for grass displacement by shrubs in drylands. Furthermore, the greater sensitivity of the grass to low soil moisture suggests that grasslands may be increasingly susceptible to shrub encroachment in the face of the predicted increases in drought intensity and frequency in the desert of the southwestern USA.

  1. Mediterranean shrub vegetation: soil protection vs. water availability

    Science.gov (United States)

    García Estringana, Pablo; Nieves Alonso-Blázquez, M.; Alegre, Alegre; Cerdà, Artemi

    2014-05-01

    Soil Erosion and Land Degradation are closely related to the changes in the vegetation cover (Zhao et al., 2013). Although other factors such as rainfall intensiy or slope (Ziadat and Taimeh, 2013) the plant covers is the main factor that controls the soil erosion (Haregeweyn, 2013). Plant cover is the main factor of soil erosion processes as the vegetation control the infiltration and runoff generation (Cerdà, 1998a; Kargar Chigani et al., 2012). Vegetation cover acts in a complex way in influencing on the one hand on runoff and soil loss and on the other hand on the amount and the way that rainfall reaches the soil surface. In arid and semiarid regions, where erosion is one of the main degradation processes and water is a scant resource, a minimum percentage of vegetation coverage is necessary to protect the soil from erosion, but without compromising the availability of water (Belmonte Serrato and Romero Diaz, 1998). This is mainly controlled by the vegetation distribution (Cerdà, 1997a; Cammeraat et al., 2010; Kakembo et al., 2012). Land abandonment is common in Mediterranean region under extensive land use (Cerdà, 1997b; García-Ruiz, 2010). Abandoned lands typically have a rolling landscape with steep slopes, and are dominated by herbaceous communities that grow on pasture land interspersed by shrubs. Land abandonment use to trigger an increase in soil erosion, but the vegetation recovery reduces the impact of the vegetation. The goal of this work is to assess the effects of different Mediterranean shrub species (Dorycnium pentaphyllum Scop., Medicago strasseri, Colutea arborescens L., Retama sphaerocarpa, L., Pistacia Lentiscus L. and Quercus coccifera L.) on soil protection (runoff and soil losses) and on rainfall reaching soil surface (rainfall partitioning fluxes). To characterize the effects of shrub vegetation and to evaluate their effects on soil protection, two field experiments were carried out. The presence of shrub vegetation reduced runoff by

  2. Trends in soil erosion and woody shrub encroachment in Ngqushwa district, Eastern Cape Province, South Africa.

    Science.gov (United States)

    Manjoro, Munyaradzi; Kakembo, Vincent; Rowntree, Kate M

    2012-03-01

    Woody shrub encroachment severely impacts on the hydrological and erosion response of rangelands and abandoned cultivated lands. These processes have been widely investigated at various spatial scales, using mostly field experimentation. The present study used remote sensing to investigate spatial and temporal patterns of soil erosion and encroachment by a woody shrub species, Pteronia incana, in a catchment in Ngqushwa district, Eastern Cape Province, South Africa between 1998 and 2008. The extreme categories of soil erosion and shrub encroachment were mapped with higher accuracy than the intermediate ones, particularly where lower spatial resolution data were used. The results showed that soil erosion in the worst category increased simultaneously with dense woody shrub encroachment on the hill slopes. This trend is related to the spatial patterning of woody shrub vegetation that increases bare soil patches--leading to runoff connectivity and concentration of overland flow. The major changes in soil erosion and shrub encroachment analysed during the 10-year period took place in the 5-9° slope category and on the concave slope form. Multi-temporal analyses, based on remote sensing, can extend our understanding of the dynamics of soil erosion and woody shrub encroachment. They may help benchmark the processes and assist in upscaling field studies.

  3. Dynamics of Understory Shrub Biomass in Six Young Plantations of Southern Subtropical China

    Directory of Open Access Journals (Sweden)

    Yuanqi Chen

    2017-11-01

    Full Text Available Understory shrubs are an important component of forest ecosystems and drive ecosystem processes, such as ecosystem carbon cycling. However, shrub biomass carbon stocks have rarely been reported, which limits our understanding of ecosystem C stock and cycling. In this study, we evaluated carbon accumulation of shrub species using allometric equations based on height and basal diameter in six subtropical plantations at the age of 1, 3, 4 and 6 years. The results showed that plantation type did not significantly affect the total biomass of shrubs, but it significantly affected the biomass of Rhodomyrtus tomentosa, Ilex asprella, Clerodendrum fortunatum and Baeckea frutescens. The biomass of dominant shrub species R. tomentosa, I. asprella, Gardenia jasminoides and Melastoma candidum increased with stand age, while the biomass of C. fortunatum and B. frutescens decreased. The inconsistent biomass-time patterns of different shrub species may be the primary reason for the altered total shrub biomass in each plantation. Consequently, we proposed that R. tomentosa, I. asprella, G. jasminoides and M. candidum could be preferable for understory carbon accumulation and should be maintained or planted because of their important functions in carbon accumulation and high economic values in the young plantations of southern subtropical China.

  4. Mapping the ecological dimensions and potential distributions of endangered relic shrubs in western Ordos biodiversity center.

    Science.gov (United States)

    Zhu, Geng-Ping; Li, Hui-Qi; Zhao, Li; Man, Liang; Liu, Qiang

    2016-05-20

    Potential distributions of endemic relic shrubs in western Ordos were poorly mapped, which hindered our implementation of proper conservation. Here we investigated the applicability of ecological niche modeling for endangered relic shrubs to detect areas of priority for biodiversity conservation and analyze differences in ecological niche spaces used by relic shrubs. We applied ordination and niche modeling techniques to assess main environmental drivers of five endemic relic shrubs in western Ordos, namely, Ammopiptanthus mongolicus, Amygdalus mongolica, Helianthemum songaricum, Potaninia mongolica, and Tetraena mongolica. We calculated niche overlap metrics in gridded environmental spaces and compared geographical projections of ecological niches to determine similarities and differences of niches occupied by relic shrubs. All studied taxa presented different responses to environmental factors, which resulted in a unique combination of niche conditions. Precipitation availability and soil quality characteristics play important roles in the distributions of most shrubs. Each relic shrub is constrained by a unique set of environmental conditions, the distribution of one species cannot be implied by the distribution of another, highlighting the inadequacy of one-fits-all type of conservation measure. Our stacked habitat suitability maps revealed regions around Yellow River, which are highly suitable for most species, thereby providing high conservation value.

  5. Climatic warming strengthens a positive feedback between alpine shrubs and fire.

    Science.gov (United States)

    Camac, James S; Williams, Richard J; Wahren, Carl-Henrik; Hoffmann, Ary A; Vesk, Peter A

    2017-08-01

    Climate change is expected to increase fire activity and woody plant encroachment in arctic and alpine landscapes. However, the extent to which these increases interact to affect the structure, function and composition of alpine ecosystems is largely unknown. Here we use field surveys and experimental manipulations to examine how warming and fire affect recruitment, seedling growth and seedling survival in four dominant Australian alpine shrubs. We found that fire increased establishment of shrub seedlings by as much as 33-fold. Experimental warming also doubled growth rates of tall shrub seedlings and could potentially increase their survival. By contrast, warming had no effect on shrub recruitment, postfire tussock regeneration, or how tussock grass affected shrub seedling growth and survival. These findings indicate that warming, coupled with more frequent or severe fires, will likely result in an increase in the cover and abundance of evergreen shrubs. Given that shrubs are one of the most flammable components in alpine and tundra environments, warming is likely to strengthen an existing feedback between woody species abundance and fire in these ecosystems. © 2017 John Wiley & Sons Ltd.

  6. [Soil moisture dynamics of artificial Caragana microphylla shrubs at different topographical sites in Horqin sandy land].

    Science.gov (United States)

    Huang, Gang; Zhao, Xue-yong; Huang, Ying-xin; Su, Yan-gui

    2009-03-01

    Based on the investigation data of vegetation and soil moisture regime of Caragana microphylla shrubs widely distributed in Horqin sandy land, the spatiotemporal variations of soil moisture regime and soil water storage of artificial sand-fixing C. microphylla shrubs at different topographical sites in the sandy land were studied, and the evapotranspiration was measured by water balance method. The results showed that the soil moisture content of the shrubs was the highest in the lowland of dunes, followed by in the middle, and in the crest of the dunes, and increased with increasing depth. No water stress occurred during the growth season of the shrubs. Soil moisture content of the shrubs was highly related to precipitation event, and the relationship of soil moisture content with precipitation was higher in deep soil layer (50-180 cm) than in shallow soil layer (0-50 cm). The variation coefficient of soil moisture content was also higher in deep layer than in shallow layer. Soil water storage was increasing in the whole growth season of the shrubs, which meant that the accumulation of soil water occurred in this area. The evapotranspiriation of the shrubs occupied above 64% of the precipitation.

  7. [Spatial distribution of aboveground biomass of shrubs in Tianlaochi catchment of the Qilian Mountains].

    Science.gov (United States)

    Liang, Bei; Di, Li; Zhao, Chuan-Yan; Peng, Shou-Zhang; Peng, Huan-Hua; Wang, Chao

    2014-02-01

    This study estimated the spatial distribution of the aboveground biomass of shrubs in the Tianlaochi catchment of Qilian Mountains based on the field survey and remote sensing data. A relationship model of the aboveground biomass and its feasibly measured factors (i. e. , canopy perimeter and plant height) was built. The land use was classified by object-oriented technique with the high resolution image (GeoEye-1) of the study area, and the distribution of shrub coverage was extracted. Then the total aboveground biomass of shrubs in the study area was estimated by the relationship model with the distribution of shrub coverage. The results showed that the aboveground biomass of shrubs in the study area was 1.8 x 10(3) t and the aboveground biomass per unit area was 1598.45 kg x m(-2). The distribution of shrubs mainly was at altitudes of 3000-3700 m, and the aboveground biomass of shrubs on the sunny slope (1.15 x 10(3) t) was higher than that on the shady slope (0.65 x 10(3) t).

  8. Mammalian herbivores confer resilience of Arctic shrub-dominated ecosystems to changing climate.

    Science.gov (United States)

    Kaarlejärvi, Elina; Hoset, Katrine S; Olofsson, Johan

    2015-09-01

    Climate change is resulting in a rapid expansion of shrubs in the Arctic. This expansion has been shown to be reinforced by positive feedbacks, and it could thus set the ecosystem on a trajectory toward an alternate, more productive regime. Herbivores, on the other hand, are known to counteract the effects of simultaneous climate warming on shrub biomass. However, little is known about the impact of herbivores on resilience of these ecosystems, that is, the capacity of a system to absorb disturbance and still remain in the same regime, retaining the same function, structure, and feedbacks. Here, we investigated how herbivores affect resilience of shrub-dominated systems to warming by studying the change of shrub biomass after a cessation of long-term experimental warming in a forest-tundra ecotone. As predicted, warming increased the biomass of shrubs, and in the absence of herbivores, shrub biomass in tundra continued to increase 4 years after cessation of the artificial warming, indicating that positive effects of warming on plant growth may persist even over a subsequent colder period. Herbivores contributed to the resilience of these systems by returning them back to the original low-biomass regime in both forest and tundra habitats. These results support the prediction that higher shrub biomass triggers positive feedbacks on soil processes and microclimate, which enable maintaining the rapid shrub growth even in colder climates. Furthermore, the results show that in our system, herbivores facilitate the resilience of shrub-dominated ecosystems to climate warming. © 2015 John Wiley & Sons Ltd.

  9. Range expansion of moose in arctic Alaska linked to warming and increased shrub habitat

    Science.gov (United States)

    Tape, Ken D.; Gustine, David D.; Reuss, Roger W.; Adams, Layne G.; Clark, Jason A.

    2016-01-01

    Twentieth century warming has increased vegetation productivity and shrub cover across northern tundra and treeline regions, but effects on terrestrial wildlife have not been demonstrated on a comparable scale. During this period, Alaskan moose (Alces alces gigas) extended their range from the boreal forest into tundra riparian shrub habitat; similar extensions have been observed in Canada (A. a. andersoni) and Eurasia (A. a. alces). Northern moose distribution is thought to be limited by forage availability above the snow in late winter, so the observed increase in shrub habitat could be causing the northward moose establishment, but a previous hypothesis suggested that hunting cessation triggered moose establishment. Here, we use recent changes in shrub cover and empirical relationships between shrub height and growing season temperature to estimate available moose habitat in Arctic Alaska c. 1860. We estimate that riparian shrubs were approximately 1.1 m tall c. 1860, greatly reducing the available forage above the snowpack, compared to 2 m tall in 2009. We believe that increases in riparian shrub habitat after 1860 allowed moose to colonize tundra regions of Alaska hundreds of kilometers north and west of previous distribution limits. The northern shift in the distribution of moose, like that of snowshoe hares, has been in response to the spread of their shrub habitat in the Arctic, but at the same time, herbivores have likely had pronounced impacts on the structure and function of these shrub communities. These northward range shifts are a bellwether for other boreal species and their associated predators.

  10. Seed distribution of four co-occurring grasses around Artemisia halodendron shrubs in a sandy habitat

    Science.gov (United States)

    Li, Feng-Rui; Zhao, Wen-Zhi; Kang, Ling-Fen; Liu, Ji-Liang; Huang, Zhi-Gang; Wang, Qi

    2009-05-01

    In a natural population of the perennial semi-shrub Artemisia halodendron in a shifting sandy habitat in the Horqin Desert of eastern Inner Mongolia, six isolated adult A. halodendron individuals of similar canopy size were chosen as target plants. The density of seeds in the top 5 cm soil depth around shrubs was measured using transects aligned to the four main wind directions and at different distances from the shrub base on both the windward and leeward sides. The effects of shrub presence on seed distribution of four co-occurring grasses were examined by linking seed distribution to seed traits. Of the four species, Setaris viridis and Eragrostis pilosa had small but similar seed mass, while Chloris virgata and Aristida adscensionis had large but similar seed mass. The species were grouped into two cohorts: small-seeded vs. large-seeded cohorts, and shrub presence effects on seed distribution of both cohorts were examined. We found marked difference in the seed distribution pattern among species, especially between the small-seeded and large-seeded cohorts. The small-seeded cohort had significantly higher seed accumulation on the windward than the leeward sides in the most and least prevailing wind directions and much higher seed accumulation on the leeward than the windward sides in the second and third most prevailing wind directions, while opposite patterns occurred in the large-seeded cohort. Four species also showed marked variation in the seed distribution pattern among transects and between windward and leeward sides of each transect. This study provided further evidence that shrubs embedded in a matrix of herbaceous plants is a key cause of spatial heterogeneity in seed availability of herbaceous species. However, seed distribution responses to the presence of shrubs will vary with species as well as with wind direction, sampling position (windward vs. leeward sides of the shrub) and distance from the shrub.

  11. Plant species effects on soil nutrients and chemistry in arid ecological zones.

    Science.gov (United States)

    Johnson, Brittany G; Verburg, Paul S J; Arnone, John A

    2016-09-01

    The presence of vegetation strongly influences ecosystem function by controlling the distribution and transformation of nutrients across the landscape. The magnitude of vegetation effects on soil chemistry is largely dependent on the plant species and the background soil chemical properties of the site, but has not been well quantified along vegetation transects in the Great Basin. We studied the effects of plant canopy cover on soil chemistry within five different ecological zones, subalpine, montane, pinyon-juniper, sage/Mojave transition, and desert shrub, in the Great Basin of Nevada all with similar underlying geology. Although plant species differed in their effects on soil chemistry, the desert shrubs Sarcobatus vermiculatus, Atriplex spp., Coleogyne ramosissima, and Larrea tridentata typically exerted the most influence on soil chemistry, especially amounts of K(+) and total nitrogen, beneath their canopies. However, the extent to which vegetation affected soil nutrient status in any given location was not only highly dependent on the species present, and presumably the nutrient requirements and cycling patterns of the plant species, but also on the background soil characteristics (e.g., parent material, weathering rates, leaching) where plant species occurred. The results of this study indicate that the presence or absence of a plant species, especially desert shrubs, could significantly alter soil chemistry and subsequently ecosystem biogeochemistry and function.

  12. Remote Sensing of Sonoran Desert Vegetation Structure and Phenology with Ground-Based LiDAR

    Directory of Open Access Journals (Sweden)

    Joel B. Sankey

    2014-12-01

    Full Text Available Long-term vegetation monitoring efforts have become increasingly important for understanding ecosystem response to global change. Many traditional methods for monitoring can be infrequent and limited in scope. Ground-based LiDAR is one remote sensing method that offers a clear advancement to monitor vegetation dynamics at high spatial and temporal resolution. We determined the effectiveness of LiDAR to detect intra-annual variability in vegetation structure at a long-term Sonoran Desert monitoring plot dominated by cacti, deciduous and evergreen shrubs. Monthly repeat LiDAR scans of perennial plant canopies over the course of one year had high precision. LiDAR measurements of canopy height and area were accurate with respect to total station survey measurements of individual plants. We found an increase in the number of LiDAR vegetation returns following the wet North American Monsoon season. This intra-annual variability in vegetation structure detected by LiDAR was attributable to a drought deciduous shrub Ambrosia deltoidea, whereas the evergreen shrub Larrea tridentata and cactus Opuntia engelmannii had low variability. Benefits of using LiDAR over traditional methods to census desert plants are more rapid, consistent, and cost-effective data acquisition in a high-resolution, 3-dimensional context. We conclude that repeat LiDAR measurements can be an effective method for documenting ecosystem response to desert climatology and drought over short time intervals and at detailed-local spatial scale.

  13. Remote sensing of Sonoran Desert vegetation structure and phenology with ground-based LiDAR

    Science.gov (United States)

    Sankey, Joel B.; Munson, Seth M.; Webb, Robert H.; Wallace, Cynthia S.A.; Duran, Cesar M.

    2015-01-01

    Long-term vegetation monitoring efforts have become increasingly important for understanding ecosystem response to global change. Many traditional methods for monitoring can be infrequent and limited in scope. Ground-based LiDAR is one remote sensing method that offers a clear advancement to monitor vegetation dynamics at high spatial and temporal resolution. We determined the effectiveness of LiDAR to detect intra-annual variability in vegetation structure at a long-term Sonoran Desert monitoring plot dominated by cacti, deciduous and evergreen shrubs. Monthly repeat LiDAR scans of perennial plant canopies over the course of one year had high precision. LiDAR measurements of canopy height and area were accurate with respect to total station survey measurements of individual plants. We found an increase in the number of LiDAR vegetation returns following the wet North American Monsoon season. This intra-annual variability in vegetation structure detected by LiDAR was attributable to a drought deciduous shrub Ambrosia deltoidea, whereas the evergreen shrub Larrea tridentata and cactus Opuntia engelmannii had low variability. Benefits of using LiDAR over traditional methods to census desert plants are more rapid, consistent, and cost-effective data acquisition in a high-resolution, 3-dimensional context. We conclude that repeat LiDAR measurements can be an effective method for documenting ecosystem response to desert climatology and drought over short time intervals and at detailed-local spatial scale.

  14. Purpose of Introduction as a Predictor of Invasiveness among Introduced Shrubs in Rwanda

    Directory of Open Access Journals (Sweden)

    Jean Leonard Seburanga

    2015-01-01

    Full Text Available The introduced shrub flora in Rwanda was analyzed and the risk of invasion was assessed based on the species’ purposes of introduction. The results showed that more than half of invasive alien shrubs in Rwanda were introduced as ornamentals. They include Agave americana L., Bryophyllum proliferum Bowie ex Hook., Caesalpinia decapetala (Roth Alston, Lantana camara L., and Tithonia diversifolia (Hemsley A. Gray. However, these represented only 3.16% of the total number of introduced ornamental shrubs. At the time when the study was conducted, no introduced food crop had become invasive. Species introduced for purposes other than food or culinary use showed higher likelihood of becoming invasive.

  15. The SMOS Mediterranean Ecosystem L-Band characterisation EXperiment (MELBEX-I) over natural shrubs

    DEFF Research Database (Denmark)

    Cano, Aurelio; Saleh, Kauzar; Wigneron, Jean-Pierre

    2010-01-01

    shrub land, as no data were available over this biome. For that purpose, multi-angular and dual polarimetric measurements (H, V) were obtained by the EMIRAD L-band radiometer from a 14-m tower. Results of this study indicate a small and constant impact of vegetation on the microwave emission of shrub...... land, and L-MEB parameters for shrub land were obtained. In addition, the study highlights the need for calibrating microwave soil roughness, which was found to be constant at the site. Depending on the number of retrieved parameters, soil moisture (SM) near the surface could be estimated with errors...

  16. Watch Out for Your Neighbor: Climbing onto Shrubs Is Related to Risk of Cannibalism in the Scorpion Buthus cf. occitanus.

    Science.gov (United States)

    Sánchez-Piñero, Francisco; Urbano-Tenorio, Fernando

    The distribution and behavior of foraging animals usually imply a balance between resource availability and predation risk. In some predators such as scorpions, cannibalism constitutes an important mortality factor determining their ecology and behavior. Climbing on vegetation by scorpions has been related both to prey availability and to predation (cannibalism) risk. We tested different hypotheses proposed to explain climbing on vegetation by scorpions. We analyzed shrub climbing in Buthus cf. occitanus with regard to the following: a) better suitability of prey size for scorpions foraging on shrubs than on the ground, b) selection of shrub species with higher prey load, c) seasonal variations in prey availability on shrubs, and d) whether or not cannibalism risk on the ground increases the frequency of shrub climbing. Prey availability on shrubs was compared by estimating prey abundance in sticky traps placed in shrubs. A prey sample from shrubs was measured to compare prey size. Scorpions were sampled in six plots (50 m x 10 m) to estimate the proportion of individuals climbing on shrubs. Size difference and distance between individuals and their closest scorpion neighbor were measured to assess cannibalism risk. The results showed that mean prey size was two-fold larger on the ground. Selection of particular shrub species was not related to prey availability. Seasonal variations in the number of scorpions on shrubs were related to the number of active scorpions, but not with fluctuations in prey availability. Size differences between a scorpion and its nearest neighbor were positively related with a higher probability for a scorpion to climb onto a shrub when at a disadvantage, but distance was not significantly related. These results do not support hypotheses explaining shrub climbing based on resource availability. By contrast, our results provide evidence that shrub climbing is related to cannibalism risk.

  17. Assessing effect of rainfall on rate of alien shrub expansion in a ...

    African Journals Online (AJOL)

    Assessing effect of rainfall on rate of alien shrub expansion in a southern African savanna. ... Keywords: aerial photography, invasion, Kyle Game Reserve, Lantana camara, patch dynamics, rainfall variability ... AJOL African Journals Online.

  18. Trees, Shrubs, and Woody Vines of the Bluff Experimental Forest, Warren County, Mississippi

    Science.gov (United States)

    Robert L. Johnson; Elbert L. Little

    1967-01-01

    Nearly 100 species of trees, shrubs, and woody vines grow naturally on the 450-acre Bluff Experimental Forest in west-central Mississippi. This publication lists the plants and provides information on silvical characteristics of the tree species.

  19. Trees and shrubs of the Bartlett Experimental Forest, Carroll County, New Hampshire

    Science.gov (United States)

    Stanley M. Filip; Elbert L., Jr. Little; Elbert L. Little

    1971-01-01

    Sixty-five species of trees and shrubs have been identified as native on the Bartlett Experimental Forest. These species are listed in this paper to provide a record of the woody vegetation of the area.

  20. Permafrost collapse after shrub removal shifts tundra ecosystem to a methane source

    DEFF Research Database (Denmark)

    Nauta, Ake L.; Heijmans, Monique P.D.; Blok, Daan

    2015-01-01

    , including expansion of woody vegetation5,6, in response to changing climate conditions. How such vegetation changes contribute to stabilization or destabilization of the permafrost is unknown. Here we present six years of field observations in a shrub removal experiment at a Siberian tundra site. Removing...... the shrub part of the vegetation initiated thawing of ice-rich permafrost, resulting in collapse of the originally elevated shrub patches into waterlogged depressions within five years. This thaw pond development shifted the plots from a methane sink into a methane source. The results of our field......-emitting wet depressions could become more abundant in the lowland tundra landscape, at the cost of permafrost-stabilizing low shrub vegetation....

  1. The initiation of a tropic shrub specia Psidium guajava

    Directory of Open Access Journals (Sweden)

    Julieta Emilia ROMOCEA

    2008-05-01

    Full Text Available Because this tropical fruit is not so popular in Europe, we sis try he initiation of an tropic shrub of Psidium guajava it was possible to make, using them seeds from the matured fruit of guava. The fruit is originally from Egypt – Alexandria. Those seeds were dry and before using them, they were kept in sterile water few hours, after that it was performed the sterilization process, and they were inoculated in 4 different experimental variants.Because them germination process was start late, after 2 months from inoculation, observations were made to the level of the germinated seeds, didn’t shown any infections, but the best results were noticed only on variant V1 (BM basic medium - MS with BA (1 mg/l + IBA (1 mg/l, where the germination capacity it was more bigger.Finally, we did noticed that after the end of this experiment, the best medium culture for the generation of stemlets with many leaves is V1 and V3, but for the root development only V2 showed a very good result. Kept in good light intensity, humidity and optimal temperature conditions, the experiment showed good results, what made this research possible.

  2. Contrasting ozone sensitivity in related evergreen and deciduous shrubs

    International Nuclear Information System (INIS)

    Calatayud, Vicent; Marco, Francisco; Cervero, Julia; Sanchez-Pena, Gerardo; Sanz, Maria Jose

    2010-01-01

    Plant responses to enhanced ozone levels have been studied in two pairs of evergreen-deciduous species (Pistacia terebinthus vs. P. lentiscus; Viburnum lantana vs. V. tinus) in Open Top Chambers. Ozone induced widespread visible injury, significantly reduced CO 2 assimilation and stomatal conductance (g s ), impaired Rubisco efficiency and regeneration capacity (V c,max, J max ) and altered fluorescence parameters only in the deciduous species. Differences in stomatal conductance could not explain the observed differences in sensitivity. In control plants, deciduous species showed higher superoxide dismutase (SOD) activity than their evergreen counterparts, suggesting metabolic differences that could make them more prone to redox imbalances. Ozone induced increases in SOD and/or peroxidase activities in all the species, but only evergreens were able to cope with the oxidative stress. The relevancy of these results for the effective ozone flux approach and for the current ozone Critical Levels is also discussed. - Mediterranean evergreen shrubs have a constitutively higher capacity to tolerate ozone stress than their deciduous relatives.

  3. Contrasting ozone sensitivity in related evergreen and deciduous shrubs

    Energy Technology Data Exchange (ETDEWEB)

    Calatayud, Vicent, E-mail: vicent@ceam.e [Fundacion CEAM, c/ Charles R. Darwin 14, Parque Tecnologico, 46980 Paterna, Valencia (Spain); Marco, Francisco; Cervero, Julia [Fundacion CEAM, c/ Charles R. Darwin 14, Parque Tecnologico, 46980 Paterna, Valencia (Spain); Sanchez-Pena, Gerardo [SPCAN, Dir. Gral. de Medio Natural y Politica Forestal, Ministerio de Medio Ambiente, y Medio Rural y Marino, Rios Rosas 24, 28003 Madrid (Spain); Sanz, Maria Jose [Fundacion CEAM, c/ Charles R. Darwin 14, Parque Tecnologico, 46980 Paterna, Valencia (Spain)

    2010-12-15

    Plant responses to enhanced ozone levels have been studied in two pairs of evergreen-deciduous species (Pistacia terebinthus vs. P. lentiscus; Viburnum lantana vs. V. tinus) in Open Top Chambers. Ozone induced widespread visible injury, significantly reduced CO{sub 2} assimilation and stomatal conductance (g{sub s}), impaired Rubisco efficiency and regeneration capacity (V{sub c,max,}J{sub max}) and altered fluorescence parameters only in the deciduous species. Differences in stomatal conductance could not explain the observed differences in sensitivity. In control plants, deciduous species showed higher superoxide dismutase (SOD) activity than their evergreen counterparts, suggesting metabolic differences that could make them more prone to redox imbalances. Ozone induced increases in SOD and/or peroxidase activities in all the species, but only evergreens were able to cope with the oxidative stress. The relevancy of these results for the effective ozone flux approach and for the current ozone Critical Levels is also discussed. - Mediterranean evergreen shrubs have a constitutively higher capacity to tolerate ozone stress than their deciduous relatives.

  4. Vegetative propagation of the Azorean endemic shrub Viburnum treleasei Gand

    Directory of Open Access Journals (Sweden)

    MÓNICA MOURA

    2009-01-01

    Full Text Available Viburnum treleasei Gand. is a threatened hermaphroditic shrub or small tree endemic to the Azores islands. In this study we aimed at defining a fast, simple and cost-efficient propagation methodology that could be used by non-skilled workers in conservation actionplans. Our objective was also to produce cleaner material for initiation of in vitro cultures and to determine the effects of season, placement of cuttings in the branch, placement of vegetative buds in cuttings and forcing solutions in shoot development. It was possible to produce clean shoots from cuttings using a forcing solution with 8-hydroxyquinoline sulphate (8-HQS, 2% sucrose and no growth regulators addition. Shoot development results obtained with apical and sub-apical cuttings indicate that V. treleasei possessesapical dominance and deep endodormancy. Apical semihardwood cuttings in autumn or airlayered branches in autumn and winter with 2 or 5% (w/w of IBA produced excellent rooting results which will allow reinforcing depleted populations of V. treleasei efficientlyand at reduced costs.

  5. Does NDVI reflect variation in the structural attributes associated with increasing shrub dominance in arctic tundra?

    Energy Technology Data Exchange (ETDEWEB)

    Boelman, Natalie T [Lamont-Doherty Earth Observatory, Columbia University, 61 Route 9W, Palisades, NY 10964 (United States); Gough, Laura; McLaren, Jennie R [Department of Biology, University of Texas at Arlington, Arlington, TX 76019 (United States); Greaves, Heather, E-mail: nboelman@ldeo.columbia.edu [Department of Forest Ecosystems and Society, Oregon State University, 321 Richardson Hall, Corvallis, OR 97331 (United States)

    2011-07-15

    This study explores relationships between the normalized difference vegetation index (NDVI) and structural characteristics associated with deciduous shrub dominance in arctic tundra. Our structural measures of shrub dominance are stature, branch abundance, aerial per cent woody stem cover (deciduous and evergreen species), and per cent deciduous shrub canopy cover. All measurements were taken across a suite of transects that together represent a gradient of deciduous shrub height. The transects include tussock tundra shrub and riparian shrub tundra communities located in the northern foothills of the Brooks Range, in northern Alaska. Plot-level NDVI measurements were made in 2010 during the snow-free period prior to deciduous shrub leaf-out (early June, NDVI{sub pre-leaf}), at the point in the growing season when canopy NDVI has reached half of its maximum growing season value (mid-June, NDVI{sub demi-leaf}) and during the period of maximum leaf-out (late July, NDVI{sub peak-leaf}). We found that: (1) NDVI{sub pre-leaf} is best suited to capturing variation in the per cent woody stem cover, maximum shrub height, and branch abundance, particularly between 10 and 50 cm height in the canopy; (2) NDVI{sub peak-leaf} is best suited to capturing variation in deciduous canopy cover; and (3) NDVI{sub demi-leaf} does not capture variability in any of our measures of shrub dominance. These findings suggest that in situ NDVI measurements made prior to deciduous canopy leaf-out could be used to identify small differences in maximum shrub height, woody stem cover, and branch abundance (particularly between 10 and 50 cm height in the canopy). Because shrubs are increasing in size and regional extent in several regions of the Arctic, investigation into spectrally based tools for monitoring these changes are worthwhile as they provide a first step towards development of remotely sensed techniques for quantifying associated changes in regional carbon cycling, albedo, radiative

  6. Variations in the Sensitivity of Shrub Growth to Climate Change along Arctic Environmental and Biotic Gradients

    Science.gov (United States)

    Beck, P. S. A.; Myers-Smith, I. H.; Elmendorf, S.; Georges, D.

    2015-12-01

    Despite evidence of rapid shrub expansion at many Arctic sites and the profound effects this has on ecosystem structure, biogeochemical cycling, and land-atmosphere feedbacks in the Arctic, the drivers of shrub growth remain poorly understood. The compilation of 41,576 annual shrub growth measurements made around the Arctic, allowed for the first systematic evaluation of the climate sensitivity of Arctic shrub growth, i.e. the strength of the relationship between annual shrub growth and monthly climate variables. The growth measurements were taken on 1821 plants of 25 species at 37 arctic and alpine sites, either as annual ring widths or as stem increments. We evaluated climate sensitivity of shrub growth for each genus-by-site combination in this data set based on the performance and parameters of linear mixed models that used CRU TS3.21 climate data as predictors of shrub growth between 1950 and 2010. 76% of genus-by-site combinations showed climate sensitive growth, but climate-growth relationships varied with soil moisture, species canopy height, and geographic position within the species ranges. Shrubs growing at sites with more soil moisture showed greater climate sensitivity, suggesting that water availability might limit shrub growth if continued warming isn't matched by a steady increase in soil moisture. Tall shrub species growing at their northern range limit were particularly climate sensitive causing climate sensitivity of shrubs to peak at the transition between Low and High Arctic, where carbon storage in permafrost is greatest. Local and regional studies have documented matching spatial and temporal patterns in dendrochronological measurements and satellite observations of vegetation indices both in boreal and Arctic regions. Yet the circumarctic comparison of patterns in dendrochronological and remote sensing data sets yielded poor levels of agreement. In much of the Arctic, steep environmental gradients generate fine spatial patterns of vegetation

  7. [Assemblage effect of ground arthropod community in desert steppe shrubs with different ages].

    Science.gov (United States)

    Liu, Ren-Tao; Zhu, Fan; Chai, Yong-Qing

    2014-01-01

    Taking the 6-, 15-, 24- and 36-year-old Caragana intermedia shrubs in desert steppe as a subject, an investigation on soil properties and ground arthropod community was carried out under the shrub and in the open to probe into the assemblage effect of ground arthropod community in desert steppe shrubs with different ages. The results were as follows: 1) In the 6-year-old shrubland, significant differences were only found in soil physical properties (soil texture, soil moisture and electrical conductivity) between the microhabitats under shrub and in the open. Beginning from the 15-year-old shrubland, however, soil organic matter and nutrition (N, P) increased significantly. 2) A total of 27 groups were captured in the studied sites which dominated by Carabidae, Tenebrionidae and Formicidae. From 6- to 15-year-old shrubland, the number of dominant groups decreased while that of common groups increased for the ground arthropod community under the shrub. From 15- to 24- and 36-year-old shrubland, the difference between the microhabitats under the shrub and in the open decreased firstly, and then increased. Some special groups appeared under the shrub in the 36-year-old shrubland, and dung beetles became dominant. 3) In the 6- and 24-year-old shrublands, there were no significant differences in group richness, abundance, and diversity index between the microhabitats under the shrub and in the open. As for the 15- and 36-year-old shrublands, however, significant differences were observed. 4) The shrub age had a stronger effect on the distribution of ground arthropods living under the shrubs compared to that in the open. The changes in soil texture, pH and electrical conductivity could significantly influence on the distribution of ground arthropods under the shrub, also in the open to some degree. It was suggested that the development of shrubland had strong impact on assemblage effect of ground arthropods, which was closely correlated with the stand age and would

  8. Ecohydrological implications of aeolian sediment trapping by sparse vegetation in drylands

    Science.gov (United States)

    Gonzales, Howell B.; Ravi, Sujith; Li, Junran; Sankey, Joel B.

    2018-01-01

    Aeolian processes are important drivers of ecosystem dynamics in drylands, and important feedbacks exist among aeolian – hydrological processes and vegetation. The trapping of wind-borne sediments by vegetation may result in changes in soil properties beneath the vegetation, which, in turn, can alter hydrological and biogeochemical processes. Despite the relevance of aeolian transport to ecosystem dynamics, the interactions between aeolian transport and vegetation in shaping dryland landscapes where sediment distribution is altered by relatively rapid changes in vegetation composition such as shrub encroachment, is not well understood. Here, we used a computational fluid dynamics (CFD) modeling framework to investigate the sediment trapping efficiencies of vegetation canopies commonly found in a shrub-grass ecotone in the Chihuahuan Desert (New Mexico, USA) and related the results to spatial heterogeneity in soil texture and infiltration measured in the field. A CFD open-source software package was used to simulate aeolian sediment movement through three-dimensional architectural depictions of Creosote shrub (Larrea tridentata) and Black Grama grass (Bouteloua eriopoda) vegetation types. The vegetation structures were created using a computer-aided design software (Blender), with inherent canopy porosities, which were derived using LIDAR (Light Detection and Ranging) measurements of plant canopies. Results show that considerable heterogeneity in infiltration and soil grain size distribution exist between the microsites, with higher infiltration and coarser soil texture under shrubs. Numerical simulations also indicate that the differential trapping of canopies might contribute to the observed heterogeneity in soil texture. In the early stages of encroachment, the shrub canopies, by trapping coarser particles more efficiently, might maintain higher infiltration rates leading to faster development of the microsites (among other factors) with enhanced ecological

  9. Linking snake habitat use to nest predation risk in grassland birds: the dangers of shrub cover.

    Science.gov (United States)

    Klug, Page E; Jackrel, Sara L; With, Kimberly A

    2010-03-01

    Extremes in rangeland management, varying from too-frequent fire and intensive grazing to the suppression of both, threaten rangeland ecosystems worldwide. Intensive fire and grazing denude and homogenize vegetation whereas their suppression increases woody cover. Although habitat loss is implicated in grassland bird declines, degradation through intensive management or neglect also decreases breeding habitat and may reduce nesting success through increased rates of nest predation. Snakes are important nest predators, but little is known about how habitat use in snakes relates to predation risk for grassland birds nesting within tallgrass prairie subjected to different grazing and fire frequencies. We evaluated nest survival in the context of habitat used by nesting songbirds and two bird-eating snakes, the eastern yellowbelly racer Coluber constrictor flaviventris and Great Plains ratsnake Pantherophis emoryi. Daily nest survival rates decreased with increasing shrub cover and decreasing vegetation height, which characterize grasslands that have been neglected or intensively managed, respectively. Discriminant function analysis revealed that snake habitats were characterized by higher shrub cover, whereas successful nests were more likely to occur in areas with tall grass and forbs but reduced shrub cover. Because snakes often use shrub habitat, birds nesting in areas with increased shrub cover may be at higher risk of nest predation by snakes in addition to other predators known to use shrub habitat (e.g., mid-sized carnivores and avian predators). Depredated nests also occurred outside the discriminant space of the snakes, indicating that other predators (e.g., ground squirrels Spermophilus spp. and bullsnakes Pituophis catenifer) may be important in areas with denuded cover. Targeted removal of shrubs may increase nest success by minimizing the activity of nest predators attracted to shrub cover.

  10. Scrub-shrub bird habitat associations at multiple spatial scales in beaver meadows in Massachusetts

    Science.gov (United States)

    Chandler, R.B.; King, D.I.; DeStefano, S.

    2009-01-01

    Most scrub-shrub bird species are declining in the northeastern United States, and these declines are largely attributed to regional declines in habitat availability. American Beaver (Castor canadensis; hereafter “beaver”) populations have been increasing in the Northeast in recent decades, and beavers create scrub-shrub habitat through their dam-building and foraging activities. Few systematic studies have been conducted on the value of beaver-modified habitats for scrub-shrub birds, and these data are important for understanding habitat selection of scrub-shrub birds as well as for assessing regional habitat availability for these species. We conducted surveys in 37 beaver meadows in a 2,800-km2 study area in western Massachusetts during 2005 and 2006 to determine the extent to which these beaver-modified habitats are used by scrub-shrub birds, as well as the characteristics of beaver meadows most closely related to bird use. We modeled bird abundance in relation to microhabitat-, patch-, and landscape-context variables while adjusting for survey-specific covariates affecting detectability using N-mixture models. We found that scrub-shrub birds of regional conservation concern occupied these sites and that birds responded differently to microhabitat, patch, and landscape characteristics of beaver meadows. Generally, scrub-shrub birds increased in abundance along a gradient of increasing vegetation complexity, and three species were positively related to patch size. We conclude that these habitats can potentially play an important role in regional conservation of scrub-shrub birds and recommend that conservation priority be given to larger beaver meadows with diverse vegetation structure and composition.

  11. Evaluation for breeding purposes of SO/sub 2/-induced damage to trees and shrubs

    Energy Technology Data Exchange (ETDEWEB)

    Bartkowiak, S; Bialobok, S; Rachwal, L

    1975-01-01

    Experiments were performed to determine the response of trees and shrubs to sulfur dioxide in the vicinity of industrial plants. Studies were carried out in the neighborhood of the factories as well as in exposure chambers in the laboratory. Species investigated were Larix liptolepis, Larix potaninii, Populus simonii, Forsythia intermedia, Ligustrum vulgare, Syringa amurensis and Syringa pekinensis. Injuries ranged from virually undamaged to severe, and there was considerable variation within each genus as well as between individual trees and shrubs.

  12. Interactions between Shrubs and Permafrost in the Torngat Mountains, Northern Labrador, Canada

    Science.gov (United States)

    Lewkowicz, A.; Way, R. G.; Hermanutz, L.; Trant, A.; Siegwart Collier, L.; Whitaker, D.

    2017-12-01

    Discontinuous permafrost is acutely sensitive to climate warming and vegetation dynamics. Shrub height is positively correlated with accumulation of snow in the tundra resulting in warming of the ground in winter, and greater shading and lower surface temperatures in summer. Rapid greening due to climate warming has been observed throughout northeastern Canada and particularly in the coastal mountainous terrain of the Torngat Mountains National Park. Our research examines how this shrubification in the Torngat Mountains is modifying permafrost characteristics using observations which extend over a 100 km south-north transect from the sporadic zone (Saglek, Torr Bay) to where permafrost is widespread (Nakvak Brook, Kangalaksiorvik Lake) and potentially continuous (Komaktorvik River). We use air and ground temperature monitoring, vegetation surveys, dendrochronology, frost probing and electrical resistivity tomography (ERT) to describe the complex interactions between shrub growth, geomorphology, climate and permafrost in a region where climate warming is rapidly altering the landscape. Preliminary analysis of field data shows low resistivity anomalies in the ERT profiles at some sites with thin permafrost, interpreted as unfrozen zones correlated with areas of tall shrubs (Alnus spp., Salix spp. and Betula glandulosa; ranging from prostrate to 2 m). Elsewhere, high resistivities extend to the base of the ERT profiles, indicating thicker permafrost, and no obvious impact of medium to low-prostrate shrubs (Salix spp., Betula glandulosa, Rhododendron spp., and Vaccinium spp.; up to 50 cm). Permafrost is interpreted to be present at most sites with low or prostrate shrubs, except where hydrological conditions favour warmer ground temperatures. We infer that the net impact of increasing shrub heights on the active layer and permafrost depends on antecedent ground temperatures and surficial geology. Increasing shrub heights may cause permafrost degradation at sites where

  13. Uniform shrub growth response to June temperature across the North Slope of Alaska

    Science.gov (United States)

    Ackerman, Daniel E.; Griffin, Daniel; Hobbie, Sarah E.; Popham, Kelly; Jones, Erin; Finlay, Jacques C.

    2018-04-01

    The expansion of woody shrubs in arctic tundra alters many aspects of high-latitude ecosystems, including carbon cycling and wildlife habitat. Dendroecology, the study of annual growth increments in woody plants, has shown promise in revealing how climate and environmental conditions interact with shrub growth to affect these key ecosystem properties. However, a predictive understanding of how shrub growth response to climate varies across the heterogeneous landscape remains elusive. Here we use individual-based mixed effects modeling to analyze 19 624 annual growth ring measurements in the stems of Salix pulchra (Cham.), a rapidly expanding deciduous shrub. Stem samples were collected at six sites throughout the North Slope of Alaska. Sites spanned four landscapes that varied in time since glaciation and hence in soil properties, such as nutrient availability, that we expected would modulate shrub growth response to climate. Ring growth was remarkably coherent among sites and responded positively to mean June temperature. The strength of this climate response varied slightly among glacial landscapes, but in contrast to expectations, this variability was not systematically correlated with landscape age. Additionally, shrubs at all sites exhibited diminishing marginal growth gains in response to increasing temperatures, indicative of alternative growth limiting mechanisms in particularly warm years, such as temperature-induced moisture limitation. Our results reveal a regionally-coherent and robust shrub growth response to early season growing temperature, with local soil properties contributing only a minor influence on shrub growth. Our conclusions strengthen predictions of changes to wildlife habitat and improve the representation of tundra vegetation dynamics in earth systems models in response to future arctic warming.

  14. Shrub encroachment alters sensitivity of soil respiration to temperature and moisture

    Science.gov (United States)

    Cable, Jessica M.; Barron-Gafford, Greg A.; Ogle, Kiona; Pavao-Zuckerman, Mitchell; Scott, Russell L.; Williams, David G.; Huxman, Travis E.

    2012-03-01

    A greater abundance of shrubs in semiarid grasslands affects the spatial patterns of soil temperature, moisture, and litter, resulting in fertile islands with potentially enhanced soil metabolic activity. The goal of this study was to quantify the microsite specificity of soil respiration in a semiarid riparian ecosystem experiencing shrub encroachment. We quantified the response of soil respiration to different microsite conditions created by big mesquite shrubs (near the trunk and the canopy edge), medium-sized mesquite, sacaton bunchgrasses, and open spaces. We hypothesized that soil respiration would be more temperature sensitive and less moisture sensitive and have a greater magnitude in shrub microsites compared with grass and open microsites. Field and incubation soil respiration data were simultaneously analyzed in a Bayesian framework to quantify the microsite-specific temperature and moisture sensitivities and magnitude of respiration. The analysis showed that shrub expansion increases the heterogeneity of respiration. Respiration has greater temperature sensitivity near the shrub canopy edge, and respiration rates are higher overall under big mesquite compared with those of the other microsites. Respiration in the microsites beneath medium-sized mesquites does not behave like a downscaled version of big mesquite microsites. The grass microsites show more similarity to big mesquite microsites than medium-sized shrubs. This study shows there can be a great deal of fine-scale spatial heterogeneity that accompanies shifts in vegetation structure. Such complexity presents a challenge in scaling soil respiration fluxes to the landscape for systems experiencing shrub encroachment, but quantifying this complexity is significantly important in determining overall ecosystem metabolic behavior.

  15. Age distributions of Greenlandic dwarf shrubs support concept of negligible actuarial senescence

    Czech Academy of Sciences Publication Activity Database

    Dahlgren, J. P.; Rizzi, S.; Schweingruber, F. H.; Hellmann, L.; Büntgen, Ulf

    2016-01-01

    Roč. 7, č. 10 (2016), č. článku e01521. ISSN 2150-8925 R&D Projects: GA MŠk(CZ) EE2.3.20.0248 Institutional support: RVO:67179843 Keywords : actuarial senescence * age distribution * age structure * Arctic dwarf shrubs * dendroecology * individual survival * mortality * penalized composite link model * plant aging * shrub demography Subject RIV: EH - Ecology, Behaviour Impact factor: 2.490, year: 2016

  16. Shift in soil microbial communities with shrub encroachment in Inner Mongolia grasslands, China

    Science.gov (United States)

    Shen, H.; Li, H.; Zhang, J.; Hu, H.; Chen, L.; Zhu, Y.; Fang, J.

    2017-12-01

    The ongoing expansion of shrub encroachment into grasslands represents a unique form of land cover change. How this process affects soil microbial communities is poorly understood. In this study, we aim to assess the effects of shrub encroachment on soil microbial biomass, abundance and composition by comparing data between shrub patches and neighboring herb patches in shrub-encroached grasslands (SEGs) in Inner Mongolia, China. Fourteen SEG sites from two ecosystem types (typical and desert grasslands) were investigated. The phospholipid fatty acid (PLFA) method was used to analyze the composition and biomass of the soil microbial community. Our results showed that the top-soil microbial biomass and abundances of gram-negative bacteria, arbuscular mycorrhizal fungi, and actinomycetes were significantly higher in shrub patches than in herb patches in both typical and desert grasslands (P fungi to bacteria ratio was significantly higher in shrub patches than in herb patches in desert grassland (P soil microbial communities, which makes the microbial communities toward a fresh organic carbon-based structure. This study highlights the importance of edaphic and climate factors in microbial community shifts in SEGs.

  17. Above- and Belowground Biomass Allocation in Shrub Biomes across the Northeast Tibetan Plateau

    Science.gov (United States)

    Yang, Yuanhe; Yang, Lucun; Zhou, Guoying

    2016-01-01

    Biomass partitioning has been explored across various biomes. However, the strategies of allocation in plants still remain contentious. This study investigated allocation patterns of above- and belowground biomass at the community level, using biomass survey from the Tibetan Plateau. We explored above- and belowground biomass by conducting three consecutive sampling campaigns across shrub biomes on the northeast Tibetan Plateau during 2011–2013. We then documented the above-ground biomass (AGB), below-ground biomass (BGB) and root: shoot ratio (R/S) and the relationships between R/S and environment factors using data from 201 plots surveyed from 67 sites. We further examined relationships between above-ground and below-ground biomass across various shrub types. Our results indicated that the median values of AGB, BGB, and R/S in Tibetan shrub were 1102.55, 874.91 g m-2, and 0.85, respectively. R/S showed significant trend with mean annual precipitation (MAP), while decreased with mean annual temperature (MAT). Reduced major axis analysis indicated that the slope of the log-log relationship between above- and belowground biomass revealed a significant difference from 1.0 over space, supporting the optimal hypothesis. Interestingly, the slopes of the allometric relationship between log AGB and log BGB differed significantly between alpine and desert shrub. Our findings supported the optimal theory of above- and belowground biomass partitioning in Tibetan shrub, while the isometric hypothesis for alpine shrub at the community level. PMID:27119379

  18. Mediterranean shrub diversity and its effect on food intake in goats

    Directory of Open Access Journals (Sweden)

    Tomislav Šarić

    2014-07-01

    Full Text Available Mediterranean ecosystem offers a variety of shrubs that were over long periods of time involved in the evolution of complex plant-animal interactions. Biochemical components of these plants enter different metabolic pathways after digestion and absorption, resulting in development of dietary preferences in browsing animals. Herbivores in general were found to perform better when grazing in a mixed plant community composed of diverse species, and show preferential feeding behaviours for mixed vs single species diet. Our findings demonstrate an asymptotic relationship among Mediterranean shrubs species diversity and their voluntary intake by goats. Shrub biomass intake showed linear increase when number of different shrubs in diet increased from one to three. However, goats did not further increase intake when the number of shrub species increased from four to eight. As the number of shrub species offered increased, goats exhibited more preferential feeding behaviour for Quercus pubescens, Fraxinus ornus, Rubus heteromorphus and Arbutus unedo and decreased the intake of Hedera helix, Juniperus oxycedrus and Helichrysum italicum. This asymptotic relationship indicates that the maintenance of plant species richness in Mediterranean shrublands can overall benefit domestic goat farming, goat’s productive performance, and the conservation of plant biodiversity.

  19. Integration of vessel traits, wood density, and height in angiosperm shrubs and trees.

    Science.gov (United States)

    Martínez-Cabrera, Hugo I; Schenk, H Jochen; Cevallos-Ferriz, Sergio R S; Jones, Cynthia S

    2011-05-01

    Trees and shrubs tend to occupy different niches within and across ecosystems; therefore, traits related to their resource use and life history are expected to differ. Here we analyzed how growth form is related to variation in integration among vessel traits, wood density, and height. We also considered the ecological and evolutionary consequences of such differences. In a sample of 200 woody plant species (65 shrubs and 135 trees) from Argentina, Mexico, and the United States, standardized major axis (SMA) regression, correlation analyses, and ANOVA were used to determine whether relationships among traits differed between growth forms. The influence of phylogenetic relationships was examined with a phylogenetic ANOVA and phylogenetically independent contrasts (PICs). A principal component analysis was conducted to determine whether trees and shrubs occupy different portions of multivariate trait space. Wood density did not differ between shrubs and trees, but there were significant differences in vessel diameter, vessel density, theoretical conductivity, and as expected, height. In addition, relationships between vessel traits and wood density differed between growth forms. Trees showed coordination among vessel traits, wood density, and height, but in shrubs, wood density and vessel traits were independent. These results hold when phylogenetic relationships were considered. In the multivariate analyses, these differences translated as significantly different positions in multivariate trait space occupied by shrubs and trees. Differences in trait integration between growth forms suggest that evolution of growth form in some lineages might be associated with the degree of trait interrelation.

  20. Phenological observations on shrubs to predict weed emergence in turf

    Science.gov (United States)

    Masin, Roberta; Zuin, Maria Clara; Zanin, Giuseppe

    2005-09-01

    Phenology is the study of periodic biological events. If we can find easily recognizable events in common plants that precede or coincide with weed emergences, these plants could be used as indicators. Weed seedlings are usually difficult to detect in turf, so the use of phenological indicators may provide an alternative approach to predict the time when a weed appears and consequently guide management decisions. A study was undertaken to determine whether the phenological phases of some plants could serve as reliable indicators of time of weed emergence in turf. The phenology of six shrubs (Crataegus monogyna Jacq., Forsythia viridissima Lindl., Sambucus nigra L., Syringa vulgaris L., Rosa multiflora Thunb., Ziziphus jujuba Miller) and a perennial herbaceous plant [Cynodon dactylon (L.) Pers.] was observed and the emergence dynamics of four annual weed species [Digitaria sanguinalis (L.) Scop., Eleusine indica (L.) Gaertner, Setaria glauca (L.) Beauv., Setaria viridis (L.) Beauv.] were studied from 1999 to 2004 in northern Italy. A correlation between certain events and weed emergence was verified. S. vulgaris and F. viridissima appear to be the best indicators: there is a quite close correspondence between the appearance of D. sanguinalis and lilac flowering and between the beginning of emergence of E. indica and the end of lilac flowering; emergences of S. glauca and S. viridis were predicted well in relation to the end of forsythia flowering. Base temperatures and starting dates required to calculate the heat unit sums to reach and complete the flowering phase of the indicators were calculated using two different methods and the resultant cumulative growing degree days were compared.

  1. Ground biomass assessment of shrub species in tehsil takht-e-nasrati, pakistan

    International Nuclear Information System (INIS)

    Khan, M.; Hussain, F.; Musharaf, S.; Musharaf, S.

    2014-01-01

    The shrub biomass of different species of Tehsil Takht-e-Nasrati was different at different altitude. In the present study it was found that the average shrub biomass was decreasing with increasing altitude. Result confirms that the biomass of Saccharum bengalense was high 5020.38 Kg.hec/sup -1/ in phase 1 and phase 2 (4331.58 Kg.hec/sup -1/). The highest ground biomass 1125.1 Kg.hec/sup -1/ of Zizyphus nummularia was found in Phase 3. Furthermore in Phase 4 the biomass of Capparis deciduas was high 437.79 Kg.hec/sup -1/. Along with shrubs average biomass of Saccharum bengalense was high 2665.12 Kg.hec/sup -1/ and low 13.47 Kg.hec/sup -1/ of Cassia angustifolia. With seasons the biomass of Saccharum bengalense (13800 Kg.hec/sup -1/) was greater during winter at Phase 1 and Periploc aaphylla (12.35 Kg.hec-1) biomass was lowers during spring at Phase 4. In comparison in season the biomass was high in winter due to the dormant stage of shrubs in phase 1 while it was low in summer in phase 4. In winter the grazing process was stop due to agriculture point of view while in hilly area the grazing was high and the low percentage of rain fall consequently the biomass was high in plain area as contrast to hilly area. The biomass of shrubs is high in winter while it was low in summer as the grazing and palatability rate was high in summer as well as low in winter. The assessment of shrub biomass in research area is a requirement for successful management at the same time as it gives a complete documentation for the area in complexity and work out unpredictable resources to help imagine shrubs potency and behavior. (author)

  2. Seed-bank structure and plant-recruitment conditions regulate the dynamics of a grassland-shrubland Chihuahuan ecotone.

    Science.gov (United States)

    Moreno-de Las Heras, Mariano; Turnbull, Laura; Wainwright, John

    2016-09-01

    Large areas of desert grasslands in the southwestern United States have shifted to sparse shrublands dominated by drought-tolerant woody species over the last 150 yr, accompanied by accelerated soil erosion. An important step toward the understanding of patterns in species dominance and vegetation change at desert grassland-shrubland transitions is the study of environmental limitations imposed by the shrub-encroachment phenomenon on plant establishment. Here, we analyze the structure of soil seed banks, environmental limitations for seed germination (i.e., soil-water availability and temperature), and simulated seedling emergence and early establishment of dominant species (black grama, Bouteloua eriopoda, and creosotebush, Larrea tridentata) across a Chihuahuan grassland-shrubland ecotone (Sevilleta National Wildlife Refuge, New Mexico, USA). Average viable seed density in soils across the ecotone is generally low (200-400 seeds/m 2 ), although is largely concentrated in densely vegetated areas (with peaks up to 800-1,200 seeds/m 2 in vegetated patches). Species composition in the seed bank is strongly affected by shrub encroachment, with seed densities of grass species sharply decreasing in shrub-dominated sites. Environmental conditions for seed germination and seedling emergence are synchronized with the summer monsoon. Soil-moisture conditions for seedling establishment of B. eriopoda take place with a recurrence interval ranging between 5 and 8 yr for grassland and shrubland sites, respectively, and are favored by strong monsoonal precipitation. Limited L. tridentata seed dispersal and a narrow range of rainfall conditions for early seedling establishment (50-100 mm for five to six consecutive weeks) constrain shrub-recruitment pulses to localized and episodic decadal events (9-25 yr recurrence intervals) generally associated with late-summer rainfall. Re-establishment of B. eriopoda in areas now dominated by L. tridentata is strongly limited by the

  3. Effect of supplementation with barley and calcium hydroxide on intake of Mediterranean shrubs

    Directory of Open Access Journals (Sweden)

    Dragan Skobic

    2011-04-01

    Full Text Available Maquis plant communities are one of the most varied vegetation types in the Mediterranean region and an important habitat for wild and domestic herbivores. Although the majority of these shrubs are nutritious, the secondary compounds are main impediments that reduce their forage value. In five experiments we determined the effect of supplementing goats with calcium hydroxide plus barley, and barley alone on intake of five dominant shrubs (Quercus ilex, Erica multiflora, Arbutus unedo, Viburnum tinus and Pistacia lentiscus of the Mediterranean maquis community. The combination of calcium hydroxide plus barley and barley alone increased utilization of all five investigated Mediterranean shrubs; therewith that intake of Arbutus unedo and Viburnum tinus was not statistically significant. Supplemented goats with calcium hydroxide plus barley or barley alone could be effective in controlling secondary compounds-rich Mediterranean shrubs where their abundance threatens biodiversity. This control can be facilitated by browsing dominant Mediterranean shrubs, which has been shown to be effective in managing Mediterranean maquis density. Calcium hydroxide and barley (energy enhance use of secondary compounds-containing plants, which may increase production of alternate forages and create a more diverse mix of plant species in the Mediterranean maquis plant community.

  4. Electrostatic Interactions between Elongated Monomers Drive Filamentation of Drosophila Shrub, a Metazoan ESCRT-III Protein

    Directory of Open Access Journals (Sweden)

    Brian J. McMillan

    2016-08-01

    Full Text Available The endosomal sorting complex required for transport (ESCRT is a conserved protein complex that facilitates budding and fission of membranes. It executes a key step in many cellular events, including cytokinesis and multi-vesicular body formation. The ESCRT-III protein Shrub in flies, or its homologs in yeast (Snf7 or humans (CHMP4B, is a critical polymerizing component of ESCRT-III needed to effect membrane fission. We report the structural basis for polymerization of Shrub and define a minimal region required for filament formation. The X-ray structure of the Shrub core shows that individual monomers in the lattice interact in a staggered arrangement using complementary electrostatic surfaces. Mutations that disrupt interface salt bridges interfere with Shrub polymerization and function. Despite substantial sequence divergence and differences in packing interactions, the arrangement of Shrub subunits in the polymer resembles that of Snf7 and other family homologs, suggesting that this intermolecular packing mechanism is shared among ESCRT-III proteins.

  5. [Rainfall and soil moisture redistribution induced by xerophytic shrubs in an arid desert ecosystem].

    Science.gov (United States)

    Wang, Zheng Ning; Wang, Xin Ping; Liu, Bo

    2016-03-01

    Rainfall partitioning by desert shrub canopy modifies the redistribution of incident rainfall under the canopy, and may affect the distribution pattern of soil moisture around the plant. This study examined the distribution of rainfall and the response of soil moisture beneath the canopy of two dominant desert shrubs, Caragana korshinskii and Artemisia ordosica, in the revegetation area at the southeastern edge of the Tengger Desert. The results showed that throughfall and stemflow ave-ragely occupied 74.4%, 11.3% and 61.8%, 5.5% of the gross precipitation for C. korshinskii and A. ordosica, respectively. The mean coefficients of variation (CV) of throughfall were 0.25 and 0.30, respectively. C. korshinski were more efficient than A. ordosica on stemflow generation. The depth of soil wetting front around the stem area was greater than other areas under shrub canopy for C. korshinski, and it was only significantly greater under bigger rain events for A. ordosica. The shrub canopy could cause the unevenness of soil wetting front under the canopy in consequence of rainfall redistribution induced by xerophytic shrub.

  6. [Effects of target tree tending on community structure and diversity in subtropical natural secondary shrubs].

    Science.gov (United States)

    Zhang, Hui; Zhou, Guo Mo; Bai, Shang Bin; Wang, Yi Xiang; You, Yu Jie; Zhu, Ting Ting; Zhang, Hua Feng

    2017-05-18

    The typical natural secondary shrub community was chosen in Lin'an of Zhejiang Pro-vince to discover its possibility of restoration to arbor forest with three kinds of forest management models being taken, i.e., no care as control, closed forest management and target tree tending. Over four years growth, compared with control, closed forest management significantly increased average DBH and height by 130% and 50%, respectively, while 260% and 110% for target tree tending. In target tree tending plots, larger trees had been emerging with 4.5-8.5 cm diameter class and 4.5-8.5 m height class and formed a new storey of 4 m compared with control. The species biodiversity indexes at shrub layer were significantly increased in closed management plots, and did not decrease in target tree tending plots. Closed forest management did not change the tree species composition, following its previous succession direction. However, target tree tending increased the importance value of target species with the high potential succession direction of mixed coniferous-broadleaved forest. The results revealed that the secondary shrub community with target tree tending achieved more desired goals on DBH and height growth of dominant trees and species composition improvement compared with closed management. If the secondary shrub community could be managed when the operational conditions existed, target tree tending model should be selected to accelerate the restoration of shrub toward arbor forest.

  7. Response of the desert shrub Krameria parvifolia after ten years of chronic gamma irradiation

    International Nuclear Information System (INIS)

    Vollmer, A.T.; Bamberg, S.A.

    1975-01-01

    A northern Mojave Desert shrub community was irradiated by a 137 Cs source for a ten-year period. Leaf and fruit production, cover, and percent live stem of Krameria parvifolia shrubs were found to respond significantly to a radiation gradient with exposure rates ranging from 0.1 to 10 R/day. Fruit and leaf production were greatly reduced at exposures over 6 R/day. Above 7 R/day 16% of the shrubs were dead compared to 1.2% in a non-irradiated area. Reduced cover, density and live stem values indicate a trend toward a lower status of Krameria in the community at cumulative exposures above 25 kR. Observations indicate that an equilibrium in response to irradiation has not yet occurred. Radiosensitivity of K. parvifolia is attributed in part to its phenology. (author)

  8. Response of the desert shrub Krameria parvifolia after ten years of chronic gamma irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Vollmer, A T; Bamberg, S A [California Univ., Los Angeles (USA). Lab. of Nuclear Medicine and Radiation Biology

    1975-12-01

    A northern Mojave Desert shrub community was irradiated by a /sup 137/Cs source for a ten-year period. Leaf and fruit production, cover, and percent live stem of Krameria parvifolia shrubs were found to respond significantly to a radiation gradient with exposure rates ranging from 0.1 to 10 R/day. Fruit and leaf production were greatly reduced at exposures over 6 R/day. Above 7 R/day 16% of the shrubs were dead compared to 1.2% in a non-irradiated area. Reduced cover, density and live stem values indicate a trend toward a lower status of Krameria in the community at cumulative exposures above 25 kR. Observations indicate that an equilibrium in response to irradiation has not yet occurred. Radiosensitivity of K. parvifolia is attributed in part to its phenology.

  9. Role of nurse shrubs for restoration planting of two conifers in southeast of Mu Us Sandland, China.

    Science.gov (United States)

    Tian, Li; Wang, Xiaoan

    2015-01-01

    Two-year-old pine seedlings, Pinus tabulaeformis and Pinus sylvestris were planted under the canopies of three shrub species and in open areas to test for facilitation during seedling establishment in southeast of Mu Us Sandland in northern part of Shaanxi, China. Pine seedlings establishment were assessed three times within three consecutive growing seasons. Height, area and volume of shrubs were measured. Microclimate conditions (light intensity, air temperature and soil temperature and moisture) were recorded in four microhabitats. Near surface light intensity, air temperature and soil temperature were lower under shrubs, which led to higher soil moisture and pine seedlings under the canopy of shrub species. Pine seedlings survival was remarkably higher when planted under the canopy of shrub species (65.7% for P. tabulaeformis and 60.6% for P. sylvestris) as compared with open areas (22.4% for P. tabulaeformis and 38% for P. sylvestris). P. tabulaeformis with shade-tolerance trait expressed high survival of seedlings as compared to that of P. sylvestris seedlings under the canopy of shrub species (Tukey test, P shrub (Caragana korshinskii and Amorpha fruticosa) showed continuously facilitation during moderate drought stress (summer 2012, 2013 and 2014), but dense and small shrub (Caragana korshinskii) reduced the establishment of seedlings possibly for light competition. Salix cheilophila showed a facilitation effect in growing seasons, but the effect of allelopathy led to high mortality of seedlings under their canopy. in addition, two pine growths were not inhibited when planted under three shrubs. In conclusions, nurse-shrub facilitation can be used as an effective restoration strategy in this sandland. However, use of shrubs as nurse plants depends on their canopy structure and ecological impacts; the selection of target species depends on their shade tolerance traits.

  10. Shrub type dominates the vertical distribution of leaf C : N : P stoichiometry across an extensive altitudinal gradient

    Science.gov (United States)

    Zhao, Wenqiang; Reich, Peter B.; Yu, Qiannan; Zhao, Ning; Yin, Chunying; Zhao, Chunzhang; Li, Dandan; Hu, Jun; Li, Ting; Yin, Huajun; Liu, Qing

    2018-04-01

    Understanding leaf stoichiometric patterns is crucial for improving predictions of plant responses to environmental changes. Leaf stoichiometry of terrestrial ecosystems has been widely investigated along latitudinal and longitudinal gradients. However, very little is known about the vertical distribution of leaf C : N : P and the relative effects of environmental parameters, especially for shrubs. Here, we analyzed the shrub leaf C, N and P patterns in 125 mountainous sites over an extensive altitudinal gradient (523-4685 m) on the Tibetan Plateau. Results showed that the shrub leaf C and C : N were 7.3-47.5 % higher than those of other regional and global flora, whereas the leaf N and N : P were 10.2-75.8 % lower. Leaf C increased with rising altitude and decreasing temperature, supporting the physiological acclimation mechanism that high leaf C (e.g., alpine or evergreen shrub) could balance the cell osmotic pressure and resist freezing. The largest leaf N and high leaf P occurred in valley region (altitude 1500 m), likely due to the large nutrient leaching from higher elevations, faster litter decomposition and nutrient resorption ability of deciduous broadleaf shrub. Leaf N : P ratio further indicated increasing N limitation at higher altitudes. Interestingly, drought severity was the only climatic factor positively correlated with leaf N and P, which was more appropriate for evaluating the impact of water status than precipitation. Among the shrub ecosystem and functional types (alpine, subalpine, montane, valley, evergreen, deciduous, broadleaf, and conifer), their leaf element contents and responses to environments were remarkably different. Shrub type was the largest contributor to the total variations in leaf stoichiometry, while climate indirectly affected the leaf C : N : P via its interactive effects on shrub type or soil. Collectively, the large heterogeneity in shrub type was the most important factor explaining the overall leaf C : N : P variations

  11. Does a decade of elevated [CO2] affect a desert perennial plant community?

    Science.gov (United States)

    Newingham, Beth A; Vanier, Cheryl H; Kelly, Lauren J; Charlet, Therese N; Smith, Stanley D

    2014-01-01

    Understanding the effects of elevated [CO2 ] on plant community structure is crucial to predicting ecosystem responses to global change. Early predictions suggested that productivity in deserts would increase via enhanced water-use efficiency under elevated [CO2], but the response of intact arid plant communities to elevated [CO2 ] is largely unknown. We measured changes in perennial plant community characteristics (cover, species richness and diversity) after 10 yr of elevated [CO2] exposure in an intact Mojave Desert community at the Nevada Desert Free-Air CO2 Enrichment (FACE) Facility. Contrary to expectations, total cover, species richness, and diversity were not affected by elevated [CO2]. Over the course of the experiment, elevated [CO2] had no effect on changes in cover of the evergreen C3 shrub, Larrea tridentata; alleviated decreases in cover of the C4 bunchgrass, Pleuraphis rigida; and slightly reduced the cover of C3 drought-deciduous shrubs. Thus, we generally found no effect of elevated [CO2] on plant communities in this arid ecosystem. Extended drought, slow plant growth rates, and highly episodic germination and recruitment of new individuals explain the lack of strong perennial plant community shifts after a decade of elevated [CO2]. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

  12. Cellular-automata model of the dwarf shrubs populations and communities dynamics

    Directory of Open Access Journals (Sweden)

    A. S. Komarov

    2015-06-01

    Full Text Available The probabilistic cellular-automata model of development and long-time dynamics of dwarf shrub populations and communities is developed. It is based on the concept of discrete description of the plant ontogenesis and joint model approaches in terms of probabilistic cellular automata and L-systems by Lindenmayer. Short representation of the basic model allows evaluation of the approach and software implementation. The main variables of the model are a number of partial bushes in clones or area projective cover. The model allows us to investigate the conditions of self-maintenance and sustainability population under different environmental conditions (inaccessibility of the territory for settlement, mosaic moisture conditions of soil and wealth. The model provides a forecast of the total biomass dynamics shrubs and their fractions (stems, leaves, roots, fine roots, fruits on the basis of the data obtained in the discrete description of ontogenesis and further information on the productivity of the plant fractions. The inclusion of the joint dynamics of biomass of shrubs and soil in EFIMOD models cycle of carbon and nitrogen to evaluate the role of shrubs in these circulations, especially at high impact, such as forest fires and clear cutting, allow forecasting of the dynamics of populations and ecosystem functions of shrubs (regulation of biogeochemical cycles maintaining biodiversity, participation in the creation of non-wood products with changing climatic conditions and strong damaging effects (logging, fires; and application of the models developed to investigate the stability and productivity of shrubs and their participation in the cycle of carbon and nitrogen in different climatic and edaphic conditions.

  13. Effects of shrub and tree cover increase on the near-surface atmosphere in northern Fennoscandia

    Directory of Open Access Journals (Sweden)

    J. H. Rydsaa

    2017-09-01

    Full Text Available Increased shrub and tree cover in high latitudes is a widely observed response to climate change that can lead to positive feedbacks to the regional climate. In this study we evaluate the sensitivity of the near-surface atmosphere to a potential increase in shrub and tree cover in the northern Fennoscandia region. We have applied the Weather Research and Forecasting (WRF model with the Noah-UA land surface module in evaluating biophysical effects of increased shrub cover on the near-surface atmosphere at a fine resolution (5.4 km  ×  5.4 km. Perturbation experiments are performed in which we prescribe a gradual increase in taller vegetation in the alpine shrub and tree cover according to empirically established bioclimatic zones within the study region. We focus on the spring and summer atmospheric response. To evaluate the sensitivity of the atmospheric response to inter-annual variability in climate, simulations were conducted for two contrasting years, one warm and one cold. We find that shrub and tree cover increase leads to a general increase in near-surface temperatures, with the highest influence seen during the snowmelt season and a more moderate effect during summer. We find that the warming effect is stronger in taller vegetation types, with more complex canopies leading to decreases in the surface albedo. Counteracting effects include increased evapotranspiration, which can lead to increased cloud cover, precipitation, and snow cover. We find that the strength of the atmospheric feedback is sensitive to snow cover variations and to a lesser extent to summer temperatures. Our results show that the positive feedback to high-latitude warming induced by increased shrub and tree cover is a robust feature across inter-annual differences in meteorological conditions and will likely play an important role in land–atmosphere feedback processes in the future.

  14. Sparse trees and shrubs confers a high biodiversity to pastures: Case study on spiders from Transylvania.

    Science.gov (United States)

    Gallé, Róbert; Urák, István; Nikolett, Gallé-Szpisjak; Hartel, Tibor

    2017-01-01

    The integration of food production and biodiversity conservation represents a key challenge for sustainability. Several studies suggest that even small structural elements in the landscape can make a substantial contribution to the overall biodiversity value of the agricultural landscapes. Pastures can have high biodiversity potential. However, their intensive and monofunctional use typically erodes its natural capital, including biodiversity. Here we address the ecological value of fine scale structural elements represented by sparsely scattered trees and shrubs for the spider communities in a moderately intensively grazed pasture in Transylvania, Eastern Europe. The pasture was grazed with sheep, cattle and buffalo (ca 1 Livestock Unit ha-1) and no chemical fertilizers were applied. Sampling sites covered the open pasture as well as the existing fine-scale heterogeneity created by scattered trees and shrub. 40 sampling locations each being represented by three 1 m2 quadrats were situated in a stratified design while assuring spatial independency of sampling locations. We identified 140 species of spiders, out of which 18 were red listed and four were new for the Romanian fauna. Spider species assemblages of open pasture, scattered trees, trees and shrubs and the forest edge were statistically distinct. Our study shows that sparsely scattered mature woody vegetation and shrubs substantially increases the ecological value of managed pastures. The structural complexity provided by scattered trees and shrubs makes possible the co-occurrence of high spider diversity with a moderately high intensity grazing possible in this wood-pasture. Our results are in line with recent empirical research showing that sparse trees and shrubs increases the biodiversity potential of pastures managed for commodity production.

  15. Recent expansion of erect shrubs in the Low Arctic: evidence from Eastern Nunavik

    International Nuclear Information System (INIS)

    Tremblay, Benoît; Lévesque, Esther; Boudreau, Stéphane

    2012-01-01

    In order to characterize shrub response near the treeline in Eastern Nunavik (Québec), a region under extensive warming since the 1990s, we compared two series (1964 and 2003) of vertical aerial photos from the vicinity of Kangiqsualujjuaq. Our study revealed a widespread increase in erect woody vegetation cover. During the 40 years spanning the two photo series, erect shrub and tree cover increased markedly on more than half of the land surface available for new colonization or infilling. Within the 7.2 km 2 analysed, areas with dense shrub and tree cover (>90%) increased from 34% to 44% whereas areas with low cover (<10%) shrank from 45% to 29%. This increase in cover of trees and shrubs occurred throughout the landscape regardless of altitude, slope angle and exposure, although to varying extents. The main shrub species involved in this increase was Betula glandulosa Michx. (dwarf birch), which was present in 98% and dominant in 85% of the 345 plots. In addition, numerous seedlings and saplings of Larix laricina (Du Roi) K Koch (eastern larch) were found above the treeline (25% of the plots), suggesting that the altitudinal treeline might shift upslope in the near future. Sites that remained devoid of erect woody vegetation in 2003 were either characterized by the absence of a suitable seedbed or by harsh local microclimatic conditions (wind exposure or excessive drainage). Our results indicate dramatic increases in shrub and tree cover at a Low Arctic site in Eastern Nunavik, contributing to a growing number of observations of woody vegetation change from various areas around the North. (letter)

  16. Age distributions of Greenlandic dwarf shrubs support concept of negligible actuarial senescence

    DEFF Research Database (Denmark)

    Dahlgren, Johan; Rizzi, Silvia; Schweingruber, Fritz

    2016-01-01

    shrub species from 863 taproot samples collected in coastal east Greenland. Penalized composite link models (pclm) were used to fill gaps in the observed age ranges, caused by low species-specific sample sizes in relation to life span. Resulting distributions indicate that mortality patterns...... are independent of age. Actuarial senescence is thus negligible in these dwarf shrub populations. We suggest that smoothing techniques such as pclm enable consideration of noisy age data for determining age distributions. These distributions may, in turn, reveal age effects on demographic rates. Moreover, age...

  17. Environmental Limits of Tall Shrubs in Alaska’s Arctic National Parks

    Science.gov (United States)

    Swanson, David K.

    2015-01-01

    We sampled shrub canopy volume (height times area) and environmental factors (soil wetness, soil depth of thaw, soil pH, mean July air temperature, and typical date of spring snow loss) on 471 plots across five National Park Service units in northern Alaska. Our goal was to determine the environments where tall shrubs thrive and use this information to predict the location of future shrub expansion. The study area covers over 80,000 km2 and has mostly tundra vegetation. Large canopy volumes were uncommon, with volumes over 0.5 m3/m2 present on just 8% of plots. Shrub canopy volumes were highest where mean July temperatures were above 10.5°C and on weakly acid to neutral soils (pH of 6 to 7) with deep summer thaw (>80 cm) and good drainage. On many sites, flooding helped maintain favorable soil conditions for shrub growth. Canopy volumes were highest where the typical snow loss date was near 20 May; these represent sites that are neither strongly wind-scoured in the winter nor late to melt from deep snowdrifts. Individual species varied widely in the canopy volumes they attained and their response to the environmental factors. Betula sp. shrubs were the most common and quite tolerant of soil acidity, cold July temperatures, and shallow thaw depths, but they did not form high-volume canopies under these conditions. Alnus viridis formed the largest canopies and was tolerant of soil acidity down to about pH 5, but required more summer warmth (over 12°C) than the other species. The Salix species varied widely from S. pulchra, tolerant of wet and moderately acid soils, to S. alaxensis, requiring well-drained soils with near neutral pH. Nearly half of the land area in ARCN has mean July temperatures of 10.5 to 12.5°C, where 2°C of warming would bring temperatures into the range needed for all of the potential tall shrub species to form large canopies. However, limitations in the other environmental factors would probably prevent the formation of large shrub canopies

  18. Soil surface temperatures reveal moderation of the urban heat island effect by trees and shrubs

    DEFF Research Database (Denmark)

    Edmondson, Jill L; Stott, Iain; Davies, Zoe G

    2016-01-01

    months increased by 0.6 °C over the 5 km from the city outskirts to the centre. Trees and shrubs in non-domestic greenspace reduced mean maximum daily soil surface temperatures in the summer by 5.7 °C compared to herbaceous vegetation, but tended to maintain slightly higher temperatures in winter. Trees...... in domestic gardens, which tend to be smaller, were less effective at reducing summer soil surface temperatures. Our findings reveal that the UHI effects soil temperatures at a city-wide scale, and that in their moderating urban soil surface temperature extremes, trees and shrubs may help to reduce...

  19. Behavior of pyrophite shrubs in mediterranean terrestrial ecosystems (i): Population and reproductive model.

    Science.gov (United States)

    Usó-Doménech, Josep-Lluis; Nescolarde-Selva, Josué-Antonio; Lloret-Climent, Miguel; González-Franco, Lucía

    2018-03-01

    The mathematical submodel ULEX is used to study the dynamic behavior of the green, floral and woody biomass of the main pyrophite shrub species, the gorse (Ulex parviflorus Pourret), and its relationship with other shrub species, typical of a Mediterranean ecosystem. The focus are the ecological conditions of post-fire stage growth, and its efficacy as a protective cover against erosion processes in the short, medium and long term, both in normal conditions and at the limits of desertification conditions. The model sets a target to observe the behavior and to anticipate and consequently intervene with adequate protection, restoration and management measures. Copyright © 2018 Elsevier Inc. All rights reserved.

  20. Does sex matter? Gender-specificity and its influence on site-chronologies in the common dioecious shrub Juniperus communis

    NARCIS (Netherlands)

    Shetti, Rohan; Buras, Allan; Smiljanic, Marko; Hallinger, Martin; Grigoriev, Andrey A.; Wilmking, Martin

    2018-01-01

    In recent years an increasing number of studies have shown shrubs to be reliable proxies of environmental conditions in regions where Trees − due to harsh climate conditions − are absent. Although many shrubs are monoecious, some are dioecious, which poses certain questions related to

  1. Effects of Width, Edge and Habitat on the Abundance and Nesting Success of Scrub-shrub Birds in Powerline Corridors

    Science.gov (United States)

    David I. King; Richard B. Chandler; Jeffrey M. Collins; Wayne R. Petersen; Thomas E. Lautzenheiser

    2009-01-01

    Concern about declines in scrub–shrub bird populations has resulted in efforts to create and maintain habitat for these species. Vegetation within powerline corridors is managed to prevent contact of vegetation with transmission lines, and comprises approximately 2% of all of habitat for scrub–shrub birds in southern New England. Although previous studies have...

  2. Dwarf shrub and grass vegetation resistant to long-term experimental warming while microarthropod abundance declines on the Falkland Islands

    NARCIS (Netherlands)

    Bokhorst, S.; Convey, P.; Huiskes, A.; Aerts, R.; Huiskes, A.

    2017-01-01

    Dwarf shrubs are a dominant plant type across many regions of the Earth and have hence a large impact on carbon and nutrient cycling rates. Climate change impacts on dwarf shrubs have been extensively studied in the Northern Hemisphere, and there appears to be large variability in response between

  3. Force of habit: shrubs, trees and contingent evolution of wood anatomical diversity using Croton (Euphorbiaceae) as a model system

    Science.gov (United States)

    Rafael Arévalo; Benjamin W. van Ee; Ricarda Riina; Paul E. Berry; Alex C. Wiedenhoeft

    2017-01-01

    Background and Aims Wood is a major innovation of land plants, and is usually a central component of the body plan for two major plant habits: shrubs and trees. Wood anatomical syndromes vary between shrubs and trees, but no prior work has explicitly evaluated the contingent evolution of wood anatomical diversity in the context...

  4. The role of rodents in the seed fate of a thorny shrub in an ancient wood pasture

    NARCIS (Netherlands)

    Scheper, Jeroen; Smit, Christian

    2011-01-01

    Thorny shrubs play a crucial role for the diversity and dynamics in wood pastures: they protect non-defended plants from large herbivores and thus facilitate tree establishment in the landscape through associational resistance. How thorny shrubs themselves establish in wood pastures - the main

  5. The effect of the halophytic shrub Lycium ruthenium (Mutt) on selected soil properties of a desert ecosystem in central Iran

    Science.gov (United States)

    Gholam Ali Jalali; Hossein Akbarian; Charles Rhoades; Hamed Yousefzadeh

    2012-01-01

    We compared soil properties beneath naturally-occurring patches of Lycium ruthenicum Murray (fam. Solanaceae) to evaluate the shrub’s potential to improve the fertility of saline soils. Soil pH, total nitrogen and carbon and extractable potassium, magnesium and phosphorus were respectively significantly higher in the A and B horizons of Lycium shrub patches...

  6. Effect of industrial air pollution on decorative trees and shrubs in the area of the Nitrogen Fertilizer Factory at Pulawy

    Energy Technology Data Exchange (ETDEWEB)

    Kawecka, A

    1973-01-01

    This paper discusses the effects that the gaseous wastes from a nitrogen fertilizer plant have on decorative trees and shrubs. It lists 28 species of broadleaved trees and shrubs, and assigns them to four groups according to their resistance or susceptibility to the pollution. 6 references.

  7. Growing Shrubs at the George O. White State Forest Nursery: What Has Worked and What Has Not

    Science.gov (United States)

    Gregory Hoss

    2006-01-01

    At the George O. White State Forest Nursery in Licking, MO, we annually grow about 20 species of shrubs. That number has been larger in some years. For most species, we purchase seeds locally and process them at our nursery. Our shrubs are used for wetland restoration, windbreaks, visual screens, riparian buffers, and wildlife plantings.

  8. Tree and shrub expansion over the past 34 years at the tree-line near Abisko, Sweden.

    Science.gov (United States)

    Rundqvist, Sara; Hedenås, Henrik; Sandström, Anneli; Emanuelsson, Urban; Eriksson, Håkan; Jonasson, Christer; Callaghan, Terry V

    2011-09-01

    Shrubs and trees are expected to expand in the sub-Arctic due to global warming. Our study was conducted in Abisko, sub-arctic Sweden. We recorded the change in coverage of shrub and tree species over a 32- to 34-year period, in three 50 x 50 m plots; in the alpine-tree-line ecotone. The cover of shrubs and trees (tree stems (> or =3.5 cm) were noted and positions determined. There has been a substantial increase of cover of shrubs and trees, particularly dwarf birch (Betula nana), and mountain birch (Betula pubescens ssp. czerepanovii), and an establishment of aspen (Populus tremula). The other species willows (Salix spp.), juniper (Juniperus communis), and rowan (Sorbus aucuparia) revealed inconsistent changes among the plots. Although this study was unable to identify the causes for the change in shrubs and small trees, they are consistent with anticipated changes due to climate change and reduced herbivory.

  9. Lizard community structure across a grassland - creosote bush ecotone in the Chihuahuan Desert

    OpenAIRE

    Menke, Sean B

    2003-01-01

    I investigated the distribution and abundance of lizard species (Aspidoscelis inornatus, Aspidoscelis tesselatus, Aspidoscelis tigris, Aspidoscelis uniparens, Cophosaurus texanus, Crotaphytus collaris, Eumeces obsoletus, Gambelia wislizenii, Holbrookia maculata, Phrynosoma cornutum, Sceloporus magister, and Uta stansburiana) across a desert grassland - creosote bush (Larrea tridentata) ecotone in Dona Ana County, New Mexico. The ecotonal area in the Jomada del Muerto basin has increased drama...

  10. Realistic Bomber Training Initiative. Environmental Impact Statement. Volume 1

    Science.gov (United States)

    2000-01-01

    arizonica Bitterweed Hymenoxys odorata Black grama Bouteloua eriopoda Broadleaf milkweed Ascelpias latifolia Broomweed Amphiachyris spp. and...Larrea tridentata Douglas fir Pseudotsuga menziesii Fragrant ash Fraxinus cuspidata Galleta grass Hilaria jamesii Gambel (=shin) oak Quercus gambelii...Guajillo Acacia berlandieri Juniper Juniperus spp. Little bluestem Schizachyrium scoparium Live oak Quercus turbinella Mesquite Prosopis spp. Mexican

  11. Seasonal Distribution and Diversity of Ground Arthropods in Microhabitats Following a Shrub Plantation Age Sequence in Desertified Steppe

    Science.gov (United States)

    Liu, Rentao; Zhu, Fan; Song, Naiping; Yang, Xinguo; Chai, Yongqing

    2013-01-01

    In desertified regions, shrub-dominated patches are important microhabitats for ground arthropod assemblages. As shrub age increases, soil, vegetation and microbiological properties can change remarkably and spontaneously across seasons. However, relatively few studies have analyzed how ground arthropods respond to the microhabitats created by shrubs of different plantation ages across seasons. Using 6, 15, 24 and 36 year-old plantations of re-vegetated shrubs (Caragana koushinskii) in the desert steppe of northwestern China as a model system, we sampled ground arthropod communities using a pitfall trapping method in the microhabitats under shrubs and in the open areas between shrubs, during the spring, summer and autumn. The total ground arthropod assemblage was dominated by Carabidae, Melolonthidae, Curculionidae, Tenebrionidae and Formicidae that were affected by plantation age, seasonal changes, or the interaction between these factors, with the later two groups also influenced by microhabitat. Overall, a facilitative effect was observed, with more arthropods and a greater diversity found under shrubs as compared to open areas, but this was markedly affected by seasonal changes. There was a high degree of similarity in arthropod assemblages and diversity between microhabitats in summer and autumn. Shrub plantation age significantly influenced the distribution of the most abundant groups, and also the diversity indices of the ground arthropods. However, there was not an overall positive relationship between shrub age and arthropod abundance, richness or diversity index. The influence of plantation age on arthropod communities was also affected by seasonal changes. From spring through summer to autumn, community indices of ground arthropods tended to decline, and a high degree of similarity in these indices (with fluctuation) was observed among different ages of shrub plantation in autumn. Altogether the recovery of arthropod communities was markedly affected by

  12. The response of Arctic vegetation to the summer climate: relation between shrub cover, NDVI, surface albedo and temperature

    Energy Technology Data Exchange (ETDEWEB)

    Blok, Daan; Heijmans, Monique M P D; Berendse, Frank [Nature Conservation and Plant Ecology Group, Wageningen University, PO Box 47, 6700 AA, Wageningen (Netherlands); Schaepman-Strub, Gabriela [Institute of Evolutionary Biology and Environmental Studies, University of Zuerich, Winterthurerstrasse 190, 8057 Zuerich (Switzerland); Bartholomeus, Harm [Centre for Geo-Information, Wageningen University, PO Box 47, 6700 AA, Wageningen (Netherlands); Maximov, Trofim C, E-mail: daan.blok@wur.nl [Biological Problems of the Cryolithozone, Russian Academy of Sciences, Siberian Division, 41, Lenin Prospekt, Yakutsk, The Republic of Sakha, Yakutia 677980 (Russian Federation)

    2011-07-15

    Recently observed Arctic greening trends from normalized difference vegetation index (NDVI) data suggest that shrub growth is increasing in response to increasing summer temperature. An increase in shrub cover is expected to decrease summer albedo and thus positively feed back to climate warming. However, it is unknown how albedo and NDVI are affected by shrub cover and inter-annual variations in the summer climate. Here, we examine the relationship between deciduous shrub fractional cover, NDVI and albedo using field data collected at a tundra site in NE Siberia. Field data showed that NDVI increased and albedo decreased with increasing deciduous shrub cover. We then selected four Arctic tundra study areas and compiled annual growing season maximum NDVI and minimum albedo maps from MODIS satellite data (2000-10) and related these satellite products to tundra vegetation types (shrub, graminoid, barren and wetland tundra) and regional summer temperature. We observed that maximum NDVI was greatest in shrub tundra and that inter-annual variation was negatively related to summer minimum albedo but showed no consistent relationship with summer temperature. Shrub tundra showed higher albedo than wetland and barren tundra in all four study areas. These results suggest that a northwards shift of shrub tundra might not lead to a decrease in summer minimum albedo during the snow-free season when replacing wetland tundra. A fully integrative study is however needed to link results from satellite data with in situ observations across the Arctic to test the effect of increasing shrub cover on summer albedo in different tundra vegetation types.

  13. Why Be a Shrub? A Basic Model and Hypotheses for the Adaptive Values of a Common Growth Form

    Science.gov (United States)

    Götmark, Frank; Götmark, Elin; Jensen, Anna M.

    2016-01-01

    Shrubs are multi-stemmed short woody plants, more widespread than trees, important in many ecosystems, neglected in ecology compared to herbs and trees, but currently in focus due to their global expansion. We present a novel model based on scaling relationships and four hypotheses to explain the adaptive significance of shrubs, including a review of the literature with a test of one hypothesis. Our model describes advantages for a small shrub compared to a small tree with the same above-ground woody volume, based on larger cross-sectional stem area, larger area of photosynthetic tissue in bark and stem, larger vascular cambium area, larger epidermis (bark) area, and larger area for sprouting, and faster production of twigs and canopy. These components form our Hypothesis 1 that predicts higher growth rate for a small shrub than a small tree. This prediction was supported by available relevant empirical studies (14 publications). Further, a shrub will produce seeds faster than a tree (Hypothesis 2), multiple stems in shrubs insure future survival and growth if one or more stems die (Hypothesis 3), and three structural traits of short shrub stems improve survival compared to tall tree stems (Hypothesis 4)—all hypotheses have some empirical support. Multi-stemmed trees may be distinguished from shrubs by more upright stems, reducing bending moment. Improved understanding of shrubs can clarify their recent expansion on savannas, grasslands, and alpine heaths. More experiments and other empirical studies, followed by more elaborate models, are needed to understand why the shrub growth form is successful in many habitats. PMID:27507981

  14. The response of Arctic vegetation to the summer climate: relation between shrub cover, NDVI, surface albedo and temperature

    International Nuclear Information System (INIS)

    Blok, Daan; Heijmans, Monique M P D; Berendse, Frank; Schaepman-Strub, Gabriela; Bartholomeus, Harm; Maximov, Trofim C

    2011-01-01

    Recently observed Arctic greening trends from normalized difference vegetation index (NDVI) data suggest that shrub growth is increasing in response to increasing summer temperature. An increase in shrub cover is expected to decrease summer albedo and thus positively feed back to climate warming. However, it is unknown how albedo and NDVI are affected by shrub cover and inter-annual variations in the summer climate. Here, we examine the relationship between deciduous shrub fractional cover, NDVI and albedo using field data collected at a tundra site in NE Siberia. Field data showed that NDVI increased and albedo decreased with increasing deciduous shrub cover. We then selected four Arctic tundra study areas and compiled annual growing season maximum NDVI and minimum albedo maps from MODIS satellite data (2000-10) and related these satellite products to tundra vegetation types (shrub, graminoid, barren and wetland tundra) and regional summer temperature. We observed that maximum NDVI was greatest in shrub tundra and that inter-annual variation was negatively related to summer minimum albedo but showed no consistent relationship with summer temperature. Shrub tundra showed higher albedo than wetland and barren tundra in all four study areas. These results suggest that a northwards shift of shrub tundra might not lead to a decrease in summer minimum albedo during the snow-free season when replacing wetland tundra. A fully integrative study is however needed to link results from satellite data with in situ observations across the Arctic to test the effect of increasing shrub cover on summer albedo in different tundra vegetation types.

  15. EFFECTS OF PLANT SIZE ON PHOTOSYNTHESIS AND WATER RELATIONS IN THE DESERT SHRUB PROSOPIS GLANDULOSA (FABACEAE)

    Science.gov (United States)

    The Jornada del Muerto basin of the Chihuahuan Desert of southern New Mexico, USA, has undergone a marked transition of plant communities. Shrubs such as mesquite (Prosopis glandulosa) have greatly increased or now dominate in areas that were previously dominated by perennial gra...

  16. Rapid root extension during water pulses enhances establishment of shrub seedlings in the Atacama Desert

    NARCIS (Netherlands)

    Leon, M.F.; Squeo, F.A.; Gutierrez, J.R.; Holmgren, M.

    2011-01-01

    Questions: (1) What is the water threshold for shrub seedling establishment in arid scrubland? (2) How do seedling root growth morphological traits affect the water threshold required for seedling establishment? Location: Arid scrubland, Atacama Desert, north-central Chile. Methods: We conducted a

  17. Physical characteristics of shrub and conifer fuels for fire behavior models

    Science.gov (United States)

    Jonathan R. Gallacher; Thomas H. Fletcher; Victoria Lansinger; Sydney Hansen; Taylor Ellsworth; David R. Weise

    2017-01-01

    The physical properties and dimensions of foliage are necessary inputs for some fire spread models. Currently, almost no data exist on these plant characteristics to fill this need. In this report, we measured the physical properties and dimensions of the foliage from 10 live shrub and conifer fuels throughout a 1-year period. We developed models to predict relative...

  18. Establishment of trees and shrubs on lands disturbed by mining in the West

    Science.gov (United States)

    Ardell J. Bjugstad

    1984-01-01

    Increased research and development of cultural practices and species has assured success of establishment of trees and shrubs on lands disturbed by surface mining. Trickle irrigation and water harvesting techniques have increased survival of planted stock by 250 percent for some species.

  19. Bayesian estimation of shrubs diversity in rangelands under two management systems in northern Syria

    NARCIS (Netherlands)

    Niane, A.A.; Singh, M.; Struik, P.C.

    2014-01-01

    The diversity of shrubs in rangelands of northern Syria is affected by the grazing management systems restricted by the increase in human and livestock populations. To describe and estimate diversity and compare the rangeland grazing management treatments, two popular indices for diversity, the

  20. Interacting effects of grass height and herbivores on the establishment of an encroaching savanna shrub

    NARCIS (Netherlands)

    Hagenah, N.; Munkert, H.; Gerhardt, K.; Olff, H.

    2009-01-01

    Shrub encroachment is a widely observed problem in Southern African savannas. Although the effects of herbivory and grass height on woody species recruitment have been studied individually, little information exists about how these factors interact. In this study seeds and seedlings of the

  1. Diversity, composition and density of trees and shrubs in agroforestry homegardens in Southern Ethiopia

    NARCIS (Netherlands)

    Abebe, T.; Sterck, F.J.; Wiersum, K.F.; Bongers, F.

    2013-01-01

    Diversity of trees and shrubs in agricultural systems contributes to provision of wood and non-wood products, and protects the environment, thereby, enhancing socioeconomic and ecological sustainability of the systems. This study characterizes the diversity, density and composition of trees in the

  2. Efficacy of exclosures in conserving local shrub biodiversity in xeric sandy grassland, Inner Mongolia, China

    Science.gov (United States)

    Feng-Rui Li; Zhi-Yu Zhou; Li-Ya Zhao; Ai-Sheng Zhang; Ling-Fen Kang

    2007-01-01

    This study investigated the abundance and frequency of occurrence of all shrub species present in the standing vegetation at four sites, including a 5-year exclosure (protected grassland) and three adjacent unprotected grazing sites that had been subjected to different levels of degradation (light, moderate and severe), in xeric sandy grassland of Inner Mongolia for...

  3. Similar tree seedling responses to shrubs and to simulated environmental changes at Pyrenean and subarctic treelines.

    NARCIS (Netherlands)

    Grau, O.; Ninot, J.M.; Cornelissen, J.H.C.; Callaghan, T.V.

    2013-01-01

    Background: Climate, land-use and disturbance regimes are key drivers of treeline dynamics worldwide, but local and regional spatio-temporal patterns indicate that additional factors play an important role. Some studies suggest that shrub-tree interactions control tree seedling recruitment patterns

  4. Natural polyploidization within tetraploid and hexaploid populations of the desert shrub Atriplex confertifolia

    Science.gov (United States)

    Stewart C. Sanderson

    2011-01-01

    Shadscale (Atriplex confertifolia) is a wind-pollinated dioecious shrub of western North America with an unusual development of apparently autoploid races, showing all even ploidy levels from 2x to 12x (base x = 9). Of these, tetraploid races are the most frequently encountered, with octoploids the next most common, and hexaploids being much less common. In this study...

  5. Age and distribution of an evergreen clonal shrub in the Coweeta basin: Rhododendron maximum L

    Science.gov (United States)

    Katherine J. Elliott; James M. Vose

    2012-01-01

    Rhododendron maximum L. is an evergreen, clonal shrub that forms a dominant sub-canopy layer and is a key species in southern Appalachian forests. We investigated the age and distribution of R. maximum across the Coweeta Basin, a 1626 ha watershed in western North Carolina. We selected 16 perennial, second-order streams and used a Global Positioning System to establish...

  6. Targeted grazing for the restoration of sub-alpine shrub-encroached grasslands

    Directory of Open Access Journals (Sweden)

    Massimiliano Probo

    2016-12-01

    Full Text Available The decline of agro-pastoral activities has led to a widespread tree and shrub-encroachment of former semi-natural meso-eutrophic grasslands in many European mountain regions. Temporary night camp areas (TNCA and mineral mix supplements for targeted cattle were arranged over shrub-encroached areas to restore grassland vegetation within the Val Troncea Natural Park (Italy. From 2011 to 2015, their effects on vegetation structure and pastoral value of forage were assessed along permanent transects. Four years after treatments, both practices were effective in reducing the shrub cover and increasing the cover and average height of the herbaceous layer, but changes were more remarkable within TNCA. Moreover, the arrangement of TNCA decreased the cover of nanophanerophytes and increased the cover of graminoids and high quality species, as well as the overall forage pastoral value. In conclusion, TNCA were the most effective pastoral practice to contrast shrub-encroachment and increase herbage mass and forage quality of sub-alpine grasslands.

  7. Removing an exotic shrub from riparian forests increases butterfly abundance and diversity

    Science.gov (United States)

    James Hanula; Scott Horn

    2011-01-01

    Invasive plants are one of the greatest threats to endangered insect species and a major threat to Lepidoptera in eastern North America. We investigated the effects of the invasive shrub Chinese privet (Ligustrum sinense) and two methods (mulching or hand-felling) of removing it from riparian forests on butterfly communities and compared them to untreated, heavily...

  8. Possibilities of cultivating ornamental trees and shrubs under conditions of air pollution with oxides of sulfur

    Energy Technology Data Exchange (ETDEWEB)

    Bialobok, S.; Bartkowiak, S.; Rachwal, L.

    1974-01-01

    The field work conducted has shown that high concentrations of SO/sub 2/ in the air can be withstood by the following trees and shrubs. Trees: Acer campestris, A. platanoides, Ailanthus altissima, Aesculus hippocastanum, Morus alba, Platanus acerifolia, Pinus strobur, P. nigra, Populus Berolinensis, P. candicans, P. Hybr. 27, P. Marilandica, P. simonii, P. Serotina, Quercus robus, Robinia pseudoacacia. Shrubs: Caragana arborescens, Crataegus oxyacantha, C. monogyna, Cerasus mehaleb, Forsythia/most of the species and varieties/, Ligustrum vulgare, Philadelphus coronaria, Ptelea trifoliata, Sambucus nigra, Salix caprea, Sorbaria sorbifolia, Sorbus aucuparia, Taxus baccata. For the selection of trees and shrubs in the laboratory, high concentrations of SO/sub 2/ were used (60-150 ppm for a period of 10 minutes). Experiments were conducted on cut shrubs kept in the gas chambers. In order to estimate the degree of their injury, they were transferred to a shaded greenhouse. A concentration of 65 ppm of SO/sub 2/ could be withstood by the following Forsythias: Forsythia intermedia Primulina, F. Densiflora, F. Spectabilis, F. giraldina, F. suspensa, F. koreana, F. ovata, F. japonica and Hippophae rhamnoides. A concentration of 130 ppm could be withstood only by F. intermedia Vitelina. A similarly high concentration of SO/sub 2/ could be withstood by shoots and leaves of Ailanthus girladii Duclouxii and by Platanus acerifolia. From among the lilacs Syringa pekinensis and S. amurensis proved resistant to high concentrations of SO/sub 2/.

  9. Trophic cascades: linking ungulates to shrub-dependent birds and butterflies.

    Science.gov (United States)

    J Teichman, Kristine; Nielsen, Scott E; Roland, Jens

    2013-11-01

    1. Studies demonstrating trophic cascades through the loss of top-down regulatory processes in productive and biologically diverse terrestrial ecosystems are limited. 2. Elk Island National Park, Alberta and surrounding protected areas have a wide range of ungulate density due to the functional loss of top predators, management for high ungulate numbers and variable hunting pressure. This provides an ideal setting for studying the effects of hyper-abundant ungulates on vegetation and shrub-dependent bird and butterfly species. 3. To examine the cascading effects of high ungulate density, we quantified vegetation characteristics and abundances of yellow warbler Dendroica petechia and Canadian tiger swallowtail Papilio canadensis under different ungulate density in and around Elk Island National Park. 4. Using Structural Equation Models we found that ungulate density was inversely related to shrub cover, whereas shrub cover was positively related to yellow warbler abundance. In addition, chokecherry Prunus virginiana abundance was inversely related to browse impact but positively related to P. canadensis abundance. 5. These results demonstrate a cascade resulting from hyper-abundant ungulates on yellow warblers and Canadian tiger swallowtails through reductions in shrub cover and larval host plant density. The combined effect of the functional loss of top predators and management strategies that maintain high ungulate numbers can decouple top-down regulation of productive temperate ecosystems. © 2013 The Authors. Journal of Animal Ecology © 2013 British Ecological Society.

  10. Soil carbon dioxide (CO 2 ) efflux of two shrubs in response to plant ...

    African Journals Online (AJOL)

    Although plant density should affect soil carbon dioxide (CO2) efflux and carbon cycling in semi-arid regions, the effects of plant density on soil CO2 efflux are not well known. This study was performed to investigate the responses of soil CO2 efflux of two dominant shrubs (Caragana korshinkii and Salix psammophila) to ...

  11. Antecedent conditions influence soil respiration differences in shrub and grass patches

    Science.gov (United States)

    Quantifying the response of soil respiration to past environmental conditions is critical for predicting how future climate and vegetation change will impact ecosystem carbon balance. Increased shrub dominance in semiarid grasslands has potentially large effects on soil carbon cycling. The goal of t...

  12. Evaluation and prediction of shrub cover in coastal Oregon forests (USA)

    Science.gov (United States)

    Becky K. Kerns; Janet L. Ohmann

    2004-01-01

    We used data from regional forest inventories and research programs, coupled with mapped climatic and topographic information, to explore relationships and develop multiple linear regression (MLR) and regression tree models for total and deciduous shrub cover in the Oregon coastal province. Results from both types of models indicate that forest structure variables were...

  13. State-space modeling indicates rapid invasion of an alien shrub in coastal dunes

    DEFF Research Database (Denmark)

    Damgaard, Christian Frølund; Nygaard, Bettina; Ejrnæs, Rasmus

    2011-01-01

    allows separation of process and sampling variance, thus enabling ecological predictions with a known degree of uncertainty. The method is applied for the invasive shrub Rosa rugosa (Japanese rose) in Danish fixed dunes. The probability of observing R. rugosa increased significantly from 0.18 to 0...

  14. Influence of shrub cover vegetal and slope length on soil bulk density

    International Nuclear Information System (INIS)

    Bienes, R.; Jimenez, R.; Ruiz, M.; Garcia-Estringana, P.; Marques, M. J.

    2009-01-01

    In arid and semiarid environments of the Mediterranean climate, the shrub species play an important role in the revegetation of abandoned lands, which enables to control the soil losses, organic material and water. In this article are compared the results obtained under different revegetation in abandoned lands in the central area of Spain. In these revegetation has been used two native shrubs: A triplex halimus (Ah) and Retama sphaerocarpa (Rs), and were analyzed the influence of these revegetation in the contents of organic material of soil and apparent density in 5 years time after planting. As control, have been considered the pieces of ground with spontaneous vegetation abandoned in the same date that the shrubs revegetation. Atriplex halimus gives to the soil a covering capable to intercept a big amount of water drops absorbing a great amount part of the kinetic energy of the rain, while provides a microclimates as a result of be able to soften the wind, the temperature and the evaporation-transpiration, which makes it efficient to control the erosion and the desertification (Le Houerou, 2000). Retama sphaerocarpa was chosen because it is a native shrub very characteristic, and, due to its symbiosis with the Bradyrhizobium, enriches the soil in nitrogen, which is taken by the nitrophilous species enhancing the spontaneous vegetal covering. (Author) 9 refs.

  15. Guide to insect borers in North American broadleaf trees and shrubs

    Science.gov (United States)

    J.D. Solomon

    1995-01-01

    This book is an illustrated guide to 300 species of inset borers that attack hardwood trees, shrubs, and other woody angiosperms in North America. The major purposes of this guide are to identify insect borers and theri damage to provide information for controlling them. Readers most likely to find this guide useful are practiving foresters, entomologists, and others...

  16. Shrub removal in reforested post-fire areas increases native plant species richness

    Science.gov (United States)

    Gabrielle N. Bohlman; Malcolm North; Hugh D. Safford

    2016-01-01

    Large, high severity fires are becoming more prevalent in Sierra Nevada mixed-conifer forests, largely due to heavy fuel loading and forest densification caused by past and current management practices. In post-fire areas distant from seed trees, conifers are often planted to re-establish a forest and to prevent a potential type-conversion to shrub fields. Typical...

  17. Insects and Related Pests of Trees, Shrubs, and Lawns. MP-25R.

    Science.gov (United States)

    Spackman, Everett W.; Lawson, Fred A.

    This document discusses identification and control of the pests of trees and shrubs. The insects are grouped according to feeding habits and the type of damage caused to plants. Categories include the sucking insects and mites, leaf eating insects, pests attacking trunks and branches, and gall causing insects. (CS)

  18. Which shrubs and trees can conserve natural enemies of aphids in spring?

    NARCIS (Netherlands)

    van Rijn, P.C.J.

    2014-01-01

    Habitats with shrubs and trees within the agricultural landscape may contribute to the maintenance of natural enemies of pests. Aphids and flowers are important resources for beneficial natural enemies such as ladybeetles, hoverflies and lacewings. Woody plants are the most likely candidates to

  19. Nitrogen-addition effects on leaf traits and photosynthetic carbon gain of boreal forest understory shrubs.

    Science.gov (United States)

    Palmroth, Sari; Bach, Lisbet Holm; Nordin, Annika; Palmqvist, Kristin

    2014-06-01

    Boreal coniferous forests are characterized by fairly open canopies where understory vegetation is an important component of ecosystem C and N cycling. We used an ecophysiological approach to study the effects of N additions on uptake and partitioning of C and N in two dominant understory shrubs: deciduous Vaccinium myrtillus in a Picea abies stand and evergreen Vaccinium vitis-idaea in a Pinus sylvestris stand in northern Sweden. N was added to these stands for 16 and 8 years, respectively, at rates of 0, 12.5, and 50 kg N ha(-1) year(-1). N addition at the highest rate increased foliar N and chlorophyll concentrations in both understory species. Canopy cover of P. abies also increased, decreasing light availability and leaf mass per area of V. myrtillus. Among leaves of either shrub, foliar N content did not explain variation in light-saturated CO2 exchange rates. Instead photosynthetic capacity varied with stomatal conductance possibly reflecting plant hydraulic properties and within-site variation in water availability. Moreover, likely due to increased shading under P. abies and due to water limitations in the sandy soil under P. sylvestris, individuals of the two shrubs did not increase their biomass or shift their allocation between above- and belowground parts in response to N additions. Altogether, our results indicate that the understory shrubs in these systems show little response to N additions in terms of photosynthetic physiology or growth and that changes in their performance are mostly associated with responses of the tree canopy.

  20. Seed germination methods for native Caribbean trees and shrubs : with emphasis on species relevant for Bonaire

    NARCIS (Netherlands)

    Burg, van der W.J.; Freitas, J.; Debrot, A.O.

    2014-01-01

    This paper is intended as a basis for nature restoration activities using seeds of trees and (larger) shrubs native to Bonaire with the aim of reforestation. It describes the main seed biology issues relevant for species from this region, to facilitate decisions on time and stage of harvesting, safe

  1. Facilitation of Quercus ilex recruitment by shrubs in Mediterranean open woodlands

    NARCIS (Netherlands)

    Smit, Christian; den Ouden, Jan; Diaz, Mario

    Question: Insufficient tree regeneration threatens the long-term persistence of biodiverse Mediterranean open oak woodlands. Could shrubs, scarce due to decades of management ( clearing and ploughing), facilitate holm oak recruitment at both acorn and seedling stages? Location: Open oak woodlands in

  2. Facilitation of Quercus ilex recruitment by shrubs in Mediterranean open woodlands

    NARCIS (Netherlands)

    Smit, C.; Ouden, den J.; Diaz, M.

    2008-01-01

    Question: Insufficient tree regeneration threatens the long-term persistence of biodiverse Mediterranean open oak woodlands. Could shrubs, scarce due to decades of management (clearing and ploughing), facilitate holm oak recruitment at both acorn and seedling stages? Location: Open oak woodlands in

  3. Diseases of Ornamental and Shade Trees, Shrubs, Vines, and Ground Covers.

    Science.gov (United States)

    Nichols, Lester P.

    This agriculture extension service publication from Pennsylvania State University covers the identification and control of common ornamental trees, shrubs, and ground cover diseases. The publication is divided into sections. The first section discusses the diseases of ornamental and shade trees, including general diseases and diseases of specific…

  4. Community structure affects annual grass weed invasion during restoration of a shrub-steppe ecosystem

    Science.gov (United States)

    Phil S. Allen; Susan E. Meyer

    2014-01-01

    Ecological restoration of shrub-steppe communities in the western United States is often hampered by invasion of exotic annual grasses during the process. An important question is how to create restored communities that can better resist reinvasion by these weeds. One hypothesis is that communities comprised of species that are functionally similar to the invader will...

  5. Spacing and shrub competition influence 20-year development of planted ponderosa pine

    Science.gov (United States)

    William W. Oliver

    1990-01-01

    Growth and stand development of ponderosa pine (Pinus ponderosa) were monitored for 20 years after planting at five different square spacings (6, 9, 12, 15, and 18 ft) in the presence or absence of competing shrubs on the westside Sierra Nevada. Mean tree size was positively correlated and stand values negatively correlated with spacing in the...

  6. Tree and shrub species integration in the crop-livestock farming ...

    African Journals Online (AJOL)

    Tree and shrub integration has been promoted as a means of enhancing rural livelihoods through sustaining watershed provision of services and products, especially in Ethiopia. However, research to support this effort has been limited. This study was conducted in Borodo watershed in central Ethiopia, to identify ...

  7. Automated classification of tropical shrub species: a hybrid of leaf shape and machine learning approach.

    Science.gov (United States)

    Murat, Miraemiliana; Chang, Siow-Wee; Abu, Arpah; Yap, Hwa Jen; Yong, Kien-Thai

    2017-01-01

    Plants play a crucial role in foodstuff, medicine, industry, and environmental protection. The skill of recognising plants is very important in some applications, including conservation of endangered species and rehabilitation of lands after mining activities. However, it is a difficult task to identify plant species because it requires specialized knowledge. Developing an automated classification system for plant species is necessary and valuable since it can help specialists as well as the public in identifying plant species easily. Shape descriptors were applied on the myDAUN dataset that contains 45 tropical shrub species collected from the University of Malaya (UM), Malaysia. Based on literature review, this is the first study in the development of tropical shrub species image dataset and classification using a hybrid of leaf shape and machine learning approach. Four types of shape descriptors were used in this study namely morphological shape descriptors (MSD), Histogram of Oriented Gradients (HOG), Hu invariant moments (Hu) and Zernike moments (ZM). Single descriptor, as well as the combination of hybrid descriptors were tested and compared. The tropical shrub species are classified using six different classifiers, which are artificial neural network (ANN), random forest (RF), support vector machine (SVM), k-nearest neighbour (k-NN), linear discriminant analysis (LDA) and directed acyclic graph multiclass least squares twin support vector machine (DAG MLSTSVM). In addition, three types of feature selection methods were tested in the myDAUN dataset, Relief, Correlation-based feature selection (CFS) and Pearson's coefficient correlation (PCC). The well-known Flavia dataset and Swedish Leaf dataset were used as the validation dataset on the proposed methods. The results showed that the hybrid of all descriptors of ANN outperformed the other classifiers with an average classification accuracy of 98.23% for the myDAUN dataset, 95.25% for the Flavia dataset and 99

  8. Responses of nocturnal rodents to shrub encroachment in Banni grasslands, Gujarat, India

    Science.gov (United States)

    Jayadevan, A.

    2016-12-01

    Shrub encroachment is one of the greatest threats to grasslands globally. These woodlands can strongly influence the behaviour of small mammals adapted to more open habitats, which rely on high visibility for early detection of predators. In semi-arid grasslands, rodents are considered keystone species. Although shrub encroachment is known to negatively affect rodent assemblages, its impact on the foraging behaviour of rodents, which is known to vary in response to risky situations, is unknown. Understanding whether shrub encroachment alters such antipredator behaviour is important as antipredator behaviour can alter the distribution, abundance and ultimately, survival of prey species. In this study, I explored the effects of shrub encroachment on the foraging behaviour of nocturnal rodent communities in the Banni grasslands, India. I examined foraging behaviour, quantified using the giving-up density (GUD) framework and the number of rodent crossings around food patches, in two habitats that differed in the extent of shrub encroachment. Under the GUD framework, the amount of food left behind by a forager in a food patch reflects the costs of feeding at the patch. Higher GUDs imply higher foraging costs. I also investigated how removal of an invasive woody plant, Prosopis juliflora would affect foraging behaviour of nocturnal rodents. High shrub encroachment was associated with higher foraging costs (higher GUDs) and lower activity than the sparsely wooded habitat, likely due to low visibility in the densely wooded habitat. The dense habitat also supported a higher richness and relative abundance of generalist rodents than the sparse habitat, likely due to the increased heterogeneity of the habitat. The tree removal experiment revealed that rodents had lower GUDs (i.e., low foraging costs) after the event of tree cutting. This may be due to the reduction of cover in the habitat, leading to higher visibility and lower predation risk. My results suggest that shrub

  9. Shrub mound formation and stability on semi-arid slopes in the Northern Negev Desert of Israel: A field and simulation study

    NARCIS (Netherlands)

    Buis, E.; Temme, A.J.A.M.; Veldkamp, A.; Boeken, B.; Jongmans, A.G.; Breemen, van N.; Schoorl, J.M.

    2010-01-01

    In semi-arid areas vegetation is scarce and often dominated by individual shrubs on raised mounds. The processes of formation of these mounds are diverse and still debated. Often, shrub mound formation is directly related to the formation of vegetation patterns, thereby assuming that shrub mound

  10. Spatial and temporal patterns of water availability in a grass-shrub ecotone and implications for grassland recovery in arid environments

    Science.gov (United States)

    Encroachment of woody shrubs into historic desert grasslands is a major problem throughout the world. Conversion of grasslands to shrub-dominated systems may result in significant alteration of biogeochemical processes and reduced resource availability in shrub interspaces, making grassland recover...

  11. Resource-use efficiencies of three indigenous tree species planted in resource islands created by shrubs: implications for reforestation of subtropical degraded shrublands

    Science.gov (United States)

    Nan Liu; Qinfeng Guo

    2012-01-01

    Shrub resource islands are characterized by resources accumulated shrubby areas surrounded by relative barren soils. This research aims to determine resource-use efficiency of native trees species planted on shrub resource islands, and to determine how the planted trees may influence the resource islands in degraded shrublands in South China. Shrub (Rhodomyrtus...

  12. Living with aliens: effects of invasive shrub honeysuckles on avian nesting.

    Directory of Open Access Journals (Sweden)

    Jason M Gleditsch

    Full Text Available Invasive species have come to the forefront of conservation biology as a major threat to native biodiversity. Habitats dominated by shrub honeysuckles (Lonicera spp. in the United States have been characterized as "ecological traps" by ecologists. Here we tested this hypothesis by investigating the effects of shrub honeysuckles on the nesting ecology of native birds in seven study sites in central Pennsylvania, USA. We examined how the abundance of shrub honeysuckles influenced the selection of nesting substrates and habitat for a community of common songbirds, and the parental-care behavior and nestling development of gray catbirds (Dumetella carolinensis. We found that birds had a strong bias towards nesting in honeysuckle shrubs, but not necessarily for nesting in honeysuckle-dominated habitats. Nest predation rates were affected by the density of nests in a habitat, but not by the overall abundance of honeysuckles in such habitats. Honeysuckle abundance in the habitat did show significant effects on some parental-care behavioral parameters: catbirds had higher nest visitation rates and shorter visit lengths in areas of high honeysuckle density. On average, Gray catbirds fed fruit 12%±0.31 s.e. of their nestling-feeding bouts, mostly fruits of shrub honeysuckles. Nestlings in sites with high honeysuckle density also showed higher mass:tarsus ratios, suggesting a good (possibly better physiological condition of catbird nestlings at the time of fledging. Our study shows that honeysuckle-dominated habitats could have equivocal effects on nesting parameters of common species of native birds. We advise more caution in the widespread denomination of novel plant communities with high densities of honeysuckle as "ecological traps" as effects can be null or positive on native birds in certain localities.

  13. Plant-soil interactions promote co-occurrence of three nonnative woody shrubs.

    Science.gov (United States)

    Kuebbing, Sara E; Classen, Aimée T; Call, Jaime J; Henning, Jeremiah A; Simberloff, Daniel

    2015-08-01

    Ecosystems containing multiple nonnative plant species are common, but mechanisms promoting their co-occurrence are understudied. Plant-soil interactions contribute to the dominance of singleton species in nonnative ranges because many nonnatives experience stronger positive feedbacks relative to co-occurring natives. Plant-soil interactions could impede other nonnatives if an individual nonnative benefits from its soil community to a greater extent than its neighboring nonnatives, as is seen with natives. However, plant-soil interactions could promote nonnative co-occurrence if a nonnative accumulates beneficial soil mutualists that also assist other nonnatives. Here, we use greenhouse and field experiments to ask whether plant-soil interactions (1) promote the codominance of two common nonnative shrubs (Ligustrum sinense and Lonicera maackii) and (2) facilitate the invasion of a less-common nonnative shrub (Rhamnus davurica) in deciduous forests of the southeastern United States. In the greenhouse, we found that two of the nonnatives, L. maackii and R. davurica, performed better in soils conditioned by nonnative shrubs compared to uninvaded forest soils, which. suggests that positive feedbacks among co-occurring nonnative shrubs can promote continued invasion of a site. In both greenhouse and field experiments, we found consistent signals that the codominance of the nonnatives L. sinense and L. maackii may be at least partially explained by the increased growth of L. sinense in L. maackii soils. Overall, significant effects of plant-soil interactions on shrub performance indicate that plant-soil interactions can potentially structure the co-occurrence patterns of these nonnatives.

  14. Is the WBE model appropriate for semi-arid shrubs subjected to clear cutting?

    Science.gov (United States)

    Issoufou, Hassane Bil-Assanou; Rambal, Serge; Le Dantec, Valérie; Oï, Monique; Laurent, Jean-Paul; Saadou, Mahamane; Seghieri, Josiane

    2015-02-01

    It is crucial to understand the adaptive mechanisms of woody plants facing periodic drought to assess their vulnerability to the increasing climate variability predicted in the Sahel. Guiera senegalensis J.F.Gmel is a semi-evergreen Combretaceae commonly found in Sahelian rangelands, fallows and crop fields because of its value as an agroforestry species. We compared canopy leafing, and allometric measurements of leaf area, stem area and stem length and their relationships with leaf water potential, stomatal conductance (gs) and soil-to-leaf hydraulic conductance (KS-L), in mature and current-year resprouts of G. senegalensis in Sahelian Niger. In mature shrubs, seasonal drought reduced the ratio of leaf area to cross-sectional stem area (AL : AS), mainly due to leaf shedding. The canopy of the current-year resprouts remained permanently leafed as the shrubs produced leaves and stems continuously, and their AL : AS ratio increased throughout the dry season. Their KS-L increased, whereas gs decreased. West, Brown and Enquist's (WBE) model can thus describe allometric trends in the seasonal life cycle of undisturbed mature shrubs, but not that of resprouts. Annual clear cutting drives allometric scaling relationships away from theoretical WBE predictions in the current-year resprouts, with scaling exponents 2.5 times greater than those of mature shrubs. High KS-L (twice that of mature shrubs) supports this intensive regeneration process. The adaptive strategy described here is probably common to many woody species that have to cope with both severe seasonal drought and regular disturbance over the long term. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  15. The evolution of dwarf shrubs in alpine environments: a case study of Alchemilla in Africa.

    Science.gov (United States)

    Gehrke, Berit; Kandziora, Martha; Pirie, Michael D

    2016-01-01

    Alpine and arctic environments worldwide, including high mountains, are dominated by short-stature woody plants (dwarf shrubs). This conspicuous life form asserts considerable influence on local environmental conditions above the treeline, creating its own microhabitat. This study reconstructs the evolution of dwarf shrubs in Alchemilla in the African tropical alpine environment, where they represent one of the largest clades and are among the most common and abundant plants. Different phylogenetic inference methods were used with plastid and nuclear DNA sequence markers, molecular dating (BEAST and RelTime), analyses of diversification rate shifts (MEDUSA and BAMM) and ancestral character and area reconstructions (Mesquite). It is inferred that African Alchemilla species originated following long-distance dispersal to tropical East Africa, but that the evolution of dwarf shrubs occurred in Ethiopia and in tropical East Africa independently. Establishing a timeframe is challenging given inconsistencies in age estimates, but it seems likely that they originated in the Pleistocene, or at the earliest in the late Miocene. The adaptation to alpine-like environments in the form of dwarf shrubs has apparently not led to enhanced diversification rates. Ancestral reconstructions indicate reversals in Alchemilla from plants with a woody base to entirely herbaceous forms, a transition that is rarely reported in angiosperms. Alchemilla is a clear example of in situ tropical alpine speciation. The dwarf shrub life form typical of African Alchemilla has evolved twice independently, further indicating its selective advantage in these harsh environments. However, it has not influenced diversification, which, although recent, was not rapid. © The Author 2015. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  16. Are biological effects of desert shrubs more important than physical effects on soil microorganisms?

    Science.gov (United States)

    Berg, Naama; Steinberger, Yosef

    2010-01-01

    Vegetation cover plays a major role in providing organic matter and in acting as a physical barrier, with both together contributing to the formation of "fertile islands," which play an active role in prolonging biological activity in desert ecosystems. By undertaking this study, a longterm research, we designed an experiment to separate the two components-the physical and biotic parts of the perennial plants-and to identify the factor that contributes the most to the ecosystem. The study site was located in the northern Negev Desert, Israel, where 50 Hammada scoparia shrubs and 50 artificial plants were randomly marked. Soil samples were collected monthly over 3 years of research at three locations: under the canopy of H. scoparia shrubs, in the vicinity of the artificial plants, and between the shrubs (control). The contribution to microbial activity was measured by evaluation of the microbial community functions in soil. The functional aspects of the microbial community that were measured were CO2 evolution, microbial biomass, microbial functional diversity, and the physiological profile of the community. The results of this study are presented in two ways: (1) according to the three locations/treatments; and (2) according to the phenological situation of the vegetation (annual and perennial plants) in the research field: the growing phase, the drying process, and the absence of annual plants. The only parameters that were found to affect microbial activity were the contribution of the organic matter of perennial shrubs and the growth of vegetation (annual and perennial) during the growing seasons. The physical component was found to have no effect on soil microbial functional diversity, which elucidates the important contribution of the desert shrub in enhancing biological multiplicity and activity.

  17. Summer warming and changes in snow depth is reflected in the growth rings of Alaskan tundra shrubs (Toolik Lake)

    Science.gov (United States)

    Buchwal, A.; Welker, J. M.

    2016-12-01

    Arctic change is being manifested by shifts in the vegetation composition and abundance throughout many regions of the Arctic. These changes are primarily reflected by increases in shrub growth and density, but the extent to which shrub growth is expressed in greater shrub ring width and the degree to which natural and experimental warming correspond and or whether the secondary effect of deeper snow in winter acts to alter shrub ring growh and or shrub biomass is yet to be determined for Arctic Alaska. In order to explore growth response of arctic shrubs to on-going and predicted temperature and snow depth increase we investigated shrubs' annual growth rings using dendrochronological methods applied to plants growing under control and experimental treatments in Toolik Lake, Northern Alaska. Specifically we evaluated the effects of a 20-year experimental warming (due to open top chambers, OTC's) and snow depth increases on the growth rings pattern of two common shrub species of Northern Alaska, i.e. Betula nana and Salix pulchra. By applying a serial sectioning method patterns of annual growth were investigated across the entire plant including below-ground parts. Moreover this procedure allowed for a complete cross-dating and a detection of irregular radial growth, including common missing and partially missing rings. We found that the natural warming in Alaska occurring over the past 20 years is stimulating shrub ring growth, more so for Betula than for Salix. Experimental warming (simulating conditions in approximately 2030) stimulated the secondary growth ratio; however the allocation pattern between below-ground and above-ground is quite variable between individual shrubs. In addition, annual growth rings analyses were supplemented by quantitative wood anatomy properties, such as vessel size and density. Our findings indicate that there can be differential growth ring responses of deciduous shrubs to natural climate warming, that growth ring increases reflect

  18. Impacts of the removal of shrubs on the physiological and biochemical characteristics of Syntrichia caninervis Mitt: in a temperate desert.

    Science.gov (United States)

    Yin, Ben-Feng; Zhang, Yuan-Ming; Lou, An-Ru

    2017-04-04

    Moss crusts play important roles in biological soil crusts biomass and soil surface stabilization. However, because of increasingly intensive human activities, especially grazing, the growth and survival of shrubs are seriously threatened. This study aimed to test whether the presence of shrubs affects the physiological state of the bryophyte Syntrichia caninervis Mitt. in this desert ecosystem. We simulated animal-grazed shrubs at three levels in the Gurbantunggut Desert and compared these simulations to exposed areas, measuring the indicators of growth and stress tolerance exhibited by bryophytes. The results showed that the removal of shrubs significantly decreased chlorophyll fluorescence activity and soluble protein content in S. caninervis, especially under the total shrub removal treatment. The ratio between the total removal of shrubs and other treatments in antioxidative enzymes and in osmotic adjustment substances of S. caninervis exhibited two types of responses. With the exception of malonyldialdehyde (MDA) and superoxide dismutase (SOD), the variables examined fitted as downward parabolic then upward parabolic temporal dynamics. The removal of shrubs is harmful to the survival of S.caninervis. In resource-constrained conditions, SOD is an important antioxidant enzyme that of peroxidase (POD), catalase (CAT) and osmotic adjustment substances, for S. caninervis survival.

  19. Agave salmiana Plant Communities in Central Mexico as Affected by Commercial Use

    Science.gov (United States)

    Martínez Salvador, Martin; Mata-González, Ricardo; Morales Nieto, Carlos; Valdez-Cepeda, Ricardo

    2012-01-01

    Agave salmiana is a native plant species harvested for the commercial production of mezcal ( Agave spirits) in the highlands of central Mexico. The objective of this study was to identify vegetation changes in natural communities where A. salmiana has been differentially harvested for commercial purposes. Three plant community categories were identified in the state of Zacatecas based on their history of A. salmiana utilization: short (less than 10 years of use), moderate (about 25 years), and long (60 or more years). Species cover, composition, and density were evaluated in field surveys by use category. A gradient of vegetation structure of the communities parallels the duration of A. salmiana use. A. salmiana density was greatest (3,125 plants ha-1) in the short-use areas and less (892 plants ha-1) in the moderate-use areas, associated with markedly greater density of shrubs (200%) and Opuntia spp. (50%) in moderate-use areas. The main shrubs were Larrea tridentata, Mimosa biuncifera, Jatropha dioica and Buddleia scordioides while the main Opuntia species were Opuntia leucotricha and Opuntia robusta. A. salmiana density was least (652 plants ha-1) in the long-use areas where shrubs were less abundant but Opuntia spp. density was 25% higher than in moderate-use areas. We suggest that shrubs may increase with moderate use creating an intermediate successional stage that facilitates the establishment of Opuntia spp. Long-term Agave use is generating new plant communities dominated by Opuntia spp. (nopaleras) as a replacement of the original communities dominated by A. salmiana (magueyeras).

  20. Rapid carbon turnover beneath shrub and tree vegetation is associated with low soil carbon stocks at a subarctic treeline.

    Science.gov (United States)

    Parker, Thomas C; Subke, Jens-Arne; Wookey, Philip A

    2015-05-01

    Climate warming at high northern latitudes has caused substantial increases in plant productivity of tundra vegetation and an expansion of the range of deciduous shrub species. However significant the increase in carbon (C) contained within above-ground shrub biomass, it is modest in comparison with the amount of C stored in the soil in tundra ecosystems. Here, we use a 'space-for-time' approach to test the hypothesis that a shift from lower-productivity tundra heath to higher-productivity deciduous shrub vegetation in the sub-Arctic may lead to a loss of soil C that out-weighs the increase in above-ground shrub biomass. We further hypothesize that a shift from ericoid to ectomycorrhizal systems coincident with this vegetation change provides a mechanism for the loss of soil C. We sampled soil C stocks, soil surface CO2 flux rates and fungal growth rates along replicated natural transitions from birch forest (Betula pubescens), through deciduous shrub tundra (Betula nana) to tundra heaths (Empetrum nigrum) near Abisko, Swedish Lapland. We demonstrate that organic horizon soil organic C (SOCorg ) is significantly lower at shrub (2.98 ± 0.48 kg m(-2) ) and forest (2.04 ± 0.25 kg m(-2) ) plots than at heath plots (7.03 ± 0.79 kg m(-2) ). Shrub vegetation had the highest respiration rates, suggesting that despite higher rates of C assimilation, C turnover was also very high and less C is sequestered in the ecosystem. Growth rates of fungal hyphae increased across the transition from heath to shrub, suggesting that the action of ectomycorrhizal symbionts in the scavenging of organically bound nutrients is an important pathway by which soil C is made available to microbial degradation. The expansion of deciduous shrubs onto potentially vulnerable arctic soils with large stores of C could therefore represent a significant positive feedback to the climate system. © 2014 John Wiley & Sons Ltd.

  1. Detecting the differences in responses of stomatal conductance to moisture stresses between deciduous shrubs and Artemisia subshrubs.

    Science.gov (United States)

    Gao, Qiong; Yu, Mei; Zhou, Chan

    2013-01-01

    Shrubs and subshrubs can tolerate wider ranges of moisture stresses in both soil and air than other plant life forms, and thus represent greater nonlinearity and uncertainty in ecosystem physiology. The objectives of this paper are to model shrub/subshrub stomatal conductance by synthesizing the field leaf gas exchanges data of 24 species in China, in order to detect the differences between deciduous shrubs and Artemisia subshrubs in their responses of stomatal conductance to changes in the moisture stresses. We revised a model of stomatal conductance by incorporating the tradeoff between xylem hydraulic efficiency and cavitation loss risk. We then fit the model at the three hierarchical levels: global (pooling all data as a single group), three functional groups (deciduous non-legume shrubs, deciduous legume shrubs, and subshrubs in Artemisia genus), and individual observations (species × sites). Bayesian inference with Markov Chain Monte Carlo method was applied to obtain the model parameters at the three levels. We found that the model at the level of functional groups is a significant improvement over that at the global level, indicating the significant differences in the stomatal behavior among the three functional groups. The differences in tolerance and sensitivities to changes in moisture stresses are the most evident between the shrubs and the subshrubs: The two shrub groups can tolerate much higher soil water stress than the subshrubs. The analysis at the observation level is also a significant improvement over that at the functional group level, indicating great variations within each group. Our analysis offered a clue for the equivocal issue of shrub encroachment into grasslands: While the invasion by the shrubs may be irreversible, the dominance of subshrubs, due to their lower resistance and tolerance to moisture stresses, may be put down by appropriate grassland management.

  2. Vegetation ecology and carbon sequestration potential of shrubs in tropics of Chhattisgarh, India.

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    Jhariya, Manoj Kumar

    2017-09-25

    Tropical forests are well known to have great species diversity and contribute substantial share in terrestrial carbon (C) stocks worldwide. Shrubs are long-neglected life form in the forest ecosystem, playing many roles in the forest and human life. Shrub has great impact on vegetation attributes which in turn modify the C storage and capture. In the present investigation, an attempt has been made to explore the dynamics of shrub species in four fire regimes, viz. high, medium, low, and no fire zones of Bhoramdeo Wildlife Sanctuary of Kawardha forest division (Chhattisgarh), India. The variations in structure, diversity, biomass, productivity, and C sequestration potential in all the sites were quantified. The density and basal area of shrub varied from 1250 to 3750 individuals ha -1 and 2.79 to 4.92 m 2  ha -1 , respectively. The diversity indices showed that the value of Shannon index was highest in medium fire zone (3.77) followed by high, low, and no fire zones as 3.25, 3.12, and 2.32, respectively. The value of Simpson's index or concentration of dominance (Cd) ranged from 0.08 to 0.20, species richness from 0.56 to 1.58, equitability from 1.41 to 1.44, and beta diversity from 1.50 to 4.20, respectively. The total biomass and C storage ranged from 6.82 to 15.71 and from 2.93 to 6.76 t ha -1 , respectively. The shrub density, importance value index (IVI), and abundance to frequency ratio (A/F) significantly correlated between high fire and medium fire zone. The basal area was found to be significantly positively correlated between high fire and medium fire, and low and no fire zones, respectively. Two-way cluster analysis reflected various patterns of clustering due to influence of the forest fire which showed that some species have distant clustering while some have smaller cluster. Principal component analysis (PCA) reflects variable scenario with respect to shrub layer. Ventilago calyculata and Zizyphus rotundifolia showed higher correlation between

  3. Co-occurring nonnative woody shrubs have additive and non-additive soil legacies.

    Science.gov (United States)

    Kuebbing, Sara E; Patterson, Courtney M; Classen, Aimée T; Simberloff, Daniel

    2016-09-01

    To maximize limited conservation funds and prioritize management projects that are likely to succeed, accurate assessment of invasive nonnative species impacts is essential. A common challenge to prioritization is a limited knowledge of the difference between the impacts of a single nonnative species compared to the impacts of nonnative species when they co-occur, and in particular predicting when impacts of co-occurring nonnative species will be non-additive. Understanding non-additivity is important for management decisions because the management of only one co-occurring invader will not necessarily lead to a predictable reduction in the impact or growth of the other nonnative plant. Nonnative plants are frequently associated with changes in soil biotic and abiotic characteristics, which lead to plant-soil interactions that influence the performance of other species grown in those soils. Whether co-occurring nonnative plants alter soil properties additively or non-additively relative to their effects on soils when they grow in monoculture is rarely addressed. We use a greenhouse plant-soil feedback experiment to test for non-additive soil impacts of two common invasive nonnative woody shrubs, Lonicera maackii and Ligustrum sinense, in deciduous forests of the southeastern United States. We measured the performance of each nonnative shrub, a native herbaceous community, and a nonnative woody vine in soils conditioned by each shrub singly or together in polyculture. Soils conditioned by both nonnative shrubs had non-additive impacts on native and nonnative performance. Root mass of the native herbaceous community was 1.5 times lower and the root mass of the nonnative L. sinense was 1.8 times higher in soils conditioned by both L. maackii and L. sinense than expected based upon growth in soils conditioned by either shrub singly. This result indicates that when these two nonnative shrubs co-occur, their influence on soils disproportionally favors persistence

  4. Examining the role of shrub expansion and fire in Arctic plant silica cycling

    Science.gov (United States)

    Carey, J.; Fetcher, N.; Parker, T.; Rocha, A. V.; Tang, J.

    2017-12-01

    All terrestrial plants accumulate silica (SiO2) to some degree, although the amount varies by species type, functional group, and environmental conditions. Silica improves overall plant fitness, providing protection from a variety of biotic and abiotic stressors. Plant silica uptake serves to retain silica in terrestrial landscapes, influencing silica export rates from terrestrial to marine systems. These export rates are important because silica is often the limiting nutrient for primary production by phytoplankton in coastal waters. Understanding how terrestrial plant processes influence silica export rates to oceanic systems is of interest on the global scale, but nowhere is this issue more important than in the Arctic, where marine diatoms rely on silica for production in large numbers and terrestrial runoff largely influences marine biogeochemistry. Moreover, the rapid rate of change occurring in the Arctic makes understanding plant silica dynamics timely, although knowledge of plant silica cycling in the region is in its infancy. This work specifically examines how shrub expansion, permafrost thaw, and fire regimes influence plant silica behavior in the Alaskan Arctic. We quantified silica accumulation in above and belowground portions of three main tundra types found in the Arctic (wet sedge, moist acidic, moist non-acidic tundra) and scaled these values to estimate how shrub expansion alters plant silica accumulation rates. Results indicate that shrub expansion via warming will increase silica storage in Arctic land plants due to the higher biomass associated with shrub tundra, whereas conversion of tussock to wet sedge tundra via permafrost thaw would produce the opposite effect in the terrestrial plant BSi pool. We also examined silica behavior in plants exposed to fire, finding that post-fire growth results in elevated plant silica uptake. Such changes in the size of the terrestrial vegetation silica reservoir could have direct consequences for the rates

  5. Ecosystem response to removal of exotic riparian shrubs and a transition to upland vegetation

    Science.gov (United States)

    Reynolds, Lindsay V.; Cooper, David J.

    2011-01-01

    Understanding plant community change over time is essential for managing important ecosystems such as riparian areas. This study analyzed historic vegetation using soil seed banks and the effects of riparian shrub removal treatments and channel incision on ecosystem and plant community dynamics in Canyon de Chelly National Monument, Arizona. We focused on how seeds, nutrients, and ground water influence the floristic composition of post-treatment vegetation and addressed three questions: (1) How does pre-treatment soil seed bank composition reflect post-treatment vegetation composition? (2) How does shrub removal affect post-treatment riparian vegetation composition, seed rain inputs, and ground water dynamics? and (3) Is available soil nitrogen increased near dead Russian olive plants following removal and does this influence post-treatment vegetation? We analyzed seed bank composition across the study area, analyzed differences in vegetation, ground water levels, and seed rain between control, cut-stump and whole-plant removal areas, and compared soil nitrogen and vegetation near removed Russian olive to areas lacking Russian olive. The soil seed bank contained more riparian plants, more native and fewer exotic plants than the extant vegetation. Both shrub removal methods decreased exotic plant cover, decreased tamarisk and Russian olive seed inputs, and increased native plant cover after 2 years. Neither method increased ground water levels. Soil near dead Russian olive trees indicated a short-term increase in soil nitrogen following plant removal but did not influence vegetation composition compared to areas without Russian olive. Following tamarisk and Russian olive removal, our study sites were colonized by upland plant species. Many western North American rivers have tamarisk and Russian olive on floodplains abandoned by channel incision, river regulation or both. Our results are widely applicable to sites where drying has occurred and vegetation

  6. Nutrient foraging strategies are associated with productivity and population growth in forest shrubs

    Science.gov (United States)

    Stone, Bram W. G.; Faillace, Cara A.; Lafond, Jonathan J.; Baumgarten, Joni M.; Mozdzer, Thomas J.; Dighton, John; Meiners, Scott J.; Grabosky, Jason C.; Ehrenfeld, Joan G.

    2017-01-01

    Background and Aims Temperate deciduous forest understoreys are experiencing widespread changes in community composition, concurrent with increases in rates of nitrogen supply. These shifts in plant abundance may be driven by interspecific differences in nutrient foraging (i.e. conservative vs. acquisitive strategies) and, thus, adaptation to contemporary nutrient loading conditions. This study sought to determine if interspecific differences in nutrient foraging could help explain patterns of shrub success and decline in eastern North American forests. Methods Using plants grown in a common garden, fine root traits associated with nutrient foraging were measured for six shrub species. Traits included the mean and skewness of the root diameter distribution, specific root length (SRL), C:N ratio, root tissue density, arbuscular mycorrhizal colonization and foraging precision. Above- and below-ground productivity were also determined for the same plants, and population growth rates were estimated using data from a long-term study of community dynamics. Root traits were compared among species and associations among root traits, measures of productivity and rates of population growth were evaluated. Key Results Species fell into groups having thick or thin root forms, which correspond to conservative vs. acquisitive nutrient foraging strategies. Interspecific variation in root morphology and tissue construction correlated with measures of productivity and rates of cover expansion. Of the four species with acquisitive traits, three were introduced species that have become invasive in recent decades, and the fourth was a weedy native. In contrast, the two species with conservative traits were historically dominant shrubs that have declined in abundance in eastern North American forests. Conclusions In forest understoreys of eastern North America, elevated nutrient availability may impose a filter on species success in addition to above-ground processes such as herbivory

  7. Reproduction and vegetative growth in the dioecious shrub Acer barbinerve in temperate forests of Northeast China.

    Science.gov (United States)

    Wang, Juan; Zhang, Chunyu; Gadow, Klaus V; Cheng, Yanxia; Zhao, Xiuhai

    2015-06-01

    Trade-off in dioecious plant. The trade-off between reproduction, vegetative growth and maintenance is a major issue in the life history of an organism and a record of the process which is producing the largest possible number of living offspring by natural selection. Dioecious species afford an excellent opportunity for detecting such possible trade-offs in resource allocation. In this study, we selected the dioecious shrub Acer barbinerve to examine possible trade-offs between reproduction and vegetative growth in both genders at different modular levels during three successive years. Reproductive and vegetative biomass values were assessed during successive years to evaluate their intra-annual and inter-annual trade-offs. These trade-offs were examined at shoot, branch and shrub modular levels in Acer barbinerve shrubs. An intra-annual trade-off was detected at the shoot level for both genders in 2011 and 2012. Both males and females showed a negative correlation between reproduction and vegetative growth, but this was more prominent in males. For the females of the species, inter-annual trade-offs were only found at branch and shrub levels. Slightly negative correlations in females were detected between the reproduction in 2012 and the reproduction in the two previous years. The gender ratio was significantly male biased during the three successive years of our investigation. Females had higher mortality rates in the larger diameter classes, both in 2011 and 2012. This study revealed a clear trade-off between reproduction and vegetative growth in Acer barbinerve, but results varied between males and females. The degree of autonomy of the different modular levels may affect the ability to detect such trade-offs.

  8. Seasonal Dynamics of Water Use Strategy of Two Salix Shrubs in Alpine Sandy Land, Tibetan Plateau.

    Science.gov (United States)

    Zhu, Yajuan; Wang, Guojie; Li, Renqiang

    2016-01-01

    Water is a limiting factor for plant growth and vegetation dynamics in alpine sandy land of the Tibetan Plateau, especially with the increasing frequency of extreme precipitation events and drought caused by climate change. Therefore, a relatively stable water source from either deeper soil profiles or ground water is necessary for plant growth. Understanding the water use strategy of dominant species in the alpine sandy land ecosystem is important for vegetative rehabilitation and ecological restoration. The stable isotope methodology of δD, δ18O, and δ13C was used to determine main water source and long-term water use efficiency of Salix psammophila and S. cheilophila, two dominant shrubs on interdune of alpine sandy land in northeastern Tibetan Plateau. The root systems of two Salix shrubs were investigated to determine their distribution pattern. The results showed that S. psammophila and S. cheilophila absorbed soil water at different soil depths or ground water in different seasons, depending on water availability and water use strategy. Salix psammophila used ground water during the growing season and relied on shallow soil water recharged by rain in summer. Salix cheilophila used ground water in spring and summer, but relied on shallow soil water recharged by rain in spring and deep soil water recharged by ground water in fall. The two shrubs had dimorphic root systems, which is coincident with their water use strategy. Higher biomass of fine roots in S. psammophila and longer fine roots in S. cheilophila facilitated to absorb water in deeper soil layers. The long-term water use efficiency of two Salix shrubs increased during the dry season in spring. The long-term water use efficiency was higher in S. psammophila than in S. cheilophila, as the former species is better adapted to semiarid climate of alpine sandy land.

  9. Tolerance of an expanding subarctic shrub, Betula glandulosa, to simulated caribou browsing.

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    Emilie Champagne

    Full Text Available Densification of the shrub layer has been reported in many subarctic regions, raising questions about the implication for large herbivores and their resources. Shrubs can tolerate browsing and their level of tolerance could be affected by browsing and soils productivity, eventually modifying resource availability for the caribou. Our objective was to assess the compensatory growth potential of a subarctic shrub, Betula glandulosa Michx., in relation with caribou browsing and nutriment availability for the plants. We used a simulated browsing (0, 25 and 75% of available shoots and nitrogen-fertilisation (0 and 10 g m(-2 experiment to test two main hypotheses linking tolerance to resource availability, the Compensatory Continuum Hypothesis and the Growth Rate Hypothesis as well as the predictions from the Limiting Resource Model. We seek to explicitly integrate the relative browsing pressure in our predictions since the amount of tissues removed could affect the capacity of long-lived plants to compensate. Birches fully compensated for moderate browsing with an overall leaf biomass similar to unbrowsed birches but undercompensated under heavy browsing pressure. The main mechanism explaining compensation appears to be the conversion of short shoots into long shoots. The leaf area increased under heavy browsing pressure but only led to undercompensation. Fertilisation for two consecutive years did not influence the response of birch, thus we conclude that our results support the LRM hypothesis of equal tolerance under both high and low nitrogen availability. Our results highlight that the potential for compensatory growth in dwarf birch is surpassed under heavy browsing pressure independently of the fertilisation regime. In the context of the worldwide decline in caribou herds, the reduction in browsing pressure could act synergistically with global climate change to promote the current shrub expansion reported in subarctic regions.

  10. Spatial patterns and natural recruitment of native shrubs in a semi-arid sandy land.

    Science.gov (United States)

    Wu, Bo; Yang, Hongxiao

    2013-01-01

    Passive restoration depending on native shrubs is an attractive approach for restoring desertified landscapes in semi-arid sandy regions. We sought to understand the relationships between spatial patterns of native shrubs and their survival ability in sandy environments. Furthermore, we applied our results to better understand whether passive restoration is feasible for desertified landscapes in semi-arid sandy regions. The study was conducted in the semi-arid Mu Us sandy land of northern China with the native shrub Artemisia ordosica. We analyzed population structures and patterns of A. ordosica at the edges and centers of land patches where sand was stabilized by A. ordosica-dominated vegetation. Saplings were more aggregated than adults, and both were more aggregated at the patch edges than at the patch centers. At the patch edges, spatial association of the saplings with the adults was mostly positive at distances 0.3-6.6 m, and turned from positive to neutral, and even negative, at other distances. At the patch centers, the saplings were spaced almost randomly around the adults, and their distances from the adults did not seem to affect their locations. A greater number of A. ordosica individuals emerged at the patch edges than at the patch centers. Such patterns may have resulted from their integrative adjustment to specific conditions of soil water supply and sand drift intensity. These findings suggest that in semi-arid sandy regions, native shrubs that are well-adapted to local environments may serve as low-cost and competent ecological engineers that can promote the passive restoration of surrounding patches of mobile sandy land.

  11. Shrub type dominates the vertical distribution of leaf C : N : P stoichiometry across an extensive altitudinal gradient

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    W. Zhao

    2018-04-01

    Full Text Available Understanding leaf stoichiometric patterns is crucial for improving predictions of plant responses to environmental changes. Leaf stoichiometry of terrestrial ecosystems has been widely investigated along latitudinal and longitudinal gradients. However, very little is known about the vertical distribution of leaf C : N : P and the relative effects of environmental parameters, especially for shrubs. Here, we analyzed the shrub leaf C, N and P patterns in 125 mountainous sites over an extensive altitudinal gradient (523–4685 m on the Tibetan Plateau. Results showed that the shrub leaf C and C : N were 7.3–47.5 % higher than those of other regional and global flora, whereas the leaf N and N : P were 10.2–75.8 % lower. Leaf C increased with rising altitude and decreasing temperature, supporting the physiological acclimation mechanism that high leaf C (e.g., alpine or evergreen shrub could balance the cell osmotic pressure and resist freezing. The largest leaf N and high leaf P occurred in valley region (altitude 1500 m, likely due to the large nutrient leaching from higher elevations, faster litter decomposition and nutrient resorption ability of deciduous broadleaf shrub. Leaf N : P ratio further indicated increasing N limitation at higher altitudes. Interestingly, drought severity was the only climatic factor positively correlated with leaf N and P, which was more appropriate for evaluating the impact of water status than precipitation. Among the shrub ecosystem and functional types (alpine, subalpine, montane, valley, evergreen, deciduous, broadleaf, and conifer, their leaf element contents and responses to environments were remarkably different. Shrub type was the largest contributor to the total variations in leaf stoichiometry, while climate indirectly affected the leaf C : N : P via its interactive effects on shrub type or soil. Collectively, the large heterogeneity in shrub type was the most

  12. Is the herb-shrub composition of veredas (Brazilian palm swamps distinguishable?

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    Diogo Pereira da Silva

    2017-11-01

    Full Text Available ABSTRACT Vereda (Brazilian palm swamp is a poorly known savannic phytophysiognomy that occurs on moist soils with high herb-shrub floristic richness. This study aimed to document the herb-shrub species of veredas of the Estação Ecológica Serra Geral do Tocantins - EESGTO, and compare this flora with other veredas in Brazil. Furthermore, we assessed the similarity of the herb-shrub flora of the studied veredas with that of inventories of other savannas and grasslands in order to evaluate whether veredas possess an exclusive flora. Ordination analysis was performed to understand the floristic relationship among these areas. We recorded 213 species, 105 genera and 49 families at EESGTO, including five new floral records for the Cerrado and 78 for the state of Tocantins. The floristic similarity among veredas at EESGTO and the other sites was low. For all sites, a total of 1,324 species were recorded, of which 342 were unique to veredas and 187 unique to moist grasslands (campos limpos úmidos. After reviewing databases, 14.3 % of these species remained exclusive to veredas and moist grasslands. The ordination analysis indicated a gradient in floristic composition from wet to dry phytophysiognomies. In conclusion, we recognize a flora that distinguishes veredas from other Cerrado phytophysiognomies.

  13. Weak Evidence of Regeneration Habitat but Strong Evidence of Regeneration Niche for a Leguminous Shrub

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    Delerue, Florian; Gonzalez, Maya; Michalet, Richard; Pellerin, Sylvain; Augusto, Laurent

    2015-01-01

    The identification of an ecological niche specific to the regeneration phase has mobilised significant attention. However, the importance of the regeneration niche concept remains unclear. Our main objective was to study the existence of such a regeneration niche for a leguminous shrub, Ulex europaeus. This study was carried out in southwest France in the context of water and nutrient stresses (mainly phosphorus limitation) due to the presence of nutrient-poor sandy soils. We analysed the regeneration of the species from the germination of seeds and emergence of new seedlings until the seedlings reached young shrub size. Our design included a P fertilisation treatment. We also investigated microsite characteristics (micro-topography and vegetation development) as they can interact with meteorological conditions and determine water availability for seeds and seedlings. We found that P availability controlled seedling growth and the time necessary to reach young shrub size. Water availability appeared to impact the species germination and seedlings survival. We also found that P and water availability depended on the interactions between microsite characteristics and climatic variations. Finally we found evidence that P and water availability are important ecological factors shaping the regeneration niche of the species, but we found weak evidence that any microsite would be appropriate for the regeneration of the species in the long term. Future studies regarding regeneration niches need to distinguish more clearly the ecological factors important for regeneration (the regeneration niche per se) and the physical world where the seedlings appear and develop (the regeneration habitat). PMID:26098877

  14. Weak Evidence of Regeneration Habitat but Strong Evidence of Regeneration Niche for a Leguminous Shrub.

    Directory of Open Access Journals (Sweden)

    Florian Delerue

    Full Text Available The identification of an ecological niche specific to the regeneration phase has mobilised significant attention. However, the importance of the regeneration niche concept remains unclear. Our main objective was to study the existence of such a regeneration niche for a leguminous shrub, Ulex europaeus. This study was carried out in southwest France in the context of water and nutrient stresses (mainly phosphorus limitation due to the presence of nutrient-poor sandy soils. We analysed the regeneration of the species from the germination of seeds and emergence of new seedlings until the seedlings reached young shrub size. Our design included a P fertilisation treatment. We also investigated microsite characteristics (micro-topography and vegetation development as they can interact with meteorological conditions and determine water availability for seeds and seedlings. We found that P availability controlled seedling growth and the time necessary to reach young shrub size. Water availability appeared to impact the species germination and seedlings survival. We also found that P and water availability depended on the interactions between microsite characteristics and climatic variations. Finally we found evidence that P and water availability are important ecological factors shaping the regeneration niche of the species, but we found weak evidence that any microsite would be appropriate for the regeneration of the species in the long term. Future studies regarding regeneration niches need to distinguish more clearly the ecological factors important for regeneration (the regeneration niche per se and the physical world where the seedlings appear and develop (the regeneration habitat.

  15. Convergent production and tolerance among 107 woody species and divergent production between shrubs and trees.

    Science.gov (United States)

    He, Wei-Ming; Sun, Zhen-Kai

    2016-02-08

    Green leaves face two fundamental challenges (i.e., carbon fixation and stress tolerance) during their lifespan. However, the relationships between leaf production potential and leaf tolerance potential have not been explicitly tested with a broad range of plant species in the same environment. To do so, we conducted a field investigation based on 107 woody plants grown in a common garden and complementary laboratory measurements. The values, as measured by a chlorophyll meter, were significantly related to the direct measurements of chlorophyll content on a leaf area basis. Area-based chlorophyll content was positively correlated with root surface area, whole-plant biomass, leaf mass per area (LMA), and force to punch. Additionally, LMA had a positive correlation with force to punch. Shrubs had a higher leaf chlorophyll content than trees; however, shrubs and trees exhibited a similar leaf lifespan, force to punch, and LMA. These findings suggest that the production potential of leaves and their tolerance to stresses may be convergent in woody species and that the leaf production potential may differ between shrubs and trees. This study highlights the possibility that functional convergence and divergence might be linked to long-term selection pressures and genetic constraints.

  16. Growth and defense in deciduous trees and shrubs under UV-B

    International Nuclear Information System (INIS)

    Julkunen-Tiitto, Riitta; Haeggman, Hely; Aphalo, Pedro J.; Lavola, Anu; Tegelberg, Riitta; Veteli, Timo

    2005-01-01

    Reflection by waxy or resinous surface structures and hairs, repair reactions of biomolecules and induction of different sheltering components provide the means of plant protection from harmful solar UV-B radiation. Secondary products, especially flavonoids and phenolic acids as defense components are also important in plant tolerance to UV-B, fulfilling the dual role as screens that reduce UV-B penetration in plant tissues, and as antioxidants protecting from damage by reactive oxidant species. Plants are sensitive to UV-B radiation, and this sensitivity can be even more clone-specific than species-specific. The results available in the literature for deciduous trees and shrubs indicate that UV-B radiation may affect several directions in the interaction of woody species with biotic (herbivores) and abiotic (CO 2 and nutrition) factors depending on the specific interaction in question. These multilevel interactions should have moderate ecological significance via the overall changed performance of woody species and shrubs. - The growth performance of deciduous trees and shrubs under UV-B irradiation is constrained by multilevel interactions with many abiotic and biotic factors

  17. [Ability of typical greenery shrubs of Beijing to adsorb and arrest PM2.5 ].

    Science.gov (United States)

    Liang, Dan; Wang, Bin; Wang, Yun-qi; Zhang, Hui-lan; Yang, Song-nan; Li, Ang

    2014-09-01

    Four typical types of green shrubs of Beijing (Euonymus japonicus, Buxus microphylla, Berberis thunbergii cv. atropurpurea, Taxus cuspidate cv. nana) were selected to study their capacities in adsorbing and arresting PM2.5 using both field observations and air chamber simulations. Concurrently, in order to analyze the pollution characteristics of Beijing in winter and spring, the PM2.5 concentrations of December 2012 to May 2013 were collected. Experimental results showed that: From the gas chamber experiments, the ability to adsorb and arrest PM2.5 was in the order of Berberis thunbergii cv. atropurpurea > Buxus microphylla > Taxus cuspidate cv. nana > Euonymus japonicus, mainly due to the differences in leaf characteristics; Outside measurement results showed that the ability to adsorb and arrest PM2.5 was ranked as Buxus microphylla > Berberis thunbergii cv. atropurpurea > Taxus cuspidate cv. nana > Euonymus japonicus. Chamber simulation and outdoor observation showed that Buxus microphylla and Berberis thunbergii cv. atropurpurea had strong ability to adsorb and arrest PM2.5; Meanwhile, the slight differences between the chamber simulation and outdoor observation results might be related to plant structure. Compared to tree species, the planting condition of shrub species was loose, and it greened quickly; By analyzing the Beijing PM2.5 concentration values in winter and spring, it was found that the PM2.5 concentration was particularly high in the winter of Beijing, and evergreen shrubs maintained the ability to adsorb and arrest PM2.5.

  18. Shrub resprouting response after fuel reduction treatments: comparison of prescribed burning, clearing and mastication.

    Science.gov (United States)

    Fernández, Cristina; Vega, José A; Fonturbel, Teresa

    2013-03-15

    Fuel reduction treatments are commonly used to reduce the risk of severe wildfire. However, more information about the effects on plant resprouting is needed to help land managers select the most appropriate treatment. To address this question, we evaluated the resprouting ability of five shrub species after the application of different types of fuel reduction methods (prescribed burning, clearing and mastication) in two contrasting shrubland areas in northern Spain. The shrub species were Erica australis, Pterospartum tridentatum and Halimium lasianthum spp. alyssoides, Ulex gallii and Erica cinerea. For most of the species under study (E. australis, P. tridentatum, H. lasianthum spp. alyssoides and U. gallii), neither plant mortality nor the number nor length of sprouted shoots per plant differed between treatments, although in E. cinerea the number of shoots was more negatively affected by prescribed burning than by clearing or mastication. The pre-treatment plant size did not affect plant mortality or plant resprouting response, suggesting that this parameter alone is not a good indicator of plant resprouting after fuel reduction treatments. Stem minimum diameter after treatments, a proxy of treatment severity, was not related to plant mortality, number or length of resprouted shoots. The duration of temperatures higher than 300 °C during burning in plant crown had a negative effect on the length of resprouted shoots, only in E. cinerea. The results show that fuel reduction treatments did not prevent shrub response in any case. Some reflections on the applicability of treatments are discussed. Copyright © 2013 Elsevier Ltd. All rights reserved.

  19. Ecophysiological and anatomical characteristics of the subtropical shrub Zanthoxylum acanthopodium (Rutaceae) in conditions of a temperate continental climate (Serbia)

    DEFF Research Database (Denmark)

    Rakic, Tamara; Sinzar-Sekulic, Jasmina; Filipovic, Biljana

    2009-01-01

    The evergreen shrub Zanthoxylum acanthopodium DC. (Rutaceae), originating from warm temperate and subtropical Asia, has existed successfully in the Jevremovac Botanical Garden in Belgrade for more than 80 years. The seasonal pattern of water management in leaves, electrolyte leakage, essential oil...... composition, and leaf anatomy were examined in order to understand the resistance and viability of this subtropical shrub in the temperate continental climate of Belgrade, Serbia....

  20. The potential for mycobiont sharing between shrubs and seedlings to facilitate tree establishment after wildfire at Alaska arctic treeline.

    Science.gov (United States)

    Hewitt, Rebecca E; Chapin, F Stuart; Hollingsworth, Teresa N; Taylor, D Lee

    2017-07-01

    Root-associated fungi, particularly ectomycorrhizal fungi (EMF), are critical symbionts of all boreal tree species. Although climatically driven increases in wildfire frequency and extent have been hypothesized to increase vegetation transitions from tundra to boreal forest, fire reduces mycorrhizal inoculum. Therefore, changes in mycobiont inoculum may potentially limit tree-seedling establishment beyond current treeline. We investigated whether ectomycorrhizal shrubs that resprout after fire support similar fungal taxa to those that associate with tree seedlings that establish naturally after fire. We then assessed whether mycobiont identity correlates with the biomass or nutrient status of these tree seedlings. The majority of fungal taxa observed on shrub and seedling root systems were EMF, with some dark septate endophytes and ericoid mycorrhizal taxa. Seedlings and adjacent shrubs associated with similar arrays of fungal taxa, and there were strong correlations between the structure of seedling and shrub fungal communities. These results show that resprouting postfire shrubs support fungal taxa compatible with tree seedlings that establish after wildfire. Shrub taxon, distance to the nearest shrub and fire severity influenced the similarity between seedling and shrub fungal communities. Fungal composition was correlated with both foliar C:N ratio and seedling biomass and was one of the strongest explanatory variables predicting seedling biomass. While correlative, these results suggest that mycobionts are important to nutrient acquisition and biomass accrual of naturally establishing tree seedlings at treeline and that mycobiont taxa shared by resprouting postfire vegetation may be a significant source of inoculum for tree-seedling establishment beyond current treeline. © 2017 John Wiley & Sons Ltd.

  1. Ungulate browsing maintains shrub diversity in the absence of episodic disturbance in seasonally-arid conifer forest.

    Directory of Open Access Journals (Sweden)

    Burak K Pekin

    Full Text Available Ungulates exert a strong influence on the composition and diversity of vegetation communities. However, little is known about how ungulate browsing pressure interacts with episodic disturbances such as fire and stand thinning. We assessed shrub responses to variable browsing pressure by cattle and elk in fuels treated (mechanical removal of fuels followed by prescribed burning and non-fuels treated forest sites in northeastern Oregon, US. Seven treatment paddocks were established at each site; three with cattle exclusion and low, moderate and high elk browsing pressure, three with elk exclusion and low, moderate and high cattle browsing pressure, and one with both cattle and elk exclusion. The height, cover and number of stems of each shrub species were recorded at multiple plots within each paddock at the time of establishment and six years later. Changes in shrub species composition over the six year period were explored using multivariate analyses. Generalized Linear Mixed Models were used to determine the effect of browsing pressure on the change in shrub diversity and evenness. Vegetation composition in un-browsed paddocks changed more strongly and in different trajectories than in browsed paddocks at sites that were not fuels treated. In fuels treated sites, changes in composition were minimal for un-browsed paddocks. Shrub diversity and evenness decreased strongly in un-browsed paddocks relative to paddocks with low, moderate and high browsing pressure at non-fuels treated sites, but not at fuels treated sites. These results suggest that in the combined absence of fire, mechanical thinning and ungulate browsing, shrub diversity is reduced due to increased dominance by certain shrub species which are otherwise suppressed by ungulates and/or fuels removal. Accordingly, ungulate browsing, even at low intensities, can be used to suppress dominant shrub species and maintain diversity in the absence of episodic disturbance events.

  2. Shrub growth and expansion in the Arctic tundra: an assessment of controlling factors using an evidence-based approach

    Science.gov (United States)

    Martin, Andrew C.; Jeffers, Elizabeth S.; Petrokofsky, Gillian; Myers-Smith, Isla; Macias-Fauria, Marc

    2017-08-01

    Woody shrubs have increased in biomass and expanded into new areas throughout the Pan-Arctic tundra biome in recent decades, which has been linked to a biome-wide observed increase in productivity. Experimental, observational, and socio-ecological research suggests that air temperature—and to a lesser degree precipitation—trends have been the predominant drivers of this change. However, a progressive decoupling of these drivers from Arctic vegetation productivity has been reported, and since 2010, vegetation productivity has also been declining. We created a protocol to (a) identify the suite of controls that may be operating on shrub growth and expansion, and (b) characterise the evidence base for controls on Arctic shrub growth and expansion. We found evidence for a suite of 23 proximal controls that operate directly on shrub growth and expansion; the evidence base focused predominantly on just four controls (air temperature, soil moisture, herbivory, and snow dynamics). 65% of evidence was generated in the warmest tundra climes, while 24% was from only one of 28 floristic sectors. Temporal limitations beyond 10 years existed for most controls, while the use of space-for-time approaches was high, with 14% of the evidence derived via experimental approaches. The findings suggest the current evidence base is not sufficiently robust or comprehensive at present to answer key questions of Pan-Arctic shrub change. We suggest future directions that could strengthen the evidence, and lead to an understanding of the key mechanisms driving changes in Arctic shrub environments.

  3. Effects of sand burial on the survival and growth of two shrubs dominant in different habitats of northern China.

    Science.gov (United States)

    Qu, Hao; Zhao, Ha-Lin; Zhao, Xue-Yong; Zuo, Xiao-An; Wang, Shao-Kun; Chen, Min

    2017-04-01

    Plants that grow in dune ecosystems always suffer from sand burial. Shrubs play implications on the healthy functioning of dune ecosystems due to control blowing sand. However, the survival and growth responses of shrubs to sand burial remain poorly understood. The survival rate and seedling height of two shrubs (Artemisia halodendron and Lespedeza davurica) along with the soil properties under different burial depths were examined in order to reveal the causing ecophysiological attributes of sand burial on shrubs in the desertified region. It was found that A. halodendron can survive a burial depth of 6 cm greater than its seedling height, which is a dominant shrub in mobile dunes with intense burial, whereas a burial depth equivalent to three fourths of its seedling height is detrimental to L. davurica, which is dominant in fixed dunes with less burial. The reasons for the shrub death under sand burial were associated with the physical barrier to vertical growth and the reduction in photosynthetic area. In conclusion, A. halodendron can facilitate the stabilization of mobile dunes because of their high tolerance to the frequent and intensive sand burial, while L. davurica can be beneficial for the recovery process because of their higher survival rates under shallow burial following restoration of mobile dunes.

  4. Assessing vegetation structure and ANPP dynamics in a grassland-shrubland Chihuahuan ecotone using NDVI-rainfall relationships

    Science.gov (United States)

    Moreno-de las Heras, M.; Diaz-Sierra, R.; Turnbull, L.; Wainwright, J.

    2015-01-01

    Climate change and the widespread alteration of natural habitats are major drivers of vegetation change in drylands. A classic case of vegetation change is the shrub-encroachment process that has been taking place over the last 150 years in the Chihuahuan Desert, where large areas of grasslands dominated by perennial grass species (black grama, Bouteloua eriopoda, and blue grama, B. gracilis) have transitioned to shrublands dominated by woody species (creosotebush, Larrea tridentata, and mesquite, Prosopis glandulosa), accompanied by accelerated water and wind erosion. Multiple mechanisms drive the shrub-encroachment process, including exogenous triggering factors such as precipitation variations and land-use change, and endogenous amplifying mechanisms brought about by soil erosion-vegetation feedbacks. In this study, simulations of plant biomass dynamics with a simple modelling framework indicate that herbaceous (grasses and forbs) and shrub vegetation in drylands have different responses to antecedent precipitation due to functional differences in plant growth and water-use patterns, and therefore shrub encroachment may be reflected in the analysis of landscape-scale vegetation-rainfall relationships. We analyze the structure and dynamics of vegetation at an 18 km2 grassland-shrubland ecotone in the northern edge of the Chihuahuan Desert (McKenzie Flats, Sevilleta National Wildlife Refuge, NM, USA) by investigating the relationship between decade-scale (2000-2013) records of medium-resolution remote sensing of vegetation greenness (MODIS NDVI) and precipitation. Spatial evaluation of NDVI-rainfall relationship at the studied ecotone indicates that herbaceous vegetation shows quick growth pulses associated with short-term (previous 2 months) precipitation, while shrubs show a slow response to medium-term (previous 5 months) precipitation. We use these relationships to (a) classify landscape types as a function of the spatial distribution of dominant vegetation

  5. Biology of Pink Hibiscus MealybugMaconellicoccushirsutus (Green on Chinese Hibiscus Shrubs in Khuzestan Province

    Directory of Open Access Journals (Sweden)

    M. Sadat Alizadeh

    2017-12-01

    Full Text Available Introduction: The pink hibiscus mealybug, Maconellicoccushirsutus (Green (Hem.:Pseudococcidae is one of the serious economic pests of agricultural crops in tropical and subtropical regions.This pesthas spread through Asia, Africa, America and Australia, and infests more than 330 host plants which some of them have the important role in theeconomy. This sap-feeding insect secrets honeydew which provides suitablemedium for black sooty moldgrowth. It also releases a toxin during feeding, which results in severe stunting, decline, and deformation of twigs. It has recorded as a pest on different host plants in southern Iranian provinces since the 1990s.In Khuzestan province, it was first observed on Chinese hibiscus shrubs in urban landscapes of Ahvaz in February 2009. The evergreen hibiscus shrub is very common in the urban landscape of warmcities of Khuzestan province. The severity of mealybug damage to hibiscus shrubs causedto becut off in some regions. As there is no data on the biology of M. hirsutus in Iran,in the present study, the biologyof this pestwas investigatedat different temperatures in laboratory conditions as well as its population fluctuations on Chinese hibiscus shrubs in urban landscapes of Ahvaz. Materials and methods: Biology of the pest species was evaluated at five laboratory constant temperatures 15, 20, 25, 30and 35±2°C (65±5% RH and a photoperiod of L: D 14:10 h on Chinese hibiscus leaves in plastic boxes (8×6×2 cm. Number ofM. hirsutusgenerations was also studied in clip cages on hibiscus shrubs in Ahvaz urban landscapes within a year. Population fluctuations of the insect were also investigated on those shrubs in two different regions of Ahvaz for 16 months. For this purpose, random sampling was done on five shrubs in each region bi-weekly. Eight twigs, 5 cm in length, were cut from the upper and lower halves of each shrub quadrant and a number of all mealybug developmental stages per twig were counted and recorded

  6. Altered Plant Litter and Microbial Composition Lead to Topsoil Organic Carbon Loss Over a Shrub-encroachment Gradient in an Inner Mongolia Grassland

    Science.gov (United States)

    Zhou, L.; Li, H.; Shen, H.; Xu, Y.; Wang, Y.; Xing, A.; Fang, J.

    2017-12-01

    Over the past 150 years, shrub encroachment has occurred in arid and semi-arid ecosystems resulting from climate change and increased human disturbance. Previous studies have revealed that shrub encroachment has substantial effects on habitat heterogeneity, aboveground biomass and bulk carbon content of grasslands, thereby affecting the regional carbon balance. Soil organic carbon (SOC) is mainly derived from aboveground litter, root litter and root exudates and is metabolized by microorganisms. The quality and quantity of plant litter together with soil microbial biomass are important drivers of SOC accumulation. However, the mechanisms regulating soil carbon accumulation by the shrub encroachment remain unclear and molecular evidence is particularly lacking. We use the data of the chemical composition of plant tissues and SOC, and the soil microbial communities to identify the effects of shrub encroachment on SOC accumulation in the top layer along a gradient of natural shrub cover in the grasslands of Inner Mongolia. Our finding indicates that nitrogen-rich legume-shrub encroachment led to soil carbon accumulation in the shrub patch, with more extensive carbon loss observed in the grassy matrix, which resulted in an overall carbon loss. In the pure grassland, a higher abundance of cutin and suberin and a lower concentration of free lipids were detected, suggesting the preservation of recalcitrant polymers derived from herb inputs. In the shrub-encroached grasslands, the labile shrub leaves did not decompose alone but were mixed with herb litter to promote the degradation of SOC via the priming of microbial activities. The SOC remained unchanged in the shrub patches with the increasing shrub cover, which might have been caused by the replacement of prior carbon decompositions with the fresh input of shrub leaves. Similarly, the SOC decreased significantly with increasing shrub cover in the grassy matrix, which likely resulted from insufficient fresh plant inputs

  7. Arctic plant ecophysiology and water source utilization in response to altered snow: isotopic (δ18O and δ2H) evidence for meltwater subsidies to deciduous shrubs.

    Science.gov (United States)

    Jespersen, R Gus; Leffler, A Joshua; Oberbauer, Steven F; Welker, Jeffrey M

    2018-06-28

    Warming-linked woody shrub expansion in the Arctic has critical consequences for ecosystem processes and climate feedbacks. The snow-shrub interaction model has been widely implicated in observed Arctic shrub increases, yet equivocal experimental results regarding nutrient-related components of this model have highlighted the need for a consideration of the increased meltwater predicted in expanding shrub stands. We used a 22-year snow manipulation experiment to simultaneously address the unexplored role of snow meltwater in arctic plant ecophysiology and nutrient-related components of the snow-shrub hypothesis. We coupled measurements of leaf-level gas exchange and leaf tissue chemistry (%N and δ 13 C) with an analysis of stable isotopes (δ 18 O and δ 2 H) in soil water, precipitation, and stem water. In deeper snow areas photosynthesis, conductance, and leaf N increased and δ 13 C values decreased in the deciduous shrubs, Betula nana and Salix pulchra, and the graminoid, Eriophorum vaginatum, with the strongest treatment effects observed in deciduous shrubs, consistent with predictions of the snow-shrub hypothesis. We also found that deciduous shrubs, especially S. pulchra, obtained much of their water from snow melt early in the growing season (40-50%), more than either E. vaginatum or the evergreen shrub, Rhododendron tomentosum (Ledum palustre). This result provides the basis for adding a meltwater-focused feedback loop to the snow-shrub interaction model of shrub expansion in the Arctic. Our results highlight the critical role of winter snow in the ecophysiology of Arctic plants, particularly deciduous shrubs, and underline the importance of understanding how global warming will affect the Arctic winter snowpack.

  8. Automated classification of tropical shrub species: a hybrid of leaf shape and machine learning approach

    Directory of Open Access Journals (Sweden)

    Miraemiliana Murat

    2017-09-01

    Full Text Available Plants play a crucial role in foodstuff, medicine, industry, and environmental protection. The skill of recognising plants is very important in some applications, including conservation of endangered species and rehabilitation of lands after mining activities. However, it is a difficult task to identify plant species because it requires specialized knowledge. Developing an automated classification system for plant species is necessary and valuable since it can help specialists as well as the public in identifying plant species easily. Shape descriptors were applied on the myDAUN dataset that contains 45 tropical shrub species collected from the University of Malaya (UM, Malaysia. Based on literature review, this is the first study in the development of tropical shrub species image dataset and classification using a hybrid of leaf shape and machine learning approach. Four types of shape descriptors were used in this study namely morphological shape descriptors (MSD, Histogram of Oriented Gradients (HOG, Hu invariant moments (Hu and Zernike moments (ZM. Single descriptor, as well as the combination of hybrid descriptors were tested and compared. The tropical shrub species are classified using six different classifiers, which are artificial neural network (ANN, random forest (RF, support vector machine (SVM, k-nearest neighbour (k-NN, linear discriminant analysis (LDA and directed acyclic graph multiclass least squares twin support vector machine (DAG MLSTSVM. In addition, three types of feature selection methods were tested in the myDAUN dataset, Relief, Correlation-based feature selection (CFS and Pearson’s coefficient correlation (PCC. The well-known Flavia dataset and Swedish Leaf dataset were used as the validation dataset on the proposed methods. The results showed that the hybrid of all descriptors of ANN outperformed the other classifiers with an average classification accuracy of 98.23% for the myDAUN dataset, 95.25% for the Flavia

  9. Comparing soil organic carbon dynamics in perennial grasses and shrubs in a saline-alkaline arid region, northwestern China.

    Science.gov (United States)

    Zhou, Yong; Pei, Zhiqin; Su, Jiaqi; Zhang, Jingli; Zheng, Yuanrun; Ni, Jian; Xiao, Chunwang; Wang, Renzhong

    2012-01-01

    Although semi-arid and arid regions account for about 40% of terrestrial surface of the Earth and contain approximately 10% of the global soil organic carbon stock, our understanding of soil organic carbon dynamics in these regions is limited. A field experiment was conducted to compare soil organic carbon dynamics between a perennial grass community dominated by Cleistogenes squarrosa and an adjacent shrub community co-dominated by Reaumuria soongorica and Haloxylon ammodendron, two typical plant life forms in arid ecosystems of saline-alkaline arid regions in northwestern China during the growing season 2010. We found that both fine root biomass and necromass in two life forms varied greatly during the growing season. Annual fine root production in the perennial grasses was 45.6% significantly higher than in the shrubs, and fine root turnover rates were 2.52 and 2.17 yr(-1) for the perennial grasses and the shrubs, respectively. Floor mass was significantly higher in the perennial grasses than in the shrubs due to the decomposition rate of leaf litter in the perennial grasses was 61.8% lower than in the shrubs even though no significance was detected in litterfall production. Soil microbial biomass and activity demonstrated a strong seasonal variation with larger values in May and September and minimum values in the dry month of July. Observed higher soil organic carbon stocks in the perennial grasses (1.32 Kg C m(-2)) than in the shrubs (1.12 Kg C m(-2)) might be attributed to both greater inputs of poor quality litter that is relatively resistant to decay and the lower ability of microorganism to decompose these organic matter. Our results suggest that the perennial grasses might accumulate more soil organic carbon with time than the shrubs because of larger amounts of inputs from litter and slower return of carbon through decomposition.

  10. Different parts, different stories: climate sensitivity of growth is stronger in root collars vs. stems in tundra shrubs.

    Science.gov (United States)

    Ropars, Pascale; Angers-Blondin, Sandra; Gagnon, Marianne; Myers-Smith, Isla H; Lévesque, Esther; Boudreau, Stéphane

    2017-08-01

    Shrub densification has been widely reported across the circumpolar arctic and subarctic biomes in recent years. Long-term analyses based on dendrochronological techniques applied to shrubs have linked this phenomenon to climate change. However, the multi-stemmed structure of shrubs makes them difficult to sample and therefore leads to non-uniform sampling protocols among shrub ecologists, who will favor either root collars or stems to conduct dendrochronological analyses. Through a comparative study of the use of root collars and stems of Betula glandulosa, a common North American shrub species, we evaluated the relative sensitivity of each plant part to climate variables and assessed whether this sensitivity is consistent across three different types of environments in northwestern Québec, Canada (terrace, hilltop and snowbed). We found that root collars had greater sensitivity to climate than stems and that these differences were maintained across the three types of environments. Growth at the root collar was best explained by spring precipitation and summer temperature, whereas stem growth showed weak and inconsistent responses to climate variables. Moreover, sensitivity to climate was not consistent among plant parts, as individuals having climate-sensitive root collars did not tend to have climate-sensitive stems. These differences in sensitivity of shrub parts to climate highlight the complexity of resource allocation in multi-stemmed plants. Whereas stem initiation and growth are driven by microenvironmental variables such as light availability and competition, root collars integrate the growth of all plant parts instead, rendering them less affected by mechanisms such as competition and more responsive to signals of global change. Although further investigations are required to determine the degree to which these findings are generalizable across the tundra biome, our results indicate that consistency and caution in the choice of plant parts are a key

  11. Multi-model comparison highlights consistency in predicted effect of warming on a semi-arid shrub

    Science.gov (United States)

    Renwick, Katherine M.; Curtis, Caroline; Kleinhesselink, Andrew R.; Schlaepfer, Daniel R.; Bradley, Bethany A.; Aldridge, Cameron L.; Poulter, Benjamin; Adler, Peter B.

    2018-01-01

    A number of modeling approaches have been developed to predict the impacts of climate change on species distributions, performance, and abundance. The stronger the agreement from models that represent different processes and are based on distinct and independent sources of information, the greater the confidence we can have in their predictions. Evaluating the level of confidence is particularly important when predictions are used to guide conservation or restoration decisions. We used a multi-model approach to predict climate change impacts on big sagebrush (Artemisia tridentata), the dominant plant species on roughly 43 million hectares in the western United States and a key resource for many endemic wildlife species. To evaluate the climate sensitivity of A. tridentata, we developed four predictive models, two based on empirically derived spatial and temporal relationships, and two that applied mechanistic approaches to simulate sagebrush recruitment and growth. This approach enabled us to produce an aggregate index of climate change vulnerability and uncertainty based on the level of agreement between models. Despite large differences in model structure, predictions of sagebrush response to climate change were largely consistent. Performance, as measured by change in cover, growth, or recruitment, was predicted to decrease at the warmest sites, but increase throughout the cooler portions of sagebrush's range. A sensitivity analysis indicated that sagebrush performance responds more strongly to changes in temperature than precipitation. Most of the uncertainty in model predictions reflected variation among the ecological models, raising questions about the reliability of forecasts based on a single modeling approach. Our results highlight the value of a multi-model approach in forecasting climate change impacts and uncertainties and should help land managers to maximize the value of conservation investments.

  12. A mechanistic modeling and data assimilation framework for Mojave Desert ecohydrology

    Science.gov (United States)

    Ng, Gene-Hua Crystal.; Bedford, David; Miller, David

    2014-01-01

    This study demonstrates and addresses challenges in coupled ecohydrological modeling in deserts, which arise due to unique plant adaptations, marginal growing conditions, slow net primary production rates, and highly variable rainfall. We consider model uncertainty from both structural and parameter errors and present a mechanistic model for the shrub Larrea tridentata (creosote bush) under conditions found in the Mojave National Preserve in southeastern California (USA). Desert-specific plant and soil features are incorporated into the CLM-CN model by Oleson et al. (2010). We then develop a data assimilation framework using the ensemble Kalman filter (EnKF) to estimate model parameters based on soil moisture and leaf-area index observations. A new implementation procedure, the “multisite loop EnKF,” tackles parameter estimation difficulties found to affect desert ecohydrological applications. Specifically, the procedure iterates through data from various observation sites to alleviate adverse filter impacts from non-Gaussianity in small desert vegetation state values. It also readjusts inconsistent parameters and states through a model spin-up step that accounts for longer dynamical time scales due to infrequent rainfall in deserts. Observation error variance inflation may also be needed to help prevent divergence of estimates from true values. Synthetic test results highlight the importance of adequate observations for reducing model uncertainty, which can be achieved through data quality or quantity.

  13. A mechanistic modeling and data assimilation framework for Mojave Desert ecohydrology

    Science.gov (United States)

    Ng, Gene-Hua Crystal; Bedford, David R.; Miller, David M.

    2014-06-01

    This study demonstrates and addresses challenges in coupled ecohydrological modeling in deserts, which arise due to unique plant adaptations, marginal growing conditions, slow net primary production rates, and highly variable rainfall. We consider model uncertainty from both structural and parameter errors and present a mechanistic model for the shrub Larrea tridentata (creosote bush) under conditions found in the Mojave National Preserve in southeastern California (USA). Desert-specific plant and soil features are incorporated into the CLM-CN model by Oleson et al. (2010). We then develop a data assimilation framework using the ensemble Kalman filter (EnKF) to estimate model parameters based on soil moisture and leaf-area index observations. A new implementation procedure, the "multisite loop EnKF," tackles parameter estimation difficulties found to affect desert ecohydrological applications. Specifically, the procedure iterates through data from various observation sites to alleviate adverse filter impacts from non-Gaussianity in small desert vegetation state values. It also readjusts inconsistent parameters and states through a model spin-up step that accounts for longer dynamical time scales due to infrequent rainfall in deserts. Observation error variance inflation may also be needed to help prevent divergence of estimates from true values. Synthetic test results highlight the importance of adequate observations for reducing model uncertainty, which can be achieved through data quality or quantity.

  14. Soil microbial responses to nitrogen addition in arid ecosystems

    Directory of Open Access Journals (Sweden)

    Robert L Sinsabaugh

    2015-08-01

    Full Text Available The N cycle of arid ecosystems is influenced by low soil organic matter, high soil pH and extremes in water potential and temperature that lead to open canopies and development of biological soil crusts (biocrusts. We investigated the effects of N amendment on soil microbial dynamics in a Larrea tridentata-Ambrosia dumosa shrubland site in southern Nevada USA. Sites were fertilized with a NO3-NH4 mix at 0, 7, and 15 kg ha-1 yr-1 from March 2012 to March 2013. In March 2013, biocrust (0-0.5 cm and bulk soils (0-10 cm were collected beneath Ambrosia canopies and in the interspaces between plants. Biomass responses were assessed as bacterial and fungal SSU rRNA gene copy number and chlorophyll a concentration. Metabolic responses were measured by five ecoenzyme activities (EEA and rates of N transformation. By most measures, nutrient availability, microbial biomass and process rates were greater in soils beneath the shrub canopy compared to the interspace between plants, and greater in the surface biocrust horizon compared to the deeper 10 cm soil profile. Most measures responded positively to experimental N addition. Effect sizes were generally greater for bulk soil than biocrust. Results were incorporated into a meta-analysis of arid ecosystem responses to N.

  15. Analysis of postfire vegetation dynamics of Mediterranean shrub species based on terrestrial and NDVI data.

    Science.gov (United States)

    Hernández-Clemente, Rocío; Cerrillo, R M Navarro; Hernández-Bermejo, J E; Royo, S Escuin; Kasimis, N A

    2009-05-01

    The present study offers an analysis of regeneration patterns and diversity dynamics after a wildfire, which occurred in 1993 and affected about 7000 ha in southern Spain. The aim of the work was to analyze the rule in the succession of shrub species after fire, relating it to the changes registered in the Normalized Difference Vegetation Index (NDVI). Fractional vegetation cover was recorded from permanent plots in 2000 and 2005. NDVI data related to each time were obtained from Landsat images. Both data sets, from fieldwork and remote sensing, were analyzed through statistical and quantitative analyses and then correlated. Results have permitted the description of the change in plant cover and species composition on a global and plot scale. It can be affirmed that, from the seventh to the twelfth year after the fire, the floristic composition within the burned area remained unchanged at a global level. However, on a smaller scale (plot level), the major shrub species, Ulex parviflorus, Rosmarinus officinalis, and Cistus clusii, underwent significant changes. The regeneration dynamics established by these species conditioned plant species composition and, consequently, diversity indexes such as Shannon (H) and Simpson (D). The changes recorded in the NDVI values corresponding to the surveyed plots were highly correlated with those found in the regrowth of the main species. Areas dominated by U. parviflorus in a senile phase were related to a decrease in NDVI values and an increase in the number of species. This result describes the successional dynamics; the dryness of the main colonizer shrub species is allowing the regrowth and re-establishment of other species. Within the study area, NDVI shows sensitivity to postfire plant cover changes and indirectly expresses the diversity dynamics.

  16. Seedling responses to water pulses in shrubs with contrasting histories of grassland encroachment.

    Directory of Open Access Journals (Sweden)

    Steven R Woods

    Full Text Available Woody plant encroachment into grasslands has occurred worldwide, but it is unclear why some tree and shrub species have been markedly more successful than others. For example, Prosopis velutina has proliferated in many grasslands of the Sonoran Desert in North America over the past century, while other shrub species with similar growth form and life history, such as Acacia greggii, have not. We conducted a glasshouse experiment to assess whether differences in early seedling development could help explain why one species and not the other came to dominate many Sonoran Desert grasslands. We established eight watering treatments mimicking a range of natural precipitation patterns and harvested seedlings 16 or 17 days after germination. A. greggii had nearly 7 times more seed mass than P. velutina, but P. velutina emerged earlier (by 3.0±0.3 d and grew faster (by 8.7±0.5 mg d⁻¹. Shoot mass at harvest was higher in A. greggii (99±6 mg seedling⁻¹ than in P. velutina (74±2 mg seedling⁻¹, but there was no significant difference in root mass (54±3 and 49±2 mg seedling⁻¹, respectively. Taproot elongation was differentially sensitive to water supply: under the highest initial watering pulse, taproots were 52±19 mm longer in P. velutina than in A. greggii. Enhanced taproot elongation under favorable rainfall conditions could give nascent P. velutina seedlings growth and survivorship advantages by helping reduce competition with grasses and maintain contact with soil water during drought. Conversely, A. greggii's greater investment in mass per seed appeared to provide little return in early seedling growth. We suggest that such differences in recruitment traits and their sensitivities to environmental conditions may help explain ecological differences between species that are highly similar as adults and help identify pivotal drivers of shrub encroachment into grasslands.

  17. Photosynthetic response of Eriophorum vaginatum to in situ shrub shading in tussock tundra of northern Alaska

    Science.gov (United States)

    Anderson-Smith, A.; Pattison, R.; Sullivan, P.; Welker, J. M.

    2009-12-01

    Eriophorum vaginatum (Cotton Grass) is an important component of moist acidic tussock tundra, a plant community that appears to be undergoing changes in species composition associated with climate warming. This species is one of the most abundant in the arctic tundra, and provides important forage for caribou in their calving grounds on the Arctic Coastal Plain and along their migratory route through the foothills of Alaska. Recently, remote sensing data, repeat photography and plot-level measurements have indicated that shrub abundance is increasing while Eriophorum abundance is either constant or decreasing. One possible explanation for the reduction of Eriophorum while Betula nana is increasing, is that lower light levels in the taller Betula canopy may be constraining Eriophorum photosynthesis and subsequently reducing plant growth. This study measured the effect of shading on the light response of Eriphorum leaf photosynthesis in four different sites near Toolik Lake Alaska during the summer of 2009. Measurements were taken in: 1) a shrub patch within the drift zone of the ITEX long term snow fence experiment, 2) an LTER shade house (50% shading) built in 1989, 3) water track site 1 and water track site 2 (i.e. control areas with no experimental manipulations) Average photosynthetic rates for Eriophorum at a light level of 800 PAR varied from 3.8 to 10.9 umol m-2 s-1 and were not significantly different in shaded and unshaded areas. This study indicates that shading by shrubs does not appear to be altering the light response of Eriophorum nor does long-term shading by itself eliminate Eriophorum from the community. An alternative explanation for the decline of Eriophorum while Betula increases in abundance under changing climates may be related to plant and soil mineral nutrition, plant water relations or biotic processes involving herbivores.

  18. Analysis of Postfire Vegetation Dynamics of Mediterranean Shrub Species Based on Terrestrial and NDVI Data

    Science.gov (United States)

    Hernández-Clemente, Rocío; Navarro Cerrillo, R. M.; Hernández-Bermejo, J. E.; Escuin Royo, S.; Kasimis, N. A.

    2009-05-01

    The present study offers an analysis of regeneration patterns and diversity dynamics after a wildfire, which occurred in 1993 and affected about 7000 ha in southern Spain. The aim of the work was to analyze the rule in the succession of shrub species after fire, relating it to the changes registered in the Normalized Difference Vegetation Index (NDVI). Fractional vegetation cover was recorded from permanent plots in 2000 and 2005. NDVI data related to each time were obtained from Landsat images. Both data sets, from fieldwork and remote sensing, were analyzed through statistical and quantitative analyses and then correlated. Results have permitted the description of the change in plant cover and species composition on a global and plot scale. It can be affirmed that, from the seventh to the twelfth year after the fire, the floristic composition within the burned area remained unchanged at a global level. However, on a smaller scale (plot level), the major shrub species, Ulex parviflorus, Rosmarinus officinalis, and Cistus clusii, underwent significant changes. The regeneration dynamics established by these species conditioned plant species composition and, consequently, diversity indexes such as Shannon (H) and Simpson (D). The changes recorded in the NDVI values corresponding to the surveyed plots were highly correlated with those found in the regrowth of the main species. Areas dominated by U. parviflorus in a senile phase were related to a decrease in NDVI values and an increase in the number of species. This result describes the successional dynamics; the dryness of the main colonizer shrub species is allowing the regrowth and re-establishment of other species. Within the study area, NDVI shows sensitivity to postfire plant cover changes and indirectly expresses the diversity dynamics.

  19. Bird communities of the arctic shrub tundra of Yamal: habitat specialists and generalists.

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    Vasiliy Sokolov

    Full Text Available BACKGROUND: The ratio of habitat generalists to specialists in birds has been suggested as a good indicator of ecosystem changes due to e.g. climate change and other anthropogenic perturbations. Most studies focusing on this functional component of biodiversity originate, however, from temperate regions. The Eurasian Arctic tundra is currently experiencing an unprecedented combination of climate change, change in grazing pressure by domestic reindeer and growing human activity. METHODOLOGY/PRINCIPAL FINDINGS: Here we monitored bird communities in a tundra landscape harbouring shrub and open habitats in order to analyse bird habitat relationships and quantify habitat specialization. We used ordination methods to analyse habitat associations and estimated the proportions of specialists in each of the main habitats. Correspondence Analysis identified three main bird communities, inhabiting upland, lowland and dense willow shrubs. We documented a stable structure of communities despite large multiannual variations of bird density (from 90 to 175 pairs/km(2. Willow shrub thickets were a hotspot for bird density, but not for species richness. The thickets hosted many specialized species whose main distribution area was south of the tundra. CONCLUSION/SIGNIFICANCE: If current arctic changes result in a shrubification of the landscape as many studies suggested, we would expect an increase in the overall bird abundance together with an increase of local specialists, since they are associated with willow thickets. The majority of these species have a southern origin and their increase in abundance would represent a strengthening of the boreal component in the southern tundra, perhaps at the expense of species typical of the subarctic zone, which appear to be generalists within this zone.

  20. Freezing resistance in Patagonian woody shrubs: the role of cell wall elasticity and stem vessel size.

    Science.gov (United States)

    Zhang, Yong-Jiang; Bucci, Sandra J; Arias, Nadia S; Scholz, Fabian G; Hao, Guang-You; Cao, Kun-Fang; Goldstein, Guillermo

    2016-08-01

    Freezing resistance through avoidance or tolerance of extracellular ice nucleation is important for plant survival in habitats with frequent subzero temperatures. However, the role of cell walls in leaf freezing resistance and the coordination between leaf and stem physiological processes under subzero temperatures are not well understood. We studied leaf and stem responses to freezing temperatures, leaf and stem supercooling, leaf bulk elastic modulus and stem xylem vessel size of six Patagonian shrub species from two sites (plateau and low elevation sites) with different elevation and minimum temperatures. Ice seeding was initiated in the stem and quickly spread to leaves, but two species from the plateau site had barriers against rapid spread of ice. Shrubs with xylem vessels smaller in diameter had greater stem supercooling capacity, i.e., ice nucleated at lower subzero temperatures. Only one species with the lowest ice nucleation temperature among all species studied exhibited freezing avoidance by substantial supercooling, while the rest were able to tolerate extracellular freezing from -11.3 to -20 °C. Leaves of species with more rigid cell walls (higher bulk elastic modulus) could survive freezing to lower subzero temperatures, suggesting that rigid cell walls potentially reduce the degree of physical injury to cell membranes during the extracellular freezing and/or thaw processes. In conclusion, our results reveal the temporal-spatial ice spreading pattern (from stem to leaves) in Patagonian shrubs, and indicate the role of xylem vessel size in determining supercooling capacity and the role of cell wall elasticity in determining leaf tolerance of extracellular ice formation. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  1. Regime shift by an exotic nitrogen-fixing shrub mediates plant facilitation in primary succession.

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    Adriano Stinca

    Full Text Available Ecosystem invasion by non-native, nitrogen-fixing species is a global phenomenon with serious ecological consequences. However, in the Mediterranean basin few studies addressed the impact of invasion by nitrogen-fixing shrubs on soil quality and hydrological properties at local scale, and the possible effects on succession dynamics and ecosystem invasibility by further species. In this multidisciplinary study we investigated the impact of Genista aetnensis (Biv. DC., an exotic nitrogen-fixing shrub, on the Vesuvius Grand Cone (Southern Italy. Specifically, we tested the hypotheses that the invasion of G. aetnensis has a significant impact on soil quality, soil hydrological regime, local microclimate and plant community structure, and that its impact increases during the plant ontogenetic cycle. We showed that G. aetnensis, in a relatively short time-span (i.e. ~ 40 years, has been able to build-up an island of fertility under its canopy, by accumulating considerable stocks of C, N, and P in the soil, and by also improving the soil hydrological properties. Moreover, G. aetnensis mitigates the daily range of soil temperature, reducing the exposure of coexisting plants to extremely high temperatures and water loss by soil evaporation, particularly during the growing season. Such amelioration of soil quality, coupled with the mitigation of below-canopy microclimatic conditions, has enhanced plant colonization of the barren Grand Cone slopes, by both herbaceous and woody species. These results suggest that the invasion of G. aetnensis could eventually drive to the spread of other, more resource-demanding exotic species, promoting alternative successional trajectories that may dramatically affect the local landscape. Our study is the first record of the invasion of G. aetnensis, an additional example of the regime shifts driven by N-fixing shrubs in Mediterranean region. Further studies are needed to identity specific management practices that can

  2. Seedling establishment in a masting desert shrub parallels the pattern for forest trees

    Science.gov (United States)

    Meyer, Susan E.; Pendleton, Burton K.

    2015-05-01

    The masting phenomenon along with its accompanying suite of seedling adaptive traits has been well studied in forest trees but has rarely been examined in desert shrubs. Blackbrush (Coleogyne ramosissima) is a regionally dominant North American desert shrub whose seeds are produced in mast events and scatter-hoarded by rodents. We followed the fate of seedlings in intact stands vs. small-scale disturbances at four contrasting sites for nine growing seasons following emergence after a mast year. The primary cause of first-year mortality was post-emergence cache excavation and seedling predation, with contrasting impacts at sites with different heteromyid rodent seed predators. Long-term establishment patterns were strongly affected by rodent activity in the weeks following emergence. Survivorship curves generally showed decreased mortality risk with age but differed among sites even after the first year. There were no detectable effects of inter-annual precipitation variability or site climatic differences on survival. Intraspecific competition from conspecific adults had strong impacts on survival and growth, both of which were higher on small-scale disturbances, but similar in openings and under shrub crowns in intact stands. This suggests that adult plants preempted soil resources in the interspaces. Aside from effects on seedling predation, there was little evidence for facilitation or interference beneath adult plant crowns. Plants in intact stands were still small and clearly juvenile after nine years, showing that blackbrush forms cohorts of suppressed plants similar to the seedling banks of closed forests. Seedling banks function in the absence of a persistent seed bank in replacement after adult plant death (gap formation), which is temporally uncoupled from masting and associated recruitment events. This study demonstrates that the seedling establishment syndrome associated with masting has evolved in desert shrublands as well as in forests.

  3. Ecophysiological aspects of the interactions between Bromus kopetdaghensis and two nurse shrubs, Astragalus meschedensis and Acantholimon raddeanam in a semiarid rangeland.

    Science.gov (United States)

    Jankju, M; Maghamnia, A

    2010-07-01

    Plant-plant interactions are known as the main biotic drivers of the vegetation dynamics. Therefore, understanding such processes is beneficial for the applied vegetation management. The aim of this research was to investigate the type and intensity of plant-plant interaction during the time course of a growth season. We studied ecophysiological aspects of facilitation and competition between two aridland shrubs, A. meschedensis Bunge and A. raddeanam Czernjak and one perennial grass, B. kopetdaghensis Krasch. Soil and plant sampling were carried out for shrubs and the grass that were either growing alone or the grass was growing under the canopy of shrubs. In Spring (May), soil humidity weight was higher under the shrubs+grass than the grass-only site. By the beginning of Summer (July) grass consumed the common soil water and rapidly terminated its yearly growth. Therefore, in August and September, soil humidity weight was lower under the shrubs+grass than shrub-only sites. Photosynthesis rate of B. kopetdaghensis was sharply reduced from the beginning towards the end of growth season, but was not varied between the different plant combinations. Leaf proline measurement in July indicated higher stress for B. kopetdaghensis that were growing under shrubs than those of open areas. In conclusion, we found facilitation effects of shrubs on the grass at the early times of growth season, but it shifted into the competition for water during summer times. The outcome of plant interaction was positive for the grass but negative for the shrubs, especially A. meschedensis.

  4. Development of Microsatellite Markers for the Coastal Shrub Scaevola taccada (Goodeniaceae

    Directory of Open Access Journals (Sweden)

    Haruko Ando

    2014-04-01

    Full Text Available Premise of the study: Microsatellite markers were developed for the coastal shrub species Scaevola taccada to estimate the population genetic structure, which may reflect different seed dispersal patterns. Methods and Results: Thirteen microsatellite primer sets were developed for S. taccada using 454 pyrosequencing. The primer sets were tested on 64 individuals sampled from two populations in Japan. Fragments were amplified using the primers, with one to 10 alleles per locus, and the expected heterozygosity ranged from 0.00 to 0.85. Conclusions: These results indicate the utility of markers in S. taccada for broad estimations of the population genetic structure of this species.

  5. Tall shrub expansion facilitated by patterned ground in the northwest Siberian Low Arctic

    Science.gov (United States)

    Frost, G. V.; Epstein, H. E.; Walker, D. A.; Matyshak, G.; Ermokhina, K.

    2011-12-01

    We integrated field observations with a time-series of satellite imagery to identify key biophysical attributes associated with tall shrub expansion and increased vegetation productivity within a forest-tundra ecotone near Kharp, northwest Siberia. Comparison of high-resolution Corona and QuickBird satellite photography indicates that alder (Alnus fruticosa) cover increased by ~10% since 1968. Additionally, areas of sharply increasing productivity detected using a Landsat TM/ETM+ time-series for 1985-2009 are consistently co-located with expanding shrub stands. Field observations made in 2011 revealed that most of the shrub expansion has occurred in areas of patterned ground in which abundant mineral-dominated microsites ("circles") have been maintained by cryogenic disturbance. In order to test whether shrub expansion was facilitated by circles, we established a series of transects according to categories of alder stand age and circle density. Along the transects, we mapped the location of alders and circles, measured soil organic depth and leaf area index (LAI), and characterized plant communities. In recent expansion areas, young alders occur almost exclusively on silt-rich circles that lack vegetation and surface organic matter. Alder abundance and LAI increased with the total area occupied by exposed circles. Analyses using spatial statistics indicate that young alders tend to occur in evenly-spaced groups that mirror the spacing of circles. This distribution pattern persists in older alder stands, especially where circles are large and widely-spaced. Stands on closely-spaced circles quickly develop dense canopies and low species-diversity. Based on ground- and satellite-based observations, we conclude that the abundance of mineral-dominated circles at Kharp has facilitated rapid alder expansion and associated alterations in plant community structure, composition, and productivity. Physical processes in areas of patterned ground promote continuous, rather than

  6. Allometric equations for estimating aboveground biomass for common shrubs in northeastern California

    Science.gov (United States)

    Steve Huff; Martin Ritchie; H. Temesgen

    2017-01-01

    Selected allometric equations and fitting strategies were evaluated for their predictive abilities for estimating above ground biomass for seven species of shrubs common to northeastern California. Size classes for woody biomass were categorized as 1-h fuels (0.1–0.6 cm), 10-h fuels (0.6–2.5 cm), 100-h fuels (2.5–7.6 cm), and 1000-h fuels (greater than 7.7 cm in...

  7. Nutrient foraging strategies are associated with productivity and population growth in forest shrubs.

    Science.gov (United States)

    Caplan, Joshua S; Stone, Bram W G; Faillace, Cara A; Lafond, Jonathan J; Baumgarten, Joni M; Mozdzer, Thomas J; Dighton, John; Meiners, Scott J; Grabosky, Jason C; Ehrenfeld, Joan G

    2017-04-01

    Temperate deciduous forest understoreys are experiencing widespread changes in community composition, concurrent with increases in rates of nitrogen supply. These shifts in plant abundance may be driven by interspecific differences in nutrient foraging (i.e. conservative vs. acquisitive strategies) and, thus, adaptation to contemporary nutrient loading conditions. This study sought to determine if interspecific differences in nutrient foraging could help explain patterns of shrub success and decline in eastern North American forests. Using plants grown in a common garden, fine root traits associated with nutrient foraging were measured for six shrub species. Traits included the mean and skewness of the root diameter distribution, specific root length (SRL), C:N ratio, root tissue density, arbuscular mycorrhizal colonization and foraging precision. Above- and below-ground productivity were also determined for the same plants, and population growth rates were estimated using data from a long-term study of community dynamics. Root traits were compared among species and associations among root traits, measures of productivity and rates of population growth were evaluated. Species fell into groups having thick or thin root forms, which correspond to conservative vs. acquisitive nutrient foraging strategies. Interspecific variation in root morphology and tissue construction correlated with measures of productivity and rates of cover expansion. Of the four species with acquisitive traits, three were introduced species that have become invasive in recent decades, and the fourth was a weedy native. In contrast, the two species with conservative traits were historically dominant shrubs that have declined in abundance in eastern North American forests. In forest understoreys of eastern North America, elevated nutrient availability may impose a filter on species success in addition to above-ground processes such as herbivory and overstorey canopy conditions. Shrubs that have

  8. Effect of Tree-to-Shrub Type Conversion in Lower Montane Forests of the Sierra Nevada (USA) on Streamflow.

    Science.gov (United States)

    Bart, Ryan R; Tague, Christina L; Moritz, Max A

    2016-01-01

    Higher global temperatures and increased levels of disturbance are contributing to greater tree mortality in many forest ecosystems. These same drivers can also limit forest regeneration, leading to vegetation type conversion. For the Sierra Nevada of California, little is known about how type conversion may affect streamflow, a critical source of water supply for urban, agriculture and environmental purposes. In this paper, we examined the effects of tree-to-shrub type conversion, in combination with climate change, on streamflow in two lower montane forest watersheds in the Sierra Nevada. A spatially distributed ecohydrologic model was used to simulate changes in streamflow, evaporation, and transpiration following type conversion, with an explicit focus on the role of vegetation size and aspect. Model results indicated that streamflow may show negligible change or small decreases following type conversion when the difference between tree and shrub leaf areas is small, partly due to the higher stomatal conductivity and the deep rooting depth of shrubs. In contrast, streamflow may increase when post-conversion shrubs have a small leaf area relative to trees. Model estimates also suggested that vegetation change could have a greater impact on streamflow magnitude than the direct hydrologic impacts of increased temperatures. Temperature increases, however, may have a greater impact on streamflow timing. Tree-to-shrub type conversion increased streamflow only marginally during dry years (annual precipitation importance of accounting for changes in vegetation communities to accurately characterize future hydrologic regimes for the Sierra Nevada.

  9. Impact of multiple soil nutrients on distribution patterns of shrubs in an arid valley, in southwest china

    International Nuclear Information System (INIS)

    Song, C.J.; Yishui, T.; Zao, L.X.

    2014-01-01

    Shrubs play key roles in arid regions and multiple interacting resources limit their distribution patterns. Identifying limiting resources and their coupling effects on shrubs is essential for developing restoration theory and practice. A survey of shrub composition, soil properties and topography was conducted in fifty-seven 15-m * 15-m plots in an arid valley of the upper Minjiang River, Southwest China. With quantitative classification method and ordination technique, 48 shrubs species were classified into four clusters and two categories along soil gradient. Cluster I and II composed Category I and had a significantly higher percentage of dominant legume shrubs than in Cluster III and Cluster IV, which made up Category II. Correlation analysis indicated that both multi-resource limitation and single resource limitation were coexisting simultaneously in this arid area, the extent of which was functional cluster-specific and also quantified hierarchical structure of multiple resource limitation: soil water played a primary limitation role, available nitrogen the next, and available phosphorus the third at community scale. Moreover, this study affirmed that both soil pH and soil texture could effectively regulate retention of soil moisture and available nutrients, respectively. Distinguishing critical limiting resources and their regulators is very meaningful to clarify couplings and controlling mechanisms in restoration practices. Therefore, decreasing soil pH and increasing soil clay content should be conducted thoroughly in plantation sites to remain abundant soil moisture and available nutrients in native restoration projects. (author)

  10. [Soil moisture dynamics and water balance of Salix psammophila shrubs in south edge of Mu Us Sandy Land].

    Science.gov (United States)

    An, Hui; An, Yu

    2011-09-01

    Taking the artificial sand-fixing Salix psammophila shrubs with different plant density (0.2, 0.6, and 0.8 plants x m(-2)) in Mu Us Sandy Land as test objects, this paper studied the soil moisture dynamics and evapotranspiration during growth season. There existed obvious differences in the soil moisture dynamics and evapotranspiration among the shrubs. The soil moisture content changed in single-hump-shape with the increase of plant density, and in "S" shape during growth season, being closely correlated with precipitation. The evapotranspiration was the highest (114.5 mm) in the shrubs with a density 0.8 plants x m(-1), accounting for 90.8% of the total precipitation during growth season, and the lowest (109.7 mm) in the shrubs with a density 0.6 plants x m(-2) Based on the soil moisture dynamics and water balance characteristics, the appropriate planting density of S. psammophila shrubs in Mu Us Sandy Land could be 0.6 plants x m(-2).

  11. [Models for biomass estimation of four shrub species planted in urban area of Xi'an city, Northwest China].

    Science.gov (United States)

    Yao, Zheng-Yang; Liu, Jian-Jun

    2014-01-01

    Four common greening shrub species (i. e. Ligustrum quihoui, Buxus bodinieri, Berberis xinganensis and Buxus megistophylla) in Xi'an City were selected to develop the highest correlation and best-fit estimation models for the organ (branch, leaf and root) and total biomass against different independent variables. The results indicated that the organ and total biomass optimal models of the four shrubs were power functional model (CAR model) except for the leaf biomass model of B. megistophylla which was logarithmic functional model (VAR model). The independent variables included basal diameter, crown diameter, crown diameter multiplied by height, canopy area and canopy volume. B. megistophylla significantly differed from the other three shrub species in the independent variable selection, which were basal diameter and crown-related factors, respectively.

  12. Functional groups in North Chilean desert shrub species, based on the water sources used

    International Nuclear Information System (INIS)

    Squeo, Francisco A; Olivares, Nancy; Olivares, Sandra; Jorquera, Carmen; Pollastri, Alberto; Aguirre, Evelyn; Aravena, Ramon; Ehleringer, James R

    1999-01-01

    Primary productivity and vegetation structure in arid ecosystems are determined by water availability. In studies conducted in the coastal dry land of North Central Chile (29 degrees 43'S; 71degrees 14'0, 300m), the mechanisms to use different water sources by shrubs species, in two contrasting rainfall years were compared. Information on pheno logical studies, root architecture and water sources used by shrubs through the use of stable isotopes is are discussed. Six functional groups based on water uptake and water use are recognized. The functional groups were defined based on their habits (deciduous and evergreen), their root systems, (shallow, dimorphic and deep), and their ability to use different water sources (surficial and/or deep). Because of the differential impact of the goat overgrazing on different functional groups, this would result on a lower utilization of surficial waters. A management and/or restoration plan should maximize the use of all water sources available to recover the primary productivity and the system stability

  13. Intraspecific Variation in Armillaria Species from Shrubs and Trees in Northwestern Spain

    Directory of Open Access Journals (Sweden)

    O. Aguín

    2004-08-01

    Full Text Available Until recently, the identification of Armillaria species relied upon morphological characteristics and mating tests, but now molecular techniques based on polymorphisms in the IGS region of the fungal rDNA are more commonly used, since these are more rapid and reliable. Differences found in RFLP patterns identifying Armillaria species have suggested the existence of intraspecific variation. In this work, 185 Armillaria isolates from different plant species (including fruit trees, broadleaf and coniferous trees, ornamental shrubs, kiwifruit and grapevine affected by white root rot were analyzed by RFLP-PCR, in order to study intraspecific variation in Armillaria and the relationship with the plant host. Armillaria mellea was found in the majority of samples (71%, and was the most frequent Armillaria species in symptomatic ornamental shrubs, kiwifruit, grapevine, fruit trees and broadleaf trees. In conifers however white root rot was generally caused by Armillaria ostoyae. Armillaria gallica was identified, although with low incidence, in ornamental, coniferous, broadleaf and fruit hosts. Intraspecies variation was recorded only in A. mellea, for which RFLP patterns mel 1 and mel 2 were found. Most plants infected with A. mellea showed the mel 2 pattern. Further research is needed to study whether Armillaria RFLP patterns are specific to certain plant hosts, and whether intraspecific variation is related to differences in pathogenicity.

  14. Energy evaluation of forest residues originated from shrub species in Galicia

    Energy Technology Data Exchange (ETDEWEB)

    Nunez-Regueira, L.; Proupin-Castineiras, J.; Rodriguez-Anon, J.A. [University of Santiago (Spain). Dept. of Applied Physics

    2004-01-01

    In this study we present an alternative for the management of the excess of shrub species that nowadays take up around 800,000 ha in Galicia (NW Spain). This alternative is based on the exploitation of the energetic resources contained in the excess of shrubs by their combustion in specially designed plants for production of electric energy. The different species were sorted into three groups: Ulex europaeus L. (furze), Sarothamnus scoparius (L.) Link (broom) and Erica sp. (heaths). Their LHV were calculated through measurements of the corresponding HHV and resulted 7600, 7300 and 7200 kJ kg{sup -1} respectively. Biomass productions (T ha{sup -1}) were also calculated resulting 20 T ha{sup -1} (furze), 30 T ha{sup -1} (broom), and 15 T ha{sup -1} (heaths). Analyses of all these values make these species very valuable for their energy exploitation. Samples were collected over one year in different zones to study the effect of the environmental conditions on the calorific values. (Author)

  15. U.S. Geological Survey shrub/grass products provide new approach to shrubland monitoring

    Science.gov (United States)

    Young, Steven M.

    2017-12-11

    In the Western United States, shrubland ecosystems provide vital ecological, hydrological, biological, agricultural, and recreational services. However, disturbances such as livestock grazing, exotic species invasion, conversion to agriculture, climate change, urban expansion, and energy development are altering these ecosystems.Improving our understanding of how shrublands are distributed, where they are changing, the extent of the historical change, and likely future change directions is critical for successful management of these ecosystems. Remote-sensing technologies provide the most likely data source for large-area monitoring of ecosystem disturbance—both near-real time and historically. A monitoring framework supported by remote-sensing data can offer efficient and accurate analysis of change across a range of spatial and temporal scales.The U.S. Geological Survey has been working to develop new remote-sensing data, tools, and products to characterize and monitor these changing shrubland landscapes. Nine individual map products (components) have been developed that quantify the percent of shrub, sagebrush, big sagebrush, herbaceous, annual herbaceous, litter, bare ground, shrub height, and sagebrush height at 1-percent intervals in each 30-meter grid cell. These component products are designed to be combined and customized to widely support different applications in rangeland monitoring, analysis of wildlife habitat, resource inventory, adaptive management, and environmental review.

  16. Desert Perennial Shrubs Shape the Microbial-Community Miscellany in Laimosphere and Phyllosphere Space.

    Science.gov (United States)

    Martirosyan, Varsik; Unc, Adrian; Miller, Gad; Doniger, Tirza; Wachtel, Chaim; Steinberger, Yosef

    2016-10-01

    Microbial function, composition, and distribution play a fundamental role in ecosystem ecology. The interaction between desert plants and their associated microbes is expected to greatly affect their response to changes in this harsh environment. Using comparative analyses, we studied the impact of three desert shrubs, Atriplex halimus (A), Artemisia herba-alba (AHA), and Hammada scoparia (HS), on soil- and leaf-associated microbial communities. DNA extracted from the leaf surface and soil samples collected beneath the shrubs were used to study associated microbial diversity using a sequencing survey of variable regions of bacterial 16S rRNA and fungal ribosomal internal transcribed spacer (ITS1). We found that the composition of bacterial and fungal orders is plant-type-specific, indicating that each plant type provides a suitable and unique microenvironment. The different adaptive ecophysiological properties of the three plant species and the differential effect on their associated microbial composition point to the role of adaptation in the shaping of microbial diversity. Overall, our findings suggest a link between plant ecophysiological adaptation as a "temporary host" and the biotic-community parameters in extreme xeric environments.

  17. Growth responses of low-alpine dwarf-shrub heath species to nitrogen deposition and management

    International Nuclear Information System (INIS)

    Britton, Andrea J.; Fisher, Julia M.

    2008-01-01

    Nitrogen deposition is a continuing problem in European alpine regions. We hypothesised that, despite climatic limitations, low-alpine Calluna heathland would respond to nitrogen addition with increased shoot growth and flowering and that fire and grazing would modify responses. In a five-year study, 0-50 kg N ha -1 y -1 were added, combined with burning (+/-) and clipping (+/-). Calluna vulgaris responded with increased shoot extension, but effects on flowering were variable. Burning enhanced the positive effect of nitrogen addition and negative effects of clipping. Sub-dominant shrubs generally did not respond to nitrogen. C. vulgaris shoot extension was stimulated by nitrogen addition of 10 kg N ha -1 y -1 (above background) supporting suggestions that alpine heathlands are sensitive to low levels of nitrogen deposition. Increased C. vulgaris growth could negatively impact on important lichen components of this vegetation through increased shading and competition. Climatic factors constrain productivity in this community, but do not prevent rapid responses to nitrogen deposition by some species. - Low levels of N deposition increase productivity in alpine dwarf-shrub heath despite strong climatic constraints

  18. Shrubs tracing sea surface temperature--Calluna vulgaris on the Faroe Islands.

    Science.gov (United States)

    Beil, Ilka; Buras, Allan; Hallinger, Martin; Smiljanić, Marko; Wilmking, Martin

    2015-11-01

    The climate of Central and Northern Europe is highly influenced by the North Atlantic Ocean due to heat transfer from lower latitudes. Detailed knowledge about spatio-temporal variability of sea surface temperature (SST) in that region is thus of high interest for climate and environmental research. Because of the close relations between ocean and coastal climate and the climate sensitivity of plant growth, annual rings of woody plants in coastal regions might be used as a proxy for SST. We show here for the first time the proxy potential of the common and widespread evergreen dwarf shrub Calluna vulgaris (heather), using the Faroe Islands as our case study. Despite its small and irregular ring structure, the species seems suitable for dendroecological investigations. Ring width showed high and significant correlations with summer and winter air temperatures and SST. The C. vulgaris chronology from the Faroe Islands, placed directly within the North Atlantic Current, clearly reflects variations in summer SSTs over an area between Iceland and Scotland. Utilising shrubs like C. vulgaris as easy accessible and annually resolved proxies offers an interesting possibility for reconstruction of the coupled climate-ocean system at high latitudes.

  19. Regeneration potential and growth of two indigenous shrubs in the desert of Saudi Arabia

    International Nuclear Information System (INIS)

    Al-Abdulqader, A.M.; Nasroun, T.H.; Assnar, S.; Al-Kahlifah, N.S.

    2008-01-01

    Ertaa (Calligonum comosum) and Ghada (Haloxylon persicum) are two important multipurpose indigenous shrubs in the desert of Saudi Arabia, supplying firewood and fodder to the local populations. Their environmental benefits in connection with sand dune fixation and microenvironment improvement are commendable. Due to over-exploitation and habitat destruction, populations of these two shrubs have become severely degraded. This study helps in the development of the appropriate techniques for their regeneration and evaluates their relative growth rate under different irrigation schedules. Productivity in the natural population and biological growth under cultivation were also evaluated. Seeds of Ertaa required no special treatment while the seeds of Ghada showed higher percentage of germination when soaked in cold water for 1 hour. The seeds of Ghada are photoblastic, which require adequate light for germination while those of Ertaa are negatively photoblastic. The growth rate of both species under different irrigation schedule proved that the increase of irrigation frequency may not proportionally influence the growth rate. The estimated productivity of natural stands in Saudi Arabia was much less than the productivity of both species from other parts of the world. The estimated biological growth function under cultivation was found to reasonably match with the natural growth for both species are in their initial growth stage. (author)

  20. Soil surface temperatures reveal moderation of the urban heat island effect by trees and shrubs.

    Science.gov (United States)

    Edmondson, J L; Stott, I; Davies, Z G; Gaston, K J; Leake, J R

    2016-09-19

    Urban areas are major contributors to air pollution and climate change, causing impacts on human health that are amplified by the microclimatological effects of buildings and grey infrastructure through the urban heat island (UHI) effect. Urban greenspaces may be important in reducing surface temperature extremes, but their effects have not been investigated at a city-wide scale. Across a mid-sized UK city we buried temperature loggers at the surface of greenspace soils at 100 sites, stratified by proximity to city centre, vegetation cover and land-use. Mean daily soil surface temperature over 11 months increased by 0.6 °C over the 5 km from the city outskirts to the centre. Trees and shrubs in non-domestic greenspace reduced mean maximum daily soil surface temperatures in the summer by 5.7 °C compared to herbaceous vegetation, but tended to maintain slightly higher temperatures in winter. Trees in domestic gardens, which tend to be smaller, were less effective at reducing summer soil surface temperatures. Our findings reveal that the UHI effects soil temperatures at a city-wide scale, and that in their moderating urban soil surface temperature extremes, trees and shrubs may help to reduce the adverse impacts of urbanization on microclimate, soil processes and human health.

  1. Fodder shrubs and fatty acids: strategies to reduce enteric methane production in cattle.

    Directory of Open Access Journals (Sweden)

    Juan Leonardo Cardona-Iglesias

    2016-12-01

    Full Text Available The aim of this study was to analyze the use of fodder shrubs and polyunsaturated fatty acids as a nutritional strategy to mitigate enteric methane production in cattle. Special emphasis was made on the use of Tithonia diversifolia (Hemsl. A. Gray (Mexican sun ower, as a species with antimethanogenic potential. Bibliographic information for this review was obtained between July and September 2015 by using key words. Methane is a powerful greenhouse gas (GHG, the increase of its atmospheric concentration is caused mainly by emissions from agriculture and industry, but it is also estimated that a proportion of methane is emitted by ruminants as a product of enteric and anaerobic fermentation of diet. This causes an environmental and productive problem in livestock production systems worldwide. Although there is controversy about the real contribution of methane by ruminants and its impact on environmental issues, the amount of emissions should try to be reduced.This document emphasizes the search for nutritional strategies such as supplementation with forage shrubs and sources of polyunsaturated fatty acids, which have shown potential to maintain animal production ef ciency and decrease enteric methane synthesis.

  2. Study of Tree and Shrub Species Diversity in Forestry Plans with Different Forest Management

    Directory of Open Access Journals (Sweden)

    nooreddin noorian

    2017-12-01

    Full Text Available The aim of this research was to investigate the diversity of tree and shrub species in forestry plan in a watershed and in almost the same ecological conditions but different in forest management plan in the part of Golestan province forest. To this end, the 6675 hectares of the watershed number of 85 in 5 different plans in series one (30-year forestry plan with University Scientific Management, series two Doctor Bahramnia (without implementation and protection, series four Shamoshak, Naharkhoran plan and Sad Abad plan were selected. Inventory grid was designed by a systematic cluster sampling method with 239 circle plots in the study area. In each sample, species composition and diameter at breast height of trees and shrubs were measured. Species diversity in different series, were performed by calculating the heterogeneity indices, species richness and evenness. Statistical analysis of significant differences between the values of biodiversity of woody species among different series was performed by Duncan’s test. The results showed that biodiversity of woody species in the one and two series of Shastkalateh forest under academic management was better than other plans and forestry plan of Naharkhoran is in an unfavorable situation in terms of diversity indices.

  3. Facilitation by a Spiny Shrub on a Rhizomatous Clonal Herbaceous in Thicketization-Grassland in Northern China: Increased Soil Resources or Shelter from Herbivores

    Directory of Open Access Journals (Sweden)

    Saixiyala

    2017-05-01

    Full Text Available The formation of fertility islands by shrubs increases soil resources heterogeneity in thicketization-grasslands. Clonal plants, especially rhizomatous or stoloniferous clonal plants, can form large clonal networks and use heterogeneously distributed resources effectively. In addition, shrubs, especially spiny shrubs, may also provide herbaceous plants with protection from herbivores, acting as ‘shelters’. The interaction between pre-dominated clonal herbaceous plants and encroaching shrubs remains unclear in thicketization-grassland under grazing pressure. We hypothesized that clonal herbaceous plants can be facilitated by encroached shrubs as a ‘shelter from herbivores’ and/or as an ‘increased soil resources’ under grazing pressure. To test this hypothesis, a total of 60 quadrats were chosen in a thicket-grassland in northern China that was previously dominated by Leymus chinensis and was encroached upon by the spiny leguminous plant Caragana intermedia. The soil and plant traits beneath and outside the shrub canopies were sampled, investigated and contrasted with an enclosure. The soil organic matter, soil total nitrogen and soil water content were significantly higher in the soil beneath the shrub canopies than in the soil outside the canopies. L. chinensis beneath the shrub canopies had significantly higher plant height, single shoot biomass, leaf length and width than outside the shrub canopies. There were no significantly differences between plant growth in enclosure and outside the shrub canopies. These results suggested that under grazing pressure in a grassland undergoing thicketization, the growth of the rhizomatous clonal herbaceous plant L. chinensis was facilitated by the spiny shrub C. intermedia as a ‘shelter from herbivores’ more than through ‘increased soil resources’. We propose that future studies should focus on the community- and ecosystem-level impacts of plant clonality.

  4. Use of AIRSAR to identify woody shrub invasion and other indicators of desertification in the Jornada LTER

    Science.gov (United States)

    Musick, H. Brad; Schaber, Gerald G.; Breed, Carol S.

    1995-01-01

    The replacement of semidesert grassland by woody shrubland is a widespread form of desertification. This change in physiognomy and species composition tends to sharply reduce the productivity of the land for grazing by domestic livestock, increase soil erosion and reduce soil fertility, and greatly alter many other aspects of ecosystem structure and functioning. Remote sensing methods are needed to assess and monitor shrubland encroachment. Detection of woody shrubs at low density would provide a particularly useful baseline on which to access changes, because an initially low shrub density often tends to increase even after cessation of the disturbance (e.g., overgrazing, drought, or fire suppression) responsible for triggering the initial stages of the invasion (Grover and Musick, 1990). Limited success has been achieved using optical remote sensing. In contrast to other forms of desertification, biomass does not consistently decrease with a shift from grassland to shrubland. Estimation of green vegetation amount (e.g., by NDVI) is thus of limited utility, unless the shrubs and herbaceous plants differ consistently in phenology and the area can be viewed during a season when only one of these is green. The objective of this study was to determine if the potential sensitivity of active microwave remote sensing to vegetation structure could be used to assess the degree of shrub invasion of grassland. Polarimetric Airborne Synthetic Aperture Radar (AIRSAR) data were acquired for a semiarid site containing varied mixtures of shrubs and herbaceous vegetation and compared with ground observations of vegetation type and other landsurface characteristics. In this preliminary report we examine the response of radar backscatter intensity to shrub density. The response of other multipolarization parameters will be examined in future work.

  5. Where to Combat Shrub Encroachment in Alpine Timberline Ecosystems: Combining Remotely-Sensed Vegetation Information with Species Habitat Modelling.

    Directory of Open Access Journals (Sweden)

    Veronika Braunisch

    Full Text Available In many cultural landscapes, the abandonment of traditional grazing leads to encroachment of pastures by woody plants, which reduces habitat heterogeneity and impacts biodiversity typical of semi-open habitats. We developed a framework of mutually interacting spatial models to locate areas where shrub encroachment in Alpine treeline ecosystems deteriorates vulnerable species' habitat, using black grouse Tetrao tetrix (L. in the Swiss Alps as a study model. Combining field observations and remote-sensing information we 1 identified and located the six predominant treeline vegetation types; 2 modelled current black grouse breeding habitat as a function thereof so as to derive optimal habitat profiles; 3 simulated from these profiles the theoretical spatial extension of breeding habitat when assuming optimal vegetation conditions throughout; and used the discrepancy between (2 and (3 to 4 locate major aggregations of homogeneous shrub vegetation in otherwise suitable breeding habitat as priority sites for habitat restoration. All six vegetation types (alpine pasture, coniferous forest, Alnus viridis (Chaix, Rhododendron-dominated, Juniperus-dominated and mixed heathland were predicted with high accuracy (AUC >0.9. Breeding black grouse preferred a heterogeneous mosaic of vegetation types, with none exceeding 50% cover. While 15% of the timberline belt currently offered suitable breeding habitat, twice that fraction (29% would potentially be suitable when assuming optimal shrub and ground vegetation conditions throughout the study area. Yet, only 10% of this difference was attributed to habitat deterioration by shrub-encroachment of dense heathland (all types 5.2% and Alnus viridis (4.8%. The presented method provides both a general, large-scale assessment of areas covered by dense shrub vegetation as well as specific target values and priority areas for habitat restoration related to a selected target organism. This facilitates optimizing the

  6. Annual increments of juniper dwarf shrubs above the tree line on the central Tibetan Plateau: a useful climatic proxy

    Science.gov (United States)

    Liang, Eryuan; Lu, Xiaoming; Ren, Ping; Li, Xiaoxia; Zhu, Liping; Eckstein, Dieter

    2012-01-01

    Background and Aims Dendroclimatology is playing an important role in understanding past climatic changes on the Tibetan Plateau. Forests, however, are mainly confined to the eastern Tibetan Plateau. On the central Tibetan Plateau, in contrast, shrubs and dwarf shrubs need to be studied instead of trees as a source of climate information. The objectives of this study were to check the dendrochronological potential of the dwarf shrub Wilson juniper (Juniperus pingii var. wilsonii) growing from 4740 to 4780 m a.s.l. and to identify the climatic factors controlling its radial growth. Methods Forty-three discs from 33 stems of Wilson juniper were sampled near the north-eastern shore of the Nam Co (Heavenly Lake). Cross-dating was performed along two directions of each stem, avoiding the compression-wood side as far as possible. A ring-width chronology was developed after a negative exponential function or a straight line of any slope had been fit to the raw measurements. Then, correlations were calculated between the standard ring-width chronology and monthly climate data recorded by a weather station around 100 km away. Key Results Our study has shown high dendrochronological potential of Wilson juniper, based on its longevity (one individual was 324 years old), well-defined growth rings, reliable cross-dating between individuals and distinct climatic signals reflected by the ring-width variability. Unlike dwarf shrubs in the circum-arctic tundra ecosystem which positively responded to above-average temperature in the growing season, moisture turned out to be growth limiting for Wilson juniper, particularly the loss of moisture caused by high maximum temperatures in May–June. Conclusions Because of the wide distribution of shrub and dwarf shrub species on the central Tibetan Plateau, an exciting prospect was opened up to extend the presently existing tree-ring networks far up into one of the largest tundra regions of the world. PMID:22210848

  7. Endemic shrubs in temperate arid and semiarid regions of northern China and their potentials for rangeland restoration.

    Science.gov (United States)

    Chu, Jianmin; Yang, Hongxiao; Lu, Qi; Zhang, Xiaoyan

    2015-06-03

    Some endemic shrubs in arid and semiarid ecosystems are in danger of extinction, and yet they can play useful roles in maintaining or restoring these ecosystems, thus practical efforts are needed to conserve them. The shrubs Amygdalus pedunculata Pall., Amygdalus mongolica (Maxim.) Ricker and Ammopiptanthus mongolicus (Maxim. ex Kom.) Cheng f. are endemic species in arid and semiarid regions of northern China, where rangeland desertification is pronounced due to chronic overgrazing. In this study, we tested the hypothesis that these endemic shrubs have developed adaptations to arid and semiarid environments and could play critical roles as nurse species to initiate the process of rangeland recovery. Based on careful vegetation surveys, we analysed the niches of these species in relation to precipitation, temperature and habitats. All sampling plots were categorized by these endemics and sorted by the non-metric multidimensional scaling method. Species ratios of each life form and species co-occurrence rates with the endemics were also evaluated. Annual average temperature and annual precipitation were found to be the key factors determining vegetation diversity and distributions. Amygdalus pedunculata prefers low hills and sandy land in temperate semiarid regions. Amygdalus mongolica prefers gravel deserts of temperate semiarid regions. Ammopiptanthus mongolicus prefers sandy land of temperate arid regions. Communities of A. pedunculata have the highest diversity and the largest ratios of long-lived grass species, whereas those of A. mongolicus have the lowest diversity but the largest ratios of shrub species. Communities of A. mongolica are a transition between the first two community types. These findings demonstrate that our focal endemic shrubs have evolved adaptations to arid and semiarid conditions, thus they can be nurse plants to stabilize sand ground for vegetation restoration. We suggest that land managers begin using these shrub species to restore

  8. Evaluation of Air Pollution Tolerance Index of Plants and Ornamental Shrubs in Enugu City: Implications for Urban Heat Island Effect

    Directory of Open Access Journals (Sweden)

    2016-11-01

    Full Text Available The study compared the air pollution tolerance indices (APTI of five plant species and five ornamental shrubs in Enugu Urban Center. Laboratory analysis was performed on the four physiological and biological parameters including leaf relative water content (RWC, ascorbic acid (AA content, total leaf chlorophyll (TCH and leaf extract pH. These parameters were used to develop an air pollution tolerance index. Factor analysis and descriptive statistics were utilized in the analysis to examine the interactions between these parameters. Vegetation monitoring in terms of its APTI acts as a \\'Bioindicator\\' of air pollution. The study also showed the possibility of utilizing APTI as a tool for selecting plants or ornamental shrubs for urban heat Island mitigation in Enugu City. The result of APTI showed order of tolerance for plants as Anacarduim occidentale (23.20, Pinus spp (22.35, Catalpa burgei (22.57, Magifera indica (23.37, and Psidum guajava (24.15.The result of APTI showed increasing order of sensitivity for ornamental shrubs from ixora red (14.32, yellow ficus(12.63, masquerade pine(12.26, Tuja pine(11.000,to Yellow bush(10.60. The APTI of all the plants examined were higher than those of ornamental shrubs. Thus suggesting that plants in general were more tolerant to air pollution than ornamental shrubs. The ornamental shrubs with lower APTI values (sensitive were recommended as bioindicator of poor urban air quality while plants with high APTI values (tolerant are planted around areas anticipated to have high air pollution load. The result of this current study is therefore handy for future planning and as well provides tolerant species for streetscape and urban heat island mitigation.

  9. Potential of native shrubs Haloxylon salicornicum and Calligonum Polygonoides for restoration of degraded lands in Arid Western Rajasthan, India.

    Science.gov (United States)

    Rathore, V S; Singh, J P; Bhardwaj, S; Nathawat, N S; Kumar, Mahesh; Roy, M M

    2015-01-01

    Shrub-induced soil property spatial heterogeneity is common in arid and semi-arid ecosystems and aids desertified land restoration. However, the effectiveness of this technique may rely on the plant species used and the habitat conditions present. To assess the degree to which planting two native species, Haloxylon salicornicum and Calligonum polygonoides, facilitates degraded land restoration, soil and herbaceous plant community properties were measured 7 years after planting. Soil samples were extracted at two depths (0-5 and 5-20 cm) from three sub-habitats, i.e., under the shrub canopy, from alleys between shrubs and from the open area. Shrub planting increased the quantity of silt + clay content (30-39 %); enhanced water holding capacities (24-30 %); increased the levels of organic carbon (48-69 %), available nitrogen (31-47 %), available phosphorus (32-41 %), and electrical conductivity (21-33 %); and decreased the pH (7-12 %) and bulk density levels (5-6 %) in the surface layer of soils beneath the canopy. Soil property changes were more significant at the surface (0-5 cm) than in the deeper layer (5-20 cm), and were more pronounced under H. salicornicum than under C. polygonoides. Furthermore, the density and biomass levels of herbaceous plants were 1.1 to 1.2 and 1.4 to 1.6 times greater, respectively, in the shrub alleys than in open area. H. salicornicum induced more robust soil amelioration and herbaceous plant facilitative properties than did C. polygonoides. Artificially planting these shrubs may thus be employed to restore degraded areas of arid regions.

  10. Annual increments of juniper dwarf shrubs above the tree line on the central Tibetan Plateau: a useful climatic proxy.

    Science.gov (United States)

    Liang, Eryuan; Lu, Xiaoming; Ren, Ping; Li, Xiaoxia; Zhu, Liping; Eckstein, Dieter

    2012-03-01

    Dendroclimatology is playing an important role in understanding past climatic changes on the Tibetan Plateau. Forests, however, are mainly confined to the eastern Tibetan Plateau. On the central Tibetan Plateau, in contrast, shrubs and dwarf shrubs need to be studied instead of trees as a source of climate information. The objectives of this study were to check the dendrochronological potential of the dwarf shrub Wilson juniper (Juniperus pingii var. wilsonii) growing from 4740 to 4780 m a.s.l. and to identify the climatic factors controlling its radial growth. Forty-three discs from 33 stems of Wilson juniper were sampled near the north-eastern shore of the Nam Co (Heavenly Lake). Cross-dating was performed along two directions of each stem, avoiding the compression-wood side as far as possible. A ring-width chronology was developed after a negative exponential function or a straight line of any slope had been fit to the raw measurements. Then, correlations were calculated between the standard ring-width chronology and monthly climate data recorded by a weather station around 100 km away. Our study has shown high dendrochronological potential of Wilson juniper, based on its longevity (one individual was 324 years old), well-defined growth rings, reliable cross-dating between individuals and distinct climatic signals reflected by the ring-width variability. Unlike dwarf shrubs in the circum-arctic tundra ecosystem which positively responded to above-average temperature in the growing season, moisture turned out to be growth limiting for Wilson juniper, particularly the loss of moisture caused by high maximum temperatures in May-June. Because of the wide distribution of shrub and dwarf shrub species on the central Tibetan Plateau, an exciting prospect was opened up to extend the presently existing tree-ring networks far up into one of the largest tundra regions of the world.

  11. Where to Combat Shrub Encroachment in Alpine Timberline Ecosystems: Combining Remotely-Sensed Vegetation Information with Species Habitat Modelling.

    Science.gov (United States)

    Braunisch, Veronika; Patthey, Patrick; Arlettaz, Raphaël

    2016-01-01

    In many cultural landscapes, the abandonment of traditional grazing leads to encroachment of pastures by woody plants, which reduces habitat heterogeneity and impacts biodiversity typical of semi-open habitats. We developed a framework of mutually interacting spatial models to locate areas where shrub encroachment in Alpine treeline ecosystems deteriorates vulnerable species' habitat, using black grouse Tetrao tetrix (L.) in the Swiss Alps as a study model. Combining field observations and remote-sensing information we 1) identified and located the six predominant treeline vegetation types; 2) modelled current black grouse breeding habitat as a function thereof so as to derive optimal habitat profiles; 3) simulated from these profiles the theoretical spatial extension of breeding habitat when assuming optimal vegetation conditions throughout; and used the discrepancy between (2) and (3) to 4) locate major aggregations of homogeneous shrub vegetation in otherwise suitable breeding habitat as priority sites for habitat restoration. All six vegetation types (alpine pasture, coniferous forest, Alnus viridis (Chaix), Rhododendron-dominated, Juniperus-dominated and mixed heathland) were predicted with high accuracy (AUC >0.9). Breeding black grouse preferred a heterogeneous mosaic of vegetation types, with none exceeding 50% cover. While 15% of the timberline belt currently offered suitable breeding habitat, twice that fraction (29%) would potentially be suitable when assuming optimal shrub and ground vegetation conditions throughout the study area. Yet, only 10% of this difference was attributed to habitat deterioration by shrub-encroachment of dense heathland (all types 5.2%) and Alnus viridis (4.8%). The presented method provides both a general, large-scale assessment of areas covered by dense shrub vegetation as well as specific target values and priority areas for habitat restoration related to a selected target organism. This facilitates optimizing the spatial

  12. Long-term experimental warming, shading and nutrient addition affect the concentration of phenolic compounds in arctic-alpine deciduous and evergreen dwarf shrubs

    DEFF Research Database (Denmark)

    Hansen, Anja Hoff; Jonasson, Sven Evert; Michelsen, Anders

    2006-01-01

    -arctic, alpine ecosystem, we investigated the effects on carbon based secondary compounds (CBSC) and nitrogen in one dominant deciduous dwarf shrub, Salix herbacea × polaris and two dominant evergreen dwarf shrubs, Cassiope tetragona and Vaccinium vitis-idaea throughout one growing season. The main aims were...

  13. Presence of understory shrubs constrains carbon gain in sunflecks by advance-regeneration seedlings: evidence from Quercus Rubra seedling grouwing in understory forest patches with or without evergreen shrubs present

    Science.gov (United States)

    E.T. Nilsen; T.T. Lei; S.W. Semones

    2009-01-01

    We investigated whether dynamic photosynthesis of understory Quercus rubra L. (Fagaceae) seedlings can acclimate to the altered pattern of sunflecks in forest patches with Rhododendron maximum L. (Ericaceae), an understory evergreen shrub. Maximum photosynthesis (A) and total CO2 accumulated during lightflecks was greatest for 400-s lightflecks, intermediate for 150-s...

  14. Physiological, morphological and allocation plasticity of a semi-deciduous shrub

    Science.gov (United States)

    Zunzunegui, M.; Ain-Lhout, F.; Barradas, M. C. Díaz; Álvarez-Cansino, L.; Esquivias, M. P.; García Novo, F.

    2009-05-01

    The main objective of this study was to look into the phenotypic plasticity of the semi-deciduous Mediterranean shrub, Halimium halimifolium. We studied morphological, allocation and physiological traits to determine which characters were more plastic and contribute in a greater extent to the acclimation ability of the species. We present a phenotypic plasticity index for morphological, physiological and allocation traits, which we have applied in the most contrasted plant communities where the species grows naturally. Data published by Díaz Barradas, M.C., García Novo, F. [1987. The vertical structure of Mediterranean scrub in Doñana National Park (SW Spain). Folia Geobotanica Phytotaxonomica 22, 415-433; 1988. Modificación y extinción de la luz a través de la copa en cuatro especies de matorral en el Parque Nacional de Doñana. Monografias Instituto Pirenaico de Ecologia 4, 503-516; 1990. Seasonal changes in canopy structure in two mediterranean dune shrubs. Journal of Vegetation Science 1, 31-40.], Díaz Barradas, M.C., Zunzunegui, M., García Novo, F. [1999a. Autoecological traits of Halimium halimifolium in contrasted habitats under Mediterranean type climate. Folia Geobotanica 34, 189-208.] and Zunzunegui et al. [Zunzunegui, M., Díaz Barradas, M.C., García Novo, F. 1997. Autoecological notes of Halimium halimifolium. Lagascalia 19, 725-736. Sevilla, Spain; Zunzunegui, M., Díaz Barradas, M.C., Fernández Baco, L., García Novo, F. 1999. Seasonal changes in photochemical efficiency in leaves of Halimium halimifolium a Mediterranean semideciduous shrub. Photosynthetica 36, 17-31; Zunzunegui, M., Díaz Barradas, M.C., García Novo, F. 2000. Different phenotypic response of Halimium halimifolium in relation to groundwater availability. Plant Ecology 148, 165-174; Zunzunegui, M., Díaz Barradas, M.C., Aguilar, F., Ain-Lhout, F., Clavijo, A., García Novo, F. 2002. Growth response of Halimium halimifolium at four sites with different soil water availability

  15. Deepened winter snow increases stem growth and alters stem δ13C and δ15N in evergreen dwarf shrub Cassiope tetragona in high-arctic Svalbard tundra

    DEFF Research Database (Denmark)

    Blok, Daan; Weijers, Stef; Welker, Jeffrey M

    2015-01-01

    Deeper winter snow is hypothesized to favor shrub growth and may partly explain the shrub expansion observed in many parts of the arctic during the last decades, potentially triggering biophysical feedbacks including regional warming and permafrost thawing. We experimentally tested the effects...... of winter snow depth on shrub growth and ecophysiology by measuring stem length and stem hydrogen ( δ2H), carbon ( δ13C), nitrogen ( δ15N) and oxygen ( δ18O) isotopic composition of the circumarctic evergreen dwarf shrub Cassiope tetragona growing in high-arctic Svalbard, Norway. Measurements were carried...... closely matched, snow depth did not change stem δ 2 H or δ 18 O, suggesting that water source usage by C. tetragona was unaltered. Instead, the deep insulating snowpack may have protected C. tetragona shrubs against frost damage, potentially compensating the detrimental effects of a shortened growing...

  16. Fuel buildup and potential fire behavior after stand-replacing fires, logging fire-killed trees and herbicide shrub removal in Sierra Nevada forests

    Science.gov (United States)

    McGinnis, Thomas W.; Keeley, Jon E.; Stephens, Scott L.; Roller, Gary B.

    2010-01-01

    Typically, after large stand-replacing fires in mid-elevation Sierra Nevada forests, dense shrub fields occupy sites formerly occupied by mature conifers, until eventually conifers overtop and shade out shrubs. Attempting to reduce fuel loads and expedite forest regeneration in these areas, the USDA Forest Service often disrupts this cycle by the logging of fire-killed trees, replanting of conifers and killing of shrubs. We measured the effects of these treatments on live and dead fuel loads and alien species and modeled potential fire behavior and fire effects on regenerating forests. Sampling occurred in untreated, logged and herbicide-treated stands throughout the Sierra Nevada in four large fire areas 4–21 years after stand-replacing fires. Logging fire-killed trees significantly increased total available dead fuel loads in the short term but did not affect shrub cover, grass and forb cover, alien species cover or alien species richness. Despite the greater available dead fuel loads, fire behavior was not modeled to be different between logged and untreated stands, due to abundant shrub fuels in both logged and untreated stands. In contrast, the herbicide treatment directed at shrubs resulted in extremely low shrub cover, significantly greater alien species richness and significantly greater alien grass and forb cover. Grass and forb cover was strongly correlated with solar radiation on the ground, which may be the primary reason that grass and forb cover was higher in herbicide treated stands with low shrub and tree cover. Repeat burning exacerbated the alien grass problem in some stands. Although modeled surface fire flame lengths and rates of spread were found to be greater in stands dominated by shrubs, compared to low shrub cover conifer plantations, surface fire would still be intense enough to kill most trees, given their small size and low crown heights in the first two decades after planting.

  17. Vegetation monitoring to detect and predict vegetation change: Connecting historical and future shrub/steppe data in Yellowstone National Park

    Science.gov (United States)

    Geneva Chong; David Barnett; Benjamin Chemel; Roy Renkin; Pamela Sikkink

    2011-01-01

    A 2002 National Research Council (NRC) evaluation of ungulate management practices in Yellowstone specifically concluded that previous (1957 to present) vegetation monitoring efforts were insufficient to determine whether climate or ungulates were more influential on shrub/steppe dynamics on the northern ungulate winter range. The NRC further recommended that the...

  18. The impact of aging on laboratory fire behaviour in masticated shrub fuelbeds of California and Oregon, USA

    Science.gov (United States)

    Jesse K. Kreye; J. Morgan Varner; Jeffrey M. Kane; Eric E. Knapp; Warren P. Reed

    2016-01-01

    Mastication of shrubs and small trees to reduce fire hazard has become a widespread management practice, yet many aspects of the fire behaviour of these unique woody fuelbeds remain poorly understood. To examine the effects of fuelbed aging on fire behaviour, we conducted laboratory burns with masticated Arctostaphylos spp. and Ceanothus...

  19. Experimental study and large eddy simulation of effect of terrain slope on marginal burning in shrub fuel beds

    Science.gov (United States)

    Xiangyang Zhou; Shankar Mahalingam; David Weise

    2007-01-01

    This paper presents a combined study of laboratory scale fire spread experiments and a three-dimensional large eddy simulation (LES) to analyze the effect of terrain slope on marginal burning behavior in live chaparral shrub fuel beds. Line fire was initiated in single species fuel beds of four common chaparral plants under various fuel bed configurations and ambient...

  20. Influence of canopy closure and shrub coverage on travel along coarse woody debris by Eastern chipmunks (Tamias striatus)

    Science.gov (United States)

    Patrick A. Zollner; Kevin J. Crane

    2003-01-01

    We investigated relationships between canopy closure, shrub cover and the use of coarse woody debris as a travel path by eastern chipmunks (Tamias striatus) in the north central United States. Fine scale movements of chipmunks were followed with tracking spools and the percentage of each movement path directly along coarse woody debris was recorded...

  1. Natural forest expansion on reclaimed coal mines in Northern Spain: the role of native shrubs as suitable microsites.

    Science.gov (United States)

    Alday, Josu G; Zaldívar, Pilar; Torroba-Balmori, Paloma; Fernández-Santos, Belén; Martínez-Ruiz, Carolina

    2016-07-01

    The characterization of suitable microsites for tree seedling establishment and growth is one of the most important tasks to achieve the restoration of native forest using natural processes in disturbed sites. For that, we assessed the natural Quercus petraea forest expansion in a 20-year-old reclaimed open-cast mine under sub-Mediterranean climate in northern Spain, monitoring seedling survival, growth, and recruitment during 5 years in three contrasting environments (undisturbed forest, mine edge, and mine center). Seedling density and proportion of dead branches decreased greatly from undisturbed forest towards the center of the mine. There was a positive effect of shrubs on Q. petraea seedling establishment in both mine environments, which increase as the environment undergoes more stress (from the mine edge to the center of the mine), and it was produced by different shrub structural features in each mine environment. Seedling survival reduction through time in three environments did not lead to a density reduction because there was a yearly recruitment of new seedlings. Seedling survival, annual growth, and height through time were greater in mine sites than in the undisturbed forest. The successful colonization patterns and positive neighbor effect of shrubs on natural seedlings establishment found in this study during the first years support the use of shrubs as ecosystem engineers to increase heterogeneity in micro-environmental conditions on reclaimed mine sites, which improves late-successional Quercus species establishment.

  2. Seasonal changes and vertical distribution of root standing biomass of graminoids and shrubs at a Siberian tundra site

    NARCIS (Netherlands)

    Wang, Peng; Mommer, L.; Ruijven, van J.; Berendse, F.; Maximov, T.; Heijmans, M.M.P.D.

    2016-01-01

    Aims

    Shrub expansion is common in the tundra biome and has been linked to climate warming. However, the underlying mechanisms are still not fully understood. This study aimed to investigate the seasonal and vertical rooting patterns of different plant functional types, which is important

  3. Testing aggregation hypotheses among Neotropical trees and shrubs: results from a 50-ha plot over 20 years of sampling.

    Science.gov (United States)

    Myster, Randall W; Malahy, Michael P

    2012-09-01

    Spatial patterns of tropical trees and shrubs are important to understanding their interaction and the resultant structure of tropical rainforests. To assess this issue, we took advantage of previously collected data, on Neotropical tree and shrub stem identified to species and mapped for spatial coordinates in a 50ha plot, with a frequency of every five years and over a 20 year period. These stems data were first placed into four groups, regardless of species, depending on their location in the vertical strata of the rainforest (shrubs, understory trees, mid-sized trees, tall trees) and then used to generate aggregation patterns for each sampling year. We found shrubs and understory trees clumped at small spatial scales of a few meters for several of the years sampled. Alternatively, mid-sized trees and tall trees did not clump, nor did they show uniform (regular) patterns, during any sampling period. In general (1) groups found higher in the canopy did not show aggregation on the ground and (2) the spatial patterns of all four groups showed similarity among different sampling years, thereby supporting a "shifting mosaic" view of plant communities over large areas. Spatial analysis, such as this one, are critical to understanding and predicting tree spaces, tree-tree replacements and the Neotropical forest patterns, such as biodiversity and those needed for sustainability efforts, they produce.

  4. Ungulate browsing maintains shrub diversity in the absence of episodic disturbance in seasonally-arid conifer forest

    Science.gov (United States)

    Burak K. Pekin; Michael J. Wisdom; Bryan A. Endress; Bridgett J. Naylor; Catherine G. Parks

    2014-01-01

    Ungulates exert a strong influence on the composition and diversity of vegetation communities. However, little is known about how ungulate browsing pressure interacts with episodic disturbances such as fire and stand thinning. We assessed shrub responses to variable browsing pressure by cattle and elk in fuels treated (mechanical removal of fuels followed by prescribed...

  5. Insect Pests of Shade Trees and Shrubs: A Guide for Commercial Nurserymen and Arborists. Publication E-41.

    Science.gov (United States)

    Schuder, Donald L.

    This guide presents information on controlling insect pests of ornamental trees and shrubs. It is organized for easy reference by nurserymen, arborists, and others desirous of controlling insect damage. General information given includes notes on spraying and sprayers, insecticides, general purpose sprays, phytotoxicity, and health precautions.…

  6. Shrub seed banks in mixed conifer forests of northern California and the role of fire in regulating abundance

    Science.gov (United States)

    Eric E. Knapp; Phillip C. Weatherspoon; Carl N. Skinner

    2012-01-01

    Understory shrubs play important ecological roles in forests of the western US, but they can also impede early tree growth and lead to fire hazard concerns when very dense. Some of the more common genera (Ceanothus, Arctostaphylos, and Prunus) persist for long periods in the seed bank, even in areas where plants have been...

  7. Both gas chromatography and an electronic nose reflect chemical polymorphism of juniper shrubs browsed or avoided by sheep.

    Science.gov (United States)

    Markó, Gábor; Novák, Ildikó; Bernáth, Jeno; Altbäcker, Vilmos

    2011-07-01

    Chemical polymorphism may contribute to variation in browsing damage by mammalian herbivores. Earlier, we demonstrated that essential oil concentration in juniper, Juniperus communis, was negatively associated with herbivore browsing. The aim of the present study was to characterize the volatile chemical composition of browsed and non-browsed J. communis. By using either gas chromatography with flame ionization detection (GC-FID) or an electronic nose device, we could separate sheep-browsed or non-browsed juniper shrubs by their essential oil pattern and complex odor matrix. The main components of the essential oil from J. communis were monoterpenes. We distinguished three chemotypes, dominated either by α-pinene, sabinene, or δ-3-carene. Shrubs belonging to the α-pinene- or sabinene-dominated groups were browsed, whereas all individuals with the δ-3-carene chemotype were unused by the local herbivores. The electronic nose also separated the browsed and non-browsed shrubs indicating that their odor matrix could guide sheep browsing. Responses of sheep could integrate the post-ingestive effects of plant secondary metabolites with sensory experience that stems from odor-phytotoxin interactions. Chemotype diversity could increase the survival rate in the present population of J. communis as certain shrubs could benefit from relatively better chemical protection against the herbivores.

  8. Synergy of extreme drought and shrub invasion reduce ecosystem functioning and resilience in water-limited climates

    Science.gov (United States)

    Caldeira, Maria C.; Lecomte, Xavier; David, Teresa S.; Pinto, Joaquim G.; Bugalho, Miguel N.; Werner, Christiane

    2015-10-01

    Extreme drought events and plant invasions are major drivers of global change that can critically affect ecosystem functioning and alter ecosystem-atmosphere exchange. Invaders are expanding worldwide and extreme drought events are projected to increase in frequency and intensity. However, very little is known on how these drivers may interact to affect the functioning and resilience of ecosystems to extreme events. Using a manipulative shrub removal experiment and the co-occurrence of an extreme drought event (2011/2012) in a Mediterranean woodland, we show that native shrub invasion and extreme drought synergistically reduced ecosystem transpiration and the resilience of key-stone oak tree species. Ecosystem transpiration was dominated by the water use of the invasive shrub Cistus ladanifer, which further increased after the extreme drought event. Meanwhile, the transpiration of key-stone tree species decreased, indicating a competitive advantage in favour of the invader. Our results suggest that in Mediterranean-type climates the invasion of water spending species and projected recurrent extreme drought events may synergistically cause critical drought tolerance thresholds of key-stone tree species to be surpassed, corroborating observed higher tree mortality in the invaded ecosystems. Ultimately, this may shift seasonally water limited ecosystems into less desirable alternative states dominated by water spending invasive shrubs.

  9. The chemical defoliation of Ligitstrum vulgare L. and Spiraea x arguta Zab. shrubs in nursery

    Directory of Open Access Journals (Sweden)

    Szczepan Marczyński

    2015-06-01

    Full Text Available To defoliate Ligustrum vulgare and Spiraea x arguta – ethephon, KJ, Mg(ClO32•6H2O, CuSO4•5H2O and (NH42SO4 in various concentrations were used alone or in mixtures. Treating plants with potassium iodide gave the best results. KJ concentrations of 0.05-0,1% and 0.1-0.% were sufficient to defoliate Spiraea and Ligusturm respectively. Magnesium chlorate at concentration of 0.24 and 2% CuSO4 were also effective, the latter however, proved slight harmful to the plants. Spraying with defoliants on Sept. 26 gave better results than treating plants on Sept. 16. Chemical defoliation decreased negligibly the frost resistance of Ligusturm vulgare shrubs.

  10. Investigation on the sensitivity of trees and shrubs for air pollution

    Energy Technology Data Exchange (ETDEWEB)

    Mooi, J

    1973-01-01

    Generally occurring species of trees and shrubs in the Netherlands were fumigated with SO/sub 2/ during some hours under field conditions to investigate their susceptibility to this gas and their capacity to recover. At the same time the resistance of the leaves to transpiration intensity is measured by means of the diffusion porometer with the aim to get information on the resistance to diffusion of SO/sub 2/ from the atmosphere into the cells. Various hard wood species were fumigated in large fumigation chambers with 1.5 ppb HF during four months and subsequently with 3 ppb HF during two months to become informed on the uptake capacity for HF of the different tree species in combination with the resistance of the trees to HF.

  11. THE ROLE OF POLYPLOIDY IN ADAPTATION AND SETTLING OF STEPPE SHRUBS IN CENTRAL ASIA

    Directory of Open Access Journals (Sweden)

    Natalia V Ekimova

    2011-03-01

    Full Text Available Chromosome numbers for some species of Central Asia steppe shrubs are given: Rhamnus erythroxylon Pall. (Rhamnaceae, Caragana buriatica Peschk. (Fabaceae, Amygdalus pedunculata Pall., Armeniaca sibirica (L. Lam. (Rosaceae, Atraphaxis pungens (Bieb. Jaub. et Spach. and A. frutescens (L. C. Koch (Polygonaceae. Chromosome numbers of some species were determined for the first time. Comparative analysis of adaptive properties of polyploid and diploid species has been conducted. It was established that natural polyploids are more adaptive to existence in extreme conditions. They possess by high potential for survival and characterized by more high level of intraspecific polymorphism, abundant flowering and fruitification, ability of propagate both generative and vegetative means, high seed germination.

  12. Dendrochronological potential of the alpine shrub Rhododendron nivale on the south-eastern Tibetan Plateau.

    Science.gov (United States)

    Liang, Eryuan; Eckstein, Dieter

    2009-09-01

    Shrubs and dwarf shrubs are wider spread on the Tibetan Plateau than trees and hence offer a unique opportunity to expand the present dendrochronological network into extreme environments beyond the survival limit of trees. Alpine shrublands on the Tibetan Plateau are characterized by rhododendron species. The dendrochronological potential of one alpine rhododendron species and its growth response to the extreme environment on the south-east Tibetan Plateau were investigated. Twenty stem discs of the alpine snowy rhododendron (Rhododendron nivale) were collected close to the tongue of the Zuoqiupu Glacier in south-east Tibet, China. The skeleton plot technique was used for inter-comparison between samples to detect the growth pattern of each stem section. The ring-width chronology was developed by fitting a negative exponential function or a straight line of any slope. Bootstrapping correlations were calculated between the standard chronology and monthly climate data. The wood of snowy rhododendron is diffuse-porous with evenly distributed small-diameter vessels. It has well-defined growth rings. Most stem sections can be visually and statistically cross-dated. The resulting 75-year-long standard ring-width chronology is highly correlated with a timberline fir chronology about 200 km apart, providing a high degree of confidence in the cross-dating. The climate/growth association of alpine snowy rhododendron and of this timberline fir is similar, reflecting an impact of monthly mean minimum temperatures in November of the previous year and in July during the year of ring formation. The alpine snowy rhododendron offers new research directions to investigate the environmental history of the Tibetan Plateau in those regions where up to now there was no chance of applying dendrochronology.

  13. Transpiration of shrub species, Alnus firma under changing atmospheric environments in montane area, Japan

    Science.gov (United States)

    Miyazawa, Y.; Maruyama, A.; Inoue, A.

    2014-12-01

    In the large caldera of Mt. Aso in Japan, grasslands have been traditionally managed by the farmers. Due to changes in the social structure of the region, a large area of the grassland has been abandoned and was invaded by the shrubs with different hydrological and ecophysiological traits. Ecophysiological traits and their responses to seasonally changing environments are fundamental to project the transpiration rates under changing air and soil water environments, but less is understood. We measured the tree- and leaf-level ecophysiological traits of a shrub, Alnus firma in montane region where both rainfall and soil water content drastically changes seasonally. Sap flux reached the annual peak in evaporative summer (July-August) both in 2013 and 2014, although the duration was limited within a short period due to the prolonged rainy season before summer (2014) and rapid decrease in the air vapor pressure deficit (D) in late summer. Leaf ecophysiological traits in close relationship with gas exchange showed modest seasonal changes and the values were kept at relatively high levels typical in plants with nitrogen fixation under nutrient-poor environments. Stomatal conductance, which was measured at leaf-level measurements and sap flux measurements, showed responses to D, which coincided with the theoretical response for isohydric leaves. A multilayer model, which estimates stand-level transpiration by scaling up the leaf-level data, successfully captured the temporal trends in sap flux, suggesting that major processes were incorporated. Thus, ecophysiological traits of A. firma were characterized by the absence of responses to seasonally changing environments and the transpiration rate was the function of the interannually variable environmental conditions.

  14. Comparing ecohydrological processes in alien vs. native ranges: perspectives from the endangered shrub Myricaria germanica

    Science.gov (United States)

    Michielon, Bruno; Campagnaro, Thomas; Porté, Annabel; Hoyle, Jo; Picco, Lorenzo; Sitzia, Tommaso

    2017-04-01

    Comparing the ecology of woody species in their alien and native ranges may provide interesting insights for theoretical ecology, invasion biology, restoration ecology and forestry. The literature which describes the biological evolution of successful plant invaders is rich and increasing. However, no general theories have been developed about the geomorphic settings which may limit or favour the alien woody species expansion along rivers. The aim of this contribution is to explore the research opportunities in the comparison of ecohydrological processes occurring in the alien vs. the native ranges of invasive tree and shrub species along the riverine corridor. We use the endangered shrub Myricaria germanica as an example. Myricaria germanica is an Euro-Asiatic pioneer species that, in the native range, develops along natural rivers, wide and dynamic. These conditions are increasingly limited by anthropogenic constraints in most European rivers. This species has been recently introduced in New Zealand, where it is spreading in some natural rivers of the Canterbury region (South Island). We present the current knowledge about the natural and anthropogenic factors influencing this species in its native range. We compare this information with the current knowledge about the same factors influencing M. germanica invasiveness and invasibility of riparian habitats in New Zealand. We stress the need to identify potential factors which could drive life-traits and growing strategies divergence which may hinder the application to the alien ranges of existing ecohydrological knowledge from native ranges. Moreover, the pattern of expansion of the alien range of species endangered in their native ranges opens new windows for research.

  15. Range expansion of invasive shrubs: implication for crown fire risk in forestlands of the southern USA.

    Science.gov (United States)

    Wang, Hsiao-Hsuan; Wonkka, Carissa L; Grant, William E; Rogers, William E

    2016-01-01

    Non-native plant invasions and changing management activities have dramatically altered the structure and composition of forests worldwide. Invasive shrubs and fire suppression have led to increased densification and biomass accumulation in forest ecosystems of the southeastern USA. Notably, Chinese and European privets are rapid growing, shade-tolerant shrubs which number among the most aggressive invasive species in these forests. Privet encroachment has caused losses of native diversity, alteration of ecosystem processes and changes in community structure. The latter has become manifest through decreases in fine herbaceous fuels concurrent with increases in coarse woody fuels in forest understoreys. These alterations in fuel structure will potentially lead to less frequent, but more severe forest fires, which threaten important forest resources during extreme weather conditions. Drawing on extensive data sets compiled by the US Forest Service, we integrated statistical forecasting and analytical techniques within a spatially explicit, agent-based, simulation framework to predict potential range expansion of Chinese and European privet (Ligustrum sinenseandL. vulgare) and the associated increase in crown fire risk over the next two decades in forestlands of Mississippi and Alabama. Our results indicate that probability of invasion is positively associated with elevation, adjacency (within 300 m) to water bodies, mean daily maximum temperature, site productivity and private land ownership, and is negatively associated with slope, stand age, artificial regeneration, distance to the nearest road and fire disturbance. Our projections suggest the total area invaded will increase from 1.36 to ≈31.39% of all forestlands in Mississippi and Alabama (≈7 million hectares) and the annual frequency of crown fires in these forestlands will approximately double within the next two decades. Such time series projections of annual range expansions and crown fire frequency

  16. Water use patterns of co-occurring C3 and C4 shrubs in the Gurbantonggut desert in northwestern China.

    Science.gov (United States)

    Tiemuerbieke, Bahejiayinaer; Min, Xiao-Jun; Zang, Yong-Xin; Xing, Peng; Ma, Jian-Ying; Sun, Wei

    2018-09-01

    In water-limited ecosystems, spatial and temporal partitioning of water sources is an important mechanism that facilitates plant survival and lessens the competition intensity of co-existing plants. Insights into species-specific root functional plasticity and differences in the water sources of co-existing plants under changing water conditions can aid in accurate prediction of the response of desert ecosystems to future climate change. We used stable isotopes of soil water, groundwater and xylem water to determine the seasonal and inter- and intraspecific differences variations in the water sources of six C 3 and C 4 shrubs in the Gurbantonggut desert. We also measured the stem water potentials to determine the water stress levels of each species under varying water conditions. The studied shrubs exhibited similar seasonal water uptake patterns, i.e., all shrubs extracted shallow soil water recharged by snowmelt water during early spring and reverted to deeper water sources during dry summer periods, indicating that all of the studied shrubs have dimorphic root systems that enable them to obtain water sources that differ in space and time. Species in the C 4 shrub community exhibited differences in seasonal water absorption and water status due to differences in topography and rooting depth, demonstrating divergent adaptations to water availability and water stress. Haloxylon ammodendron and T. ramosissima in the C 3 /C 4 mixed community were similar in terms of seasonal water extraction but differed with respect to water potential, which indicated that plant water status is controlled by both root functioning and shoot eco-physiological traits. The two Tamarix species in the C 3 shrub community were similar in terms of water uptake and water status, which suggests functional convergence of the root system and physiological performance under same soil water conditions. In different communities, Haloxylon ammodendron differed in terms of summer water extraction

  17. Effect of Tree-to-Shrub Type Conversion in Lower Montane Forests of the Sierra Nevada (USA on Streamflow.

    Directory of Open Access Journals (Sweden)

    Ryan R Bart

    Full Text Available Higher global temperatures and increased levels of disturbance are contributing to greater tree mortality in many forest ecosystems. These same drivers can also limit forest regeneration, leading to vegetation type conversion. For the Sierra Nevada of California, little is known about how type conversion may affect streamflow, a critical source of water supply for urban, agriculture and environmental purposes. In this paper, we examined the effects of tree-to-shrub type conversion, in combination with climate change, on streamflow in two lower montane forest watersheds in the Sierra Nevada. A spatially distributed ecohydrologic model was used to simulate changes in streamflow, evaporation, and transpiration following type conversion, with an explicit focus on the role of vegetation size and aspect. Model results indicated that streamflow may show negligible change or small decreases following type conversion when the difference between tree and shrub leaf areas is small, partly due to the higher stomatal conductivity and the deep rooting depth of shrubs. In contrast, streamflow may increase when post-conversion shrubs have a small leaf area relative to trees. Model estimates also suggested that vegetation change could have a greater impact on streamflow magnitude than the direct hydrologic impacts of increased temperatures. Temperature increases, however, may have a greater impact on streamflow timing. Tree-to-shrub type conversion increased streamflow only marginally during dry years (annual precipitation < 800 mm, with most streamflow change observed during wetter years. These modeling results underscore the importance of accounting for changes in vegetation communities to accurately characterize future hydrologic regimes for the Sierra Nevada.

  18. Effect of Tree-to-Shrub Type Conversion in Lower Montane Forests of the Sierra Nevada (USA) on Streamflow

    Science.gov (United States)

    Tague, Christina L.; Moritz, Max A.

    2016-01-01

    Higher global temperatures and increased levels of disturbance are contributing to greater tree mortality in many forest ecosystems. These same drivers can also limit forest regeneration, leading to vegetation type conversion. For the Sierra Nevada of California, little is known about how type conversion may affect streamflow, a critical source of water supply for urban, agriculture and environmental purposes. In this paper, we examined the effects of tree-to-shrub type conversion, in combination with climate change, on streamflow in two lower montane forest watersheds in the Sierra Nevada. A spatially distributed ecohydrologic model was used to simulate changes in streamflow, evaporation, and transpiration following type conversion, with an explicit focus on the role of vegetation size and aspect. Model results indicated that streamflow may show negligible change or small decreases following type conversion when the difference between tree and shrub leaf areas is small, partly due to the higher stomatal conductivity and the deep rooting depth of shrubs. In contrast, streamflow may increase when post-conversion shrubs have a small leaf area relative to trees. Model estimates also suggested that vegetation change could have a greater impact on streamflow magnitude than the direct hydrologic impacts of increased temperatures. Temperature increases, however, may have a greater impact on streamflow timing. Tree-to-shrub type conversion increased streamflow only marginally during dry years (annual precipitation < 800 mm), with most streamflow change observed during wetter years. These modeling results underscore the importance of accounting for changes in vegetation communities to accurately characterize future hydrologic regimes for the Sierra Nevada. PMID:27575592

  19. Communities of Putative Ericoid Mycorrhizal Fungi Isolated from Alpine Dwarf Shrubs in Japan: Effects of Host Identity and Microhabitat.

    Science.gov (United States)

    Koizumi, Takahiko; Nara, Kazuhide

    2017-06-24

    Dwarf shrubs of the family Ericaceae are common in arctic and alpine regions. Many of these plants are associated with ericoid mycorrhizal (ERM) fungi, which allow them to take nutrients and water from the soil under harsh environmental conditions and, thus, affect host plant survival. Despite the importance of ERM fungi to alpine plant communities, limited information is available on the effects of microhabitat and host identity on ERM fungal communities. We investigated the communities of putative ERM fungi isolated from five dwarf shrub species (Arcterica nana, Diapensia lapponica, Empetrum nigrum, Loiseleuria procumbens, and Vaccinium vitis-idaea) that co-occur in an alpine region of Japan, with reference to distinct microhabitats provided by large stone pine (Pinus pumila) shrubs (i.e. bare ground, the edge of stone pine shrubs, and the inside of stone pine shrubs). We obtained 703 fungal isolates from 222 individual plants. These isolates were classified into 55 operational taxonomic units (OTUs) based on the sequencing of internal transcribed spacer regions in ribosomal DNA. These putative ERM fungal communities were dominated by Helotiales fungi for all host species. Cistella and Trimmatostroma species, which have rarely been detected in ERM roots in previous studies, were abundant. ERM fungal communities were significantly different among microhabitats (R 2 =0.28), while the host effect explained less variance in the fungal communities after excluding the microhabitat effect (R 2 =0.17). Our results suggest that the host effect on ERM fungal communities is minor and the distributions of hosts and fungal communities may be assessed based on microhabitat conditions.

  20. Potential of fodder tree/shrub legumes as a feed resource for dry season supplementation of smallholder ruminant animals

    International Nuclear Information System (INIS)

    Simbaya, J.

    2002-01-01

    Fodder tree/shrub legumes have the potential for alleviating some of the feed shortages and nutritional deficiencies experienced in the dry season on smallholder farms. Zambia has a wide range of naturally occurring tree/shrub species that can be used as fodder for ruminants. Over the years a number of trees have been selected for their agronomic qualities and are currently being used in arable farming systems to promote soil fertility and erosion control. There is a need to evaluate them for use as fodder for ruminants in the dry season. Because of their high content of protein, minerals and vitamins and availability in the dry season, fodder tree/shrub legumes have the capacity to complement the feeding of crop-residues and natural pastures. Tree/shrub legumes also have other advantages in that they are available on-farm and can also be used as a source of food, timber and medicines at village level. Being deep rooted, fodder trees are rarely affected by seasonal climatic changes. The main limitation to their use as a feed resource for ruminants is the high tannin content which may have detrimental effects on the performance of animals. A number of techniques including, wilting, sun-drying, treatment with chemicals and ammoniation have been developed to minimize their adverse effects. Controlled intake through stall feeding or mixing of tree/shrub fodder with basal diets could also be used to mitigate their toxic effects. Research is currently under way to establish rumen microbes that have capacity to detoxify tannins. To promote increased use of fodder trees on smallholder farms, farmers must be provided with information on the good quality fodder trees and the approaches to effectively utilise them. They should also be encouraged to start planting fodder trees in their food crop farming systems or establishing fodder gardens on fallow lands. (author)

  1. Arctic tundra shrub invasion and soot deposition: Consequences for spring snowmelt and near-surface air temperatures

    Science.gov (United States)

    Strack, John E.; Pielke, Roger A.; Liston, Glen E.

    2007-12-01

    Invasive shrubs and soot pollution both have the potential to alter the surface energy balance and timing of snow melt in the Arctic. Shrubs reduce the amount of snow lost to sublimation on the tundra during the winter leading to a deeper end-of-winter snowpack. The shrubs also enhance the absorption of energy by the snowpack during the melt season by converting incoming solar radiation to longwave radiation and sensible heat. Soot deposition lowers the albedo of the snow, allowing it to more effectively absorb incoming solar radiation and thus melt faster. This study uses the Colorado State University Regional Atmospheric Modeling System version 4.4 (CSU-RAMS 4.4), equipped with an enhanced snow model, to investigate the effects of shrub encroachment and soot deposition on the atmosphere and snowpack in the Kuparuk Basin of Alaska during the May-June melt period. The results of the simulations suggest that a complete invasion of the tundra by shrubs leads to a 2.2°C warming of 3 m air temperatures and a 108 m increase in boundary layer depth during the melt period. The snow-free date also occurred 11 d earlier despite having a larger initial snowpack. The results also show that a decrease in the snow albedo of 0.1, owing to soot pollution, caused the snow-free date to occur 5 d earlier. The soot pollution caused a 1.0°C warming of 3 m air temperatures and a 25 m average deepening of the boundary layer.

  2. Radiative transfer in shrub savanna sites in Niger: preliminary results from HAPEX-Sahel. 2. Photosynthetically active radiation interception of the woody layer

    International Nuclear Information System (INIS)

    Bégué, A.; Hanan, N.P.; Prince, S.D.

    1994-01-01

    Interception by the woody layer of photosynthetically active radiation (PAR) was measured and calculated for two Guiera senegalensis J.F. Gmel, shrub savannas in Ouallam, Western Niger, in 1991 as part of the HAPEX-Sahel experiment. Two different scales were considered. At the plant scale, PAR interception was measured throughout the day with amorphous silicon sensors, together with detailed measurements of the structure of the shrubs (size of the ‘envelope’ of the shrub, area index, and angular distribution of the leaves and the branches). These data permitted us to develop and validate a simple radiative transfer model in which the shrubs are represented by porous cylinders; the total transmissivity (or porosity) of the shrubs estimated by the model was approximately 0.4. It indicates that semi-arid shrubs cannot be considered opaque objects and that the fraction of ground covered with plants is a poor indicator of the PAR interception efficiency of the canopy. The model was also applied at a landscape scale to calculate the daily PAR interception of two shrub savanna sites. This value is needed to model primary production in conjunction with remotely sensed and production data acquired simultaneously on the sites. (author)

  3. [Dynamics and modeling of water content of ten shrub species in their growth period in Maoershan Mountain region of Northeast China].

    Science.gov (United States)

    Jin, Sen; Yan, Xue-Jiao

    2012-12-01

    Based on the two successive years observation of the water content of ten representative shrub species in Maoershan Mountain region of Northeast China, this paper studied the dynamics of the water content of these shrub species during their growth period and related affecting factors, with the prediction models of the shrub water content established. For the ten shrub species, their minimal water content during growth period was higher than 100% , and most of the species had a water content higher than 200% within the period from the late phase of leaf-unfolding to early phase of leaf-falling. Euonymus verrucosus, Sorbaria sorbifolia, and Sambucus williamsii were incombustible in their whole growth period due to the extremely high water content, while Syringa reticulate, Philadelphus schrenkii, Euonymus verrucosus, Spiraea chamaedryfolia, Lonicera maackii, Lonicera ruprechtiana, and Rhamnus parvifolia were combustible only in the phases of budding and leaf-falling. Soil moisture content and daily maximum temperature had effects on the water content of most (7) of the ten shrubs, and canopy drought severity index affected the water content of 5 of the ten shrubs. The established 9 prediction models could explain more than 35% of the water content variance of the shrub species, with a mean MRE of 35.9% and a mean MRE of 13.4%.

  4. Soil water availability and microsite mediate fungal and bacterial phospholipid fatty acid biomarker abundances in Mojave Desert soils exposed to elevated atmospheric CO2

    Science.gov (United States)

    Jin, V. L.; Schaeffer, S. M.; Ziegler, S. E.; Evans, R. D.

    2011-06-01

    Changes in the rates of nitrogen (N) cycling, microbial carbon (C) substrate use, and extracellular enzyme activities in a Mojave Desert ecosystem exposed to elevated atmospheric CO2 suggest shifts in the size and/or functional characteristics of microbial assemblages in two dominant soil microsites: plant interspaces and under the dominant shrub Larrea tridentata. We used ester-linked phospholipid fatty acid (PLFA) biomarkers as a proxy for microbial biomass to quantify spatial and temporal differences in soil microbial communities from February 2003 to May 2005. Further, we used the 13C signature of the fossil CO2 source for elevated CO2 plots to trace recent plant C inputs into soil organic matter (SOM) and broad microbial groups using δ13C (‰). Differences between individual δ13CPLFA and δ13CSOM for fungal biomarkers indicated active metabolism of newer C in elevated CO2 soils. Total PLFA-C was greater in shrub microsites compared to plant interspaces, and CO2 treatment differences within microsites increased under higher soil water availability. Total, fungal, and bacterial PLFA-C increased with decreasing soil volumetric water content (VWC) in both microsites, suggesting general adaptations to xeric desert conditions. Increases in fungal-to-bacterial PLFA-C ratio with decreasing VWC reflected functional group-specific responses to changing soil water availability. While temporal and spatial extremes in resource availability in desert ecosystems contribute to the difficulty in identifying common trends or mechanisms driving microbial responses in less extreme environments, we found that soil water availability and soil microsite interacted with elevated CO2 to shift fungal and bacterial biomarker abundances in Mojave Desert soils.

  5. Short-term regeneration dynamics of Wyoming big sagebrush at two sites in northern Utah

    Science.gov (United States)

    The herbicide tebuthiuron has been used historically to control cover of Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis - complete taxonomic designation), a widespread shrub across the western United States, with the intent of increasing herbaceous plant cover. Although the tebuthiur...

  6. Attempting to restore herbaceous understories in Wyoming big sagebrush communities with mowing and seeding

    Science.gov (United States)

    Shrub steppe communities with depleted perennial herbaceous understories need to be restored to increase resilience, provide quality wildlife habitat, and improve ecosystem function. Mowing has been applied to Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis Beetle &Young) steppe...

  7. CO2 EFFECTS ON MOJAVE DESERT PLANT INTERACTIONS

    Energy Technology Data Exchange (ETDEWEB)

    L. A. DEFALCO; G. C. FERNANDEZ; S. D. SMITH; R. S. NOWAK

    2004-01-01

    Seasonal and interannual droughts characteristic of deserts have the potential to modify plant interactions as atmospheric CO{sub 2} concentrations continue to rise. At the Nevada Desert FACE (free-air CO{sub 2} enrichment) facility in the northern Mojave Desert, the effects of elevated atmospheric C02 (550 vs. ambient {approx}360 {micro}mol mol{sup -1}) on plant interactions were examined during two years of high and low rainfall. Results suggest that CO{sub 2} effects on the interaction between native species and their understory herbs are dependent on the strength of competition when rainfall is plentiful, but are unimportant during annual drought. Seasonal rainfall for 1999 was 23% the long-term average for the area, and neither elevated CO{sub 2} nor the low production of herbaceous neighbors had an effect on relative growth rate (RGR, d{sup -1}) and reproductive effort (RE, number of flowers g{sup -1}) for Achnatherum hymenoides (early season perennial C{sub 3} grass), Pleuraphis rigida (late season perennial C{sub 4} grass), and Larrea tridentata (evergreen C{sub 3} shrub). In contrast, 1998 received 213% the average rainfall. Consequently, the decrease in RGR and increase in RE for Achnatherum, whose period of growth overlaps directly with that of its neighbors, was exaggerated at elevated CO{sub 2}. However, competitive effects of neighbors on Eriogonum trichopes (a winter annual growing in shrub interspaces), Pleuraphis and Larrea were not affected by elevated CO{sub 2}, and possible explanations are discussed. Contrary to expectations, the invasive annual neighbor Bromus madritensis ssp. rubens had little influence on target plant responses because densities in 1998 and 1999 at this site were well below those found in other studies where it has negatively affected perennial plant growth. The extent that elevated CO{sub 2} reduces the performance of Achnatherum in successive years to cause its loss from the plant community depends more on future pressure

  8. The use of Mediterranean shrub to flight against the land degradation. The rainfall partitioning fluxes

    Science.gov (United States)

    García-Estringana, Pablo; Nieves Alonso-Blazquez, M.; Alegre, Jesús; Cerdà, Artemi

    2014-05-01

    Desertification can be triggered by the lost of vegetation (Izzo et al., 2013). One of the impacts of the lack of vegetation is the increase in the effective rainfall and then higher soil and water losses. Vegetation can reduce the effective rainfall by interception. To recover the land that is affected by Desertification we must select plant species that will intercept the rainfall, but will not avoid the rainfall to reach the soil. This is why, studies on the plant rainfall interception are relevant to flight Land Degradation processes. Soil erosion is highly dependent on the effective rainfall (Cerdà and Lasanta, 2005; Haile and Fetene; 2012; Miao et al., 2012, Prokop and Poręba, 2012). The amount of rainfall that reaches the soil surface and can contribute to detach and transport material is determined by the interception of plants. Interception is also a key factor of the watershed hydrology (Zema et al., 2012). The importance of the rainfall partitioning fluxes is related to the climatic conditions, as climate control the plant cover and the soil properties, and then the soil losses (Cerdà, 1998). Although the shrubs has been seen as a key vegetation cover in semiarid lands to control the soil and water losses (Cerdà and Doerr, 2007) little information is available about rainfall interception in Mediterranean shrub vegetation, due to technical difficulties to measure them in such small-sized vegetation (Belmonte Serrato and Romero Diaz, 1998). The aim of this work was to assess the influence of different Mediterranean shrubs (Retama sphaerocarpa, Colutea arborescens, Dorycnium pentaphyllum, Medicago strasseri, Pistacia Lentiscus and Quercus coccifera) on rainfall partitioning fluxes (interception losses, throughfall and stemflow) in semiarid environments. The experiment was carried out under natural rainfall conditions with live specimens during two years, with automatic measurement of rainfall partitioning fluxes. In order to assess the influence of

  9. Attempts to deactivate tannins in fodder shrubs with physical and chemical treatments

    Energy Technology Data Exchange (ETDEWEB)

    Ben Salem, H. [Institut National de la Recherche Agronomique de Tunisie, Laboratoire des Productions Animales et Fourrageres, Ariana (Tunisia)]. E-mail: bensalem.hichem@iresa.agrinet.tn; Saghrouni, L. [Institut National de la Recherche Agronomique de Tunisie, Laboratoire des Productions Animales et Fourrageres, Ariana (Tunisia); Ecole Superieure d' Agriculture de Mateur, Mateur (Tunisia); Nefzaoui, A. [Institut National de la Recherche Agronomique de Tunisie, Laboratoire des Productions Animales et Fourrageres, Ariana (Tunisia)

    2005-08-19

    Chopping, water sprinkling, storage under aerobic and anaerobic conditions, urea, wood ash, activated charcoal and polyethylene glycol 4000 (PEG) treatments were evaluated for their efficiency in deactivating tannins in shrub foliage. In a first trial, fresh leaves of Acacia cyanophylla Lindl. (acacia) were stored after chopping or without chopping and spraying or without spraying with water under aerobic or anaerobic conditions. The plant material was stored for 1, 7 and 14 days and analysed thereafter for extractable total phenols (TP), extractable total tannins (TT) and extractable condensed tannins (CT) contents. Chopping and water spraying substantially decreased the levels of TP, TT and CT of acacia. The rate of tannin deactivation increased in acacia stored under anaerobic conditions. Acacia stored for 7 days exhibited lower TP, TT and CT contents than that stored for only 1 day. Compared to the 7-day storage period, there was a further non-significant decrease in the level of these phenolic compounds when the storage duration was extended to 14 days. The highest level of rumen degradation of crude protein (CP) in sheep rumen was obtained with chopped, water sprinkled acacia leaves stored under anaerobic conditions. The second trial investigated the effect of increasing levels of urea (0, 20, 40, 60 and 80 g/kg) and treatment duration (7, 14, 21 and 28 days) on CP, TP, TT and CT in acacia leaves. The 20 g/kg urea level was sufficient to totally deactivate tannins in acacia even with the shortest storage period, i.e. 7 days. However, urea treatment increased ash-free neutral detergent fibre content and did not improve in sacco acacia degradation. In the third trial air-dried 1 mm ground samples of acacia and kermes oak (Quercus coccifera L.) leaves were added to water (control), acacia wood ash, activated charcoal or PEG solutions (100 g/kg) at 1:10 (w/v) and shaken for 20 min. All these four treatments decreased TP, TT and CT contents and could be classified

  10. Report and recommendations of the task force on tree and shrub planting on active oil sands tailings dams

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2011-02-15

    In oil sands reclamation operations in Canada there is a conflict between dam safety and the planting of trees and woody shrubs. Indeed, tree planting is being restricted on the downstream slopes of dams to avoid damage to drains and to ensure the integrity of visual and instrumentation monitoring conflicting thus with progressive reclamation. Alberta Environment hired the Oil Sands Research and Information Network (OSRIN), an independent organization which analyzes and interprets available knowledge on soil and water reclamation in the oil sands mining sector, to address this issue and make recommendations. The organization appointed a Task Force which presented its final report in March 2011. The Task Force recommended that the Engineer of Record should be responsible for determining the tree and shrub planting zones and that he should submit his plans to Alberta Environment for approval.

  11. Pathogenicity of the bioherbicide fungus chondrostereum purpureum to some trees and shrubs of southern Vancouver Island. FRDA report No. 246

    Energy Technology Data Exchange (ETDEWEB)

    Wall, R.E.

    1996-11-01

    Chondrostereum purpureum is a common stem-invading fungus of trees and shrubs. The fungus has attracted interest as a bioherbicide, but a better understanding of its biology is required. This study was undertaken to determine the range of virulence of isolates of C. purpureum from a given region on major hardwood species in British Columbia. The investigators inoculated wounds of stems of standing red alder (Alnus rubra) and bigleaf maple (Acer macrophyllum) saplings with 11 isolates of the fungus and measured the resulting stem cankers as an index of virulence. They also inoculated eight hardwood and shrub species with two isolates to demonstrate the range of susceptibility of species to the fungus, as well as the intraspecific variation.

  12. Influence of trees and shrubs on microclimate and sanitary state of air layers close to the ground surface at industrial sites of metallurgical works

    Energy Technology Data Exchange (ETDEWEB)

    Reva, M L; Filatova, R Ya

    1976-01-01

    The effect of trees and shrubs on working conditions was investigated at metallurgical works in the Ukraine. Indices used included air temperature and humidity, sulfuric anhydride, carbon monoxide and nitrogen oxide content. Indices were measured at varying distances from the sources of the industrial waste. In areas with trees and shrubs, air temperature was 3 to 5 degrees lower and relative humidity 8 to 10 degrees higher than out in the open. The level of industrial waste given off as gas was consistently less prevalent in areas with trees and shrubs than out in the open. Trees and shrubs were concluded to be essential for the health and well-being of the workers.

  13. The role of summer precipitation and summer temperature in establishment and growth of dwarf shrub Betula nana in northeast Siberian tundra

    DEFF Research Database (Denmark)

    Li, Bingxi; Heijmans, Monique M P D; Berendse, Frank

    2016-01-01

    It is widely believed that deciduous tundra-shrub dominance is increasing in the pan-Arctic region, mainly due to rising temperature. We sampled dwarf birch (Betula nana L.) at a northeastern Siberian tundra site and used dendrochronological methods to explore the relationship between climatic...... variables and local shrub dominance. We found that establishment of shrub ramets was positively related to summer precipitation, which implies that the current high dominance of B. nana at our study site could be related to high summer precipitation in the period from 1960 to 1990. The results confirmed...... that early summer temperature is most influential to annual growth rates of B. nana. In addition, summer precipitation stimulated shrub growth in years with warm summers, suggesting that B. nana growth may be co-limited by summer moisture supply. The dual controlling role of temperature and summer...

  14. Stable Isotopic Analysis on Water Utilization of Two Xerophytic Shrubs in a Revegetated Desert Area: Tengger Desert, China

    OpenAIRE

    Lei Huang; Zhishan Zhang

    2015-01-01

    Stable isotope studies on stable isotope ratios of hydrogen and oxygen in water within plants provide new information on water sources and water use patterns under natural conditions. In this study, the sources of water uptake for two typical xerophytic shrubs, Caragana korshinskii and Artemisia ordosica, were determined at four different-aged revegetated sites (1956, 1964, 1981, and 1987) in the Tengger Desert, a revegetated desert area in China. Samples from precipitation, soil water at dif...

  15. Electrical Resistivity Tomography Reveals Upward Redistribution of Soil-Water by Coyote Brush in a Shrub-Grassland Ecotone

    Science.gov (United States)

    Manning, J. E.; Schulz, M. S.; Lambrecht, D. S.

    2016-12-01

    Species imbalance within many California plant assemblages may arise due to more intense wildfires as well as climate warming. Given this, coyote brush (Baccharis pilularis DC), a native evergreen shrub known as a ready colonizer of disturbed soil, may become more dominant. While prolonged spring soil moisture is required for seedling establishment, 1+ year-old coyote brush can withstand low soil water potentials (-1.2 MPa). Beyond this, little is known about its soil-water dynamics. Hydraulic redistribution of water within the soil profile by plant roots has been established in numerous species in the past 20 years. Recent quantification of the water quantity re-distributed by root systems are beginning to provide detail that could inform ET, weathering, and carbon cycling models. Electrical resistivity tomography (ERT) has been used to study soil hydraulics in natural as well as cropland settings. This study is the first known to use ERT to investigate hydraulic redistribution in coyote brush. One mid-size shrub surrounded by open grassland was selected at the study site, located on a coastal marine terrace west of Santa Cruz, CA. The soil profile, previously characterized with ERT and auger-based soil-water sampling, includes a clay-rich B horizon and is texturally non-uniform due to bioturbation to 0.6 meter. The 12-m ERT survey transect had 48 semi-permanent electrodes, with the 4-m wide shrub canopy at probes 16 to 32. Five repeats of evening and morning surveys were conducted. Heterogeneous texture and severe soil drying necessitated qualitative comparison across time. Overnight resistivity changes using differences plots of the modelled data revealed increased moisture beneath the shrub canopy during the night. Areas beyond the canopy—presumably outside the root zone—experienced variable overnight changes, with moisture increasing in the clay-rich horizon. Preliminary analysis suggests that coyote brush roots redistribute water upward within the soil

  16. Transpiration and stomatal conductance in a young secondary tropical montane forest: contrasts between native trees and invasive understorey shrubs.

    Science.gov (United States)

    Ghimire, Chandra Prasad; Bruijnzeel, L Adrian; Lubczynski, Maciek W; Zwartendijk, Bob W; Odongo, Vincent Omondi; Ravelona, Maafaka; van Meerveld, H J Ilja

    2018-04-21

    It has been suggested that vigorous secondary tropical forests can have very high transpiration rates, but sap flow and stomatal conductance dynamics of trees and shrubs in these forests are understudied. In an effort to address this knowledge gap, sap flow (thermal dissipation method, 12 trees) and stomatal conductance (porometry, six trees) were measured for young (5-7 years) Psiadia altissima (DC.) Drake trees, a widely occurring species dominating young regrowth following abandonment of swidden agriculture in upland eastern Madagascar. In addition, stomatal conductance (gs) was determined for three individuals of two locally common invasive shrubs (Lantana camara L. and Rubus moluccanus L.) during three periods with contrasting soil moisture conditions. Values of gs for the three investigated species were significantly higher and more sensitive to climatic conditions during the wet period compared with the dry period. Further, gs of the understorey shrubs was much more sensitive to soil moisture content than that of the trees. Tree transpiration rates (Ec) were relatively stable during the dry season and were only affected somewhat by soil water content at the end of the dry season, suggesting the trees had continued access to soil water despite drying out of the topsoil. The Ec exhibited a plateau-shaped relation with vapour pressure deficit (VPD), which was attributed to stomatal closure at high VPD. Vapour pressure deficit was the major driver of variation in Ec, during both the wet and the dry season. Overall water use of the trees was modest, possibly reflecting low site fertility after three swidden cultivation cycles. The observed contrast in gs response to soil water and climatic conditions for the trees and shrubs underscores the need to take root distributions into account when modelling transpiration from regenerating tropical forests.

  17. Abundance of Alnus incana ssp. rugosa in Adirondack Mountain shrub wetlands and its influence on inorganic nitrogen

    International Nuclear Information System (INIS)

    Kiernan, B.D.; Hurd, T.M.; Raynal, D.J.

    2003-01-01

    The presence of the nitrogen-fixing shrub, Alnus incana ssp. rugosa, influences the concentration of inorganic nitrogen in surface waters in the Adirondack Mountain region of northern New York. - The purpose of this research was to determine the abundance of the nitrogen-fixing shrub, Alnus incana ssp. rugosa (speckled alder), in shrub wetlands of the Adirondack Mountain region of New York State and to determine whether its abundance affects the concentration or accumulation of inorganic nitrogen in wetland substrates. Alder/willow wetlands are the second most common wetland type in the Adirondack region. The Adirondack Park Agency's digital GIS database of wetland types was used to determine the areal extent of alder/willow wetlands in the Adirondacks. Randomly selected wetlands were sampled to determine the size and abundance of alder. Alder densities averaged ∼7000 stems ha -1 and alder was present in 75% of the wetlands. As an indication of short-term accumulation of NO 3 - and NH 4 + in wetland substrates, ion exchange resins were used to sample ground water in high and low alder density wetlands as well as from wetlands lacking alder and dominated by conifers. Additionally, NO 3 - and NH 4 + concentrations in ground water samples were measured. NH 4 + accumulation levels from exchange resins were low for all wetland types while groundwater NH 4 + concentration was highest in the low-density alder sites. Wetlands with high alder density had approximately six times higher NO 3 - accumulation than other wetlands. Substrate groundwater NO 3 - concentrations in wetlands of high-density alder exceeded by three times levels in low or no alder wetlands, showing the importance of alder to local N budgets. To assess the recovery of shrub wetlands from acidification, future studies should determine the fate of fixed N in wetland systems

  18. A tale of ENSO, PDO, and increasing aridity impacts on drought-deciduous shrubs in the Death Valley region.

    Science.gov (United States)

    Ehleringer, James R; Sandquist, Darren R

    2018-06-28

    Germination, establishment, phenology, and death among three drought-deciduous shrubs were influenced by ENSO/PDO and precipitation, based on 37 years of annual surveys. Encelia farinosa forms near monospecific stands on slopes, whereas E. frutescens and Ambrosia salsola dominate wash habitats. All shrubs exhibited phenological coherence. While germination, establishment, and mortality patterns were similar among wash species, these dynamics contrasted with E. farinosa on slopes. Germination was associated with El Niño years. Slope plant establishment was dependent on precipitation in the subsequent year, but not evidently so in wash species. Major mortality events were episodic, with Encelia mortality just as likely to occur in years with below or above average precipitation. In both Encelia species, mortality was associated with transitions to a cold PDO phase. In E. frutescens this response was more rapid, whereas in E. farinosa mortality lagged 1 year, resulting in contrasting slope-wash mortality patterns. 50% of newly established shrubs died within 5, 5, and 18 years for E. frutescens, E. farinosa, and A. salsola, respectively. The 90% mortality ages were 26 years for E. frutescens, 24 years for E. farinosa, and 51 years for A. salsola. While maximum life expectancies are unknown, estimated maximum life expectancies were 56, 66, and 86 years for E. frutescens, E. farinosa, and A. salsola, respectively. Overall, as the climate has become more arid over the past four decades, the populations in both slope and wash habitats have exhibited similar responses: reduced shrub abundances and reduced total supportable leaf areas.

  19. Evaluation of heavy metal pollution in bogs of Tomsk region on change in biogeochemical activity of ericaceous shrubs

    Science.gov (United States)

    Gaskova, L. P.

    2018-01-01

    The article discusses the change in biogeochemical activity of plant species in bogs under the influence of various types of human impact (roads, cities, drainage of mires, fire). It has been established that ericaceous shrubs, depending on the species, react with varying degrees of intensity to anthropogenic influences. The biogeochemical activity of species increased by 2.5 to 4.8 times in polluted sites.

  20. Parasitic macrofungi (Basidiomycetes on fruit shrubs and trees in the Tarnów town (S Poland

    Directory of Open Access Journals (Sweden)

    Marcin Piątek

    2014-08-01

    Full Text Available Results of 6 years of research carried out in the Tarnów town, southern Poland, are presented. Total number of 27 species of Basidiomycetes were recorded on 7 species of fruit shrubs and trees. Some of them were found on hosts new for Poland, on Malus domestica - Abortiporus biennis, Ganoderma australe, Meripilus giganteus, Stereum hirsutum and Volvariella bombycina; on Juglans regia - Ganoderma applanalum and Hineola auricula-judae.

  1. Ground based remote sensing and physiological measurements provide novel insights into canopy photosynthetic optimization in arctic shrubs

    Science.gov (United States)

    Magney, T. S.; Griffin, K. L.; Boelman, N.; Eitel, J.; Greaves, H.; Prager, C.; Logan, B.; Oliver, R.; Fortin, L.; Vierling, L. A.

    2014-12-01

    Because changes in vegetation structure and function in the Arctic are rapid and highly dynamic phenomena, efforts to understand the C balance of the tundra require repeatable, objective, and accurate remote sensing methods for estimating aboveground C pools and fluxes over large areas. A key challenge addressing the modelling of aboveground C is to utilize process-level information from fine-scale studies. Utilizing information obtained from high resolution remote sensing systems could help to better understand the C source/sink strength of the tundra, which will in part depend on changes in photosynthesis resulting from the partitioning of photosynthetic machinery within and among deciduous shrub canopies. Terrestrial LiDAR and passive hyperspectral remote sensing measurements offer an effective, repeatable, and scalable method to understand photosynthetic performance and partitioning at the canopy scale previously unexplored in arctic systems. Using a 3-D shrub canopy model derived from LiDAR, we quantified the light regime of leaves within shrub canopies to gain a better understanding of how light interception varies in response to the Arctic's complex radiation regime. This information was then coupled with pigment sampling (i.e., xanthophylls, and Chl a/b) to evaluate the optimization of foliage photosynthetic capacity within shrub canopies due to light availability. In addition, a lab experiment was performed to validate evidence of canopy level optimization via gradients of light intensity and leaf light environment. For this, hyperspectral reflectance (photochemical reflectance index (PRI)), and solar induced fluorescence (SIF)) was collected in conjunction with destructive pigment samples (xanthophylls) and chlorophyll fluorescence measurements in both sunlit and shaded canopy positions.

  2. Maternal habitat affects germination requirements of Anabasis setifera, a succulent shrub of the Arabian deserts

    Directory of Open Access Journals (Sweden)

    Ali El-Keblawy

    2016-03-01

    Full Text Available The effects of maternal habitat on light and temperature requirements during germination were assessed for the succulent desert shrub Anabasis setifera. Seeds were collected from the Mediterranean habitats of Egypt and the hyper-arid subtropical habitats of the United Arab Emirates (UAE. Seeds from the two populations were germinated in three temperature treatments in both a light/dark regime and continuous darkness. Seeds from the Egyptian population germinated significantly greater and faster than those of UAE. Seeds stored for four months at room temperatures have little dormancy and germinate at wide range of temperatures and light conditions, but seeds stored four months in the natural habitat lost their ability to germinate and rotted 10 days after incubation. The germination response to temperature depended on the habitat type. Seeds of the Egyptian population attained a significantly greater germination at lower temperatures, compared with seeds from the UAE population, but there was no difference in germination between the two populations at higher temperatures. Germination of A. setifera was very fast; most seeds germinated within four days. These results reflect the adaptive strategy of germination in both populations, and may help explain the wide distribution of this species in different climatic regions.

  3. Enzymatic Saccharification of Shrub Willow Genotypes with Differing Biomass Composition for Biofuel Production

    Directory of Open Access Journals (Sweden)

    Michelle J. Serapiglia

    2013-03-01

    Full Text Available In the conversion of woody biomass feedstocks into liquid fuel ethanol, the pretreatment process is the most critical and costly step. Variations in biomass composition based on genetic differences or environmental effects have a significant impact on the degree of accessibility accomplished by pretreatment and subsequent sugar release by enzymatic hydrolysis. To evaluate this, biomass from 10 genetically diverse, genotypes of shrub willow (Salix spp. was pretreated with a hot-water process at two levels of severity, hydrolyzed using a combination of two commercial enzyme cocktails, and the release of hexose and pentose monomers was quantified by HPLC. Among the genotypes selected for analysis, cellulose content ranged from 39 to 45% (w/w and lignin content ranged from 20 to 23% (w/w at harvest. Differences in the effectiveness of the pretreatment process were observed among the various willow genotypes. Correlations were identified between total sugar release and % cellulose and % lignin content. There was a significant effect of pretreatment severity on polysaccharide accessibility, but the response to pretreatments was different among the genotypes. At the high severity pretreatment ‘SV1’ was the least recalcitrant with sugar release representing as much as 60% of total biomass. These results suggest that structural, as well as chemical characteristics of the biomass may influence pretreatment and hydrolytic efficiency.

  4. Hybridization of an invasive shrub affects tolerance and resistance to defoliation by a biological control agent

    Science.gov (United States)

    Williams, Wyatt I.; Friedman, Jonathan M.; Gaskin, John F.; Norton, Andrew P.

    2014-01-01

    Evolution has contributed to the successful invasion of exotic plant species in their introduced ranges, but how evolution affects particular control strategies is still under evaluation. For instance, classical biological control, a common strategy involving the utilization of highly specific natural enemies to control exotic pests, may be negatively affected by host hybridization because of shifts in plant traits, such as root allocation or chemical constituents. We investigated introgression between two parent species of the invasive shrub tamarisk (Tamarix spp.) in the western United States, and how differences in plant traits affect interactions with a biological control agent. Introgression varied strongly with latitude of origin and was highly correlated with plant performance. Increased levels of T. ramosissima introgression resulted in both higher investment in roots and tolerance to defoliation and less resistance to insect attack. Because tamarisk hybridization occurs predictably on the western U.S. landscape, managers may be able to exploit this information to maximize control efforts. Genetic differentiation in plant traits in this system underpins the importance of plant hybridization and may explain why some biological control releases are more successful than others.

  5. Climate change and the potential distribution of an invasive shrub, Lantana camara L.

    Directory of Open Access Journals (Sweden)

    Subhashni Taylor

    Full Text Available The threat posed by invasive species, in particular weeds, to biodiversity may be exacerbated by climate change. Lantana camara L. (lantana is a woody shrub that is highly invasive in many countries of the world. It has a profound economic and environmental impact worldwide, including Australia. Knowledge of the likely potential distribution of this invasive species under current and future climate will be useful in planning better strategies to manage the invasion. A process-oriented niche model of L. camara was developed using CLIMEX to estimate its potential distribution under current and future climate scenarios. The model was calibrated using data from several knowledge domains, including phenological observations and geographic distribution records. The potential distribution of lantana under historical climate exceeded the current distribution in some areas of the world, notably Africa and Asia. Under future scenarios, the climatically suitable areas for L. camara globally were projected to contract. However, some areas were identified in North Africa, Europe and Australia that may become climatically suitable under future climates. In South Africa and China, its potential distribution could expand further inland. These results can inform strategic planning by biosecurity agencies, identifying areas to target for eradication or containment. Distribution maps of risk of potential invasion can be useful tools in public awareness campaigns, especially in countries that have been identified as becoming climatically suitable for L. camara under the future climate scenarios.

  6. Shrub-Steppe Seasons A Natural History of the Mid-Columbia Basin

    Energy Technology Data Exchange (ETDEWEB)

    LE Rogers

    1995-08-01

    This book collects and updates a series of articles about the natural history of the Mid-Columbia region. The articles first appeared as a monthly column titled ''Natural History'' in the Tri-City Herald, beginning in May 1991. My approach has been to condense the best of what is known about the ecology of the region to a manageable length with little in the way of technical language and terms. Admittedly, there is a bias toward those topics and species on which I have either been personally involved or observed as part of the ecology research programs conducted on the Fitzner/Eberhardt Arid Lands Ecology (ALE) Reserve. The ALE Reserve is situated on the northeast-facing flank of the Rattlesnake Hills. Rattlesnake Mountain with a crest of over 3,600 feet is visible throughout much of the Mid-Columbia. Shrub-steppe grasslands once covered a large part of the western United States but most have been converted to other uses. The ALE site is the only remaining sizeable acreage (120 square miles) that is in near pristine condition and provides the only clear indication as to what the early trappers, traders, pioneers, and tribal members may have encountered in their day-to-day activities. In this respect, ALE provides a visible touchstone linking the past with the present for all of us.

  7. Productive performance of naked neck chickens that were fed leaf meal shrubs

    Directory of Open Access Journals (Sweden)

    Santos M Herrera G.

    2015-12-01

    Full Text Available Objective. To compare the productive performance of naked neck chickens (phases of initiation, growth and final that were fed meals Gliricidia sepium, Cajanus cajan and Morus alba leaves. Materials and methods. 192 chickens, 1-84 days of age were distributed in a randomized block design with three experimental groups (5% of shrub in the diet, 48 animals/ group, eight replicates/ treatment, six animals/ reply and three animals/ sex in each replicate were used. The control group consumed diet based on corn and soybeans. They were reared on floor. Weighed every seven days. Weight gain, voluntary intake, conversion, balance and efficiency of feed utilization were calculated. Results. The highest total feed intake and average daily gain in rearing were 37.43g 9509.96 g respectively for M. alba (p<0.05, which also presented the best efficiency of energy and protein. Meanwhile, G. sepium showed the lowest values. Conclusions. It is possible to replace 5% of corn and soy in the diet of naked neck chickens, with the inclusion of leaf meal M. alba and get a favorable productive behavior.

  8. An evaluation of fuelwood properties of some Aravally mountain tree and shrub species of Western India

    Energy Technology Data Exchange (ETDEWEB)

    Nirmal Kumar, J.I.; Patel, Kanti; Bhoi, Rohit Kumar [P.G. Department of Environmental Science and Technology, Institute of Science and Technology for Advanced Studies and Research (ISTAR), Vallabh Vidyanagar 388 120, Gujarat (India); Kumar, Rita N. [Department of Biological and Environmental Science, N.V. Patel college of Pure and Applied Sciences, Vallabh Vidyanagar 388 120, Gujarat (India)

    2011-01-15

    The study analyses the fuelwood characteristics of 26 trees including shrub species from the dry deciduous forest in Aravally region, Rajasthan, Western India was carried out to explore trees with potential for fuelwood production. Fuelwood value index (FVI) based on the properties of calorific value, wood density and ash. Calorific value was ranged between 18.54 {+-} 0.04 and 27.44 {+-} 0.09 KJ g{sup -1} in Jatropha curcus and Wrightia tinctoria respectively. Wood density varied from 0.538 {+-} 0.01 to 0.966 {+-} 0.07 g/cm{sup 3} in J. curcus and Acacia nilotica. Same way ash and moisture content was highest in J. curcus (3.38 {+-} 0.19%) and Sterculia urens (70.28 {+-} 7.52%) and lowest in Miliusa tomentosa (0.85 {+-} 0.06%) and Azadirachta indica (30.7 {+-} 10.02%) respectively. On the basis, of the 26 species analyzed, M. tomentosa has the highest FVI, followed by Lannea coromandelica, Acacia leucophloea, Madhuca indica, A. nilotica, W. tinctoria, Butea monosperma, Zizyphus nummularia, S. urens, Boswellia serrata, A. indica, Grewia tenax, Syzygium cuminii, Tectona grandis and Dalbergia sissoo were shown to have promising fuelwood production. (author)

  9. Physiological and Biochemical Responses in Two Ornamental Shrubs to Drought Stress.

    Science.gov (United States)

    Toscano, Stefania; Farieri, Elisa; Ferrante, Antonio; Romano, Daniela

    2016-01-01

    Drought stress is one of the most important abiotic stress limiting the plant survival and growth in the Mediterranean environment. In this work, two species typically grown in Mediterranean areas with different drought responses were used. Two shrubs, with slow (Photinia × fraseri Dress 'Red Robin') or fast (Eugenia uniflora L. 'Etna Fire') adaptation ability to drought, were subjected to three water regimes: well-watered (WW), moderate (MD), and severe (SD) drought stress conditions for 30 days. Net photosynthetic rate, stomatal conductance, maximum quantum efficiency of PSII photochemistry (Fv/Fm), relative water content (RWC), chlorophyll content, proline, malondialdehyde (MDA), and antioxidant enzyme activities (superoxide dismutase, catalase, and peroxidase) were measured. Results showed that RWC and proline were higher in Eugenia than in Photinia, demonstrating the greater tolerance of the latter to the water stress. The drought stress levels applied did not compromise photosynthetic efficiency through stomatal regulation, while a reduction of Fv/Fm ratio was observed at the end of the experimental period. MDA significantly increased after 30 days in both species. The antioxidant enzyme activities showed different responses to water stress conditions. In both species, the water stress scores showed positive, while proline content showed negative correlations with all physiological parameters.

  10. Identification of major backscattering sources in trees and shrubs at 10 GHz

    Science.gov (United States)

    Zoughi, R.; Wu, L. K.; Moore, R. K.

    1986-01-01

    A short-range very-fine-resolution FM-CW radar scatterometer has been used to identify the primary contributors to 10-GHz radar backscatter from pine, pin oak, American sycamore and sugar maple trees, and from creeping juniper shrubs. This system provided a range resolution of 11 cm and gave a 16-cm diameter illumination area at the target range of about 4 m. For a pine tree, the needles caused the strongest backscatter as well as the strongest attenuation in the radar signal. Cones, although insignificant contributors to the total backscatter, were more important for backscattering than for attenuation. For the rest of the trees, leaves were the strongest cause of backscattering and attenuation. However, in the absence of leaves, the petioles, small twigs, and branches gave relatively strong backscatter. For American sycamore and sugar maple trees, the fruits did not affect the total backscatter unless they were packed in clusters. For creeping juniper the backscattered energy and attenuation in the radar signal were mainly due to the top two layers of the evergreen scales. The contribution of the tree trunks was not determined.

  11. Quantification of tannins in tree and shrub foliage. A laboratory manual

    International Nuclear Information System (INIS)

    Makkar, H.P.S.

    2003-01-01

    Animal production systems in the tropical and subtropical countries utilize a wide range of feedstuffs; the main amongst these being the crop and industrial by-products, grasses, legumes, trees and shrubs. Trees and shrubs are of importance in animal production because they can provide significant protein supplements, especially in the dry season. But, the amount of tannins that they contain vary widely and largely unpredictably, and their effects on animals range from beneficial to toxicity and death. Similarly many agro-industrial by-products contain tannins. With a better understanding of tannin properties and proper management, they could become invaluable source of protein for strategic supplementation. As the demand for food rises, these unconventional feedstuffs must play an increasingly important part in the diet of animals, in particular for ruminants in small-holder farming in developing countries. It is therefore critical that proper techniques be used to measure and manage the anti-nutritional effects they cause. The analysis of tannins remains highly problematic. Various chemical assays for hydrolysable tannins and condensed tannins are available. Most tannin-containing feedstuffs contain both hydrolysable tannins and condensed tannins, but unfortunately only condensed tannins are generally analysed, probably because of simplicity of the assays measuring these; and the feedstuffs termed as tannin-containing or tannin-free feedstuffs. Furthermore, the biological effects are ascribed to mostly the condensed tannins (or the synonym: proanthocyanidins), which might be misleading. This paper reviews the available assays for hydrolysable tannins and condensed tannins and highlights the advantages and disadvantages of each. Protein precipitation assays, both isotopic and non-isotopic, representing the operational property of both hydrolysable tannins and condensed tannins; a tannin bioassay based on an in vitro simulation of the rumen and measurement of

  12. Contrasting growth phenology of native and invasive forest shrubs mediated by genome size.

    Science.gov (United States)

    Fridley, Jason D; Craddock, Alaä

    2015-08-01

    Examination of the significance of genome size to plant invasions has been largely restricted to its association with growth rate. We investigated the novel hypothesis that genome size is related to forest invasions through its association with growth phenology, as a result of the ability of large-genome species to grow more effectively through cell expansion at cool temperatures. We monitored the spring leaf phenology of 54 species of eastern USA deciduous forests, including native and invasive shrubs of six common genera. We used new measurements of genome size to evaluate its association with spring budbreak, cell size, summer leaf production rate, and photosynthetic capacity. In a phylogenetic hierarchical model that differentiated native and invasive species as a function of summer growth rate and spring budbreak timing, species with smaller genomes exhibited both faster growth and delayed budbreak compared with those with larger nuclear DNA content. Growth rate, but not budbreak timing, was associated with whether a species was native or invasive. Our results support genome size as a broad indicator of the growth behavior of woody species. Surprisingly, invaders of deciduous forests show the same small-genome tendencies of invaders of more open habitats, supporting genome size as a robust indicator of invasiveness. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

  13. Energetic evaluation of indigenous tree and shrub species in Basilicata, Southern Italy

    Directory of Open Access Journals (Sweden)

    Todaro L

    2007-01-01

    Full Text Available An evaluation of energetic characteristics such as high calorific value (on ash-free dry weight basis, ash, carbon, nitrogen, and moisture content of 12 indigenous tree and shrub species of Southern Italy (Basilicata Region was carried out. The studied species are the most abundant in this area: Quercus cerris L., Quercus pubescens Willd., Fraxinus ornus L., Populus canescens (Aiton Smith, Salix alba L., Alnus cordata L., Robinia pseudoacacia L., Olea europaea L., Spartium junceum L., Rubus hirtus W., Onopordum illirium L., Arundo donax L. For Q. cerris, Q. pubescens and O. europaea L., the energetic characteristics were measured by separating the wood components from the leaves. Q. cerris leaves contained the greatest high calorific value. F. ornus leaves had a greater ash content than the other samples while the lowest values were measured for S. junceum, Q. pubescens and R. pseudoacacia. The highest content of Carbon was in O. europaea leaves. A. donax and O. illirium had the lower level of high calorific value and Carbon than all the other species. The highest Nitrogen content was measured in Q. cerris leaves and the lowest one in F. ornus wood components.

  14. Invasive Shrub Mapping in an Urban Environment from Hyperspectral and LiDAR-Derived Attributes.

    Science.gov (United States)

    Chance, Curtis M; Coops, Nicholas C; Plowright, Andrew A; Tooke, Thoreau R; Christen, Andreas; Aven, Neal

    2016-01-01

    Proactive management of invasive species in urban areas is critical to restricting their overall distribution. The objective of this work is to determine whether advanced remote sensing technologies can help to detect invasions effectively and efficiently in complex urban ecosystems such as parks. In Surrey, BC, Canada, Himalayan blackberry ( Rubus armeniacus ) and English ivy ( Hedera helix ) are two invasive shrub species that can negatively affect native ecosystems in cities and managed urban parks. Random forest (RF) models were created to detect these two species using a combination of hyperspectral imagery, and light detection and ranging (LiDAR) data. LiDAR-derived predictor variables included irradiance models, canopy structural characteristics, and orographic variables. RF detection accuracy ranged from 77.8 to 87.8% for Himalayan blackberry and 81.9 to 82.1% for English ivy, with open areas classified more accurately than areas under canopy cover. English ivy was predicted to occur across a greater area than Himalayan blackberry both within parks and across the entire city. Both Himalayan blackberry and English ivy were mostly located in clusters according to a Local Moran's I analysis. The occurrence of both species decreased as the distance from roads increased. This study shows the feasibility of producing highly accurate detection maps of plant invasions in urban environments using a fusion of remotely sensed data, as well as the ability to use these products to guide management decisions.

  15. Effects of artificial sand fixing on community characteristics of a rare desert shrub.

    Science.gov (United States)

    Liu, Huiliang; Tao, Ye; Qiu, Dong; Zhang, Daoyuan; Zhang, Yongkuan

    2013-10-01

    Eremosparton songoricum (Fabaceae) is a rare, native, clonal small shrub of the deserts of central Asia. Although human activities have greatly fragmented the distribution of E. songoricum, it occurs in areas where artificial sand fixing (AS) has been implemented. We sought to explore whether AS promotes survival and growth of E. songoricum. In the Gurbantunggut Desert of northwestern China in June 2010, we established 10 plots in an area where sand fixing occurred (5-10 years previously) and 11 plots on original sand substrate on which some plants had settled without fixing sand. Sand fixing changed soil properties and biological characteristics in sand-fixed plots. The soil surface where sand fixing occurred was covered by algal crusts and some lichen, but not bare sand (BS). Soil nutrients; water content of deep soil (30-150 cm); overall plant and herbaceous species richness, diversity, abundance, and cover; above- and belowground biomass; and cover, biomass, and height of E. songoricum in the sand-fixed plots were significantly greater than in plots of BS. However, distribution of E. songoricum individuals in the 2 types of plots did not differ. Our results indicate AS may enhance survival of E. songoricum and increase the overall diversity and stability of the desert plant community. We suggest AS as a way to protect this rare desert plant in situ. © 2013 Society for Conservation Biology.

  16. [Characteristics of foliar delta13C values of common shrub species in various microhabitats with different karst rocky desertification degrees].

    Science.gov (United States)

    Du, Xue-Lian; Wang, Shi-Jie; Rong, Li

    2011-12-01

    By measuring the foliar delta13C values of 5 common shrub species (Rhamnus davurica, Pyracantha fortuneana, Rubus biflorus, Zanthoxylum planispinum, and Viburnum utile) growing in various microhabitats in Wangjiazhai catchment, a typical karst desertification area in Guizhou Province, this paper studied the spatial heterogeneity of plant water use at niche scale and the response of the heterogeneity to different karst rocky desertification degrees. The foliar delta13C values of the shrub species in the microhabitats followed the order of stony surface > stony gully > stony crevice > soil surface, and those of the majority of the species were more negative in the microhabitat soil surface than in the others. The foliar delta13C values decreased in the sequence of V. utile > R. biflorus > Z. planispinum > P. fortuneana > R. davurica, and the mean foliar delta13C value of the shrubs and that of typical species in various microhabitats all increased with increasing karst rocky desertification degree, differed significantly among different microhabitats. It was suggested that with the increasing degree of karst rocky desertification, the structure and functions of karst habitats were impaired, microhabitats differentiated gradually, and drought degree increased.

  17. Feeding of tropical trees and shrub foliages as a strategy to reduce ruminal methanogenesis: studies conducted in Cuba.

    Science.gov (United States)

    Delgado, Denia Caridad; Galindo, Juana; González, Rogelio; González, Niurca; Scull, Idania; Dihigo, Luís; Cairo, Juan; Aldama, Ana Irma; Moreira, Onidia

    2012-06-01

    The aim of this paper was to present the main results obtained in Cuba on the effects of feeding tropical trees and shrubs on rumen methanogenesis in animals fed with low quality fibrous diets. More than 20 tree and shrub foliages were screened for phytochemicals and analyzed for chemical constituents. From these samples, seven promising plants (Samanea saman, Albizia lebbeck, Tithonia diversifolia, Leucaena leucocephala, Trichantera gigantea, Sapindus saponaria, and Morus alba) were evaluated for methane reduction using an in vitro rumen fermentation system. Results indicated that the inclusion levels of 25% of Sapindo, Morus, or Trichantera foliages in the foliages/grass mixtures (grass being Pennisetum purpureum) reduced (P lebbeck, or T. diversifolia accession 23 foliages when mixed at the rate of 30% in Cynodon nlemfuensis grass produced lower methane compared to the grass alone. Inclusion levels of 15% and 25% of a ruminal activator supplement containing 29% of L. leucocehala foliage meal reduced methane by 37% and 42% when compared to the treatment without supplementation. In vivo experiment with sheep showed that inclusion of 27% of L. leucocephala in the diet increased the DM intake but did not show significant difference in methane production compared to control diet without this foliage. The results of these experiments suggest that the feeding of tropical tree and shrub foliages could be an attractive strategy for reduction of ruminal methanogenesis from animals fed with low-quality forage diets and for improving their productivity.

  18. Habitat Effect on Allometry of a Xeric Shrub (Artemisia ordosica Krasch in the Mu Us Desert of Northern China

    Directory of Open Access Journals (Sweden)

    Weiwei She

    2015-12-01

    Full Text Available Allometric models are useful for assessment of aboveground net primary productivity (ANPP and aboveground biomass (AGB of forests and shrubs, and are widely implemented in forest inventory and management. Multiple forms of allometric models have been used to estimate vegetation carbon storage for desert shrubland, but their validity for biomass estimation has not been tested at a region scale with different habitats. To verify the validity of habitat-specific models, general models (combining data from all habitats/sites, and previously developed models for biomass prediction, we developed both general models and habitat-specific models for aboveground biomass and ANPP of Artemisia ordosica Krasch, a dominant shrub of the Mu Us Desert. Our results showed that models based on crown area or canopy volume consistently explained large parts of the variations in aboveground biomass and ANPP. Model fitting highlighted that general allometric models were inadequate across different habitats, and habitat-specific models were useful for that specific habitat. Previous models might be inappropriate for other sites because of site quality differences. There was a strong habitat effect on the allometric relationships of A. ordosica. Although our study is a case in point, the results indicate that allometric models for desert shrubs should be used with caution and require robust validation if adopted from other studies or applied to different sites/habitats.

  19. Dynamic responses of photosystem II in the Namib Desert shrub, Zygophyllum prismatocarpum, during and after foliar deposition of limestone dust

    International Nuclear Information System (INIS)

    Heerden, P.D.R. van; Krueger, G.H.J.; Kilbourn Louw, M.

    2007-01-01

    The effects of limestone dust deposition on vegetation in desert ecosystems have not yet been reported. We investigated these effects in a succulent shrub from the Namib Desert at a limestone quarry near Skorpion Zinc mine (Namibia). Effects of limestone dust were determined in Zygophyllum prismatocarpum (dollar bush) plants with heavy, moderate and no visible foliar dust cover by means of chlorophyll a fluorescence measurements. Limestone dust deposition decreased overall plant performance through loss of chlorophyll content, inhibition of CO 2 assimilation, uncoupling of the oxygen-evolving complex and decreased electron transport. Importantly, dynamic recovery occurred after termination of limestone extraction at the quarry. Recovery was accelerated by rainfall, mainly because of dust removal from leaves and stimulation of new growth. These results indicate that limestone dust has severe effects on photosynthesis in desert shrubs, but that recovery is possible and that, in arid environments, this process is modulated by rainfall. - Limestone dust deposition reduced photosynthetic capacity in the Namib Desert shrub, Zygophyllum prismatocarpum

  20. Species richness, alpha and beta diversity of trees, shrubs and herbaceous plants in the woodlands of swat, pakistan

    International Nuclear Information System (INIS)

    Akhtar, N.; Bergmeier, E.

    2015-01-01

    The variation in species richness and diversity of trees, shrubs and herbs in the mountains of Miandam, Swat, North Pakistan, along an elevation gradient between 1600 m and 3400 m was explored. Field data were collected in 18 altitudinal intervals of 100 m each. Polynomial regression was used to find relations of the different growth forms with elevation. The Shannon index was used for calculating α-diversity and the Simpson index for β-diversity. Species richness and α-diversity of herbs were unrelated to elevation. Herbaceous species turnover was high, ranging between 0.46 and 0.89, with its maximum between 2700 and 3000 m. Hump-shaped relationship was observed for shrubs with maximum richness between 2000 and 2200 m; and α-diversity decreased monotonically. Turnover of shrub species was highest between 2000 and 2500 m. Tree species richness was highest at low elevations, and α-diversity was relatively low along the entire gradient. Tree species turnover was also high in the lower zone and again at 2600-2800 m. Species richness of all vascular plants was highest at 2200-2500 m, and α-diversity was highest in the lower part of the gradient. Beta diversity of all growth forms was quite high ranging between 0.53 and 0.87 along the entire gradient reflecting high species and structural turnover. (author)

  1. Contrasting seasonal overlaps between primary and secondary growth are linked to wood anatomy in Mediterranean sub-shrubs.

    Science.gov (United States)

    Camarero, J J; Palacio, S; Montserrat-Martí, G

    2013-09-01

    Whole-plant approaches allow quantification of the temporal overlap between primary and secondary growth. If the amount of time available to grow is short, there may be a high temporal overlap between shoot growth and wood formation. We hypothesise that such overlap depends on the duration of the growing season and relates to wood anatomy. We evaluated wood anatomy, shoot longitudinal and radial growth rates, fine root production and the concentrations of non-structural carbohydrates (NSC) in the wood of six sub-shrub species growing in sites with contrasting climatic conditions (Lepidium subulatum, Linum suffruticosum, Salvia lavandulifolia, Satureja montana, Ononis fruticosa, Echinospartum horridum). Sub-shrub species living in sites with a short growing season displayed a high overlap between aboveground primary and secondary growth and formed wide vessels, whereas species from the warmest and driest sites presented the reverse characteristics. The highest overlap was linked to a rapid shoot extension and thickening through the enhanced hydraulic conductivity provided by wide vessels. The reductions in NSC concentrations when growth peaked were low or moderate, indicating that sub-shrubs accumulate NSC in excess, as do trees. The temporal overlap among primary and secondary growth in woody plants may be connected to the duration and rates of shoot and wood growth, which in turn depend on the vessel lumen area. © 2012 German Botanical Society and The Royal Botanical Society of the Netherlands.

  2. Spatial Heterogeneity of the Forest Canopy Scales with the Heterogeneity of an Understory Shrub Based on Fractal Analysis

    Directory of Open Access Journals (Sweden)

    Catherine K. Denny

    2017-04-01

    Full Text Available Spatial heterogeneity of vegetation is an important landscape characteristic, but is difficult to assess due to scale-dependence. Here we examine how spatial patterns in the forest canopy affect those of understory plants, using the shrub Canada buffaloberry (Shepherdia canadensis (L. Nutt. as a focal species. Evergreen and deciduous forest canopy and buffaloberry shrub presence were measured with line-intercept sampling along ten 2-km transects in the Rocky Mountain foothills of west-central Alberta, Canada. Relationships between overstory canopy and understory buffaloberry presence were assessed for scales ranging from 2 m to 502 m. Fractal dimensions of both canopy and buffaloberry were estimated and then related using box-counting methods to evaluate spatial heterogeneity based on patch distribution and abundance. Effects of canopy presence on buffaloberry were scale-dependent, with shrub presence negatively related to evergreen canopy cover and positively related to deciduous cover. The effect of evergreen canopy was significant at a local scale between 2 m and 42 m, while that of deciduous canopy was significant at a meso-scale between 150 m and 358 m. Fractal analysis indicated that buffaloberry heterogeneity positively scaled with evergreen canopy heterogeneity, but was unrelated to that of deciduous canopy. This study demonstrates that evergreen canopy cover is a determinant of buffaloberry heterogeneity, highlighting the importance of spatial scale and canopy composition in understanding canopy-understory relationships.

  3. Radiative transfer in shrub savanna sites in Niger: preliminary results from HAPEX-Sahel. 1. Modelling surface reflectance using a geometric-optical approach

    International Nuclear Information System (INIS)

    Franklin, J.; Duncan, J.; Huete, A.R.; Leeuwen, W.J.D. van; Li, X.; Bégué, A.

    1994-01-01

    To use optical remote sensing to monitor land surface-climate interactions over large areas, algorithms must be developed to relate multispectral measurements to key variables controlling the exchange of matter (water, carbon dioxide) and energy between the land surface and the atmosphere. The proportion of the ground covered by vegetation and the interception of photosynthetically active radiation (PAR) by vegetation are examples of two variables related to evapotranspiration and primary production, respectively. An areal-proportion model of the multispectral reflectance of shrub savanna, composed of scattered shrubs with a grass, forb or soil understory, predicted the reflectance of two 0.5 km 2 sites as the area-weighted average of the shrub and understory or ‘background’ reflectances. Although the shaded crown and shaded background have darker reflectances, ignoring them in the area-weighted model is not serious when shrub cover is low and solar zenith angle is small. A submodel predicted the reflectance of the shrub crown as a function of the foliage reflectance and amount of plant material within the crown, and the background reflectance scattered or transmitted through canopy gaps (referred to as a soil—plant ‘spectral interaction’ term). One may be able to combine these two models to estimate both the fraction of vegetation cover and interception of PAR by green vegetation in a shrub savanna. (author)

  4. Short-Term Response of Native Flora to the Removal of Non-Native Shrubs in Mixed-Hardwood Forests of Indiana, USA

    Directory of Open Access Journals (Sweden)

    Joshua M. Shields

    2015-05-01

    Full Text Available While negative impacts of invasive species on native communities are well documented, less is known about how these communities respond to the removal of established populations of invasive species. With regard to invasive shrubs, studies examining native community response to removal at scales greater than experimental plots are lacking. We examined short-term effects of removing Lonicera maackii (Amur honeysuckle and other non-native shrubs on native plant taxa in six mixed-hardwood forests. Each study site contained two 0.64 ha sample areas—an area where all non-native shrubs were removed and a reference area where no treatment was implemented. We sampled vegetation in the spring and summer before and after non-native shrubs were removed. Cover and diversity of native species, and densities of native woody seedlings, increased after shrub removal. However, we also observed significant increases in L. maackii seedling densities and Alliaria petiolata (garlic mustard cover in removal areas. Changes in reference areas were less pronounced and mostly non-significant. Our results suggest that removing non-native shrubs allows short-term recovery of native communities across a range of invasion intensities. However, successful restoration will likely depend on renewed competition with invasive species that re-colonize treatment areas, the influence of herbivores, and subsequent control efforts.

  5. A comparison of multi-spectral, multi-angular, and multi-temporal remote sensing datasets for fractional shrub canopy mapping in Arctic Alaska

    Science.gov (United States)

    Selkowitz, D.J.

    2010-01-01

    Shrub cover appears to be increasing across many areas of the Arctic tundra biome, and increasing shrub cover in the Arctic has the potential to significantly impact global carbon budgets and the global climate system. For most of the Arctic, however, there is no existing baseline inventory of shrub canopy cover, as existing maps of Arctic vegetation provide little information about the density of shrub cover at a moderate spatial resolution across the region. Remotely-sensed fractional shrub canopy maps can provide this necessary baseline inventory of shrub cover. In this study, we compare the accuracy of fractional shrub canopy (> 0.5 m tall) maps derived from multi-spectral, multi-angular, and multi-temporal datasets from Landsat imagery at 30 m spatial resolution, Moderate Resolution Imaging SpectroRadiometer (MODIS) imagery at 250 m and 500 m spatial resolution, and MultiAngle Imaging Spectroradiometer (MISR) imagery at 275 m spatial resolution for a 1067 km2 study area in Arctic Alaska. The study area is centered at 69 ??N, ranges in elevation from 130 to 770 m, is composed primarily of rolling topography with gentle slopes less than 10??, and is free of glaciers and perennial snow cover. Shrubs > 0.5 m in height cover 2.9% of the study area and are primarily confined to patches associated with specific landscape features. Reference fractional shrub canopy is determined from in situ shrub canopy measurements and a high spatial resolution IKONOS image swath. Regression tree models are constructed to estimate fractional canopy cover at 250 m using different combinations of input data from Landsat, MODIS, and MISR. Results indicate that multi-spectral data provide substantially more accurate estimates of fractional shrub canopy cover than multi-angular or multi-temporal data. Higher spatial resolution datasets also provide more accurate estimates of fractional shrub canopy cover (aggregated to moderate spatial resolutions) than lower spatial resolution datasets

  6. Spatial pattern of Baccharis platypoda shrub as determined by sex and life stages

    Science.gov (United States)

    Fonseca, Darliana da Costa; de Oliveira, Marcio Leles Romarco; Pereira, Israel Marinho; Gonzaga, Anne Priscila Dias; de Moura, Cristiane Coelho; Machado, Evandro Luiz Mendonça

    2017-11-01

    Spatial patterns of dioecious species can be determined by their nutritional requirements and intraspecific competition, apart from being a response to environmental heterogeneity. The aim of the study was to evaluate the spatial pattern of populations of a dioecious shrub reporting to sex and reproductive stage patterns of individuals. Sampling was carried out in three areas located in the meridional portion of Serra do Espinhaço, where in individuals of the studied species were mapped. The spatial pattern was determined through O-ring analysis and Ripley's K-function and the distribution of individuals' frequencies was verified through x2 test. Populations in two areas showed an aggregate spatial pattern tending towards random or uniform according to the observed scale. Male and female adults presented an aggregate pattern at smaller scales, while random and uniform patterns were verified above 20 m for individuals of both sexes of the areas A2 and A3. Young individuals presented an aggregate pattern in all areas and spatial independence in relation to adult individuals, especially female plants. The interactions between individuals of both genders presented spatial independence with respect to spatial distribution. Baccharis platypoda showed characteristics in accordance with the spatial distribution of savannic and dioecious species, whereas the population was aggregated tending towards random at greater spatial scales. Young individuals showed an aggregated pattern at different scales compared to adults, without positive association between them. Female and male adult individuals presented similar characteristics, confirming that adult individuals at greater scales are randomly distributed despite their distinct preferences for environments with moisture variation.

  7. Environmental niche divergence among three dune shrub sister species with parapatric distributions.

    Science.gov (United States)

    Chozas, Sergio; Chefaoui, Rosa M; Correia, Otília; Bonal, Raúl; Hortal, Joaquín

    2017-05-01

    The geographical distributions of species are constrained by their ecological requirements. The aim of this work was to analyse the effects of environmental conditions, historical events and biogeographical constraints on the diversification of the three species of the western Mediterranean shrub genus Stauracanthus , which have a parapatric distribution in the Iberian Peninsula. Ecological niche factor analysis and generalized linear models were used to measure the response of all Stauracanthus species to the environmental gradients and map their potential distributions in the Iberian Peninsula. The bioclimatic niche overlap between the three species was determined by using Schoener's index. The genetic differentiation of the Iberian and northern African populations of Stauracanthus species was characterized with GenalEx. The effects on genetic distances of the most important environmental drivers were assessed through Mantel tests and non-metric multidimensional scaling. The three Stauracanthus species show remarkably similar responses to climatic conditions. This supports the idea that all members of this recently diversified clade retain common adaptations to climate and consequently high levels of climatic niche overlap. This contrasts with the diverse edaphic requirements of Stauracanthus species. The populations of the S. genistoides-spectabilis clade grow on Miocene and Pliocene fine-textured sedimentary soils, whereas S. boivinii , the more genetically distant species, occurs on older and more coarse-textured sedimentary substrates. These patterns of diversification are largely consistent with a stochastic process of geographical range expansion and fragmentation coupled with niche evolution in the context of spatially complex environmental fluctuations. : The combined analysis of the distribution, realized environmental niche and phylogeographical relationships of parapatric species proposed in this work allows integration of the biogeographical

  8. Is shade beneficial for mediterranean shrubs experiencing periods of extreme drought and late-winter frosts?

    Science.gov (United States)

    Valladares, Fernando; Zaragoza-Castells, Joana; Sánchez-Gómez, David; Matesanz, Silvia; Alonso, Beatriz; Portsmuth, Angelika; Delgado, Antonio; Atkin, Owen K

    2008-12-01

    Plants are naturally exposed to multiple, frequently interactive stress factors, most of which are becoming more severe due to global change. Established plants have been reported to facilitate the establishment of juvenile plants, but net effects of plant-plant interactions are difficult to assess due to complex interactions among environmental factors. An investigation was carried out in order to determine how two dominant evergreen shrubs (Quercus ilex and Arctostaphylos uva-ursi) co-occurring in continental, Mediterranean habitats respond to multiple abiotic stresses and whether the shaded understorey conditions ameliorate the negative effects of drought and winter frosts on the physiology of leaves. Microclimate and ecophysiology of sun and shade plants were studied at a continental plateau in central Spain during 2004-2005, with 2005 being one of the driest and hottest years on record; several late-winter frosts also occurred in 2005. Daytime air temperature and vapour pressure deficit were lower in the shade than in the sun, but soil moisture was also lower in the shade during the spring and summer of 2005, and night-time temperatures were higher in the shade. Water potential, photochemical efficiency, light-saturated photosynthesis, stomatal conductance and leaf 13C composition differed between sun and shade individuals throughout the seasons, but differences were species specific. Shade was beneficial for leaf-level physiology in Q. ilex during winter, detrimental during spring for both species, and of little consequence in summer. The results suggest that beneficial effects of shade can be eclipsed by reduced soil moisture during dry years, which are expected to be more frequent in the most likely climate change scenarios for the Mediterranean region.

  9. Effects of flowering phenology and synchrony on the reproductive success of a long-flowering shrub

    Science.gov (United States)

    Rodríguez-Pérez, Javier; Traveset, Anna

    2016-01-01

    Flowering phenology and synchrony with biotic and abiotic resources are crucial traits determining the reproductive success in insect-pollinated plants. In seasonal climates, plants flowering for long periods should assure reproductive success when resources are more predictable. In this work, we evaluated the relationship between flowering phenology and synchrony and reproductive success in Hypericum balearicum, a shrub flowering all year round but mainly during spring and summer. We studied two contrasting localities (differing mostly in rainfall) during 3 years, and at different biological scales spanning from localities to individual flowers and fruits. We first monitored (monthly) flowering phenology and reproductive success (fruit and seed set) of plants, and assessed whether in the locality with higher rainfall plants had longer flowering phenology and synchrony and relatively higher reproductive success within or outside the flowering peak. Secondly, we censused pollinators on H. balearicum individuals and measured reproductive success along the flowering peak of each locality to test for an association between (i) richness and abundance of pollinators and (ii) fruit and seed set, and seed weight. We found that most flowers (∼90 %) and the highest fruit set (∼70 %) were produced during the flowering peak of each locality. Contrary to expectations, plants in the locality with lower rainfall showed more relaxed flowering phenology and synchrony and set more fruits outside the flowering peak. During the flowering peak of each locality, the reproductive success of early-flowering individuals depended on a combination of both pollinator richness and abundance and rainfall; by contrast, reproductive success of late-flowering individuals was most dependent on rainfall. Plant species flowering for long periods in seasonal climates, thus, appear to be ideal organisms to understand how flowering phenology and synchrony match with biotic and abiotic resources, and

  10. Diurnal Freeze-Thaw Cycles Modify Winter Soil Respiration in a Desert Shrub-Land Ecosystem

    Directory of Open Access Journals (Sweden)

    Peng Liu

    2016-07-01

    Full Text Available Winter soil respiration (Rs is becoming a significant component of annual carbon budgets with more warming in winter than summer. However, little is known about the controlling mechanisms of winter Rs in dryland. We made continuous measurements of Rs in four microsites (non-crust (BS, lichen (LC, moss (MC, and a mixture of moss and lichen (ML in a desert shrub-land ecosystem northern China, to investigate the causes of Rs dynamics in winter. The mean winter Rs ranged from 0.10 to 0.17 µmol CO2 m−2·s−1 across microsites, with the highest value in BS. Winter Q10 (known as the increase in respiration rate per 10 °C increase in temperature values (2.8–19 were much higher than those from the growing season (1.5. Rs and Q10 were greatly enhanced in freeze-thaw cycles compared to frozen days. Diurnal patterns of Rs between freeze-thaw and frozen days differed. Although the freeze-thaw period was relatively short, its cumulative Rs contributed significantly to winter Rs. The presence of biocrust might induce lower temperature, thus having fewer freeze-thaw cycles relative to bare soil, leading to the lower Rs for microsites with biocrusts. In conclusion, winter Rs in drylands was sensitive to soil temperature (Ts and Ts-induced freeze-thaw cycles. The temperature impact on Rs varied among soil cover types. Winter Rs in drylands may become more important as the climate is continuously getting warmer.

  11. High Correlated Paternity Leads to Negative Effects on Progeny Performance in Two Mediterranean Shrub Species.

    Directory of Open Access Journals (Sweden)

    Sofia Nora

    Full Text Available Anthropogenic habitat deterioration can promote changes in plant mating systems that subsequently may affect progeny performance, thereby conditioning plant recruitment for the next generation. However, very few studies yet tested mating system parameters other than outcrossing rates; and the direct effects of the genetic diversity of the pollen received by maternal plants (i.e. correlated paternity has often been overlooked. In this study, we investigated the relation between correlated paternity and progeny performance in two common Mediterranean shrubs, Myrtus communis and Pistacia lentiscus. To do so, we collected open-pollinated progeny from selected maternal plants, calculated mating system parameters using microsatellite genotyping and conducted sowing experiments under greenhouse and field conditions. Our results showed that some progeny fitness components were negatively affected by the high correlated paternity of maternal plants. In Myrtus communis, high correlated paternity had a negative effect on the proportion and timing of seedling emergence in the natural field conditions and in the greenhouse sowing experiment, respectively. In Pistacia lentiscus, seedling emergence time under field conditions was also negatively influenced by high correlated paternity and a progeny survival analysis in the field experiment showed greater mortality of seedlings from maternal plants with high correlated paternity. Overall, we found effects of correlated paternity on the progeny performance of Myrtus communis, a self-compatible species. Further, we also detected effects of correlated paternity on the progeny emergence time and survival in Pistacia lentiscus, an obligate outcrossed species. This study represents one of the few existing empirical examples which highlight the influence that correlated paternity may exert on progeny performance in multiple stages during early seedling growth.

  12. Comparative Assessment of Response to Cadmium in Heavy Metal-Tolerant Shrubs Cultured In Vitro.

    Science.gov (United States)

    Wiszniewska, A; Hanus-Fajerska, E; Muszyńska, E; Smoleń, S

    2017-01-01

    Two species of Pb-adapted shrubs, Alyssum montanum and Daphne jasminea , were evaluated in vitro for their tolerance to elevated concentrations of cadmium. Shoot cultures were treated with 0.5, 2.5, and 5.0 μM CdCl 2 for 16 weeks and analyzed for their organogenic response, biomass accretion, pigment content, and macronutrient status. Cadmium accumulation and its root-to-shoot translocation were also determined. In both species, rooted microplantlets, suitable for acclimatization, were obtained in the presence of Cd applied as selection agent. In A. montanum , low and moderate dose of Cd stimulated multiplication, rooting, and biomass production. Growth tolerance index (GTI) in Cd-treated shoots ranged from 120 to 215%, while in the roots 51-202%. In turn, in Cd-treated D. jasminea proliferation and rooting were inhibited, and GTI for shoots decreased with increasing doses of Cd. However, roots exposed to Cd had higher biomass accretion. Both species accumulated Cd in developed organs, and its content increased with increasing CdCl 2 dose. Interestingly, D. jasminea accumulated higher amounts of Cd in the roots than A. montanum and immobilized this metal in the root system. On the contrary, A. montanum translocated some part of accumulated Cd to the shoots, but with low efficiency. In the presence of Cd, A. montanum maintained macronutrient homeostasis and synthesized higher amounts of phytosynthetic pigments in the shoots. D. jasminea accumulated root biomass, immobilized Cd, and restricted its translocation at the expense of nutrient balance. Considering remediation potential, A. montanum could be exploited in phytoextraction, while D. jasminea in phytostabilization of polluted substrate.

  13. Genetic population structure of the desert shrub species lycium ruthenicum inferred from chloroplast dna

    International Nuclear Information System (INIS)

    Chen, H.; Yonezawa, T.

    2014-01-01

    Lycium ruthenicum (Solananeae), a spiny shrub mostly distributed in the desert regions of north and northwest China, has been shown to exhibit high tolerance to the extreme environment. In this study, the phylogeography and evolutionary history of L. ruthenicum were examined, on the basis of 80 individuals from eight populations. Using the sequence variations of two spacer regions of chloroplast DNA (trnH-psbA and rps16-trnK) , the absence of a geographic component in the chloroplast DNA genetic structure was identified (GST = 0.351, NST = 0.304, NST< GST), which was consisted with the result of SAMOVA, suggesting weak phylogeographic structure of this species. Phylogenetic and network analyses showed that a total of 10 haplotypes identified in the present study clustered into two clades, in which clade I harbored the ancestral haplotypes that inferred two independent glacial refugia in the middle of Qaidam Basin and the western Inner Mongolia. The existence of regional evolutionary differences was supported by GENETREE, which revealed that one of the population in Qaidam Basin and the two populations in Tarim Basin had experienced rapid expansion, and the other populations retained relatively stable population size during the Pleistocene . Given the results of long-term gene flow and pairwise differences, strong gene flow was insufficient to reduce the genetic differentiation among populations or within populations, probably due to the genetic composition containing a common haplotype and the high number of private haplotypes fixed for most of the population. The divergence times of different lineages were consistent with the rapid uplift phases of the Qinghai-Tibetan Plateau and the initiation and expansion of deserts in northern China, suggesting that the origin and evolution of L. ruthenicum were strongly influenced by Quaternary environment changes. (author)

  14. Aliens will provide: avian responses to a new temporal resource offered by ornithocorous exotic shrubs.

    Science.gov (United States)

    Vergara-Tabares, David L; Toledo, Martín; García, Emiliano; Peluc, Susana I

    2018-06-26

    Frugivorous birds are able to track spatiotemporal changes in fruit availability. Food resource fluctuations, characteristic of seasonal environments, can be affected by the naturalization of exotic ornithocorous plants. In the mountain forest of central Argentina, invasive shrubs of the genus Pyracantha provide a new temporal resource that modifies fluctuations of natural resource availability because the invasives fructify in autumn-winter (largely uncoupled with the fruiting of native species). The contrasting patterns of resource fluctuation between non-invaded and invaded areas throughout the year provide a good study system to test predictions of the fruit-tracking hypothesis, and to understand the relationship between food resources offered by fleshy fruited invasives and abundances of avian trophic guilds. By means of point counts conducted during five time periods at invaded and non-invaded sites we found that the presence of Pyracantha, and time periods, significantly affected frugivorous bird abundance, which in autumn-winter was greater in invaded sites and in spring-summer similar between invaded and non-invaded sites. On the other hand, granivores and insectivores did not show a significant relationship with the presence of Pyracantha. Abundances of the most common seed disperser were significantly affected by the interaction between time period and presence of Pyracantha. These results indicate that the abundances of birds that legitimately disperse Pyracantha seeds are temporally and spatially associated with fruit abundance provided by this exotic plant. This underscores fruit availability as an important ecological factor affecting frugivorous bird abundance, and suggests that Pyracantha seed dispersers are capable of detecting changes in the availability of its fruit, likely contributing to the effectiveness of its dispersal.

  15. Snowpack, fire, and forest disturbance: interactions affect montane invasions by non-native shrubs.

    Science.gov (United States)

    Stevens, Jens T; Latimer, Andrew M

    2015-06-01

    Montane regions worldwide have experienced relatively low plant invasion rates, a trend attributed to increased climatic severity, low rates of disturbance, and reduced propagule pressure relative to lowlands. Manipulative experiments at elevations above the invasive range of non-native species can clarify the relative contributions of these mechanisms to montane invasion resistance, yet such experiments are rare. Furthermore, global climate change and land use changes are expected to cause decreases in snowpack and increases in disturbance by fire and forest thinning in montane forests. We examined the importance of these factors in limiting montane invasions using a field transplant experiment above the invasive range of two non-native lowland shrubs, Scotch broom (Cytisus scoparius) and Spanish broom (Spartium junceum), in the rain-snow transition zone of the Sierra Nevada of California. We tested the effects of canopy closure, prescribed fire, and winter snow depth on demographic transitions of each species. Establishment of both species was most likely at intermediate levels of canopy disturbance, but at this intermediate canopy level, snow depth had negative effects on winter survival of seedlings. We used matrix population models to show that an 86% reduction in winter snowfall would cause a 2.8-fold increase in population growth rates in Scotch broom and a 3.5-fold increase in Spanish broom. Fall prescribed fire increased germination rates, but decreased overall population growth rates by reducing plant survival. However, at longer fire return intervals, population recovery between fires is likely to keep growth rates high, especially under low snowpack conditions. Many treatment combinations had positive growth rates despite being above the current invasive range, indicating that propagule pressure, disturbance, and climate can all strongly affect plant invasions in montane regions. We conclude that projected reductions in winter snowpack and increases in

  16. Attitudes of ornamental trees and shrubs producers towards nursery production of ornamental beech cultivars in Serbia

    Directory of Open Access Journals (Sweden)

    Nonić Marina

    2016-01-01

    Full Text Available European beech (Fagus sylvatica L. is, along with its significance as a forest species, renowned as an ornamental species, due to its numerous cultivars. Ornamental beech cultivars are planted in various green spaces, but a small number of such trees have ascertained in Serbia. For the time being, production of beech cultivars is represented in a very small number of nurseries, with a negligible share of those seedlings in their total assortment. The aim of this research is to study the attitudes of ornamental trees and shrubs producers towards the nursery production of ornamental beech cultivars, and possibilities of its improvements in Serbia. “Door to door” survey and in-depth interviews were used as research techniques. Surveys with the representatives of 65 nurseries in Serbia (in the selected statistical region Šumadija and Western Serbia were conducted in the first stage of data collection. In the second stage of data collection were interviewed the representatives of the 10 nurseries who, during the survey, pointed out that they produce ornamental beech cultivars. Nurserymen’s attitudes suggest that there is a possibility to improve the production of ornamental beech cultivars in Serbia, with the appropriate support measures and increased interest of customers on the market, i.e. with the provision of subsidies for the production of seedlings and greater use of cultivars by utility companies in the cities of Serbia. [Projekat Ministarstva nauke Republike Srbije, br. ТP 31041: Establishment of forest plantations to increase the afforested areas in Serbia

  17. Differential nitrogen cycling in semiarid sub-shrubs with contrasting leaf habit.

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    Sara Palacio

    Full Text Available Nitrogen (N is, after water, the most limiting resource in semiarid ecosystems. However, knowledge on the N cycling ability of semiarid woody plants is still very rudimentary. This study analyzed the seasonal change in the N concentrations and pools of the leaves and woody organs of two species of semiarid sub-shrubs with contrasting leaf habit. The ability of both species to uptake, remobilize and recycle N, plus the main storage organ for N during summer drought were evaluated. We combined an observational approach in the field with experimental (15N labelling of adult individuals grown in sand culture. Seasonal patterns of N concentrations were different between species and organs and foliar N concentrations of the summer deciduous Lepidium subulatum were almost double those of the evergreen Linum suffruticosum. L. subulatum up took ca. 60% more external N than the evergreen and it also had a higher N resorption efficiency and proficiency. Contrastingly, L. suffruticosum relied more on internal N remobilization for shoot growth. Differently to temperate species, the evergreen stored N preferentially in the main stem and old trunks, while the summer deciduous stored it in the foliage and young stems. The higher ability of L. subulatum to uptake external N can be related to its ability to perform opportunistic growth and exploit the sporadic pulses of N typical of semiarid ecosystems. Such ability may also explain its high foliar N concentrations and its preferential storage of N in leaves and young stems. Finally, L. suffruticosum had a lower ability to recycle N during leaf senescence. These strategies contrast with those of evergreen and deciduous species from temperate and boreal areas, highlighting the need of further studies on semiarid and arid plants.

  18. Future stratospheric ozone depletion will affect a subarctic dwarf shrub ecosystem

    Energy Technology Data Exchange (ETDEWEB)

    Johanson, Ulf

    1997-02-01

    The stratospheric ozone depletion and the concomitant increase in ultraviolet-B (UV-B, 280-320 nm) radiation is of global concern due to the effects of UV-B on living organisms. To investigate the effects of increased levels of UV-B, a field irradiation system was established at a subarctic dwarf shrub heath in Northern Sweden (68 deg N). An ozone depletion of 15% under clear sky conditions was simulated over a naturally growing ecosystem. The response of both individual components and processes was studied to reveal changes in ecosystem structure and function. Species with different life strategies (evergreen or deciduous) responded differently both in magnitude and direction. The evergreen species were more responsive to UV-B regarding shoot growth, which could be due to cumulative effects in long-lived tissues, since the retardation in relative growth increased over time of exposure. Leaves of evergreen species became thicker under enhanced UV-B, while leaves of deciduous species became thinner. Decomposition studies (laboratory and in situ) showed that indirect effects of UV-B, due to changes in leaf tissue chemistry affected microbial activity and slowed down the decomposition rate. More directly, UV-B decreased the abundance of some fungal species and hence the composition of species. However, no altered decomposition rate was found when decomposition progressed under high UV-B even if the microorganisms were fewer. This could be due to the increased direct photo degradation of litter that compensates for lower microbial activity. The decomposition rate is therefore strongly dependent on the interception of UV-B at the litter layer. This research has shown that ecosystem components and processes are affected in a number of ways and that there are indications of changes in species composition in a long-term perspective due to differences in responsiveness between the different species. 128 refs, 7 figs

  19. Acacia shrubs respond positively to high severity wildfire: Implications for conservation and fuel hazard management.

    Science.gov (United States)

    Gordon, Christopher E; Price, Owen F; Tasker, Elizabeth M; Denham, Andrew J

    2017-01-01

    High severity wildfires pose threats to human assets, but are also perceived to impact vegetation communities because a small number of species may become dominant immediately after fire. However there are considerable gaps in our knowledge about species-specific responses of plants to different fire severities, and how this influences fuel hazard in the short and long-term. Here we conduct a floristic survey at sites before and two years after a wildfire of unprecedented size and severity in the Warrumbungle National Park (Australia) to explore relationships between post-fire growth of a fire responsive shrub genera (Acacia), total mid-story vegetation cover, fire severity and fuel hazard. We then survey 129 plots surrounding the park to assess relationships between mid-story vegetation cover and time-since-fire. Acacia species richness and cover were 2.3 and 4.3 times greater at plots after than before the fire. However the same common dominant species were present throughout the study. Mid-story vegetation cover was 1.5 times greater after than before the wildfire, and Acacia species contribution to mid-story cover increased from 10 to 40%. Acacia species richness was not affected by fire severity, however strong positive associations were observed between Acacia and total mid-story vegetation cover and severity. Our analysis of mid-story vegetation recovery showed that cover was similarly high between 2 and 30years post-fire, then decreased until 52years. Collectively, our results suggest that Acacia species are extremely resilient to high severity wildfire and drive short to mid-term increases in fuel hazard. Our results are discussed in relation to fire regime management from the twin perspectives of conserving biodiversity and mitigating human losses due to wildfire. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. Influence of alkaline hydrothermal pretreatment on shrub wood Tamarix ramosissima: Characteristics of degraded lignin

    International Nuclear Information System (INIS)

    Xiao, Ling-Ping; Bai, Yuan-Yuan; Shi, Zheng-Jun; Lu, Qiang; Sun, Run-Cang

    2014-01-01

    The objective of this work was to evaluate the influence of alkaline hydrothermal (AH) pretreatment on the physicochemical properties of the degraded lignins, attempt to upgrade the potential of lignin for value-added chemicals and fuel production. For this purpose, shrub wood Tamarix ramosissima lignin was fractionated using a two-stage process based on an AH pretreatment followed by an alkaline ethanol post-treatment. The recovered lignin fractions were investigated by comparison with milled wood lignin (MWL) in terms of fractionation yield, carbohydrate composition, gel permeation chromatography, Fourier transform infrared spectroscopy, 13 C and 2D heteronuclear single quantum correlation nuclear magnetic resonance, as well as pyrolysis-gas chromatography/mass spectrometry. The result showed that AH pretreatment led to the degradation of β-O-4 linkages and consequently the increased severity caused a release of more S-units lignin fractions with molecular weights between 1300 and 2500 g/mol in the liquid but higher molecular weights (3000–4400 g/mol) in the residues. Moreover, it was found that the lignin syringyl-to-guaiacyl (S/G) ratios from analytical pyrolysis slightly changed after AH pretreatment (S/G, 1.8–2.3) but higher than those of MWL (S/G, 1.7). Overall, the present study demonstrates that these lignins dissolved during AH pretreatment and those recovered from the solid residues isolated with alkaline ethanol post-treatment could be profitably exploited as feedstock in integrated forest biorefineries, rather than traditional use as low-value energy sources.- Highlights: • Alkaline hydrothermal pretreatment and alkaline ethanol post-treatment were proposed. • The influence of AH pretreatment on the lignin structural changes was characterized. • Aryl-O-ether linkages of lignin were extensively cleaved. • Lignin recovered from solid residue is a potential resource for the production of value-added chemicals

  1. Effects of drought season length on live moisture content dynamic in Mediterranean shrubs: 8 years of data

    Science.gov (United States)

    Pellizzaro, Grazia; Ventura, Andrea; Bortolu, Sara; Duce, Pierpaolo

    2017-04-01

    Mediterranean shrubs are an important component of Mediterranean vegetation communities. In this kind of vegetation, live fuel is a relevant component of the available fuel which catches fire and, consequently, its water content plays an important role in determining fire occurrence and spread. In live plant, water content patterns are related to both environmental conditions (e.g. meteorological variables, soil water availability) and ecophysiological characteristics of the plant species. According to projections on future climate, an increase in risk of summer droughts is likely to take place in Southern Europe. More prolonged drought seasons induced by climatic changes are likely to influence general flammability characteristics of fuel. In addition, variations in precipitation and mean temperature could directly affect fuel water status and length of critical periods of high ignition danger for Mediterranean ecosystems. The aims of this work were to analyse the influence of both weather seasonality and inter-annual weather variability on live fuel moisture content within and among some common Mediterranean species, and to investigate the effects of prolonged drought season on live moisture content dynamic. The study was carried out in North Sardinia (Italy). Measurements of LFMC seasonal pattern of two really common and flammable Mediterranean shrub species (Cistus monspeliensis and Rosmarinus officinalis) were performed periodically for 8 years. Meteorological variables were also recorded. Relationships between live fuel moisture content and environmental conditions (i.e. rainfall, air temperature and soil moisture) were investigated and effects of different lengths of drought season on LFMC pattern were analysed. Results showed that distribution and amount of rainfall affected seasonal variation of live fuel moisture content. In particular more prolonged drought seasons caused a longer period in which LFMC was below 95 -100% that is commonly considered as

  2. Force of habit: shrubs, trees and contingent evolution of wood anatomical diversity using Croton (Euphorbiaceae) as a model system.

    Science.gov (United States)

    Arévalo, Rafael; van Ee, Benjamin W; Riina, Ricarda; Berry, Paul E; Wiedenhoeft, Alex C

    2017-03-01

    Wood is a major innovation of land plants, and is usually a central component of the body plan for two major plant habits: shrubs and trees. Wood anatomical syndromes vary between shrubs and trees, but no prior work has explicitly evaluated the contingent evolution of wood anatomical diversity in the context of these plant habits. Phylogenetic comparative methods were used to test for contingent evolution of habit, habitat and wood anatomy in the mega-diverse genus Croton (Euphorbiaceae), across the largest and most complete molecular phylogeny of the genus to date. Plant habit and habitat are highly correlated, but most wood anatomical features correlate more strongly with habit. The ancestral Croton was reconstructed as a tree, the wood of which is inferred to have absent or indistinct growth rings, confluent-like axial parenchyma, procumbent ray cells and disjunctive ray parenchyma cell walls. The taxa sampled showed multiple independent origins of the shrub habit in Croton , and this habit shift is contingent on several wood anatomical features (e.g. similar vessel-ray pits, thick fibre walls, perforated ray cells). The only wood anatomical trait correlated with habitat and not habit was the presence of helical thickenings in the vessel elements of mesic Croton . Plant functional traits, individually or in suites, are responses to multiple and often confounding contexts in evolution. By establishing an explicit contingent evolutionary framework, the interplay between habit, habitat and wood anatomical diversity was dissected in the genus Croton . Both habit and habitat influence the evolution of wood anatomical characters, and conversely, the wood anatomy of lineages can affect shifts in plant habit and habitat. This study hypothesizes novel putatively functional trait associations in woody plant structure that could be further tested in a variety of other taxa. Published by Oxford University Press on behalf of the Annals of Botany Company 2017. This work is

  3. Usefulness of pioneer vegetation for the phytomanagement of metal(loid)s enriched tailings: grasses vs. shrubs vs. trees.

    Science.gov (United States)

    Parraga-Aguado, Isabel; Querejeta, Jose-Ignacio; González-Alcaraz, María-Nazaret; Jiménez-Cárceles, Francisco J; Conesa, Héctor M

    2014-01-15

    The goal of this work was to assess the selection of the most suitable combination of plant species for the phytomanagement of mine tailings, by comparing among different plant life-forms (grasses, shrubs and trees). A comparison on induced rhizosphere changes generated by four plant species (the grass Piptatherum miliaceum, the shrub Helichrysum decumbens, and the trees, Pinus halepensis and Tetraclinis articulata) and high density vegetation patches (fertility islands) at a mine tailing located at Southeast Spain and the description of their physiological status employing stable isotopes analyses were carried out. The edaphic niches for plant growth were determined by salinity, organic matter and total soil nitrogen while metal(loid)s concentrations played a minor role. Induced changes in plant rhizospheres had a significant impact in soil microbiology. While grasses and shrubs may play an important role in primary ecological succession, trees seem to be the key to the development of fertility islands. The low δ(15)N values (-8.00‰) in P. halepensis needles may reflect higher ectomycorrhizal dependence. Large differences in leaf δ(18)O among the plant species indicated contrasting and complementary water acquisition strategies. Leaf δ(13)C values (-27.6‰) suggested that T. articulata had higher water use efficiency than the rest of species (-29.9‰). The implement of a diverse set of plant species with contrasting life forms for revegetating tailings may result in a more efficient employment of water resources and a higher biodiversity not only in relation to flora but soil microbiology too. Copyright © 2013 Elsevier Ltd. All rights reserved.

  4. Effects of shrub revegetation with Atriplex halimus L. and Retama sphaerocarpa L. in gypsiferous soils. Influence in soil properties

    Science.gov (United States)

    Bienes, Ramón; Marques, Maria Jose; Ruiz-Colmenero, Marta; Arevalo, Diana; Sastre, Blanca; Garcia-Diaz, Andrés

    2014-05-01

    The low crop yield obtained in semi-arid climates has led to the decline of agriculture and the abandonment of large areas resulting in a high risk of land degradation due to the lack of vegetation. Revegetation with shrubs is considered a way to prevent land degradation and enhance soil conditions, particularly in problematic soils. The study area is located in Colmenar de Oreja (Madrid, Spain, UTM 30T X=455236, Y=4436368). This is a semi-arid region, close to aridity in certain years, with a mean annual rainfall of 390 mm and annual evapotranspiration (Thornthwaite) of 769 mm. The soil is developed over gypsum marls with a xeric moisture regime. These soils are frequent in semiarid and arid countries in the world because leaching is prevented due to low rainfall. They usually show shallow depth, high penetration resistance and compaction, particularly when the soil is dry. Moreover they exhibit low fertility and small water retention capacity. All these circumstances hinder the development of roots and therefore the spontaneous recovery of vegetation after abandonment. Two different species of shrubs -Atriplex halimus L. and Retama sphaerocarpa L.- were planted in USLE plots (80 m2) in 2003 in a sloping area (average 10%). Changes in the physical and chemical properties of soils beneath these different treatments were studied since then, and they were compared with spontaneous vegetation. We considered soil indicators such as bulk density, intrapedal porosity, soil organic matter content, aggregate stability and soil penetration resistance. Two years after planting, vegetation coverage in the low part of the plots covered 70% of soil, rising 80% after the third year. The litter generated by shrubs did not change soil organic matter content at the site where it occurred, but rather a few feet below, where it was deposited by water erosion. Five years later, the lower section of the plots exhibited an increase in soil organic matter (from 2.3 to 3.2%), a decrease

  5. Ethnobotanical survey of medicinally important shrubs and trees of Himalayan region of Azad Jammu and Kashmir, Pakistan.

    Science.gov (United States)

    Rashid, Sofia; Ahmad, Mushtaq; Zafar, Muhammad; Sultana, Shazia; Ayub, Muhammad; Khan, Mir Ajab; Yaseen, Ghulam

    2015-05-26

    Present study was commenced with an aim to document the indigenous knowledge of medicinally important shrubs and trees of Himalayan region of Azad Jammu and Kashmir, Pakistan. This is the first contribution to the quantitative ethnobotany of this region, as no reported data focusing on shrubs and trees from the area have been published. Study reported the ethnobotanical significance of medicinal plants for the treatment of various diseases. Study was conducted during 2012-2014 following standard ethnobotanical methods. The ethnomedicinal data was collected through informed consent semi- structured interviews of 160 key informants. Documented data was analyzed by using quantitative indices of informant consensus factor (ICF), fidelity level (FL), use value (UV) and relative frequency citation (RFC). A total of 73 shrub and tree species belonging to 56 genera and 37 families were reported to be used ethnomedicinally for the treatment of various ailments. Medicinal plant diversity showed that Rosaceae was dominating family with (9 spp.) followed by Moraceae (7 spp.), Euphorbiaceae, Mimosaceae, Pinaceae, Rhamnaceae (4 spp. each), Oleaceae (3 spp.), Apocynaceae, Caesalpinaceae, Ebenaceae, Fagaceae, Lythraceae, Papilionaceae, Acanthaceae, Verbenaceae (2 spp. each) while remaining 22 families were represented by one species each. Leaves (23%) were highly utilized plant parts, followed by fruits (22%), bark (18%), seeds (10%), roots (9%), flowers (8%), whole plant and aerial parts (4% each) and stem (2%). Modes of preparation fall into 14 categories including powder (33 reports) followed by decoction (29 reports), paste (22 reports), juice (18 reports), infusion (12 reports), raw (8 reports), extract and latex (5 reports each), gum and oil (4 reports each), fresh part and pulp (2 reports each), chewed and cooked (1 report each). The highest FIC was recorded for Gastro-intestinal disorders (0.58) followed by nail, skin and hair disorders (0.44). Maximum fidelity level (FL

  6. Improvement of Seed Germination and In Vitro Propagation of a Multipurpose Plateau Shrub Species Sophora Moorcroftiana

    International Nuclear Information System (INIS)

    Fu, Y.; Yao, W.; Li, S.; Li, H.

    2016-01-01

    Sophora moorcroftiana (Benth.) Baker (Fabaceae) with blue flowers is a shrub species in Qinghai-Tibet Plateau. This species is an important ornamental, ecological and economical species mainly distributed in the wide valleys of Yarlung Tsangpo and Lhasa River. It contains strong drought, solar radiation and sand burial resistance. However, it is on the verge of extinction because of over-exploitation in recent years, seedling production is a bottleneck in this plant's development, and information is lacking on an In vitro propagation system for S. moorcroftiana. Therefore, an effective propagation technique is urgently needed. In the present study, S. moorcroftiana seed germinations both In vitro and on an open moistened filter paper were significantly improved. The best germination percentage (88.67+-0.67) and percentage of cotyledons presented (69.67+-0.33) were obtained when the seeds were placed in moistened filter paper for 30 d after treatment with 98 percent concentration sulphuric acid for 70 min, and then treated with either Gibberellic acid (GA3) 100 mg L/sup-1/ or 500 mg L/sup -1/. Besides, an In vitro propagation system was developed for this species, the impacts of various media combined with different plant growth regulators (PGR) on multiple shoots proliferation were evaluated. The result showed Woody Plant Medium (WPM) supplemented with 1.0 mg L/sup -1/ N/sup 6/ -Benzyladenine (BA) and 0.2 mg L/sup -1/ alpha-Naphthalene acetic acid (NAA) was found to be optimum for production of multiple shoots (89.33 percent shoot regeneration frequency and 18.67 shoots per explant) using cotyledonary node. The best rooted medium for regenerated shoots (89.72 percent, 4.68 roots per shoot) was half-strength Murashige and Skoog (1/2 MS) supplemented with 0.5 mg L/sup -1/ indole-3-butyric acid (IBA) and 0.02 mg L/sup -1/ NAA. The rooted plantlets were successfully acclimated, and survival of plantlets was 75 percent after transfer to soil. These results could be

  7. Process-Based Model for Computation of Erosion and Deposition on Shrub-Protected Banks

    Science.gov (United States)

    Kean, J. W.; Smith, J.

    2001-12-01

    Determination of erosion and deposition rates on riverbanks requires a detailed knowledge of the near-bank boundary shear stress field. Riverbanks typically are irregular in planiform geometry owing to the presence of vegetation on them, and the effects of vegetation-caused bank irregularity in reducing flow in the neighborhood of the toes of banks must be taken into account in calculating the appropriate boundary shear stress fields. Form drag on roots, stems, and branches of shrubs and trees that protrude into the flow must be carefully evaluated. Methods for calculating the boundary shear stress and sediment transport fields on and near vegetated banks have been developed over the past several years. More recently, the direct effects of roots, stems, and branches in reducing the shear stresses on banks have been investigated in conjunction with research on arroyo channels having nearly trapezoidal cross sections and banks covered with sandbar willow and tamarisk. A model for computing flow and sediment transport in such channels is presented and then used to demonstrate the relative importance of the various environmental factors and their interactions. The primary environmental factors include (1) the cross-sectional geometry of the flow, which controls the structure of the cross-sectional distribution of the streamwise-averaged boundary shear stress, (2) the micro topography of the bed and banks, which determines the local ratio of streamwise-averaged boundary shear stress to skin friction and, thus, the cross-sectional structure of the sediment transport field in the channel, and (3) the bed-sediment size distribution, which controls the importance of density stratification in the flow and, thereby, the vertical structure of the velocity field. The model demonstrates that woody vegetation on sloping banks affects the flow in several ways. First, it forces the high velocity core toward the center of the channel, increasing the streamwise-averaged boundary

  8. Gross rainfall amount and maximum rainfall intensity in 60-minute influence on interception loss of shrubs: a 10-year observation in the Tengger Desert.

    Science.gov (United States)

    Zhang, Zhi-Shan; Zhao, Yang; Li, Xin-Rong; Huang, Lei; Tan, Hui-Juan

    2016-05-17

    In water-limited regions, rainfall interception is influenced by rainfall properties and crown characteristics. Rainfall properties, aside from gross rainfall amount and duration (GR and RD), maximum rainfall intensity and rainless gap (RG), within rain events may heavily affect throughfall and interception by plants. From 2004 to 2014 (except for 2007), individual shrubs of Caragana korshinskii and Artemisia ordosica were selected to measure throughfall during 210 rain events. Various rainfall properties were auto-measured and crown characteristics, i.e., height, branch and leaf area index, crown area and volume of two shrubs were also measured. The relative interceptions of C. korshinskii and A. ordosica were 29.1% and 17.1%, respectively. Rainfall properties have more contributions than crown characteristics to throughfall and interception of shrubs. Throughfall and interception of shrubs can be explained by GR, RI60 (maximum rainfall intensities during 60 min), RD and RG in deceasing importance. However, relative throughfall and interception of two shrubs have different responses to rainfall properties and crown characteristics, those of C. korshinskii were closely related to rainfall properties, while those of A. ordosica were more dependent on crown characteristics. We highlight long-term monitoring is very necessary to determine the relationships between throughfall and interception with crown characteristics.

  9. Evaluation of Drought Stress Thresholds in Ornamental Barberry (Berberis thunbergii cv. Atropurpurea Shrub in Mashhad Condition

    Directory of Open Access Journals (Sweden)

    Reyhane Setayesh

    2017-08-01

    Full Text Available Introduction: The population growth and water requirement for domestic consumption, industry, agriculture and urban development in Mashhad megacity, increase pressures on freshwater resources. Therefore, planning for water use optimization is necessary. The new allocation of water resources for landscape greenish, especially in arid and semi-arid is difficult. Therefore, water allocation to landscape is valuable and should be used efficiently. According to water resource limitation, using drought-tolerant plant species and determine threshold of drought tolerance in landscape can improve water use management. Plants that naturally survive in your area are the ones best adapted to your soil, climate and rainfall. By selecting plants that either avoid or tolerate dry conditions, a beautiful, thriving landscape can be made possible. Drought-tolerant plants survive long periods of drought by storing water internally or by developing extensive root systems that sink deep into the soil. Many drought-tolerant plants have additional protection through a waxy coating that reduces evaporation or hairs on the leaf surface that reflect some of the light, insulating the plant. Most drought-tolerant plants use several of these features to survive on low amounts of precipitation. Japanese barberry is a compact woody deciduous shrub with arching branches. Leaf colours include green, bluish-green to dark red and purple. B. thunbergii's progress in the United States has, to date, been held in check to the south by, probably, its need for cold winter temperatures for stratification of the seeds, and to the west by, probably, drought conditions. Although very drought tolerant once established, a very dry terrain would tend to discourage its incursion. Rugged, adaptable, no serious problems or pests, easy to maintain, transplants readily, shade and drought tolerant, deer resistant is typical ad copy found at any site offering this shrub of colourful fall foliage. In

  10. Investigation of seedlings growth and development of some trees and shrubs grown on energetic ashes of two types. [Acer negundo; Fraxinus pennsylvanica; Populus alba; Myricaria germanica

    Energy Technology Data Exchange (ETDEWEB)

    Kluczynski, B

    1973-01-01

    Pot experiments concerning the degree of resistance, of chosen species of trees and shrubs to unfavorable physical and chemical properties of energetic ashes, obtained from burning brown (K) and pit (O) coal, were carried out. Seeds were sown out in prepared substrates, in 8 combinations. The investigation consisted of two parts. Seeds of 11 species of trees and shrubs and 1 herb plant were used in the first part. Seeds of 6 species of trees and shrubs were used in the second part. All the environmental variants were investigated in 4 replications (replication = pot). Each species was evaluated according to several features determining its usefulness on various substrates. These features were divided into two groups, characterizing seedlings survival (feature group ..cap alpha..) and health conditions and general vitality (feature group ..beta..). The obtained results indicate a need of examining the usefulness for dump recultivation in field conditions of Acer negundo, Fraxinus pennsylvanica, Populus alba and probably Myricaria germanica. 8 references, 17 tables.

  11. Floristic diversity of the shrub-arboreal stratum of homegardens in the Mariana re-settlement, Tocantins State, Brazil

    Directory of Open Access Journals (Sweden)

    Ícaro Gonçalves Santos

    2017-12-01

    Full Text Available The objective was to analyze the floristic, diversity and equability of the tree shrub stratum of home gardens (QA in Mariana re-settlement located between Palmas and Porto Nacional municipalities in Tocantins State, Brazil. Three 20 x 30 m plots were installed in each home garden, totalizing 0.72 ha of sampled area. All shrub-tree individuals had its circumference at 1.3 m above ground level (CBH measured when CBH ≥ 10 cm. A total of 477 individuals, 81 species, 34 families and 73 genera were verified in all QA. Shannon diversity index (H’ was 3.68 and Pielou equability indice (J’ was 0.83, for all sampled area. Individually, QA1, QA2, QA3 and QA4 presented H’ = 2.52; 3.27; 2.66 and 2.94, and J’ = 0.78; 0.90; 0.77 and 0.85, respectively. It was possible to infer that the studied QA showed high richness and diversity, evidencing great environmental heterogeneity and low ecological dominance.

  12. A greener Greenland? Climatic potential and long-term constraints on future expansions of trees and shrubs

    Science.gov (United States)

    Normand, Signe; Randin, Christophe; Ohlemüller, Ralf; Bay, Christian; Høye, Toke T.; Kjær, Erik D.; Körner, Christian; Lischke, Heike; Maiorano, Luigi; Paulsen, Jens; Pearman, Peter B.; Psomas, Achilleas; Treier, Urs A.; Zimmermann, Niklaus E.; Svenning, Jens-Christian

    2013-01-01

    Warming-induced expansion of trees and shrubs into tundra vegetation will strongly impact Arctic ecosystems. Today, a small subset of the boreal woody flora found during certain Plio-Pleistocene warm periods inhabits Greenland. Whether the twenty-first century warming will induce a re-colonization of a rich woody flora depends on the roles of climate and migration limitations in shaping species ranges. Using potential treeline and climatic niche modelling, we project shifts in areas climatically suitable for tree growth and 56 Greenlandic, North American and European tree and shrub species from the Last Glacial Maximum through the present and into the future. In combination with observed tree plantings, our modelling highlights that a majority of the non-native species find climatically suitable conditions in certain parts of Greenland today, even in areas harbouring no native trees. Analyses of analogous climates indicate that these conditions are widespread outside Greenland, thus increasing the likelihood of woody invasions. Nonetheless, we find a substantial migration lag for Greenland's current and future woody flora. In conclusion, the projected climatic scope for future expansions is strongly limited by dispersal, soil development and other disequilibrium dynamics, with plantings and unintentional seed dispersal by humans having potentially large impacts on spread rates. PMID:23836785

  13. Moderate irrigation intervals facilitate establishment of two desert shrubs in the Taklimakan Desert Highway Shelterbelt in China.

    Science.gov (United States)

    Li, Congjuan; Shi, Xiang; Mohamad, Osama Abdalla; Gao, Jie; Xu, Xinwen; Xie, Yijun

    2017-01-01

    Water influences various physiological and ecological processes of plants in different ecosystems, especially in desert ecosystems. The purpose of this study is to investigate the response of physiological and morphological acclimation of two shrubs Haloxylon ammodendron and Calligonum mongolicunl to variations in irrigation intervals. The irrigation frequency was set as 1-, 2-, 4-, 8- and 12-week intervals respectively from March to October during 2012-2014 to investigate the response of physiological and morphological acclimation of two desert shrubs Haloxylon ammodendron and Calligonum mongolicunl to variations in the irrigation system. The irrigation interval significantly affected the individual-scale carbon acquisition and biomass allocation pattern of both species. Under good water conditions (1- and 2-week intervals), carbon assimilation was significantly higher than other treatments; while, under water shortage conditions (8- and 12-week intervals), there was much defoliation; and under moderate irrigation intervals (4 weeks), the assimilative organs grew gently with almost no defoliation occurring. Both studied species maintained similar ecophysiologically adaptive strategies, while C. mongolicunl was more sensitive to drought stress because of its shallow root system and preferential belowground allocation of resources. A moderate irrigation interval of 4 weeks was a suitable pattern for both plants since it not only saved water but also met the water demands of the plants.

  14. The invasive shrub Prosopis juliflora enhances the malaria parasite transmission capacity of Anopheles mosquitoes: a habitat manipulation experiment.

    Science.gov (United States)

    Muller, Gunter C; Junnila, Amy; Traore, Mohamad M; Traore, Sekou F; Doumbia, Seydou; Sissoko, Fatoumata; Dembele, Seydou M; Schlein, Yosef; Arheart, Kristopher L; Revay, Edita E; Kravchenko, Vasiliy D; Witt, Arne; Beier, John C

    2017-07-05

    A neglected aspect of alien invasive plant species is their influence on mosquito vector ecology and malaria transmission. Invasive plants that are highly attractive to Anopheles mosquitoes provide them with sugar that is critical to their survival. The effect on Anopheles mosquito populations was examined through a habitat manipulation experiment that removed the flowering branches of highly attractive Prosopis juliflora from selected villages in Mali, West Africa. Nine villages in the Bandiagara district of Mali were selected, six with flowering Prosopis juliflora, and three without. CDC-UV light traps were used to monitor their Anopheles spp. vector populations, and recorded their species composition, population size, age structure, and sugar feeding status. After 8 days, all of the flowering branches were removed from three villages and trap catches were analysed again. Villages where flowering branches of the invasive shrub Prosopis juliflora were removed experienced a threefold drop in the older more dangerous Anopheles females. Population density dropped by 69.4% and the species composition shifted from being a mix of three species of the Anopheles gambiae complex to one dominated by Anopheles coluzzii. The proportion of sugar fed females dropped from 73 to 15% and males from 77 to 10%. This study demonstrates how an invasive plant shrub promotes the malaria parasite transmission capacity of African malaria vector mosquitoes. Proper management of invasive plants could potentially reduce mosquito populations and malaria transmission.

  15. Effect of petroleum on decomposition of shrub-grass litters in soil in Northern Shaanxi of China.

    Science.gov (United States)

    Zhang, Xiaoxi; Liu, Zengwen; Yu, Qi; Luc, Nhu Trung; Bing, Yuanhao; Zhu, Bochao; Wang, Wenxuan

    2015-07-01

    The impacts of petroleum contamination on the litter decomposition of shrub-grass land would directly influence nutrient cycling, and the stability and function of ecosystem. Ten common shrub and grass species from Yujiaping oil deposits were studied. Litters from these species were placed into litterbags and buried in petroleum-contaminated soil with 3 levels of contamination (slight, moderate and serious pollution with petroleum concentrations of 15, 30 and 45 g/kg, respectively). A decomposition experiment was then conducted in the lab to investigate the impacts of petroleum contamination on litter decomposition rates. Slight pollution did not inhibit the decomposition of any litters and significantly promoted the litter decomposition of Hippophae rhamnoides, Caragana korshinskii, Amorpha fruticosa, Ziziphus jujuba var. spinosa, Periploca sepium, Medicago sativa and Bothriochloa ischaemum. Moderate pollution significantly inhibited litter decomposition of M. sativa, Coronilla varia, Artemisia vestita and Trrifolium repens and significantly promoted the litter decomposition of C. korshinskii, Z. jujuba var. spinosa and P. sepium. Serious pollution significantly inhibited the litter decomposition of H. rhamnoides, A. fruticosa, B. ischaemum and A. vestita and significantly promoted the litter decomposition of Z. jujuba var. spinosa, P. sepium and M. sativa. In addition, the impacts of petroleum contamination did not exhibit a uniform increase or decrease as petroleum concentration increased. Inhibitory effects of petroleum on litter decomposition may hinder the substance cycling and result in the degradation of plant communities in contaminated areas. Copyright © 2015. Published by Elsevier B.V.

  16. Influence of summer marine fog and low cloud stratus on water relations of evergreen woody shrubs (Arctostaphylos: Ericaceae) in the chaparral of central California.

    Science.gov (United States)

    Vasey, Michael C; Loik, Michael E; Parker, V Thomas

    2012-10-01

    Mediterranean-type climate (MTC) regions around the world are notable for cool, wet winters and hot, dry summers. A dominant vegetation type in all five MTC regions is evergreen, sclerophyllous shrubland, called chaparral in California. The extreme summer dry season in California is moderated by a persistent low-elevation layer of marine fog and cloud cover along the margin of the Pacific coast. We tested whether late dry season water potentials (Ψ(min)) of chaparral shrubs, such as Arctostaphylos species in central California, are influenced by this coast-to-interior climate gradient. Lowland coastal (maritime) shrubs were found to have significantly less negative Ψ(min) than upland interior shrubs (interior), and stable isotope (δ(13)C) values exhibited greater water use efficiency in the interior. Post-fire resprouter shrubs (resprouters) had significantly less negative Ψ(min) than co-occurring obligate seeder shrubs (seeders) in interior and transitional chaparral, possibly because resprouters have deeper root systems with better access to subsurface water than shallow-rooted seeders. Unexpectedly, maritime resprouters and seeders did not differ significantly in their Ψ(min), possibly reflecting more favorable water availability for shrubs influenced by the summer marine layer. Microclimate and soil data also suggest that maritime habitats have more favorable water availability than the interior. While maritime seeders constitute the majority of local Arctostaphylos endemics, they exhibited significantly greater vulnerability to xylem cavitation than interior seeders. Because rare seeders in maritime chaparral are more vulnerable to xylem cavitation than interior seeders, the potential breakdown of the summer marine layer along the coast is of potential conservation concern.

  17. Impact of ultraviolet-beta radiation on two species of forest dwarf shrubs: bilberry (Vaccinium myrtillus L.) and cowberry (Vaccinium vitis-idaea L.)

    International Nuclear Information System (INIS)

    Robakowski, P.

    1999-01-01

    The impact of UV-B radiation on chlorophyll content and chlorophyll fluoroscence of two dwarth shrub species was investigated. The plants originating from different latitudes were used. Three variants of ultraviolet-B radiation were applied: control = 0, lower dose = 11,32 and higher dose = 22,64 kJ/square m/day. Measurements of chlorophyll fluorescence and chlorophyll content were carried out. The response of dwarf shrubs to the increased UV-B radiation depended on UV-B dose, species traits and provenance

  18. Impact of decade-long warming, nutrient addition and shading on emission and carbon isotopic composition of CO2 from two subarctic dwarf shrub heaths

    DEFF Research Database (Denmark)

    Ravn, Nynne R.; Ambus, Per Lennart; Michelsen, Anders

    2017-01-01

    This study investigated ecosystem respiration, soil respiration and carbon isotopic composition in CO2 emitted from two subarctic shrub heaths with contrasting moisture regimes. The reported measurements were conducted 22 years (mesic heath) and 12 years (wet heath) upon initiation of in situ...... the growing season. However, there was a tendency across growing season towards an increased δ13C source value after 22 years of warming in the mesic shrub heath, and the effect was statistically significant in June, indicating increased decomposition of 13C enriched material. Hence, although more of the old...

  19. Changes in Soil Organic Matter Abundance, Molecular Composition, and Diversity in an Arid Ecosystem in Response to Long-term Elevated CO2 Manipulation.

    Science.gov (United States)

    Hess, N. J.; Tfaily, M.; Evans, R. D.; Koyama, A.

    2017-12-01

    Little is known about how soils in arid ecosystems will respond to rising atmospheric CO2 concentration yet arid and semi-arid ecosystems cover more than 40% of Earth's land surface. Previous work in the Mojave Desert (Evans et al., 2014 Nature Climate Change) reported higher soil organic carbon (SOC) and total nitrogen (N) concentrations following 10 years exposure to elevated atmospheric CO2 at the Nevada Desert Free-Air-Carbon dioxide-Enrichment (FACE) Facility (NDFF). In this study, we investigated potential mechanisms that resulted in increased SOC and total N accumulation and stabilization using high resolution mass spectrometry at the NDFF site. Samples were collected from soil profiles to 1 m in depth with a 0.2 m a increment under the dominant evergreen shrub Larrea tridentata. The differences in the molecular composition and diversity of soil organic matter (SOM) were more evident in surface soils and declined with depth, and were consistent with higher SOC and total N concentrations under elevated than ambient CO2. Our molecular analysis also suggested increased root exudation and/or microbial necromass from stabilization of labile C and N contributed to SOM and N stocks. Increased microbial activity and metabolism under elevated CO2 compared to ambient plots suggested that elevated CO2 altered microbial carbon (C) use patterns, reflecting changes in the quality and quantity of SOC inputs. We found that plant-derived compounds were primary substrates for microbial activity under elevated CO2 and microbial products were the main constituents of stabilized SOM. Our results suggest that arid ecosystems are a potential large C sink under elevated CO2, give the extensive coverage of the land surface, and that labile compounds are transformed to stable SOM via microbial processes. Arid systems are limited by water, and thus may have a different C storage potential under changing climates than other ecosystems that are limited by nitrogen or phosphorus.

  20. Soil bacterial and fungal community responses to nitrogen addition across soil depth and microhabitat in an arid shrubland

    Science.gov (United States)

    Mueller, Rebecca C.; Belnap, Jayne; Kuske, Cheryl R.

    2015-01-01

    Arid shrublands are stressful environments, typified by alkaline soils low in organic matter, with biologically-limiting extremes in water availability, temperature, and UV radiation. The widely-spaced plants and interspace biological soil crusts in these regions provide soil nutrients in a localized fashion, creating a mosaic pattern of plant- or crust-associated microhabitats with distinct nutrient composition. With sporadic and limited rainfall, nutrients are primarily retained in the shallow surface soil, patterning biological activity. We examined soil bacterial and fungal community responses to simulated nitrogen (N) deposition in an arid Larrea tridentata-Ambrosia dumosa field experiment in southern Nevada, USA, using high-throughput sequencing of ribosomal RNA genes. To examine potential interactions among the N application, microhabitat and soil depth, we sampled soils associated with shrub canopies and interspace biological crusts at two soil depths (0–0.5 or 0–10 cm) across the N-amendment gradient (0, 7, and 15 kg ha−1 yr−1). We hypothesized that localized compositional differences in soil microbiota would constrain the impacts of N addition to a microhabitat distribution that would reflect highly localized geochemical conditions and microbial community composition. The richness and community composition of both bacterial and fungal communities differed significantly by microhabitat and with soil depth in each microhabitat. Only bacterial communities exhibited significant responses to the N addition. Community composition correlated with microhabitat and depth differences in soil geochemical features. Given the distinct roles of soil bacteria and fungi in major nutrient cycles, the resilience of fungi and sensitivity of bacteria to N amendments suggests that increased N input predicted for many arid ecosystems could shift nutrient cycling toward pathways driven primarily by fungal communities.

  1. Soil bacterial and fungal community responses to nitrogen addition across soil depths and microhabitat in an arid shrubland

    Directory of Open Access Journals (Sweden)

    Rebecca C Mueller

    2015-09-01

    Full Text Available Arid shrublands are stressful environments, typified by alkaline soils low in organic matter, with biologically-limiting extremes in water availability, temperature and UV radiation. The widely-spaced plants and interspace biological soil crusts in these regions provide soil nutrients in a localized fashion, creating a mosaic pattern of plant- or crust-associated microhabitats with distinct nutrient composition. With sporadic and limited rainfall, nutrients are primarily retained in the shallow surface soil, patterning biological activity. We examined soil bacterial and fungal community responses to simulated nitrogen (N deposition in an arid Larrea tridentata-Ambrosia dumosa field experiment in southern Nevada, USA, using high-throughput sequencing of ribosomal RNA genes. To examine potential interactions among the N application, microhabitat and soil depth, we sampled soils associated with shrub canopies and interspace biological crusts at two soil depths (0-0.5 cm or 0-10 cm across the N-amendment gradient (0, 7 and 15 kg ha-1 yr-1. We hypothesized that localized compositional differences in soil microbiota would constrain the impacts of N addition to a microhabitat distribution that would reflect highly localized geochemical conditions and microbial community composition. The richness and community composition of both bacterial and fungal communities differed significantly by microhabitat and with soil depth in each microhabitat. Only bacterial communities exhibited significant responses to the N addition. Community composition correlated with microhabitat and depth differences in soil geochemical features. Given the distinct roles of soil bacteria and fungi in major nutrient cycles, the resilience of fungi and sensitivity of bacteria to N amendments suggests that increased N input predicted for many arid ecosystems could shift nutrient cycling toward pathways driven primarily by fungal communities.

  2. Estimating vegetation biomass and cover across large plots in shrub and grass dominated drylands using terrestrial lidar and machine learning

    Science.gov (United States)

    Anderson, Kyle E.; Glenn, Nancy F.; Spaete, Lucas P.; Shinneman, Douglas; Pilliod, David S.; Arkle, Robert; McIlroy, Susan; Derryberry, DeWayne R.

    2018-01-01

    Terrestrial laser scanning (TLS) has been shown to enable an efficient, precise, and non-destructive inventory of vegetation structure at ranges up to hundreds of meters. We developed a method that leverages TLS collections with machine learning techniques to model and map canopy cover and biomass of several classes of short-stature vegetation across large plots. We collected high-definition TLS scans of 26 1-ha plots in desert grasslands and big sagebrush shrublands in southwest Idaho, USA. We used the Random Forests machine learning algorithm to develop decision tree models predicting the biomass and canopy cover of several vegetation classes from statistical descriptors of the aboveground heights of TLS points. Manual measurements of vegetation characteristics collected within each plot served as training and validation data. Models based on five or fewer TLS descriptors of vegetation heights were developed to predict the canopy cover fraction of shrubs (R2 = 0.77, RMSE = 7%), annual grasses (R2 = 0.70, RMSE = 21%), perennial grasses (R2 = 0.36, RMSE = 12%), forbs (R2 = 0.52, RMSE = 6%), bare earth or litter (R2 = 0.49, RMSE = 19%), and the biomass of shrubs (R2 = 0.71, RMSE = 175 g) and herbaceous vegetation (R2 = 0.61, RMSE = 99 g) (all values reported are out-of-bag). Our models explained much of the variability between predictions and manual measurements, and yet we expect that future applications could produce even better results by reducing some of the methodological sources of error that we encountered. Our work demonstrates how TLS can be used efficiently to extend manual measurement of vegetation characteristics from small to large plots in grasslands and shrublands, with potential application to other similarly structured ecosystems. Our method shows that vegetation structural characteristics can be modeled without classifying and delineating individual plants, a challenging and time-consuming step common in previous

  3. Comparison of respiratory and growth characteristics of two co-occurring shrubs from a cold desert, Coleogyne ramosissima (blackbrush) and Atriplex confertifolia (shadscale)

    Science.gov (United States)

    H. A. Summers; B. N. Smith; L. D. Hansen

    2009-01-01

    Coleogyne ramosissima Torr. (blackbrush) and Atriplex confertifolia [Torr. & Frem.] Wats. (shadscale) are cold desert shrubs from different families. Despite very different life histories they often grow in close geographic proximity in the Great Basin and the Colorado Plateau between 800 and 2000 m elevation. The purpose of...

  4. The distribution of a non-native (Rosa multiflora) and native (Kalmia latifolia) shrub in mature closed-canopy forests across soil fertility gradients

    Science.gov (United States)

    Cynthia D. Huebner; Jim Steinman; Todd F. Hutchinson; Todd E. Ristau; Alejandro A. Royo

    2014-01-01

    Background and aims. A soil fertility gradient, ranging from infertile to highly fertile soils, may define whether or not a plant will establish and spread at a site. We evaluated whether or not such a fertility gradient exists for Rosa multiflora Thunb., a nonnative invasive shrub, and Kalmia latifolia L., a...

  5.  Invasibility of three major non-native invasive shrubs and associated factors in Upper Midwest U.S. forest lands

    Science.gov (United States)

    W. Keith Moser; Zhaofei Fan; Mark H. Hansen; Michael K. Crosby; Shirley X. Fan

    2016-01-01

    We used non-native invasive plant data from the US Forest Service’s Forest Inventory and Analysis (FIA) program, spatial statistical methods, and the space (cover class)-for-time approach to quantify the invasion potential and success ("invasibility") of three major invasive shrubs (multiflora rose, non-native bush honeysuckles, and common buckthorn...

  6. Simulation of water-limited growth of the forage shrub saltbush (Atriplex nummularia Lindl.) in a low-rainfall environment of southern Australia

    NARCIS (Netherlands)

    Descheemaeker, K.K.E.; Smith, A.P.; Robertson, M.J.; Whitbread, A.; Huth, N.I.; Davoren, W.; Emms, J.; Llewellyn, R.

    2014-01-01

    Old man saltbush (Atriplex nummularia Lindl.) is a useful forage shrub for livestock in the low-rainfall areas of the world, and particularly in Australia. In these semi-arid and arid environments, saltbush is valuable for increasing the production from otherwise marginal areas of the farm and

  7. Effects of an experimental increase of temperature and drought on the photosynthetic performance of two ericaceous shrub species along a north-south European gradient

    DEFF Research Database (Denmark)

    Llorens, L.; Penuelas, J.; Beier, C.

    2004-01-01

    ericaceous shrubs (Erica multiflora and Calluna vulgaris) along a European gradient of temperature and precipitation (UK, Denmark, The Netherlands, and Spain). At each site, a passive warming treatment was applied during the night throughout the whole year, whereas the drought treatment excluded rain events...

  8. The impact of temperature regimes on development, dormancy breaking and germination of dwarf shrub seeds from arctic, alpine and boreal sites

    DEFF Research Database (Denmark)

    Graae, Bente Jessen; Alsos, Inger Greve; Ejrnæs, Rasmus

    2008-01-01

    It has been suggested that the infrequent sexual reproduction of arctic dwarf shrubs might be related to the harsh environmental conditions in which they live. If this is the case, then increases in temperature resulting from global climate change might drastically affect regeneration of arctic...

  9. PESTS OF ORNAMENTAL TREES AND SHRUBS IN THE PARKS OF PITEŞTI AND METHODS OF FIGHTING THEM

    Directory of Open Access Journals (Sweden)

    Daniela Bărbuceanu

    2012-04-01

    Full Text Available The observations carried-out in 2008 to ornamental trees and shrubs from parks of ADP Pitesti conducted to identified of the follows pests species: Macrosiphum rosae (L., Aphis spiraephaga Müll., Cinara cupressi Buckton, Hyphantria cunea Drury, Oxycarenus lavaterae (F.. Cinara cupressi and Oxycarenus lavaterae are mentioned for the first time in Romania. Cinara cupressi was noticed on an imported Abies nordmanniana specimen in a park from this city. O. lavaterae, a Mediterranean species from Tilia sp., currently it is expanding his area in northern regions. We recommend carefully monitoring of imported ornamental plants, because they can be infested and open ways to invasion for the pests with devastated potential.

  10. Floristic and structure of the shrub-arboreal component of a remnant of cerrado sensustricto, Gurupi, Tocantins, Brazil

    Directory of Open Access Journals (Sweden)

    Bruno Aurélio Aguiar

    2018-01-01

    Full Text Available The objective was to characterize a floristic and phytosociology of a fragment of cerrado sensu stricto, located in Gurupi, Tocantins. The study was carried out in the legal Reserve of the experimental farm of the Federal University of Tocantins, Campus of Gurupi, Tocantins, Brazil. Five porcelains of 20x50m were implanted, totaling 5000sqm and all compostations with a circumference greater than or equal to 10 cm, at 0 cm at the soil level (CAS were implanted. Foramaler 906 aphid shrub-arboreal belonging to 42 families, 102 species and 78 genera. The families that stood out in number of individuals, frequency, dominance were Myrtacea, Vochystaceae, Burseraceae and Fabaceae, among the indications of the main beings Myrcia fallax (Rich DC, Protium heptaphyllum (Aubl Marchand and Qualea multiflora Mart. The diversity index of Shannon (H ' was 3.70 and equability J'0,80, being considered for the cerrado region.

  11. On the use of radiative surface temperature to estimate sensible heat flux over sparse shrubs in Nevada

    Science.gov (United States)

    Chehbouni, A.; Nichols, W. D.; Qi, J.; Njoku, E. G.; Kerr, Y. H.; Cabot, F.

    1994-01-01

    The accurate partitioning of available energy into sensible and latent heat flux is crucial to the understanding of surface atmosphere interactions. This issue is more complicated in arid and semi arid regions where the relative contribution to surface fluxes from the soil and vegetation may vary significantly throughout the day and throughout the season. A three component model to estimate sensible heat flux over heterogeneous surfaces is presented. The surface was represented with two adjacent compartments. The first compartment is made up of two components, shrubs and shaded soil, the second of open 'illuminated' soil. Data collected at two different sites in Nevada (U.S.) during the Summers of 1991 and 1992 were used to evaluate model performance. The results show that the present model is sufficiently general to yield satisfactory results for both sites.

  12. Effects of land conversion from native shrub to pistachio orchard on soil erodibility in an arid region.

    Science.gov (United States)

    Yakupoglu, Tugrul; Gundogan, Recep; Dindaroglu, Turgay; Kara, Zekeriya

    2017-10-29

    Land-use change through degrading natural vegetation for agricultural production adversely affects many of soil properties particularly organic carbon content of soils. The native shrub land and grassland of Gaziantep-Adiyaman plateau that is an important pistachio growing eco-region have been cleared to convert into pistachio orchard for the last 50 to 60 years. In this study, the effects of conversion of natural vegetation into agricultural uses on soil erodibility have been investigated. Soil samples were collected from surface of agricultural fields and adjacent natural vegetation areas, and samples were analyzed for some soil erodibility indices such as dispersion ratio (DR), erosion ratio (ER), structural stability index (SSI), Henin's instability index (I s ), and aggregate size distribution after wet sieving (AggSD). According to the statistical evaluation, these two areas were found as different from each other in terms of erosion indices except for I s index (P < 0.001 for DR and ER or P < 0.01 for SSI). In addition, native shrub land and converted land to agriculture were found different in terms of AggSD in all aggregate size groups. As a contrary to expectations, correlation tests showed that there were no any interaction between soil organic carbon and measured erodibility indices in two areas. In addition, significant relationships were determined between measured variables and soil textural fractions as statistical. These obtaining findings were attributed to changing of textural component distribution and initial aggregate size distribution results from land-use change in the study area. Study results were explained about hierarchical aggregate formation mechanism.

  13. Growth and phenology of three dwarf shrub species in a six-year soil warming experiment at the alpine treeline.

    Science.gov (United States)

    Anadon-Rosell, Alba; Rixen, Christian; Cherubini, Paolo; Wipf, Sonja; Hagedorn, Frank; Dawes, Melissa A

    2014-01-01

    Global warming can have substantial impacts on the phenological and growth patterns of alpine and Arctic species, resulting in shifts in plant community composition and ecosystem dynamics. We evaluated the effects of a six-year experimental soil warming treatment (+4°C, 2007-2012) on the phenology and growth of three co-dominant dwarf shrub species growing in the understory of Larix decidua and Pinus uncinata at treeline in the Swiss Alps. We monitored vegetative and reproductive phenology of Vaccinium myrtillus, Vaccinium gaultherioides and Empetrum hermaphroditum throughout the early growing season of 2012 and, following a major harvest at peak season, we measured the biomass of above-ground ramet fractions. For all six years of soil warming we measured annual shoot growth of the three species and analyzed ramet age and xylem ring width of V. myrtillus. Our results show that phenology of the three species was more influenced by snowmelt timing, and also by plot tree species (Larix or Pinus) in the case of V. myrtillus, than by soil warming. However, the warming treatment led to increased V. myrtillus total above-ground ramet biomass (+36% in 2012), especially new shoot biomass (+63% in 2012), as well as increased new shoot increment length and xylem ring width (+22% and +41%, respectively; average for 2007-2012). These results indicate enhanced overall growth of V. myrtillus under soil warming that was sustained over six years and was not caused by an extended growing period in early summer. In contrast, E. hermaphroditum only showed a positive shoot growth response to warming in 2011 (+21%), and V. gaultherioides showed no significant growth response. Our results indicate that V. myrtillus might have a competitive advantage over the less responsive co-occurring dwarf shrub species under future global warming.

  14. Growth and phenology of three dwarf shrub species in a six-year soil warming experiment at the alpine treeline.

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    Alba Anadon-Rosell

    Full Text Available Global warming can have substantial impacts on the phenological and growth patterns of alpine and Arctic species, resulting in shifts in plant community composition and ecosystem dynamics. We evaluated the effects of a six-year experimental soil warming treatment (+4°C, 2007-2012 on the phenology and growth of three co-dominant dwarf shrub species growing in the understory of Larix decidua and Pinus uncinata at treeline in the Swiss Alps. We monitored vegetative and reproductive phenology of Vaccinium myrtillus, Vaccinium gaultherioides and Empetrum hermaphroditum throughout the early growing season of 2012 and, following a major harvest at peak season, we measured the biomass of above-ground ramet fractions. For all six years of soil warming we measured annual shoot growth of the three species and analyzed ramet age and xylem ring width of V. myrtillus. Our results show that phenology of the three species was more influenced by snowmelt timing, and also by plot tree species (Larix or Pinus in the case of V. myrtillus, than by soil warming. However, the warming treatment led to increased V. myrtillus total above-ground ramet biomass (+36% in 2012, especially new shoot biomass (+63% in 2012, as well as increased new shoot increment length and xylem ring width (+22% and +41%, respectively; average for 2007-2012. These results indicate enhanced overall growth of V. myrtillus under soil warming that was sustained over six years and was not caused by an extended growing period in early summer. In contrast, E. hermaphroditum only showed a positive shoot growth response to warming in 2011 (+21%, and V. gaultherioides showed no significant growth response. Our results indicate that V. myrtillus might have a competitive advantage over the less responsive co-occurring dwarf shrub species under future global warming.

  15. Growth and reproduction of the alpine grasshopper Miramella alpina feeding on CO2-enriched dwarf shrubs at treeline.

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    Asshoff, Roman; Hättenschwiler, Stephan

    2005-01-01

    The consequences for plant-insect interactions of atmospheric changes in alpine ecosystems are not well understood. Here, we tested the effects of elevated CO(2) on leaf quality in two dwarf shrub species (Vaccinium myrtillus and V. uliginosum) and the response of the alpine grasshopper (Miramella alpina) feeding on these plants in a field experiment at the alpine treeline (2,180 m a.s.l.) in Davos, Switzerland. Relative growth rates (RGR) of M. alpina nymphs were lower when they were feeding on V. myrtillus compared to V. uliginosum, and were affected by elevated CO(2) depending on plant species and nymph developmental stage. Changes in RGR correlated with CO(2)-induced changes in leaf water, nitrogen, and starch concentrations. Elevated CO(2) resulted in reduced female adult weight irrespective of plant species, and prolonged development time on V. uliginosum only, but there were no significant differences in nymphal mortality. Newly molted adults of M. alpina produced lighter eggs and less secretion (serving as egg protection) under elevated CO(2). When grasshoppers had a choice among four different plant species grown either under ambient or elevated CO(2), V. myrtillus and V. uliginosum consumption increased under elevated CO(2) in females while it decreased in males compared to ambient CO(2)-grown leaves. Our findings suggest that rising atmospheric CO(2) distinctly affects leaf chemistry in two important dwarf shrub species at the alpine treeline, leading to changes in feeding behavior, growth, and reproduction of the most important insect herbivore in this system. Changes in plant-grasshopper interactions might have significant long-term impacts on herbivore pressure, community dynamics and ecosystem stability in the alpine treeline ecotone.

  16. Functional identification of a GORK potassium channel from the ancient desert shrub Ammopiptanthus mongolicus (Maxim.) Cheng f.

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    Li, Junlin; Zhang, Huanchao; Lei, Han; Jin, Man; Yue, Guangzhen; Su, Yanhua

    2016-04-01

    A GORK homologue K(+) channel from the ancient desert shrub Ammopiptanthus mongolicus (Maxim.) Cheng f. shows the functional conservation of the GORK channels among plant species. Guard cell K(+) release through the outward potassium channels eventually enables the closure of stomata which consequently prevents plant water loss from severe transpiration. Early patch-clamp studies with the guard cells have revealed many details of such outward potassium currents. However, genes coding for these potassium-release channels have not been sufficiently characterized from species other than the model plant Arabidopsis thaliana. We report here the functional identification of a GORK (for Gated or Guard cell Outward Rectifying K(+) channels) homologue from the ancient desert shrub Ammopiptanthus mongolicus (Maxim.) Cheng f. AmGORK was primary expressed in shoots, where the transcripts were regulated by stress factors simulated by PEG, NaCl or ABA treatments. Patch-clamp measurements on isolated guard cell protoplasts revealed typical depolarization voltage gated outward K(+) currents sensitive to the extracelluar K(+) concentration and pH, resembling the fundamental properties previously described in other species. Two-electrode voltage-clamp analysis in Xenopus lavies oocytes with AmGORK reconstituted highly similar characteristics as assessed in the guard cells, supporting that the function of AmGORK is consistent with a crucial role in mediating stomatal closure in Ammopiptanthus mongolicus. Furthermore, a single amino acid mutation D297N of AmGORK eventually abolishes both the voltage-gating and its outward rectification and converts the channel into a leak-like channel, indicating strong involvement of this residue in the gating and voltage dependence of AmGORK. Our results obtained from this anciently originated plant support a strong functional conservation of the GORK channels among plant species and maybe also along the progress of revolution.

  17. Using Mediterranean shrubs for the phytoremediation of a soil impacted by pyritic wastes in Southern Spain: a field experiment.

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    Moreno-Jiménez, Eduardo; Vázquez, Saúl; Carpena-Ruiz, Ramón O; Esteban, Elvira; Peñalosa, Jesús M

    2011-06-01

    Re-vegetation is the main aim of ecological restoration projects, and in Mediterranean environments native plants are desirable to achieve successful restoration. In 1998, the burst of a tailings dam flooded the Guadiamar river valley downstream from Aznalcóllar (Southern Spain) with sludges that contained elevated concentrations of metals and metalloids, polluting soils and waters. A phytoremediation experiment to assess the potential use of native shrub species for the restoration of soils affected by the spillage was per