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Sample records for shrub invasion decreases

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

    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

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

    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.

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

    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.

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

    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.

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

    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.

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

    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. Synergy of extreme drought and shrub invasion reduce ecosystem functioning and resilience in water-limited climates

    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.

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

    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

  9. Range expansion of invasive shrubs: implication for crown fire risk in forestlands of the southern USA.

    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

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

    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...

  11. Snowpack, fire, and forest disturbance: interactions affect montane invasions by non-native shrubs.

    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

  12. Invasive Shrub Mapping in an Urban Environment from Hyperspectral and LiDAR-Derived Attributes.

    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.

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

    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...

  14. Use of AIRSAR to identify woody shrub invasion and other indicators of desertification in the Jornada LTER

    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.

  15. Arctic tundra shrub invasion and soot deposition: Consequences for spring snowmelt and near-surface air temperatures

    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.

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

    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...

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

    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...

  18.  Invasibility of three major non-native invasive shrubs and associated factors in Upper Midwest U.S. forest lands

    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...

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

    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.

  20. Contrasting growth phenology of native and invasive forest shrubs mediated by genome size.

    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.

  1. Climate change and the potential distribution of an invasive shrub, Lantana camara L.

    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.

  2. Hybridization of an invasive shrub affects tolerance and resistance to defoliation by a biological control agent

    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.

  3. The invasive shrub Prosopis juliflora enhances the malaria parasite transmission capacity of Anopheles mosquitoes: a habitat manipulation experiment.

    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.

  4. Transpiration and stomatal conductance in a young secondary tropical montane forest: contrasts between native trees and invasive understorey shrubs.

    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.

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

    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...

  6. Competition for soil nitrate and invasive weed resistance of three shrub-steppe growth forms

    Eamonn D. Leonard

    2007-01-01

    Determining mechanisms responsible for weed resistance and invasion success are two issues that have potential in aiding successful land management decisions. The first experiment evaluates the competitive effects of an invasive annual grass downy brome (Bromus tectorum L.), an invasive biennial forb dyer's woad (Isatis tinctoria...

  7. Plasticity to salinity and transgenerational effects in the nonnative shrub Baccharis halimifolia: Insights into an estuarine invasion.

    Caño, Lidia; Fuertes-Mendizabal, Teresa; García-Baquero, Gonzalo; Herrera, Mercedes; González-Moro, M Begoña

    2016-05-01

    Abiotic constraints act as selection filters for plant invasion in stressful habitats. Adaptive phenotypic plasticity and transgenerational effects play a major role in colonization of heterogeneous habitats when the scale of environmental variation is smaller than that of gene flow. We investigated how plasticity and parental salinity conditions influence the performance of the invasive dioecious shrub Baccharis halimifolia, which replaces heterogeneous estuarine communities in Europe with monospecific and continuous stands. In two greenhouse experiments, we grew plants derived from seeds and cuttings collected through interspersed patches differing in edaphic salinity from an invasive population. We estimated parental environmental salinity from leaf Na(+) content in parental plants, and we measured fitness and ion homeostasis of the offspring grown in contrasting salinity conditions. Baccharis halimifolia tolerates high salinity but experiences drastic biomass reduction at moderate salinity. At moderate salinity, responses to salinity are affected by the parental salinity: flowering initiation in seedlings and male cuttings is positively correlated with parental leaf Na(+) content, and biomass is positively correlated with maternal leaf Na(+) in female cuttings and seedlings. Plant height, leaf production, specific leaf area, and ionic homeostasis at the low part of the gradient are also affected by parental salinity, suggesting enhanced shoot growth as parental salinity increases. Our results support plasticity to salinity and transgenerational effects as factors with great potential to contribute to the invasive ability of B. halimifolia through estuarine communities of high conservation value. © 2016 Botanical Society of America.

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

    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.

  9. Exotic Invasive Shrub Glossy Buckthorn Reduces Restoration Potential for Native Forest Herbs

    Caroline Hamelin

    2017-02-01

    Full Text Available Invasive glossy buckthorn could reduce restoration potential for understory native forest herbs by compromising their growth and biodiversity. Few studies of glossy buckthorn’s effects on forest herbs exist, and none were done in early-successional, partially open hardwood forests. This study was conducted in a mature hybrid poplar plantation invaded by buckthorn, located in southeastern Québec. We tested the effect of buckthorn removal on the growth of three forest herb species, whether this effect varied among species, and if canopy type (two poplar clones influenced this effect. Forest herbs were planted in herbicide (buckthorn removed and control treatments in the plantation understory, an environment similar to that of early-successional hardwood forests. Over the first two growing seasons, species showed specific reactions to buckthorn cover. Mean relative growth rate (RGR for Asarum canadense and Polygonatum pubescens was increased in the herbicide treatment (48% and 33%, respectively and decreased in the control treatment (−35% and −33%, respectively. Sanguinaria canadensis growth was the highest among species, with no difference between treatments. No effects of canopy type were detected. Results suggest that planting forest herbs for restoration purposes may be unsuccessful if buckthorn is present. Important changes in understory flora biodiversity are likely to occur over the long term in forests invaded by buckthorn.

  10. Asymmetric effects of native and exotic invasive shrubs on ecology of the West Nile virus vector Culex pipiens (Diptera: Culicidae).

    Gardner, Allison M; Allan, Brian F; Frisbie, Lauren A; Muturi, Ephantus J

    2015-06-16

    Exotic invasive plants alter the structure and function of native ecosystems and may influence the distribution and abundance of arthropod disease vectors by modifying habitat quality. This study investigated how invasive plants alter the ecology of Culex pipiens, an important vector of West Nile virus (WNV) in northeastern and midwestern regions of the United States. Field and laboratory experiments were conducted to test the hypothesis that three native leaf species (Rubus allegheniensis, blackberry; Sambucus canadensis, elderberry; and Amelanchier laevis, serviceberry), and three exotic invasive leaf species (Lonicera maackii, Amur honeysuckle; Elaeagnus umbellata, autumn olive; and Rosa multiflora, multiflora rose) alter Cx. pipiens oviposition site selection, emergence rates, development time, and adult body size. The relative abundance of seven bacterial phyla in infusions of the six leaf species also was determined using quantitative real-time polymerase chain reaction to test the hypothesis that variation in emergence, development, and oviposition site selection is correlated to differences in the diversity and abundance of bacteria associated with different leaf species, important determinants of nutrient quality and availability for mosquito larvae. Leaf detritus from invasive honeysuckle and autumn olive yielded significantly higher adult emergence rates compared to detritus from the remaining leaf species and honeysuckle alleviated the negative effects of intraspecific competition on adult emergence. Conversely, leaves of native blackberry acted as an ecological trap, generating high oviposition but low emergence rates. Variation in bacterial flora associated with different leaf species may explain this asymmetrical production of mosquitoes: emergence rates and oviposition rates were positively correlated to bacterial abundance and diversity, respectively. We conclude that the displacement of native understory plant species by certain invasive shrubs

  11. Hybridization of an invasive shrub affects tolerance and resistance to defoliation by a biological control agent

    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 introgressi...

  12. Population-level consequences of herbivory, changing climate, and source-sink dynamics on a long-lived invasive shrub.

    van Klinken, R D; Pichancourt, J B

    2015-12-01

    Long-lived plant species are highly valued environmentally, economically, and socially, but can also cause substantial harm as invaders. Realistic demographic predictions can guide management decisions, and are particularly valuable for long-lived species where population response times can be long. Long-lived species are also challenging, given population dynamics can be affected by factors as diverse as herbivory, climate, and dispersal. We developed a matrix model to evaluate the effects of herbivory by a leaf-feeding biological control agent released in Australia against a long-lived invasive shrub (mesquite, Leguminoseae: Prosopis spp.). The stage-structured, density-dependent model used an annual time step and 10 climatically diverse years of field data. Mesquite population demography is sensitive to source-sink dynamics as most seeds are consumed and redistributed spatially by livestock. In addition, individual mesquite plants, because they are long lived, experience natural climate variation that cycles over decadal scales, as well as anthropogenic climate change. The model therefore explicitly considered the effects of both net dispersal and climate variation. Herbivory strongly regulated mesquite populations through reduced growth and fertility, but additional mortality of older plants will be required to reach management goals within a reasonable time frame. Growth and survival of seeds and seedlings were correlated with daily soil moisture. As a result, population dynamics were sensitive to rainfall scenario, but population response times were typically slow (20-800 years to reach equilibrium or extinction) due to adult longevity. Equilibrium population densities were expected to remain 5% higher, and be more dynamic, if historical multi-decadal climate patterns persist, the effect being dampened by herbivory suppressing seed production irrespective of preceding rainfall. Dense infestations were unlikely to form under a drier climate, and required net

  13. Elevated native terrestrial snail abundance and diversity in association with an invasive understory shrub, Berberis thunbergii, in a North American deciduous forest

    Utz, Ryan M.; Pearce, Timothy A.; Lewis, Danielle L.; Mannino, Joseph C.

    2018-01-01

    Invasive terrestrial plants often substantially reshape environments, yet how such invasions affect terrestrial snail assemblages remains understudied. We investigated how snail assemblages in deciduous forest soils with dense Berberis thunbergii (Japanese barberry), an invasive shrub in eastern North America, differ from forest areas lacking the shrub. Leaf litter and soil samples were collected from forest patches with dense B. thunbergii understories and adjacent control areas within two exurban forest tracts in western Pennsylvania, U.S.A. Snails were identified to species and quantified by standard diversity metrics. Contrary to our expectations, snails were significantly more abundant and diverse in B. thunbergii-invaded areas. Despite differences in abundance, the snail community composition did not differ between invaded and control habitats. The terrestrial snail assemblage we observed, which was composed entirely of native species, appears to respond favorably to B. thunbergii invasion and therefore may not be negatively impacted by physicochemical changes to soils typically observed in association with the plant. Such findings could reflect the fact that B. thunbergii likely creates more favorable habitat for snails by creating cooler, more humid, and more alkaline soil environments. However, the snail assemblages we retrieved may consist mostly of species with high tolerance to environmental degradation due to a legacy of land use change and acid deposition in the region.

  14. Pruning Shrubs

    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.

  15. Recruitment Dynamics of the Relict Palm, Jubaea chilensis: Intricate and Pervasive Effects of Invasive Herbivores and Nurse Shrubs in Central Chile.

    Fleury, Marina; Marcelo, Wara; Vásquez, Rodrigo A; González, Luis Alberto; Bustamante, Ramiro O

    2015-01-01

    Shrubs can have a net positive effect on the recruitment of other species, especially relict species in dry-stressful conditions. We tested the effects of nurse shrubs and herbivory defoliation on performance (survival and growth) of nursery-grown seedlings of the largest living palm, the relict wine palm Jubaea chilensis. During an 18-month period, a total of more than 300 seedlings were exposed to of four possible scenarios produced by independently weakening the effects of nurse shrubs and browsers. The experiment followed a two-way fully factorial design. We found consistent differences in survival between protected and unprotected seedlings (27.5% and 0.7%, respectively), and herbivory had a dramatic and overwhelmingly negative effect on seedling survival. The invasive rabbit (Oryctolagus cuniculus) is clearly creating a critical bottleneck in the regeneration process and might, therefore, partially explain the general lack of natural regeneration of wine palms under natural conditions. Apparently biotic filters mediated by ecological interactions are more relevant in the early stages of recruitment than abiotic, at least in invaded sites of central Chile. Our data reveal that plant-plant facilitation relationship may be modulated by plant-animal interactions, specifically by herbivory, a common and widespread ecological interaction in arid and semi-arid environments whose role has been frequently neglected. Treatments that protect young wine palm seedlings are mandatory to enable the seedlings to attain a height at which shoots are no longer vulnerable to browsing. Such protection is an essential first step toward the conservation and reintroduction of this emblematic and threatened species.

  16. Large-Scale Removal of Invasive Honeysuckle Decreases Mosquito and Avian Host Abundance.

    Gardner, Allison M; Muturi, Ephantus J; Overmier, Leah D; Allan, Brian F

    2017-12-01

    Invasive species rank second only to habitat destruction as a threat to native biodiversity. One consequence of biological invasions is altered risk of exposure to infectious diseases in human and animal populations. The distribution and prevalence of mosquito-borne diseases depend on the complex interactions between the vector, the pathogen, and the human or wildlife reservoir host. These interactions are highly susceptible to disturbance by invasive species, including terrestrial plants. We conducted a 2-year field experiment using a Before-After/Control-Impact design to examine how removal of invasive Amur honeysuckle (Lonicera maackii) in a forest fragment embedded within a residential neighborhood affects the abundance of mosquitoes, including two of the most important vectors of West Nile virus, Culex pipiens and Cx. restuans. We also assessed any potential changes in avian communities and local microclimate associated with Amur honeysuckle removal. We found that (1) removal of Amur honeysuckle reduces the abundance of both vector and non-vector mosquito species that commonly feed on human hosts, (2) the abundance and composition of avian hosts is altered by honeysuckle removal, and (3) areas invaded with honeysuckle support local microclimates that are favorable to mosquito survival. Collectively, our investigations demonstrate the role of a highly invasive understory shrub in determining the abundance and distribution of mosquitoes and suggest potential mechanisms underlying this pattern. Our results also give rise to additional questions regarding the general impact of invasive plants on vector-borne diseases and the spatial scale at which removal of invasive plants may be utilized to effect disease control.

  17. Field Spectroscopy in the VNIR-SWIR Region to Discriminate between Mediterranean Native Plants and Exotic-Invasive Shrubs Based on Leaf Tannin Content

    Jan Rudolf Karl Lehmann

    2015-01-01

    Full Text Available The invasive shrub, Acacia longifolia, native to southeastern Australia, has a negative impact on vegetation and ecosystem functioning in Portuguese dune ecosystems. In order to spectrally discriminate A. longifolia from other non-native and native species, we developed a classification model based on leaf reflectance spectra (350–2500 nm and condensed leaf tannin content. High variation of leaf tannin content is common for Mediterranean shrub and tree species, in particular between N-fixing and non-N-fixing species, as well as within the genus, Acacia. However, variation in leaf tannin content has not been studied in coastal dune ecosystems in southwest Portugal. We hypothesized that condensed tannin concentration varies significantly across species, further allowing for distinguishing invasive, nitrogen-fixing A. longifolia from other vegetation based on leaf spectral reflectance data. Spectral field measurements were carried out using an ASD FieldSpec FR spectroradiometer attached to an ASD leaf clip in order to collect 750 in situ leaf reflectance spectra of seven frequent plant species at three study sites in southwest Portugal. We applied partial least squares (PLS regression to predict the obtained leaf reflectance spectra of A. longifolia individuals to their corresponding tannin concentration. A. longifolia had the lowest tannin concentration of all investigated species. Four wavelength regions (675–710 nm, 1060–1170 nm, 1360–1450 nm and 1630–1740 nm were identified as being highly correlated with tannin concentration. A spectra-based classification model of the different plant species was calculated using a principal component analysis-linear discriminant analysis (PCA-LDA. The best prediction of A. longifolia was achieved by using wavelength regions between 1360–1450 nm and 1630–1740 nm, resulting in a user’s accuracy of 98.9%. In comparison, selecting the entire wavelength range, the best user accuracy only reached 86

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

    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)

  19. Temperate trees and shrubs as global invaders: the relationship between invasiveness and native distribution depends on biological traits

    Pyšek, Petr; Jarošík, Vojtěch; Pergl, Jan; Moravcová, Lenka; Chytrý, M.; Kühn, I.

    2014-01-01

    Roč. 16, č. 3 (2014), s. 577-589 ISSN 1387-3547 R&D Projects: GA ČR(CZ) GAP504/11/1028; GA ČR GA206/09/0563 Institutional support: RVO:67985939 Keywords : woody species * invasiveness * species traits Subject RIV: EF - Botanics Impact factor: 2.586, year: 2014

  20. Ericaceous dwarf shrubs affect ectomycorrhizal fungal community of the invasive Pinus strobus and native Pinus sylvestris in a pot experiment

    Kohout, Petr; Sýkorová, Zuzana; Bahram, M.; Hadincová, Věroslava; Albrechtová, Jana; Tedersoo, L.; Vohník, Martin

    2011-01-01

    Roč. 21, č. 5 (2011), s. 403-412 ISSN 0940-6360 Institutional research plan: CEZ:AV0Z60050516 Keywords : plant invasions * mycorrhizal symbioses * seedlings establishment Subject RIV: EF - Botanics Impact factor: 2.630, year: 2011

  1. Herbivory by an introduced Asian weevil negatively affects population growth of an invasive Brazilian shrub in Florida.

    Stricker, Kerry Bohl; Stiling, Peter

    2012-08-01

    The enemy release hypothesis (ERH) is often cited to explain why some plants successfully invade natural communities while others do not. This hypothesis maintains that plant populations are regulated by coevolved enemies in their native range but are relieved of this pressure where their enemies have not been co-introduced. Some studies have shown that invasive plants sustain lower levels of herbivore damage when compared to native species, but how damage affects fitness and population dynamics remains unclear. We used a system of co-occurring native and invasive Eugenia congeners in south Florida (USA) to experimentally test the ERH, addressing deficiencies in our understanding of the role of natural enemies in plant invasion at the population level. Insecticide was used to experimentally exclude insect herbivores from invasive Eugenia uniflora and its native co-occurring congeners in the field for two years. Herbivore damage, plant growth, survival, and population growth rates for the three species were then compared for control and insecticide-treated plants. Our results contradict the ERH, indicating that E. uniflora sustains more herbivore damage than its native congeners and that this damage negatively impacts stem height, survival, and population growth. In addition, most damage to E. uniflora, a native of Brazil, is carried out by Myllocerus undatus, a recently introduced weevil from Sri Lanka, and M. undatus attacks a significantly greater proportion of E. uniflora leaves than those of its native congeners. This interaction is particularly interesting because M. undatus and E. uniflora share no coevolutionary history, having arisen on two separate continents and come into contact on a third. Our study is the first to document negative population-level effects for an invasive plant as a result of the introduction of a novel herbivore. Such inhibitory interactions are likely to become more prevalent as suites of previously noninteracting species continue to

  2. A New Method for Post-introduction Risk Assessment of Biological Invasions Among Introduced Shrubs in Developing Countries.

    Seburanga, J L; Bizuru, E; Mwavu, E N; Kampungu, K G; Gatesire, T; Kaplin, B A

    2016-03-01

    Risk-assessment methods are useful in collecting data that can help decision making to prevent the introduction of new species that have the potential of invading as well as in management of established taxa. Not only the complexity and unaffordability of available pre-introduction risk-assessment models make them rarely or inconsistently applied in the least-developed countries, but also there is lack of tools to assess the status of already introduced plant species. In this study, an affordable and rapid method of assessment of invasiveness among introduced plant species was developed and tested in Rwanda. This method defines three invasion stages (potential, effective, and suppressive invaders) and four levels of risk assessment: post-introduction assessment of species inherent invasive potential (Level 1), post-establishment assessment of species capacity of regeneration (Level 2), post-naturalization assessment of species range of occurrence and ability for long-distance dispersal (Level 3), and post-naturalization assessment of species ability to outcompete other plants in the community and transform the landscape (Level 4). A review of invasive species in Rwanda was developed through desk review, examination of herbarium records, and vegetation surveys. This method should be applicable in other countries that lack the means for a more conventional scientific investigation or under any circumstance where a quick and inexpensive assessment is needed. The method could be useful to environmental managers for timely intervention with strategies specific to different stages of invasion (post-introduction, post-establishment, or post-naturalization) and allocate resources accordingly.

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

    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

  4. Chapter 22. Rosaceous shrubs

    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...

  5. Daphnetin inhibits invasion and migration of LM8 murine osteosarcoma cells by decreasing RhoA and Cdc42 expression

    Fukuda, Hiroki [Department of Clinical and Translational Physiology, Kyoto Pharmaceutical University, Kyoto (Japan); Nakamura, Seikou [Department of Pharmacognosy, Kyoto Pharmaceutical University, Kyoto (Japan); Chisaki, Yugo [Education and Research Center for Clinical Pharmacy, Kyoto Pharmaceutical University, Kyoto (Japan); Takada, Tetsuya [Department of Clinical and Translational Physiology, Kyoto Pharmaceutical University, Kyoto (Japan); Toda, Yuki [Department of Medicinal Chemistry, Kyoto Pharmaceutical University, Kyoto (Japan); Murata, Hiroaki [Department of Orthopedics, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto (Japan); Department of Orthopedic Surgery, Matsushita Memorial Hospital, Osaka (Japan); Itoh, Kazuyuki [Department of Biology, Osaka Medical Center of Cancer and Cardiovascular Diseases, Osaka (Japan); Yano, Yoshitaka [Education and Research Center for Clinical Pharmacy, Kyoto Pharmaceutical University, Kyoto (Japan); Takata, Kazuyuki [Department of Clinical and Translational Physiology, Kyoto Pharmaceutical University, Kyoto (Japan); Ashihara, Eishi, E-mail: ash@mb.kyoto-phu.ac.jp [Department of Clinical and Translational Physiology, Kyoto Pharmaceutical University, Kyoto (Japan)

    2016-02-26

    Daphnetin, 7,8-dihydroxycoumarin, present in main constituents of Daphne odora var. marginatai, has multiple pharmacological activities including anti-proliferative effects in cancer cells. In this study, using a Transwell system, we showed that daphnetin inhibited invasion and migration of highly metastatic murine osteosarcoma LM8 cells in a dose-dependent manner. Following treatment by daphnetin, cells that penetrated the Transwell membrane were rounder than non-treated cells. Immunofluorescence analysis revealed that daphnetin decreased the numbers of intracellular stress fibers and filopodia. Moreover, daphnetin treatment dramatically decreased the expression levels of RhoA and Cdc42. In summary, the dihydroxycoumarin derivative daphnetin inhibits the invasion and migration of LM8 cells, and therefore represents a promising agent for use against metastatic cancer. - Highlights: • Daphnetin, a coumarin-derivative, inhibited invasion and migration of LM8 cells. • Stress fibers and filopodia were decreased by daphnetin treatment. • Daphnetin decreased RhoA and Cdc42 protein expression.

  6. Daphnetin inhibits invasion and migration of LM8 murine osteosarcoma cells by decreasing RhoA and Cdc42 expression

    Fukuda, Hiroki; Nakamura, Seikou; Chisaki, Yugo; Takada, Tetsuya; Toda, Yuki; Murata, Hiroaki; Itoh, Kazuyuki; Yano, Yoshitaka; Takata, Kazuyuki; Ashihara, Eishi

    2016-01-01

    Daphnetin, 7,8-dihydroxycoumarin, present in main constituents of Daphne odora var. marginatai, has multiple pharmacological activities including anti-proliferative effects in cancer cells. In this study, using a Transwell system, we showed that daphnetin inhibited invasion and migration of highly metastatic murine osteosarcoma LM8 cells in a dose-dependent manner. Following treatment by daphnetin, cells that penetrated the Transwell membrane were rounder than non-treated cells. Immunofluorescence analysis revealed that daphnetin decreased the numbers of intracellular stress fibers and filopodia. Moreover, daphnetin treatment dramatically decreased the expression levels of RhoA and Cdc42. In summary, the dihydroxycoumarin derivative daphnetin inhibits the invasion and migration of LM8 cells, and therefore represents a promising agent for use against metastatic cancer. - Highlights: • Daphnetin, a coumarin-derivative, inhibited invasion and migration of LM8 cells. • Stress fibers and filopodia were decreased by daphnetin treatment. • Daphnetin decreased RhoA and Cdc42 protein expression.

  7. Relieving dyspnoea by non-invasive ventilation decreases pain thresholds in amyotrophic lateral sclerosis.

    Dangers, Laurence; Laviolette, Louis; Georges, Marjolaine; Gonzalez-Bermejo, Jésus; Rivals, Isabelle; Similowski, Thomas; Morelot-Panzini, Capucine

    2017-03-01

    Dyspnoea is a threatening sensation of respiratory discomfort that presents many similarities with pain. Experimental dyspnoea in healthy subjects induces analgesia. This 'dyspnoea-pain counter-irritation' could, in reverse, imply that relieving dyspnoea in patients with chronic respiratory diseases would lower their pain thresholds. We first determined pressure pain thresholds in 25 healthy volunteers (22-31 years; 13 men; handheld algometer), during unloaded breathing (BASELINE) and during inspiratory threshold loading (ITL). Two levels of loading were used, adjusted to induce dyspnoea self-rated at 60% or 80% of a 10 cm visual analogue scale (ITL6 and ITL8). 18 patients with chronic respiratory failure due to amyotrophic lateral sclerosis (ALS) were then studied during unassisted breathing and after 30 and 60 min of non-invasive ventilation-NIV30 and NIV60-(same dyspnoea evaluation). In healthy volunteers, pressure pain thresholds increased significantly in the deltoid during ITL6 (pNIV30 and NIV60 (pNIV in patients with ALS having respiratory failure is associated with decreased pressure pain thresholds. Clinical implications have yet to be determined, but this observation suggests that patients with ALS could become more susceptible to pain after the institution of NIV, hence the need for reinforced attention towards potentially painful diagnostic and therapeutic interventions. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

  8. RNAi knockdown of Hop (Hsp70/Hsp90 organising protein) decreases invasion via MMP-2 down regulation.

    Walsh, Naomi

    2011-07-28

    We previously identified Hop as over expressed in invasive pancreatic cancer cell lines and malignant tissues of pancreatic cancer patients, suggesting an important role for Hop in the biology of invasive pancreatic cancer. Hop is a co-chaperone protein that binds to both Hsp70\\/Hsp90. We hypothesised that by targeting Hop, signalling pathways modulating invasion and client protein stabilisation involving Hsp90-dependent complexes may be altered. In this study, we show that Hop knockdown by small interfering (si)RNA reduces the invasion of pancreatic cancer cells, resulting in decreased expression of the downstream target gene, matrix metalloproteinases-2 (MMP-2). Hop in conditioned media co-immunoprecipitates with MMP-2, implicating a possible extracellular function for Hop. Knockdown of Hop expression also reduced expression levels of Hsp90 client proteins, HER2, Bcr-Abl, c-MET and v-Src. Furthermore, Hop is strongly expressed in high grade PanINs compared to lower PanIN grades, displaying differential localisation in invasive ductal pancreatic cancer, indicating that the localisation of Hop is an important factor in pancreatic tumours. Our data suggests that the attenuation of Hop expression inactivates key signal transduction proteins which may decrease the invasiveness of pancreatic cancer cells possibly through the modulation of Hsp90 activity. Therefore, targeting Hop in pancreatic cancer may constitute a viable strategy for targeted cancer therapy.

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

    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

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

    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...

  11. Dna c-values of 20 invasive alien species and 3 native species in south china

    Gong Ni; Wang Yu-Tao; Björn Lars Olof; Li Shao-Shan

    2014-01-01

    Cultivated fields and forests in South China are experiencing serious damage due to invasive alien plants. We investigated the relation between DNA C-values and invasiveness. The DNA C-values of 23 species ranged from 0.39 pg to 3.37 pg. Herbs, perennials and native species had higher mean DNA C-values than shrubs, annuals and invasive alien species. DNA C-values decreased with increasing invasiveness. Paederia scandens, a harmful native species, has the lo...

  12. AGE-modified basement membrane cooperates with Endo180 to promote epithelial cell invasiveness and decrease prostate cancer survival

    Rodriguez-Teja, Mercedes; Gronau, Julian H; Breit, Claudia

    2015-01-01

    Biomechanical strain imposed by age-related thickening of the basal lamina and augmented tissue stiffness in the prostate gland coincides with increased cancer risk. Here we hypothesized that the structural alterations in the basal lamina associated with age can induce mechanotransduction pathways...... in prostate epithelial cells (PECs) to promote invasiveness and cancer progression. To demonstrate this, we developed a 3D model of PEC acini in which thickening and stiffening of basal lamina matrix was induced by advanced glycation end-product (AGE)-dependent non-enzymatic crosslinking of its major......(Δ) (Ex2-6/) (Δ) (Ex2-6) mice, with constitutively exposed CTLD2 and decreased survival of men with early (non-invasive) prostate cancer with high epithelial Endo180 expression and levels of AGE. These findings indicate that AGE-dependent modification of the basal lamina induces invasive behaviour...

  13. Overexpression of CD97 confers an invasive phenotype in glioblastoma cells and is associated with decreased survival of glioblastoma patients.

    Michael Safaee

    Full Text Available Mechanisms of invasion in glioblastoma (GBM relate to differential expression of proteins conferring increased motility and penetration of the extracellular matrix. CD97 is a member of the epidermal growth factor seven-span transmembrane family of adhesion G-protein coupled receptors. These proteins facilitate mobility of leukocytes into tissue. In this study we show that CD97 is expressed in glioma, has functional effects on invasion, and is associated with poor overall survival. Glioma cell lines and low passage primary cultures were analyzed. Functional significance was assessed by transient knockdown using siRNA targeting CD97 or a non-target control sequence. Invasion was assessed 48 hours after siRNA-mediated knockdown using a Matrigel-coated invasion chamber. Migration was quantified using a scratch assay over 12 hours. Proliferation was measured 24 and 48 hours after confirmed protein knockdown. GBM cell lines and primary cultures were found to express CD97. Knockdown of CD97 decreased invasion and migration in GBM cell lines, with no difference in proliferation. Gene-expression based Kaplan-Meier analysis was performed using The Cancer Genome Atlas, demonstrating an inverse relationship between CD97 expression and survival. GBMs expressing high levels of CD97 were associated with decreased survival compared to those with low CD97 (p = 0.007. CD97 promotes invasion and migration in GBM, but has no effect on tumor proliferation. This phenotype may explain the discrepancy in survival between high and low CD97-expressing tumors. This data provides impetus for further studies to determine its viability as a therapeutic target in the treatment of GBM.

  14. Measuring carbon in shrubs. Chapter 5

    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...

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

    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.

  16. Dna c-values of 20 invasive alien species and 3 native species in south china

    Gong Ni

    2014-01-01

    Full Text Available Cultivated fields and forests in South China are experiencing serious damage due to invasive alien plants. We investigated the relation between DNA C-values and invasiveness. The DNA C-values of 23 species ranged from 0.39 pg to 3.37 pg. Herbs, perennials and native species had higher mean DNA C-values than shrubs, annuals and invasive alien species. DNA C-values decreased with increasing invasiveness. Paederia scandens, a harmful native species, has the lowest DNA C-value among the perennials, indicating that native species with low nuclear content may also possess an invasive potential.

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

    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.

  18. Renin-Angiotensin Inhibitors Decrease Recurrence after Transurethral Resection of Bladder Tumor in Patients with Nonmuscle Invasive Bladder Cancer.

    Blute, Michael L; Rushmer, Timothy J; Shi, Fangfang; Fuller, Benjamin J; Abel, E Jason; Jarrard, David F; Downs, Tracy M

    2015-11-01

    Prior reports suggest that renin-angiotensin system inhibition may decrease nonmuscle invasive bladder cancer recurrence. We evaluated whether angiotensin converting enzyme inhibitor or angiotensin receptor blocker treatment at initial surgery was associated with decreased recurrence or progression in patients with nonmuscle invasive bladder cancer. Using an institutional bladder cancer database we identified 340 patients with data available on initial transurethral resection of bladder tumor. Progression was defined as an increase to stage T2. Cox proportional hazards models were used to evaluate associations with recurrence-free and progression-free survival. Median patient age was 69.6 years. During a median followup of 3 years (IQR 1.3-6.1) 200 patients (59%) had recurrence and 14 (4.1%) had stage progression. Of those patients 143 were receiving angiotensin converting enzyme inhibitor/angiotensin receptor blockers at the time of the first transurethral resection. On univariate analysis factors associated with improved recurrence-free survival included carcinoma in situ (p = 0.040), bacillus Calmette-Guérin therapy (p = 0.003) and angiotensin converting enzyme inhibitor/angiotensin receptor blocker therapy (p = 0.009). Multivariate analysis demonstrated that patients treated with bacillus Calmette-Guérin therapy (HR 0.68, 95% CI 0.47-0.87, p = 0.002) or angiotensin converting enzyme inhibitor/angiotensin receptor blocker therapy (HR 0.61, 95% CI 0.45-0.84, p = 0.005) were less likely to experience tumor recurrence. The 5-year recurrence-free survival rate was 45.6% for patients treated with angiotensin converting enzyme inhibitor/angiotensin receptor blockers and 28.1% in those not treated with angiotensin converting enzyme inhibitor/angiotensin receptor blockers (p = 0.009). Subgroup analysis was performed to evaluate nonmuscle invasive bladder cancer pathology (Ta, T1 and carcinoma in situ) in 85 patients on bacillus Calmette-Guérin therapy alone and in

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

    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.

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

    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.

  1. RNAi Knockdown of Hypoxia-Inducible Factor-1α Decreased the Proliferation, Migration, and Invasion of Hypoxic Hepatocellular Carcinoma Cells.

    Chen, ChengShi; Liu, Rong; Wang, JianHua; Yan, ZhiPing; Qian, Sheng; Zhang, Wei

    2015-04-01

    The obstruction of hepatic arterial blood flow results in tumor tissue hypoxia and elevated expression of hypoxia-inducible factor-1alpha (HIF-1α). Our study evaluated whether lentivirus-mediated short interference RNA against HIF-1α inhibits proliferation, invasion, and migration of hepatocellular carcinoma (HCC) cells under hypoxia. RNA interference knockdown of HIF-1α was achieved by HIF-1α-directed lentiviral shRNA, in a rat HCC cell line cultured under hypoxia condition for varying length of times. The expression levels of HIF-1α and vascular endothelial growth factor were examined using reverse transcription polymerase chain reaction and western blot analyses. Cell proliferation, migration, and invasion were measured by cell viability, transwell migration, and invasion assays, respectively. Inhibition of HIF-1α expression by shRNA suppressed vascular endothelial growth factor mRNA and protein levels under both normoxia and hypoxia. It also suppressed cell migration and invasion, which were enhanced under hypoxic conditions. RNAi knockdown of HIF-1α further suppressed hypoxia-mediated inhibition of the cell proliferation. These data suggest that shRNA of HIF-1α could antagonize the hypoxia-mediated increase in hepatic cancer cell migration and invasion, and synergize with hypoxia to inhibit the cell proliferation in HCC cells.

  2. Quercetin inhibits the invasion of murine melanoma B16-BL6 cells by decreasing pro-MMP-9 via the PKC pathway.

    Zhang, Xian-Ming; Huang, Shao-Peng; Xu, Qiang

    2004-01-01

    On the basis of the inhibitory effect of quercetin on the invasion of melanoma B16-BL6 cells previously reported by us, the mechanisms of quercetin-mediated inhibition of invasion were further investigated in the present study. The ability of B16-BL6 cells to invade and migrate was evaluated in terms of the numbers of cells penetrating a reconstituted basement membrane in the Transwell coculture system. The relative levels and activities of matrix metalloproteinase-9 (MMP-9) and MMP-2 were determined by gelatin zymography and quantified using LabWorks 4.0 software. The quercetin-mediated inhibition of invasion was partially blocked by phorbol-12,13-dibutyrate (PDB), a PKC (protein kinase C) activator, and by doxorubicin, a PKC inhibitor. Only the proforms of MMP-9 (92 kDa) and MMP-2 (72 kDa) were detected by gelatin zymography. Quercetin dose-dependently decreased the gelatinolytic activity of pro-MMP-9. Doxorubicin also markedly reversed the quercetin-induced decrease. Quercetin showed a dose-dependent antagonism of increases in gelatinolytic activity of pro-MMP-9 induced by PDB and free fatty acid (another PKC activator). Together with the report that quercetin directly reduces PKC activity, the results reported here suggest that quercetin may inhibit the invasion of B16-BL6 cells by decreasing pro-MMP-9 via the PKC pathway.

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

    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.

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

    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.

  5. Diamond, graphite, and graphene oxide nanoparticles decrease migration and invasiveness in glioblastoma cell lines by impairing extracellular adhesion

    Wierzbicki, Mateusz; Jaworski, Slawomir; Kutwin, Marta

    2017-01-01

    The highly invasive nature of glioblastoma is one of the most significant problems regarding the treatment of this tumor. Diamond nanoparticles (ND), graphite nanoparticles (NG), and graphene oxide nanoplatelets (nGO) have been explored for their biomedical applications, especially for drug...... that nanoparticles could be used in biomedical applications as a low toxicity active compound for glioblastoma treatment....

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

    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.

  7. Naringenin decreases invasiveness and metastasis by inhibiting TGF-β-induced epithelial to mesenchymal transition in pancreatic cancer cells.

    Changjie Lou

    Full Text Available Epithelial to mesenchymal transition (EMT promotes cellular motility, invasiveness and metastasis during embryonic development and tumorigenesis. Transforming growth factor-β (TGF-β signaling pathway is a key regulator of EMT. A lot of evidences suggest that this process is Smad3-dependent. Herein we showed that exposure of aspc-1 and panc-1 pancreatic cancer cells to TGF-β1 resulted in characteristic morphological alterations of EMT, and enhancement of cell motility and gemcitabine (Gem resistance along with an up-regulation of EMT markers genes such as vimentin, N-cadherin, MMP2 and MMP9. Naringenin (Nar down-regulated EMT markers expression in both mRNA and protein levels by inhibiting TGF-β1/Smad3 signal pathway in the pancreatic cancer cells. Consequently, Nar suppressed the cells migration and invasion and reversed their resistance to Gem.

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

    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...

  9. Shrub expansion in SW Greenland

    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...

  10. Root systems of chaparral shrubs.

    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.

  11. Genetic disruption of tubulin acetyltransferase, αTAT1, inhibits proliferation and invasion of colon cancer cells through decreases in Wnt1/β-catenin signaling

    Oh, Somi; You, Eunae; Ko, Panseon; Jeong, Jangho; Keum, Seula; Rhee, Sangmyung

    2017-01-01

    Microtubules are required for diverse cellular processes, and abnormal regulation of microtubule dynamics is closely associated with severe diseases including malignant tumors. In this study, we report that α-tubulin N-acetyltransferase (αTAT1), a regulator of α-tubulin acetylation, is required for colon cancer proliferation and invasion via regulation of Wnt1 and its downstream genes expression. Public transcriptome analysis showed that expression of ATAT1 is specifically upregulated in colon cancer tissue. A knockout (KO) of ATAT1 in the HCT116 colon cancer cell line, using the CRISPR/Cas9 system showed profound inhibition of proliferative and invasive activities of these cancer cells. Overexpression of αTAT1 or the acetyl-mimic K40Q α-tubulin mutant in αTAT1 KO cells restored the invasiveness, indicating that microtubule acetylation induced by αTAT1 is critical for HCT116 cell invasion. Analysis of colon cancer-related gene expression in αTAT1 KO cells revealed that the loss of αTAT1 decreased the expression of WNT1. Mechanistically, abrogation of tubulin acetylation by αTAT1 knockout inhibited localization of β-catenin to the plasma membrane and nucleus, thereby resulting in the downregulation of Wnt1 and of its downstream genes including CCND1, MMP-2, and MMP-9. These results suggest that αTAT1-mediated Wnt1 expression via microtubule acetylation is important for colon cancer progression. - Highlights: • Ablation of αTAT1 inhibits HCT116 colon cancer cell invasion. • αTAT1/acetylated microtubules regulate expression of Wnt1/β-catenin target genes. • Acetylated microtubules regulate cellular localization of β-catenin. • Loss of αTAT1 prevents Wnt1 from inducing β-catenin-dependent and -independent pathways.

  12. Prolactin receptor attenuation induces zinc pool redistribution through ZnT2 and decreases invasion in MDA-MB-453 breast cancer cells

    Bostanci, Zeynep; Alam, Samina; Soybel, David I.; Kelleher, Shannon L.

    2014-01-01

    Prolactin receptor (PRL-R) activation regulates cell differentiation, proliferation, cell survival and motility of breast cells. Prolactin (PRL) and PRL-R over-expression are strongly implicated in breast cancer, particularly contributing to tumor growth and invasion in the more aggressive estrogen-receptor negative (ER−) disease. PRL-R antagonists have been suggested as potential therapeutic agents; however, mechanisms through which PRL-R antagonists exert their actions are not well-understood. Zinc (Zn) is a regulatory factor for over 10% of the proteome, regulating critical cell processes such as proliferation, cell signaling, transcription, apoptosis and autophagy. PRL-R signaling regulates Zn metabolism in breast cells. Herein we determined effects of PRL-R attenuation on cellular Zn metabolism and cell function in a model of ER-, PRL-R over-expressing breast cancer cells (MDA-MB-453). PRL-R attenuation post-transcriptionally increased ZnT2 abundance and redistributed intracellular Zn pools into lysosomes and mitochondria. ZnT2-mediated lysosomal Zn sequestration was associated with reduced matrix metalloproteinase 2 (MMP-2) activity and decreased invasion. ZnT2-mediated Zn accumulation in mitochondria was associated with increased mitochondrial oxidation. Our results suggest that PRL-R antagonism in PRL-R over-expressing breast cancer cells may reduce invasion through the redistribution of intracellular Zn pools critical for cellular function. - Highlights: • PRL-R attenuation increased ZnT2 expression. • PRL-R attenuation increased lysosomal and mitochondrial Zn accumulation. • PRL-R attenuation decreased MMP-2 and invasion. • PRL-R antagonists may modulate lysosomal and mitochondrial Zn pools

  13. Prolactin receptor attenuation induces zinc pool redistribution through ZnT2 and decreases invasion in MDA-MB-453 breast cancer cells

    Bostanci, Zeynep, E-mail: zbostanci@hmc.psu.edu [The Pennsylvania State University, Department of Nutritional Sciences, 209 Chandlee Lab, University Park, PA 16802 (United States); The Pennsylvania State University Milton S. Hershey Medical Center, Department of Surgery, 500 University Dr., Hershey, PA 17033 (United States); Alam, Samina, E-mail: sra116@psu.edu [The Pennsylvania State University, Department of Nutritional Sciences, 209 Chandlee Lab, University Park, PA 16802 (United States); The Pennsylvania State University Milton S. Hershey Medical Center, Department of Surgery, 500 University Dr., Hershey, PA 17033 (United States); Soybel, David I., E-mail: dsoybel@hmc.psu.edu [The Pennsylvania State University, Department of Nutritional Sciences, 209 Chandlee Lab, University Park, PA 16802 (United States); The Pennsylvania State University Milton S. Hershey Medical Center, Department of Surgery, 500 University Dr., Hershey, PA 17033 (United States); The Pennsylvania State University College of Medicine, Department of Cell and Molecular Physiology, 500 University Dr., Hershey, PA 17033 (United States); Kelleher, Shannon L., E-mail: slk39@psu.edu [The Pennsylvania State University, Department of Nutritional Sciences, 209 Chandlee Lab, University Park, PA 16802 (United States); The Pennsylvania State University Milton S. Hershey Medical Center, Department of Surgery, 500 University Dr., Hershey, PA 17033 (United States); The Pennsylvania State University College of Medicine, Department of Cell and Molecular Physiology, 500 University Dr., Hershey, PA 17033 (United States)

    2014-02-15

    Prolactin receptor (PRL-R) activation regulates cell differentiation, proliferation, cell survival and motility of breast cells. Prolactin (PRL) and PRL-R over-expression are strongly implicated in breast cancer, particularly contributing to tumor growth and invasion in the more aggressive estrogen-receptor negative (ER−) disease. PRL-R antagonists have been suggested as potential therapeutic agents; however, mechanisms through which PRL-R antagonists exert their actions are not well-understood. Zinc (Zn) is a regulatory factor for over 10% of the proteome, regulating critical cell processes such as proliferation, cell signaling, transcription, apoptosis and autophagy. PRL-R signaling regulates Zn metabolism in breast cells. Herein we determined effects of PRL-R attenuation on cellular Zn metabolism and cell function in a model of ER-, PRL-R over-expressing breast cancer cells (MDA-MB-453). PRL-R attenuation post-transcriptionally increased ZnT2 abundance and redistributed intracellular Zn pools into lysosomes and mitochondria. ZnT2-mediated lysosomal Zn sequestration was associated with reduced matrix metalloproteinase 2 (MMP-2) activity and decreased invasion. ZnT2-mediated Zn accumulation in mitochondria was associated with increased mitochondrial oxidation. Our results suggest that PRL-R antagonism in PRL-R over-expressing breast cancer cells may reduce invasion through the redistribution of intracellular Zn pools critical for cellular function. - Highlights: • PRL-R attenuation increased ZnT2 expression. • PRL-R attenuation increased lysosomal and mitochondrial Zn accumulation. • PRL-R attenuation decreased MMP-2 and invasion. • PRL-R antagonists may modulate lysosomal and mitochondrial Zn pools.

  14. Chapter 23. Shrubs of other families

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

    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

  16. Interference with PSMB4 Expression Exerts an Anti-Tumor Effect by Decreasing the Invasion and Proliferation of Human Glioblastoma Cells

    Yu-Chen Cheng

    2018-01-01

    Full Text Available Background/Aims: Glioblastoma (GBM is a malignant brain tumor with a poor prognosis. Proteasome subunit beta type-4 (PSMB4 is an essential subunit that contributes to the assembly of the 20S proteasome complex. However, the role of PSMB4 in glioblastomas remains to be clarified. The aim of this study was to investigate the role of PSMB4 in GBM tumor progression. Methods: We first analyzed the PSMB4 protein and mRNA expression in 80 clinical brain specimens and 77 datasets from the National Center for Biotechnology Information (NCBI Gene Expression Omnibus (GEO database. Next, we inhibited the PSMB4 expression by siRNA in cellular and animal models to explore PSMB4’s underlying mechanisms. The cell survival after siPSMB4 transfection was assayed by MTT assay. Annexin V and propidium iodide staining was used to monitor the apoptosis by flow cytometric analysis. Moreover, the migration and invasion were evaluated by wound healing and Transwell assays. The expression of migration-related and invasion-related proteins after PSMB4 inhibition was detected by Western blotting. In addition, an orthotropic xenograft mouse model was used to assay the effect of PSMB4 knockdown in the in vivo study. Results: Basis on the results of bioinformatics study, glioma patients with higher PSMB4 expression had a shorter survival time than those with lower PSMB4 expression. The staining of clinical brain tissues showed elevated PSMB4 expression in GBM tissues compared with normal brain tissues. The PSMB4 inhibition decreased proliferation, migration and invasion abilities in human GBM cells. Downregulated PSMB4 resulted in cell cycle arrest and apoptosis in vitro. In an orthotropic xenograft mouse model, the glioma tumors progression was reduced when PSMB4 was down-regulated. The decreased PSMB4 enhanced the anti-tumor effect of temozolomide (TMZ on tumor growth. In addition, the absence of PSMB4 decreased the expression of phosphorylated focal adhesion kinase and

  17. Quercetin inhibits the invasion and mobility of murine melanoma B16-BL6 cells through inducing apoptosis via decreasing Bcl-2 expression.

    Zhang, X; Xu, Q; Saiki, I

    2000-01-01

    Quercetin has been known to have anti-tumor and anti-oxidation activities. In the present study, we have investigated its in vitro anti-metastatic activity. Quercetin inhibited the invasion and mobility of murine melanoma B16-BL6 cells in a dose-dependent manner but did not affect their adhesion to either laminin, fibronectin, or type VI collagen. Moreover, quercetin significantly inhibited the proliferation of B16-BL6 cells only in the case of time incubation longer than 48 h. Quercetin dose-dependently decreased the cell rates in S and G2-M phases of cell cycle. The effect of quercetin to cause a remarkable apoptosis of B16-BL6 cells was also demonstrated by flow cytometric assay as well as DNA fragmentation with a typical 180-bp ladder band in agarose electrophoresis and a quantitative analysis. Furthermore, quercetin markedly inhibited the expression of anti-apoptotic protein Bcl-2 but hardly influenced Bcl-XL. These results suggest that the inhibition of quercetin on invasiveness and migration of B16-BL6 cells are closely associated with the arrest of cell cycle as well as the induction of apoptosis by decreasing the Bcl-2 expression.

  18. Chemicals from trees and shrubs

    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.

  19. Leptin and insulin up-regulate miR-4443 to suppress NCOA1 and TRAF4, and decrease the invasiveness of human colon cancer cells

    Meerson, Ari; Yehuda, Hila

    2016-01-01

    Obesity is a risk factor for colorectal cancer (CRC). Normal and tumor cells respond to metabolic hormones, such as leptin and insulin. Thus, obesity-associated resistance to these hormones likely leads to changes in gene expression and behavior of tumor cells. However, the mechanisms affected by leptin and insulin signaling in CRC cells remain mostly unknown. We hypothesized that microRNAs (miRNAs) are involved in the regulation of tumorigenesis-related gene expression in CRC cells by leptin and insulin. To test this hypothesis, miRNA levels in the CRC-derived cell lines HCT-116, HT-29 and DLD-1 were profiled, following leptin and insulin treatment. Candidate miRNAs were validated by RT-qPCR. Predicted miRNA targets with known roles in cancer, were validated by immunoblots and reporter assays in HCT-116 cells. Transfection of HCT-116 cells with candidate miRNA mimic was used to test in vitro effects on proliferation and invasion. Of ~800 miRNAs profiled, miR-4443 was consistently up-regulated by leptin and insulin in HCT-116 and HT-29, but not in DLD-1, which lacked normal leptin receptor expression. Dose response experiments showed that leptin at 100 ng/ml consistently up-regulated miR-4443 in HCT-116 cells, concomitantly with a significant decrease in cell invasion ability. Transfection with miR-4443 mimic decreased invasion and proliferation of HCT-116 cells. Moreover, leptin and miR-4443 transfection significantly down-regulated endogenous NCOA1 and TRAF4, both predicted targets of miR-4443 with known roles in cancer metastasis. miR-4443 was found to directly regulate TRAF4 and NCOA1, as validated by a reporter assay. The up-regulation of miR-4443 by leptin or insulin was attenuated by the inhibition of MEK1/2. Our findings suggest that miR-4443 acts in a tumor-suppressive manner by down-regulating TRAF4 and NCOA1 downstream of MEK-C/EBP-mediated leptin and insulin signaling, and that insulin and/or leptin resistance (e.g. in obesity) may suppress this pathway

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

    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.

  1. Decreased expression of miR‑490‑3p in colorectal cancer predicts poor prognosis and promotes cell proliferation and invasion by targeting RAB14.

    Wang, Bo; Yin, Mujun; Cheng, Cheng; Jiang, Hongpeng; Jiang, Kewei; Shen, Zhanlong; Ye, Yingjiang; Wang, Shan

    2018-06-19

    Growing evidence indicates a potential role for miR‑490‑3p in tumorigenesis. However, its function in colorectal carcinoma (CRC) remains undefined. In this study, miR‑490‑3p was markedly downregulated in fifty colorectal cancer tissue samples compared with the corresponding adjacent non‑cancerous specimens, by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The expression levels of miR‑490‑3p were closely associated with tumor differentiation and distant metastasis. In addition, both Kaplan-Meier and multivariate analyses indicated CRC patients with elevated miR‑490‑3p amounts had prolonged overall survival. Overexpression of miR‑490‑3p markedly reduced proliferation, colony formation and invasion in CRC cells by enhancing apoptosis and promoting G2/M phase arrest. Furthermore, ectopic expression of miR‑490‑3p resulted in decreased expression of RAB14, which was directly targeted by miR‑490‑3p, as shown by the dual-luciferase reporter gene assay. Finally, in a nude mouse model, miR‑490‑3p overexpression significantly suppressed the growth of CRC cells. The above results indicated that miR‑490‑3p might constitute a prognostic indicator and a novel molecular target for miRNA-based CRC therapy.

  2. Suppression of adhesion-induced protein tyrosine phosphorylation decreases invasive and metastatic potentials of B16-BL6 melanoma cells by protein tyrosine kinase inhibitor genistein.

    Yan, C; Han, R

    1997-01-01

    Protein tyrosine kinase (PTK) appears to be involved in the activation of signaling during cell attachment to and spreading on extracellular matrix (ECM) in the metastatic cascade. To verify the assumption that PTK inhibitors might impair ECM signaling and prevent cancer metastasis, the highly metastatic B16-BL6 mouse melanoma cells were exposed to the PTK inhibitor genistein for 3 days. The ability of the cells to invade through reconstituted basement membrane (Matrigel) and to establish experimental pulmonary metastatic foci in C57BL/6 mice decreased after genistein exposure. The genistein-treated cells were also prevented from attaching to Matrigel and spread extremely poorly on the ECM substratum. Immunoblot analysis showed that tyrosine phosphorylation of a 125-kD protein in response to cell spreading on Matrigel was suppressed in the genistein-treated cells. Adhesion-induced protein tyrosine phosphorylation represents the earlier and specific event in the activation of ECM signaling, so this result implied ECM signaling was impaired in the treated cells. With immunofluorescence microscopy, the adhesion-induced tyrosine phosphorylated proteins were located at the pericytoplasms of well-spread cells, but not at the periphery of poorly spread genistein-treated cells. Therefore, this paper suggests that genistein might impair ECM signaling and subsequently prevent cancer cells from spreading well and invading or establishing metastasis through the suppression of adhesion-induced protein tyrosine phosphorylation. PTKs and adhesion-induced protein tyrosine phosphorylation might play a role in the control of invasion and metastasis.

  3. Uprooting and burial of invasive alien plants

    Kollmann, Johannes Christian; Brink-Jensen, Kasper; Frandsen, Sally I.

    2011-01-01

    (Japanese Rose), an invasive shrub in north-western Europe with negative effects on coastal biodiversity. Two months after uprooting and burial in dunes of north-eastern Denmark, 89% of the 58 shrubs resprouted from roots and rhizomes; on average 41 resprouts per shrub. Resprout density was twice as high...... at former shrub margins compared with the center; resprouts were taller and originated from more superficial soil layers at the margin than in the center. Resprouting was negatively correlated with fragment depth, and no resprouts were observed from greater than 15 cm depth. The number of resprouts...... increased with fragment dry mass (0.5–168.5 g). After 18 months with harrowing the species was still resprouting, flowering, and fruiting, albeit with no difference between shrub margin and center. Resprouts were taller (26 cm) and coverage was higher (0–4%) after two compared with three times harrowing...

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

    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.

  5. Stem secondary growth of tundra shrubs

    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...

  6. Short-Term Response of Native Flora to the Removal of Non-Native Shrubs in Mixed-Hardwood Forests of Indiana, USA

    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.

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

    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.

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

    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.

  9. Fire and grazing influence site resistance to Bromus tectorum through their effects on shrub, bunchgrass and biocrust communities in the Great Basin (USA)

    Condon, Lea A.; Pyke, David A.

    2018-01-01

    Shrubs, bunchgrasses and biological soil crusts (biocrusts) are believed to contribute to site resistance to plant invasions in the presence of cattle grazing. Although fire is a concomitant disturbance with grazing, little is known regarding their combined impacts on invasion resistance. We are the first to date to test the idea that biotic communities mediate the effects of disturbance on site resistance. We assessed cover of Bromus tectorum, shrubs, native bunchgrasses, lichens and mosses in 99 burned and unburned plots located on similar soils where fires occurred between 12 and 23 years before sampling. Structural equation modeling was used to test hypothesized relationships between environmental and disturbance characteristics, the biotic community and resistance to B. tectorum cover. Characteristics of fire and grazing did not directly relate to cover of B. tectorum. Relationships were mediated through shrub, bunchgrass and biocrust communities. Increased site resistance following fire was associated with higher bunchgrass cover and recovery of bunchgrasses and mosses with time since fire. Evidence of grazing was more pronounced on burned sites and was positively correlated with the cover of B. tectorum, indicating an interaction between fire and grazing that decreases site resistance. Lichen cover showed a weak, negative relationship with cover of B. tectorum. Fire reduced near-term site resistance to B. tectorum on actively grazed rangelands. Independent of fire, grazing impacts resulted in reduced site resistance to B. tectorum, suggesting that grazing management that enhances plant and biocrust communities will also enhance site resistance.

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

    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

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

    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

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

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

    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.

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

    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

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

    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.

  16. Altered Plant Litter and Microbial Composition Lead to Topsoil Organic Carbon Loss Over a Shrub-encroachment Gradient in an Inner Mongolia Grassland

    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

  17. Arctic plant ecophysiology and water source utilization in response to altered snow: isotopic (δ18O and δ2H) evidence for meltwater subsidies to deciduous shrubs.

    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.

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

    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

  19. GSD Update: What are invasive species? ... And do we really need to worry about them?

    Catherine Dold

    2011-01-01

    Invasive species are the focus of the September 2011 issue of GSDUpdate: What Are Invasive Species? And Do We Really Need to Worry About Them? An invasive species is any species - non-native or native to a region - that could cause economic or ecological harm to an area. Invasives can be weeds, shrubs and trees, insects, mollusks, vertebrates and even microorganisms...

  20. Regime shift by an exotic nitrogen-fixing shrub mediates plant facilitation in primary succession.

    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

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

    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.

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

    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.

  3. Luteolin decreases invasiveness, deactivates STAT3 signaling, and reverses interleukin-6 induced epithelial–mesenchymal transition and matrix metalloproteinase secretion of pancreatic cancer cells

    Huang XC

    2015-10-01

    Full Text Available Xince Huang,1 Shengjie Dai,1 Juji Dai,1 Yuwu Xiao,1 Yongyu Bai,1 Bicheng Chen,1,2 Mengtao Zhou1 1Department of Surgery, The First Affiliated Hospital, Wenzhou Medical University, Wenzhou, Zhejiang Province, People’s Republic of China; 2Zhejiang Provincial Top Key Discipline in Surgery, Wenzhou Key Laboratory of Surgery, Wenzhou, Zhejiang Province, People’s Republic of China Abstract: Luteolin, a flavone, has been shown to exhibit anticancer properties. Here, we investigated whether luteolin affects epithelial–mesenchymal transition (EMT and invasiveness of pancreatic cancer cell lines and their underlying mechanism. Pancreatic cancer cell lines PANC-1 and SW1990 were used in our study, and their EMT characters, matrix metalloproteinase (MMP expression level, invasiveness, and signal transducer and activator of transcription 3 (STAT3 activity were determined after luteolin treatment. We also treated pancreatic cancer cells with interleukin-6 (IL-6 to see whether IL-6-induced activation of STAT3, EMT, and MMP secretion was affected by luteolin. We found that luteolin inhibits EMT and MMP2, MMP7, and MMP9 expression in a dose-dependent manner, similar to STAT3 signaling. Through Transwell assay, we found that invasiveness of pancreatic cancer cells was inhibited by luteolin. EMT characters and MMP secretion increase with STAT3 activity after IL-6 treatment and these effects, caused by IL-6, were inhibited by luteolin. We concluded that luteolin inhibits invasiveness of pancreatic cancer cells, and we speculated that luteolin inhibits EMT and MMP secretion likely through deactivation of STAT3 signaling. Luteolin has potential antitumor effects and merits further investigation. Keywords: epithelial–mesenchymal transition, matrix metalloproteinase, luteolin, STAT3

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

    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)

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

    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

  6. Shrubs and vines for northeastern wildlife

    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.

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

    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.

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

    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 ...

  9. Shrub water use dynamics in arctic Alaska

    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.

  10. Effectiveness of environmental control measures to decrease the risk of invasive aspergillosis in acute leukaemia patients during hospital building work.

    Combariza, J F; Toro, L F; Orozco, J J

    2017-08-01

    Invasive aspergillosis (IA) is a significant problem in acute leukaemia patients. Construction work near hospital wards caring for immunocompromised patients is one of the main risk factors for developing invasive pulmonary aspergillosis (IPA). To assess the impact of environmental control measures used during hospital construction for the prevention of IA in acute leukaemia patients. A retrospective cohort study was developed to evaluate the IA incidence in acute leukaemia patients with different environmental control measures employed during hospital construction. We used European Organisation for the Research and Treatment of Cancer (EORTC) criterial diagnosis parameters for definition of IA. A total of 175 episodes of inpatient care were evaluated, 62 of which did not have any environmental control measures (when an outbreak occurred), and 113 that were subject to environmental control measures directed to preventing IA. The study showed an IA incidence of 25.8% for the group without environmental control measures vs 12.4% for those who did receive environmental control measures (P=0.024). The relative risk for IA was 0.595 (95% confidence interval: 0.394-0.897) for the group with environmental control measures. The current study suggests that the implementation of environmental control measures during a hospital construction has a positive impact for prevention of IA in patients hospitalized with acute leukaemia. Copyright © 2017 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.

  11. Inhibitory effect of berberine on the invasion of human lung cancer cells via decreased productions of urokinase-plasminogen activator and matrix metalloproteinase-2

    Peng, P.-L.; Hsieh, Y.-S.; Wang, C.-J.; Hsu, J.-L.; Chou, F.-P.

    2006-01-01

    Berberine, a compound isolated from medicinal herbs, has been reported with many pharmacological effects related to anti-cancer and anti-inflammation capabilities. In this study, we observed that berberine exerted a dose- and time-dependent inhibitory effect on the motility and invasion ability of a highly metastatic A549 cells under non-cytotoxic concentrations. In cancer cell migration and invasion process, matrix-degrading proteinases are required. A549 cell treated with berberine at various concentrations showed reduced ECM proteinases including matrix metalloproteinase-2 (MMP2) and urokinase-plasminogen activator (u-PA) by gelatin and casein zymography analysis. The inhibitory effect is likely to be at the transcriptional level, since the reduction in the transcripts levels was corresponding to the proteins. Moreover, berberine also exerted its action via regulating tissue inhibitor of metalloproteinase-2 (TIMP-2) and urokinase-plasminogen activator inhibitor (PAI). The upstream mediators of the effect involved c-jun, c-fos and NF-κB, as evidenced by reduced phosphorylation of the proteins. These findings suggest that berberine possesses an anti-metastatic effect in non-small lung cancer cell and may, therefore, be helpful in clinical treatment

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

    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.

  13. Stable alterations of CD44 isoform expression in prostate cancer cells decrease invasion and growth and alter ligand binding and chemosensitivity

    Yang, Kui; Tang, Yaqiong; Habermehl, Gabriel K; Iczkowski, Kenneth A

    2010-01-01

    Dysregulated CD44 expression characterizes most human cancers, including prostate cancer (PCa). PCa loses expression of CD44 standard (CD44s) that is present in benign epithelium, and overexpresses the novel splice variant isoform, CD44v7-10. Using retroviral gene delivery to PC-3M PCa cells, we expressed luciferase-only, enforced CD44s re-expression as a fusion protein with luciferase at its C-terminus or as a protein separate from luciferase, or knocked down CD44v7-10 by RNAi. Invasion, migration, proliferation, soft agar colony formation, adhesion, Docetaxel sensitivity, and xenograft growth assays were carried out. Expression responses of merlin, a CD44 binding partner, and growth-permissive phospho-merlin, were assessed by western blot. Compared to luciferase-only PC-3M cells, all three treatments reduced invasion and migration. Growth and soft agar colony formation were reduced only by re-expression of CD44s as a separate or fusion protein but not CD44v7-10 RNAi. Hyaluronan and osteopontin binding were greatly strengthened by CD44s expression as a separate protein, but not a fusion protein. CD44v7-10 RNAi in PC-3M cells caused marked sensitization to Docetaxel; the two CD44s re-expression approaches caused minimal sensitization. In limited numbers of mouse subcutaneous xenografts, all three alterations produced only nonsignificant trends toward slower growth compared with luciferase-only controls. The expression of CD44s as a separate protein, but not a fusion protein, caused emergence of a strongly-expressed, hypophosphorylated species of phospho-merlin. Stable re-expression of CD44s reduces PCa growth and invasion in vitro, and possibly in vivo, suggesting CD44 alterations have potential as gene therapy. When the C-terminus of CD44s is fused to another protein, most phenotypic effects are lessened, particularly hyaluronan adhesion. Finally, CD44v7-10, although it was not functionally significant for growth, may be a target for chemosensitization

  14. Quercetin inhibits epithelial–mesenchymal transition, decreases invasiveness and metastasis, and reverses IL-6 induced epithelial–mesenchymal transition, expression of MMP by inhibiting STAT3 signaling in pancreatic cancer cells

    Yu D

    2017-09-01

    Full Text Available Dinglai Yu,1 Tingting Ye,1 Yukai Xiang,1 Zhehao Shi,1 Jie Zhang,1 Bin Lou,1 Fan Zhang,1 Bicheng Chen,1,2 Mengtao Zhou1 1Department of Surgery, The First Affiliated Hospital, Wenzhou Medical University, Wenzhou, Zhejiang Province, People’s Republic of China; 2Zhejiang Provincial Top Key Discipline in Surgery, Wenzhou Key Laboratory of Surgery, Wenzhou, Zhejiang Province, People’s Republic of China Abstract: Quercetin, a flavone, is multifaceted, having anti-oxidative, anti-inflammatory, and anticancer properties. In the present study, we explored the effects of quercetin on the epithelial–mesenchymal transition (EMT and invasion of pancreatic cancer cells and the underlying mechanisms. We noted that quercetin exerted pronounced inhibitory effects in PANC-1 and PATU-8988 cells. Moreover, quercetin inhibited EMT and decreased the secretion of matrix metalloproteinase (MMP. Meanwhile, we determined the activity of STAT3 after quercetin treatment. STAT3 phosphorylation decreased following treatment with quercetin. We also used activating agent of STAT3, IL-6, to induce an increase in cell malignancy and to observe the effects of treatment with quercetin. As expected, the EMT and MMP secretion increased with activation of the STAT3 signaling pathway, and quercetin reversed IL-6-induced EMT, invasion, and migration. Therefore, our results demonstrate that quercetin triggers inhibition of EMT, invasion, and metastasis by blocking the STAT3 signaling pathway, and thus, quercetin merits further investigation. Keywords: quercetin, EMT, MMPs, STAT3, pancreatic cancer

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

    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. Local biotic adaptation of trees and shrubs to plant neighbors

    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

  17. Estimating shrub biomass from basal stem diameters

    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. Estimating shrub biomass from basal stem diameters

    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.

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

    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

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

    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

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

    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.

  2. Home telemonitoring of non-invasive ventilation decreases healthcare utilisation in a prospective controlled trial of patients with amyotrophic lateral sclerosis.

    Pinto, Anabela; Almeida, José Pedro; Pinto, Susana; Pereira, João; Oliveira, António Gouveia; de Carvalho, Mamede

    2010-11-01

    Non-invasive ventilation (NIV) is an efficient method for treating respiratory failure in patients with amyotrophic lateral sclerosis (ALS). However, it requires a process of adaptation not always achieved due to poor compliance. The role of telemonitoring of NIV is not yet established. To test the advantage of using modem communication in NIV of ALS patients. Prospective, single blinded controlled trial. Population and methods According to their residence, 40 consecutive ventilated ALS patients were assigned to one of two groups: a control group (G1, n=20) in which compliance and ventilator parameter settings were assessed during office visits; or an intervention group (G2, n=20) in which patients received a modem device connected to the ventilator. The number of office and emergency room visits and hospital admissions during the entire span of NIV use and the number of parameter setting changes to achieve full compliance were the primary outcome measurements. Demographic and clinical features were similar between the two groups at admission. No difference in compliance was found between the groups. The incidence of changes in parameter settings throughout the survival period with NIV was lower in G2 (p<0.0001) but it was increased during the initial period needed to achieve full compliance. The number of office or emergency room visits and inhospital admissions was significantly lower in G2 (p<0.0001). Survival showed a trend favouring G2 (p=0.13). This study shows that telemonitoring reduces health care utilisation with probable favourable implications on costs, survival and functional status.

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

    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.

  4. Climate sensitivity of shrub growth across the tundra biome

    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...

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

    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

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

    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)

  7. The distribution of a non-native (Rosa multiflora) and native (Kalmia latifolia) shrub in mature closed-canopy forests across soil fertility gradients

    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...

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

    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.

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

    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.

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

    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.

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

    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

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

    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.

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

    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 ...

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

    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

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

    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

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

    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.

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

    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...

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

    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

  19. Comparing ecohydrological processes in alien vs. native ranges: perspectives from the endangered shrub Myricaria germanica

    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.

  20. Effect of Tree-to-Shrub Type Conversion in Lower Montane Forests of the Sierra Nevada (USA) on Streamflow.

    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.

  1. Impact of multiple soil nutrients on distribution patterns of shrubs in an arid valley, in southwest china

    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)

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

    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.

  3. Spatial analysis of root hemiparasitic shrubs and their hosts

    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...

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

    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

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

    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...

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

    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...

  7. Methods for measuring arctic and alpine shrub growth

    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...

  8. Shrub expansion in SW Greenland under modest regional warming

    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...

  9. Distribution of the invasive alien weed, Lantana camara , and its ...

    Lantana camara (lantana) is a major invasive shrub globally, impacting upon biodiversity, economies, ecosystem services, and driving socio-ecological change. The aim of this study was to determine the current and potential distribution of lantana in eastern Africa and its livelihood impacts in one region in Uganda.

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

    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)

  11. Potential of native shrubs Haloxylon salicornicum and Calligonum Polygonoides for restoration of degraded lands in Arid Western Rajasthan, India.

    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.

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

    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

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

    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

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

    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.

  15. U.S. Geological Survey shrub/grass products provide new approach to shrubland monitoring

    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. Invasive Candidiasis

    ... Waterborne, and Environmental Diseases Mycotic Diseases Branch Invasive Candidiasis Recommend on Facebook Tweet Share Compartir Global Emergence ... antifungal drugs. Learn more about C. auris Invasive candidiasis is an infection caused by a yeast (a ...

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

    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

  18. Natural forest expansion on reclaimed coal mines in Northern Spain: the role of native shrubs as suitable microsites.

    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.

  19. Seed bank survival of an invasive species, but not of two native species, declines with invasion.

    Orrock, John L; Christopher, Cory C; Dutra, Humberto P

    2012-04-01

    Soil-borne seed pathogens may play an important role in either hindering or facilitating the spread of invasive exotic plants. We examined whether the invasive shrub Lonicera maackii (Caprifoliaceae) affected fungi-mediated mortality of conspecific and native shrub seeds in a deciduous forest in eastern Missouri. Using a combination of L. maackii removal and fungicide treatments, we found no effect of L. maackii invasion on seed viability of the native Symphoricarpos orbiculatus (Caprifoliaceae) or Cornus drummondii (Cornaceae). In contrast, fungi were significant agents of L. maackii seed mortality in invaded habitats. Losses of L. maackii to soil fungi were also significant in invaded habitats where L. maackii had been removed, although the magnitude of the effect of fungi was lower, suggesting that changes in soil chemistry or microhabitat caused by L. maackii were responsible for affecting fungal seed pathogens. Our work suggests that apparent competition via soil pathogens is not an important factor contributing to impacts of L. maackii on native shrubs. Rather, we found that fungal seed pathogens have density-dependent effects on L. maackii seed survival. Therefore, while fungal pathogens may provide little biotic resistance to early invasion by L. maackii, our study illustrates that more work is needed to understand how changes in fungal pathogens during the course of an invasion contribute to the potential for restoration of invaded systems. More generally, our study suggests that increased rates of fungal pathogen attack may be realized by invasive plants, such as L. maackii, that change the chemical or physical environment of the habitats they invade.

  20. Effects of Mediterranean shrub species on rainfall interception

    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.

  1. Can shrubs help to reconstruct historical glacier retreats?

    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)

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

    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

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

    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

  4. Appetite - decreased

    Loss of appetite; Decreased appetite; Anorexia ... Any illness can reduce appetite. If the illness is treatable, the appetite should return when the condition is cured. Loss of appetite can cause weight ...

  5. Effect of Tree-to-Shrub Type Conversion in Lower Montane Forests of the Sierra Nevada (USA on Streamflow.

    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.

  6. Effect of Tree-to-Shrub Type Conversion in Lower Montane Forests of the Sierra Nevada (USA) on Streamflow

    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

  7. Phenotypic Plasticity in Reproductive Traits of the Perennial Shrub Ulex europaeus in Response to Shading: A Multi-Year Monitoring of Cultivated Clones.

    Anne Atlan

    Full Text Available Phenotypic plasticity may be advantageous for plants to be able to rapidly cope with new and changing environments associated with climate change or during biological invasions. This is especially true for perennial plants, as they may need a longer period to respond genetically to selective pressures than annuals, and also because they are more likely to experience environmental changes during their lifespan. However, few studies have explored the plasticity of the reproductive life history traits of woody perennial species. This study focuses on a woody shrub, Ulex europaeus (common gorse, and on the response of its reproductive traits to one important environmental factor, shading. The study was performed on clones originating from western France (within the native range of this invasive species and grown for seven years. We compared traits of plants grown in a shade treatment (with two successive shade levels vs. full natural light. The traits monitored included flowering onset, pod production and seed predation. All traits studied responded to shading, exhibiting various levels of plasticity. In particular, dense shade induced a radical but reversible decrease in flower and pod production, while moderate shade had little effect on reproductive traits. The magnitude of the response to dense shade depended on the genotype, showing a genetically based polymorphism of plasticity. The level of plasticity also showed substantial variations between years, and the effect of environmental variations was cumulative over time. This suggests that plasticity can influence the lifetime fitness of U. Europaeus and is involved in the capacity of the species to grow under contrasting environmental conditions.

  8. Phenotypic Plasticity in Reproductive Traits of the Perennial Shrub Ulex europaeus in Response to Shading: A Multi-Year Monitoring of Cultivated Clones.

    Atlan, Anne; Hornoy, Benjamin; Delerue, Florian; Gonzalez, Maya; Pierre, Jean-Sébastien; Tarayre, Michèle

    2015-01-01

    Phenotypic plasticity may be advantageous for plants to be able to rapidly cope with new and changing environments associated with climate change or during biological invasions. This is especially true for perennial plants, as they may need a longer period to respond genetically to selective pressures than annuals, and also because they are more likely to experience environmental changes during their lifespan. However, few studies have explored the plasticity of the reproductive life history traits of woody perennial species. This study focuses on a woody shrub, Ulex europaeus (common gorse), and on the response of its reproductive traits to one important environmental factor, shading. The study was performed on clones originating from western France (within the native range of this invasive species) and grown for seven years. We compared traits of plants grown in a shade treatment (with two successive shade levels) vs. full natural light. The traits monitored included flowering onset, pod production and seed predation. All traits studied responded to shading, exhibiting various levels of plasticity. In particular, dense shade induced a radical but reversible decrease in flower and pod production, while moderate shade had little effect on reproductive traits. The magnitude of the response to dense shade depended on the genotype, showing a genetically based polymorphism of plasticity. The level of plasticity also showed substantial variations between years, and the effect of environmental variations was cumulative over time. This suggests that plasticity can influence the lifetime fitness of U. Europaeus and is involved in the capacity of the species to grow under contrasting environmental conditions.

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

    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

    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.

    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)

    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

    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 ...

    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

    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 ...

    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

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

    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.

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

    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…

  20. Environmental indices for common Michigan trees and shrubs.

    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.

  1. Ecology and utilization of desert shrub rangelands in Iraq

    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

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

    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.

  3. Analysis of postfire vegetation dynamics of Mediterranean shrub species based on terrestrial and NDVI data.

    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.

  4. Photosynthetic response of Eriophorum vaginatum to in situ shrub shading in tussock tundra of northern Alaska

    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.

  5. Analysis of Postfire Vegetation Dynamics of Mediterranean Shrub Species Based on Terrestrial and NDVI Data

    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.

  6. Seedling establishment in a masting desert shrub parallels the pattern for forest trees

    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.

  7. Dynamic responses of photosystem II in the Namib Desert shrub, Zygophyllum prismatocarpum, during and after foliar deposition of limestone dust

    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

  8. Managing invasions at the cost of native habitat? An experimental test of the impact of fire on the invasion of Chromolaena odorata in a South African savanna

    te Beest, Mariska; Cromsigt, Joris P. G. M.; Ngobese, Johan; Olff, Han

    2012-01-01

    Successfully managing invasive plants in natural systems is extremely difficult. Recently however, progress has been made with an approach focused on changing ecosystem processes through the disturbance regime. We performed a large-scale (3 ha) full-factorial field experiment in densely invaded woodland in Hluhluwe-iMfolozi Park, a savanna reserve in South Africa, to study the effect of fire on the control of the pan-tropical invasive exotic shrub Chromolaena odorata in combination with the c...

  9. Fodder shrubs and fatty acids: strategies to reduce enteric methane production in cattle.

    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.

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

    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

  11. Generating new varieties of shrubs for landscapes in Malaysia

    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)

  12. Shrub Abundance Mapping in Arctic Tundra with Misr

    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

  13. Aliens will provide: avian responses to a new temporal resource offered by ornithocorous exotic shrubs.

    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.

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

    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.

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

    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.

  16. Are invasive aliens a real threat to biodiversity in South Africa?

    Van Wilgen, B

    2011-01-01

    Full Text Available South Africa has abundant biodiversity, but also many invasive alien species, especially plants and fish, that can transform ecosystems. Invading alien trees and shrubs impact on fynbos and threaten up to a quarter of the nation's plant species...

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

    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. [Characteristics of foliar delta13C values of common shrub species in various microhabitats with different karst rocky desertification degrees].

    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.

  19. Species richness, alpha and beta diversity of trees, shrubs and herbaceous plants in the woodlands of swat, pakistan

    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)

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

    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.

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

    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...

  2. A greener Greenland? Climatic potential and long-term constraints on future expansions of trees and shrubs

    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

  3. The chemical defoliation of Ligitstrum vulgare L. and Spiraea x arguta Zab. shrubs in nursery

    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.

  4. Woody invasions of urban trails and the changing face of urban forests in the great plains, USA

    Nemec, K.T.; Allen, Craig R.; Alai, A.; Clements, G.; Kessler, A.C.; Kinsell, T.; Major, A.; Stephen, B.J.

    2011-01-01

    Corridors such as roads and trails can facilitate invasions by non-native plant species. The open, disturbed habitat associated with corridors provides favorable growing conditions for many non-native plant species. Bike trails are a corridor system common to many urban areas that have not been studied for their potential role in plant invasions. We sampled five linear segments of urban forest along bike trails in Lincoln, Nebraska to assess the invasion of woody non-native species relative to corridors and to assess the composition of these urban forests. The most abundant plant species were generally native species, but five non-native species were also present: white mulberry (Morus alba), common buckthorn (Rhamnus cathartica), tree-of-heaven (Ailanthus altissima), honeysuckle (Lonicera spp.) and elm (Ulmus spp.). The distribution of two of the woody species sampled, common buckthorn and honeysuckle, significantly decreased with increasing distance from a source patch of vegetation (P = 0.031 and 0.030). These linear habitats are being invaded by non-native tree and shrub species, which may change the structure of these urban forest corridors. If non-native woody plant species become abundant in the future, they may homogenize the plant community and reduce native biodiversity in these areas. ?? 2011 American Midland Naturalist.

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

    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.

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

    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.

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

    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.

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

    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.

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

    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

  10. PESTS OF ORNAMENTAL TREES AND SHRUBS IN THE PARKS OF PITEŞTI AND METHODS OF FIGHTING THEM

    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.

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

    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.

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

    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

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

    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

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

    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.

  15. The invasive species Ulex europaeus (Fabaceae) shows high dynamism in a fragmented landscape of south-central Chile.

    Altamirano, Adison; Cely, Jenny Paola; Etter, Andrés; Miranda, Alejandro; Fuentes-Ramirez, Andres; Acevedo, Patricio; Salas, Christian; Vargas, Rodrigo

    2016-08-01

    Ulex europaeus (gorse) is an invasive shrub deemed as one of the most invasive species in the world. U. europaeus is widely distributed in the south-central area of Chile, which is considered a world hotspot for biodiversity conservation. In addition to its negative effects on the biodiversity of natural ecosystems, U. europaeus is one of the most severe pests for agriculture and forestry. Despite its importance as an invasive species, U. europaeus has been little studied. Although information exists on the potential distribution of the species, the interaction of the invasion process with the spatial dynamic of the landscape and the landscape-scale factors that control the presence or absence of the species is still lacking. We studied the spatial and temporal dynamics of the landscape and how these relate to U. europaeus invasion in south-central Chile. We used supervised classification of satellite images to determine the spatial distribution of the species and other land covers for the years 1986 and 2003, analysing the transitions between the different land covers. We used logistic regression for modelling the increase, decrease and permanence of U. europaeus invasion considering landscape variables. Results showed that the species covers only around 1 % of the study area and showed a 42 % reduction in area for the studied period. However, U. europaeus was the cover type which presented the greatest dynamism in the landscape. We found a strong relationship between changes in land cover and the invasion process, especially connected with forest plantations of exotic species, which promotes the displacement of U. europaeus. The model of gorse cover increase presented the best performance, and the most important predictors were distance to seed source and landscape complexity index. Our model predicted high spread potential of U. europaeus in areas of high conservation value. We conclude that proper management for this invasive species must take into account

  16. Transpiration of shrub species, Alnus firma under changing atmospheric environments in montane area, Japan

    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.

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

    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,...

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

    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

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

    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...

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

    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...

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

    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.

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

    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...

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

    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...

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

    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...

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

    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...

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

    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

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

    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 ...

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

    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…

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

    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...

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

    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)

  11. Attempts to deactivate tannins in fodder shrubs with physical and chemical treatments

    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

  12. Alien and invasive woody species in the dunes of the Wadden Sea Island of Vlieland: a remote sensing approach

    Hantson, W.; Kooistra, L.; Slim, P.A.

    2010-01-01

    In this study we mapped (alien) invasive shrubs for management and conservation purposes. On the study site, the Wadden Sea Island of Vlieland, they are a serious treat for the quality of the grey dune habitat. We developed a remote sensing approach that delivers detailed and standardized maps of

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

    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.

  14. Potential reversal of a phase shift: the rapid decrease in the cover of the invasive green macroalga Dictyosphaeria cavernosa Forsskål on coral reefs in Kāne`ohe Bay, Oahu, Hawai`i

    Stimson, J.; Conklin, E.

    2008-12-01

    The native green macroalga Dictyosphaeria cavernosa dominated most of the reef slope habitat in Kāne‘ohe Bay, Hawai‘i for 40 years prior to 2006 and had displaced corals from the habitats they created. This has been one of the most oft-cited examples of a phase shift occurring on a coral reef. After decades of relatively constant, high abundance of the alga, percent cover declined dramatically throughout the bay between February and June 2006. The sudden decrease in cover of this alga appears to be the result of an unusually protracted cloudy, rainy period in March 2006, which may have reduced irradiance and caused the alga to lose weight. Corals and red macroalgae living at the same depths and in some of the same habitats were apparently not affected by this 42-day period of rain and overcast skies. Competition between corals and D. cavernosa for space on reef slopes has been virtually eliminated by the death of this alga, but the unstable rubble formations, which remain in much of the area formerly covered by D. cavernosa may not be conducive to rapid increase in cover by the remaining corals or to establishment by coral recruits. Two years later, there was still no recovery of D. cavernosa. This represents a rare example of decline in macroalgal dominance on a reef and a partial reversal, possibly only temporary, of a phase shift.

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

    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)

  16. Volatile diterpene emission by two Mediterranean Cistaceae shrubs.

    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.

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

    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.

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

    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

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

    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 ...

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

    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

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

    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.

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

    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.

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

    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.

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

    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.

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

    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).

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

    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.

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

    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.

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

    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.

  9. The effects of exotic weed Flaveria bidentis with different invasion ...

    Aghomotsegin

    community, especially its effect pattern at different invasion stages. In this study, soil ... invasion significantly decreased the richness of soil bacterial community, and the decline contents were positively ...... in nitrogen turnover. Agric. Ecosyst.

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

    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...

  11. Earthworm invasion in North America: Food resource competition affects native millipede survival and invasive earthworm reproduction

    Bruce Snyder; Mac Callaham; Christopher Lowe; Paul Hendrix

    2013-01-01

    The invasive non-native earthworm Amynthas agrestis (Goto and Hatai, 1899) has recently been documented invading forests of the Appalachian Mountains in the southeastern United States. This epigeic earthworm decreases the depth of organic soil horizons, and this may play a role in the decrease of millipede richness and abundance associated with A. agrestis invasion. To...

  12. Effects of shrub revegetation with Atriplex halimus L. and Retama sphaerocarpa L. in gypsiferous soils. Influence in soil properties

    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

  13. Minimally Invasive Parathyroidectomy

    Lee F. Starker

    2011-01-01

    Full Text Available Minimally invasive parathyroidectomy (MIP is an operative approach for the treatment of primary hyperparathyroidism (pHPT. Currently, routine use of improved preoperative localization studies, cervical block anesthesia in the conscious patient, and intraoperative parathyroid hormone analyses aid in guiding surgical therapy. MIP requires less surgical dissection causing decreased trauma to tissues, can be performed safely in the ambulatory setting, and is at least as effective as standard cervical exploration. This paper reviews advances in preoperative localization, anesthetic techniques, and intraoperative management of patients undergoing MIP for the treatment of pHPT.

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

    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)

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

    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

  16. Effect of petroleum on decomposition of shrub-grass litters in soil in Northern Shaanxi of China.

    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.

  17. Biological invasions, ecological resilience and adaptive governance.

    Chaffin, Brian C; Garmestani, Ahjond S; Angeler, David G; Herrmann, Dustin L; Stow, Craig A; Nyström, Magnus; Sendzimir, Jan; Hopton, Matthew E; Kolasa, Jurek; Allen, Craig R

    2016-12-01

    In a world of increasing interconnections in global trade as well as rapid change in climate and land cover, the accelerating introduction and spread of invasive species is a critical concern due to associated negative social and ecological impacts, both real and perceived. Much of the societal response to invasive species to date has been associated with negative economic consequences of invasions. This response has shaped a war-like approach to addressing invasions, one with an agenda of eradications and intense ecological restoration efforts towards prior or more desirable ecological regimes. This trajectory often ignores the concept of ecological resilience and associated approaches of resilience-based governance. We argue that the relationship between ecological resilience and invasive species has been understudied to the detriment of attempts to govern invasions, and that most management actions fail, primarily because they do not incorporate adaptive, learning-based approaches. Invasive species can decrease resilience by reducing the biodiversity that underpins ecological functions and processes, making ecosystems more prone to regime shifts. However, invasions do not always result in a shift to an alternative regime; invasions can also increase resilience by introducing novelty, replacing lost ecological functions or adding redundancy that strengthens already existing structures and processes in an ecosystem. This paper examines the potential impacts of species invasions on the resilience of ecosystems and suggests that resilience-based approaches can inform policy by linking the governance of biological invasions to the negotiation of tradeoffs between ecosystem services. Copyright © 2016. Published by Elsevier Ltd.

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

    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.

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

    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.

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

    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.

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

    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....

  2. The initiation of a tropic shrub specia Psidium guajava

    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.

  3. Contrasting ozone sensitivity in related evergreen and deciduous shrubs

    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.

  4. Contrasting ozone sensitivity in related evergreen and deciduous shrubs

    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.

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

    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.

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

    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

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

    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

  8. Treating downy brome with herbicide and seeding with native shrubs

    Suzanne Owen; Carolyn Sieg

    2011-01-01

    Downy brome or cheatgrass (Bromus tectorum L.) is one of the most invasive and widespread exotic plants in North America. Downy brome can reduce soil nutrient availability, alter native plant community composition, and increase fire frequencies. The effectiveness of Plateau® imazapic herbicide in reducing downy brome cover has been variable, and there is uncertainty...

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

    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.

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

    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.

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

    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

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

    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.

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

    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.

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

    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

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

    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.

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

    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.

  17. Invasive rats on tropical islands: Their population biology and impacts on native species

    Harper, Grant A.; Bunbury, Nancy

    2015-01-01

    The three most invasive rat species, black or ship rat Rattus rattus, brown or Norway rats, R. norvegicus and Pacific rat, R. exulans have been incrementally introduced to islands as humans have explored the world’s oceans. They have caused serious deleterious effects through predation and competition, and extinction of many species on tropical islands, many of which are biodiversity hotspots. All three rat species are found in virtually all habitat types, including mangrove and arid shrub la...

  18. When perception reflects reality: Non-native grass invasion alters small mammal risk landscapes and survival

    Ceradnini, Joseph P.; Chalfoun, Anna

    2017-01-01

    Modification of habitat structure due to invasive plants can alter the risk landscape for wildlife by, for example, changing the quality or availability of refuge habitat. Whether perceived risk corresponds with actual fitness outcomes, however, remains an important open question. We simultaneously measured how habitat changes due to a common invasive grass (cheatgrass, Bromus tectorum) affected the perceived risk, habitat selection, and apparent survival of a small mammal, enabling us to assess how well perceived risk influenced important behaviors and reflected actual risk. We measured perceived risk by nocturnal rodents using a giving-up density foraging experiment with paired shrub (safe) and open (risky) foraging trays in cheatgrass and native habitats. We also evaluated microhabitat selection across a cheatgrass gradient as an additional assay of perceived risk and behavioral responses for deer mice (Peromyscus maniculatus) at two spatial scales of habitat availability. Finally, we used mark-recapture analysis to quantify deer mouse apparent survival across a cheatgrass gradient while accounting for detection probability and other habitat features. In the foraging experiment, shrubs were more important as protective cover in cheatgrass-dominated habitats, suggesting that cheatgrass increased perceived predation risk. Additionally, deer mice avoided cheatgrass and selected shrubs, and marginally avoided native grass, at two spatial scales. Deer mouse apparent survival varied with a cheatgrass–shrub interaction, corresponding with our foraging experiment results, and providing a rare example of a native plant mediating the effects of an invasive plant on wildlife. By synthesizing the results of three individual lines of evidence (foraging behavior, habitat selection, and apparent survival), we provide a rare example of linkage between behavioral responses of animals indicative of perceived predation risk and actual fitness outcomes. Moreover, our results

  19. Mapping invasive woody species in coastal dunes in the Netherlands: a remote sensing approach using LIDAR and high-resolution aerial photographs

    Hantson, W.P.R.; Kooistra, L.; Slim, P.A.

    2012-01-01

    Questions Does remote sensing improve classification of invasive woody species in dunes, useful for shrub management? Does additional height information and an object-based classifier increase woody species classification accuracy? Location The dunes of Vlieland, one of the Wadden Sea Islands, the

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

    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. The use of Mediterranean shrub to flight against the land degradation. The rainfall partitioning fluxes

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

    2014-05-01

    biotic and abiotic factors on rainfall partitioning fluxes and their seasonal variation, twenty rainfall events, ten small-size events (P≤10 mm) and ten major events (P>10 mm), were selected. Great differences were observed among species, with interception losses varying between 10% for R. sphaerocarpa to greater than 36% for D. pentaphyllum and M. strasseri, and with stemflow percentages changing between less than 11% for D. pentaphyllum and M. strasseri and 20% for R. sphaerocarpa (Garcia-Estringana, 2011). Pistacia Lentiscus intercepted 21 % of the rainfall and Quercus coccifera 31 %. Species was the most important biotic factor, rainfall volume was the most significant abiotic factor. Stemflow percentages increased and interception losses percentages decreased as rainfall volume increased, both until a stable value reached when rainfall volume was greater than 10 mm. Stemflow and interception losses varied greatly in small events, consequently it is difficult to predict rainfall interception fluxes in semiarid regions, where small events are the most frequent ones. Rainfall volume events greater than 10 mm are much less frequent, but more rainfall is concentrated around the stem base, being during these events when species which used stemflow as an adaptive mechanism to aridity store water in deep soil layers. Stemflow reached their maximum values in autumn and winter, and their minimum values in summer, unlike interception losses, which were higher in summer, except for M. strasseri because it sheds all its leaves. Hydrologic impact of shrubs was very variable depending on the species, and its capacity to form dense communities. Therefore it makes this type of vegetation of great interest in the Mediterranean region, not only by the effect on soil protection (Garcia-Estringana et al., 2010), but also by the effect on hydrology and water availability in a region where water is a scarce resource and shrub vegetation is proliferating as a result of agricultural

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

    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.

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

    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.

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

    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.

  5. Effects of invasive plants on arthropods.

    Litt, Andrea R; Cord, Erin E; Fulbright, Timothy E; Schuster, Greta L

    2014-12-01

    Non-native plants have invaded nearly all ecosystems and represent a major component of global ecological change. Plant invasions frequently change the composition and structure of vegetation communities, which can alter animal communities and ecosystem processes. We reviewed 87 articles published in the peer-reviewed literature to evaluate responses of arthropod communities and functional groups to non-native invasive plants. Total abundance of arthropods decreased in 62% of studies and increased in 15%. Taxonomic richness decreased in 48% of studies and increased in 13%. Herbivorous arthropods decreased in response to plant invasions in 48% of studies and increased in 17%, likely due to direct effects of decreased plant diversity. Predaceous arthropods decreased in response to invasive plants in 44% of studies, which may reflect indirect effects due to reductions in prey. Twenty-two percent of studies documented increases in predators, which may reflect changes in vegetation structure that improved mobility, survival, or web-building for these species. Detritivores increased in 67% of studies, likely in response to increased litter and decaying vegetation; no studies documented decreased abundance in this functional group. Although many researchers have examined effects of plant invasions on arthropods, sizeable information gaps remain, specifically regarding how invasive plants influence habitat and dietary requirements. Beyond this, the ability to predict changes in arthropod populations and communities associated with plant invasions could be improved by adopting a more functional and mechanistic approach. Understanding responses of arthropods to invasive plants will critically inform conservation of virtually all biodiversity and ecological processes because so many organisms depend on arthropods as prey or for their functional roles, including pollination, seed dispersal, and decomposition. Given their short generation times and ability to respond rapidly to

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

    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)

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

    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.

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

    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.

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

    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.

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

    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.

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

    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)

  12. Comparative Assessment of Response to Cadmium in Heavy Metal-Tolerant Shrubs Cultured In Vitro.

    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. Future stratospheric ozone depletion will affect a subarctic dwarf shrub ecosystem

    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

  14. Acacia shrubs respond positively to high severity wildfire: Implications for conservation and fuel hazard management.

    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.

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

    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...

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

    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

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

    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...

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

    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.

  19. Growth and reproduction of the alpine grasshopper Miramella alpina feeding on CO2-enriched dwarf shrubs at treeline.

    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.

  20. Using Mediterranean shrubs for the phytoremediation of a soil impacted by pyritic wastes in Southern Spain: a field experiment.

    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 performed from 2005 to 2007, with soils divided into two groups: pH  5. Four native shrubs (Myrtus communis, Retama sphaerocarpa, Rosmarinus officinalis and Tamarix gallica) were planted and left to grow without intervention. Trace element concentrations in soils and plants, their extractability in soils, transfer factors and plant survival were used to identify the most-interesting species for phytoremediation. Total As was higher in soils with pH soils, but arsenic was extracted more efficiently when soil pH was >5. Unlike As, which was either fixed by Fe oxides or retained as sulphide, the extractable metals showed significant relationships with the corresponding total soil metal concentration and inverse relationships with soil pH. T. gallica, R. officinalis and R. sphaerocarpa survived better in soils with pH > 5, while M. communis had better survival at pH soils. Trace element transfer from soil to harvestable parts was low for all species and elements, and some species may have been able to decrease trace element availability in the soil. Our results suggest that R. sphaerocarpa is an adequate plant species for phytostabilising these soils, although more research is needed to address the self-sustainability of this remediation technique and the associated environmental changes. Copyright © 2011 Elsevier Ltd. All rights reserved.

  1. Spatial and temporal functional changes in alpine summit vegetation are driven by increases in shrubs and graminoids.

    Venn, Susanna; Pickering, Catherine; Green, Ken

    2014-01-01

    Classical approaches to investigating temporal and spatial changes in community composition offer only partial insight into the ecology that drives species distribution, community patterns and processes, whereas a functional approach can help to determine many of the underlying mechanisms that drive such patterns. Here, we aim to bring these two approaches together to understand such drivers, using an elevation gradient of sites, a repeat species survey and species functional traits. We used data from a repeat vegetation survey on five alpine summits and measured plant height, leaf area, leaf dry matter content and specific leaf area (SLA) for every species recorded in the surveys. We combined species abundances with trait values to produce a community trait-weighted mean (CTWM) for each trait, and then combined survey results with the CTWMs. Across the gradient of summits, more favourable conditions for plant growth (warmer, longer growing season) occurred at the lower elevations. Vegetation composition changes between 2004 and 2011 (according to non-metric multi-dimensional scaling ordination) were strongly affected by the high and increasing abundance of species with high SLA at high elevations. Species life-form categories strongly affected compositional changes and functional composition, with increasing dominance of tall shrubs and graminoids at the lower-elevation summits, and an overall increase in graminoids across the gradient. The CTWM for plant height and leaf dry matter content significantly decreased with elevation, whereas for leaf area and SLA it significantly increased. The significant relationships between CTWM and elevation may suggest specific ecological processes, namely plant competition and local productivity, influencing vegetation preferentially across the elevation gradient, with the dominance of shrubs and graminoids driving the patterns in the CTWMs.

  2. From observations to experiments in phenology research: investigating climate change impacts on trees and shrubs using dormant twigs.

    Primack, Richard B; Laube, Julia; Gallinat, Amanda S; Menzel, Annette

    2015-11-01

    Climate change is advancing the leaf-out times of many plant species and mostly extending the growing season in temperate ecosystems. Laboratory experiments using twig cuttings from woody plant species present an affordable, easily replicated approach to investigate the relative importance of factors such as winter chilling, photoperiod, spring warming and frost tolerance on the leafing-out times of plant communities. This Viewpoint article demonstrates how the results of these experiments deepen our understanding beyond what is possible via analyses of remote sensing and field observation data, and can be used to improve climate change forecasts of shifts in phenology, ecosystem processes and ecological interactions. The twig method involves cutting dormant twigs from trees, shrubs and vines on a single date or at intervals over the course of the winter and early spring, placing them in containers of water in controlled environments, and regularly recording leaf-out, flowering or other phenomena. Prior to or following leaf-out or flowering, twigs may be assigned to treatment groups for experiments involving temperature, photoperiod, frost, humidity and more. Recent studies using these methods have shown that winter chilling requirements and spring warming strongly affect leaf-out and flowering times of temperate trees and shrubs, whereas photoperiod requirements are less important than previously thought for most species. Invasive plant species have weaker winter chilling requirements than native species in temperate ecosystems, and species that leaf-out early in the season have greater frost tolerance than later leafing species. This methodology could be extended to investigate additional drivers of leaf-out phenology, leaf senescence in the autumn, and other phenomena, and could be a useful tool for education and outreach. Additional ecosystems, such as boreal, southern hemisphere and sub-tropical forests, could also be investigated using dormant twigs to

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

    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

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

    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...

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

    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

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

    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...

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

    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

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

    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...

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

    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.

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

    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.

  11. Removing an invasive shrub (Chinese privet) increases native bee diversity and abundance in riparian forests of the southeastern United States

    James L. Hanula; Scott Horn

    2011-01-01

    1. Chinese privet (Ligustrum sinense Lour.) was removed from riparian forests in the Piedmont of Georgia in November 2005 by mulching with a track-mounted mulching machine or by chainsaw felling. The remaining privet in the herbaceous layer was killed with herbicide in December 2006. 2. Bee (Hymentoptera: Apoidea) abundance, diversity and community similarity in the...

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

    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.

  13. A review of impacts by invasive exotic plants on forest ecosystem services

    Kevin Devine; Songlin. Fei

    2011-01-01

    Many of our forest ecosystems are at risk due to the invasion of exotic invasive plant species. Invasive plant species pose numerous threats to ecosystems by decreasing biodiversity, deteriorating ecosystem processes, and degrading ecosystem services. Literature on Kentucky's most invasive exotic plant species was examined to understand their potential impacts on...

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

    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

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

    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

  16. A systematic review of context bias in invasion biology.

    Robert J Warren

    Full Text Available The language that scientists use to frame biological invasions may reveal inherent bias-including how data are interpreted. A frequent critique of invasion biology is the use of value-laden language that may indicate context bias. Here we use a systematic study of language and interpretation in papers drawn from invasion biology to evaluate whether there is a link between the framing of papers and the interpretation of results. We also examine any trends in context bias in biological invasion research. We examined 651 peer-reviewed invasive species competition studies and implemented a rigorous systematic review to examine bias in the presentation and interpretation of native and invasive competition in invasion biology. We predicted that bias in the presentation of invasive species is increasing, as suggested by several authors, and that bias against invasive species would result in misinterpreting their competitive dominance in correlational observational studies compared to causative experimental studies. We indeed found evidence of bias in the presentation and interpretation of invasive species research; authors often introduced research with invasive species in a negative context and study results were interpreted against invasive species more in correlational studies. However, we also found a distinct decrease in those biases since the mid-2000s. Given that there have been several waves of criticism from scientists both inside and outside invasion biology, our evidence suggests that the subdiscipline has somewhat self-corrected apparent biases.

  17. A systematic review of context bias in invasion biology.

    Warren, Robert J; King, Joshua R; Tarsa, Charlene; Haas, Brian; Henderson, Jeremy

    2017-01-01

    The language that scientists use to frame biological invasions may reveal inherent bias-including how data are interpreted. A frequent critique of invasion biology is the use of value-laden language that may indicate context bias. Here we use a systematic study of language and interpretation in papers drawn from invasion biology to evaluate whether there is a link between the framing of papers and the interpretation of results. We also examine any trends in context bias in biological invasion research. We examined 651 peer-reviewed invasive species competition studies and implemented a rigorous systematic review to examine bias in the presentation and interpretation of native and invasive competition in invasion biology. We predicted that bias in the presentation of invasive species is increasing, as suggested by several authors, and that bias against invasive species would result in misinterpreting their competitive dominance in correlational observational studies compared to causative experimental studies. We indeed found evidence of bias in the presentation and interpretation of invasive species research; authors often introduced research with invasive species in a negative context and study results were interpreted against invasive species more in correlational studies. However, we also found a distinct decrease in those biases since the mid-2000s. Given that there have been several waves of criticism from scientists both inside and outside invasion biology, our evidence suggests that the subdiscipline has somewhat self-corrected apparent biases.

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

    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...

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

    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

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

    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...

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

    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.

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

    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

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

    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

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

    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

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

    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...

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

    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

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

    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...

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

    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...

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

    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/.

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

    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.

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

    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 ...

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

    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...

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

    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...

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

    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

    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

    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.

    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?

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

    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

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

    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

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

    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

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

    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…

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

    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...

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

    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 ...

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

    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

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

    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

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

    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...

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

    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...

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

    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.

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

    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.

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

    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

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

    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.

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

    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.

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

    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

  15. [Invasive yeast infections in neutropenic patients].

    Ruiz Camps, Isabel; Jarque, Isidro

    2016-01-01

    Invasive fungal diseases caused by yeasts still play an important role in the morbidity and mortality in neutropenic patients with haematological malignancies. Although the overall incidence of invasive candidiasis has decreased due to widespread use of antifungal prophylaxis, the incidence of non-Candida albicans Candida species is increasing compared with that of C.albicans, and mortality of invasive candidiasis continues to be high. In addition, there has been an increase in invasive infections caused by an array of uncommon yeasts, including species of the genus Malassezia, Rhodotorula, Trichosporon and Saprochaete, characterised by their resistance to echinocandins and poor prognosis. Copyright © 2016 Asociación Española de Micología. Publicado por Elsevier España, S.L.U. All rights reserved.

  16. Deeply invasive candidiasis.

    Ostrosky-Zeichner, L.; Rex, J.H.; Bennett, J.; Kullberg, B.J.

    2002-01-01

    The incidence of invasive candidiasis is on the rise because of increasing numbers of immunocompromised hosts and more invasive medical technology. Recovery of Candida spp from several body sites in a critically ill or immunocompromised patient should raise the question of disseminated disease.

  17. Cryptic invasions: a review

    Morais, Pedro Miguel; Reichard, Martin

    613-614, February (2018), s. 1438-1448 ISSN 0048-9697 R&D Projects: GA ČR GA13-05872S Institutional support: RVO:68081766 Keywords : Conspecific invader * Biological invasions * Bibliometric * Invasiveness Subject RIV: EG - Zoology OBOR OECD: Environmental sciences (social aspects to be 5.7) Impact factor: 4.900, year: 2016

  18. Factors influencing plant invasiveness

    Yvette Ortega; Dean Pearson

    2009-01-01

    Invasiveness of spotted knapweed and biological control agents. Dean and Yvette are examining the influence of drought on the invasiveness of spotted knapweed (Centaurea maculosa) and its susceptibility to herbivory by biological control agents. In collaboration with the University of Montana and Forest Health Protection, researchers have constructed 150...

  19. Diversity reduces invasibility in experimental plant communities: the role of plant species

    Van Ruijven, J.; De Deyn, G.B.; Berendse, F.

    2003-01-01

    Several studies have presented experimental evidence that diversity reduces invasibility in grassland communities. The interpretation of these results has been disputed recently and it was proposed that sampling effects were responsible for the observed decrease of invasibility with diversity. The

  20. Alien invasive birds.

    Brochier, B; Vangeluwe, D; van den Berg, T

    2010-08-01

    A bird species is regarded as alien invasive if it has been introduced, intentionally or accidentally, to a location where it did not previously occur naturally, becomes capable of establishing a breeding population without further intervention by humans, spreads and becomes a pest affecting the environment, the local biodiversity, the economy and/or society, including human health. European Starling (Sturnus vulgaris), Common Myna (Acridotheres tristis) and Red-vented Bulbul (Pycnonotus cafer) have been included on the list of '100 of the World's Worst Invasive Alien Species', a subset of the Global Invasive Species Database. The 'Delivering Alien Invasive Species Inventories for Europe' project has selected Canada Goose (Branta canadensis), Ruddy Duck (Oxyura jamaicensis), Rose-ringed Parakeet (Psittacula krameri) and Sacred Ibis (Threskiornis aethiopicus) as among 100 of the worst invasive species in Europe. For each of these alien bird species, the geographic range (native and introduced range), the introduction pathway, the general impacts and the management methods are presented.

  1. Minimally invasive orthognathic surgery.

    Resnick, Cory M; Kaban, Leonard B; Troulis, Maria J

    2009-02-01

    Minimally invasive surgery is defined as the discipline in which operative procedures are performed in novel ways to diminish the sequelae of standard surgical dissections. The goals of minimally invasive surgery are to reduce tissue trauma and to minimize bleeding, edema, and injury, thereby improving the rate and quality of healing. In orthognathic surgery, there are two minimally invasive techniques that can be used separately or in combination: (1) endoscopic exposure and (2) distraction osteogenesis. This article describes the historical developments of the fields of orthognathic surgery and minimally invasive surgery, as well as the integration of the two disciplines. Indications, techniques, and the most current outcome data for specific minimally invasive orthognathic surgical procedures are presented.

  2. Positive feedback between mycorrhizal fungi and plants influences plant invasion success and resistance to invasion.

    Zhang, Qian; Yang, Ruyi; Tang, Jianjun; Yang, Haishui; Hu, Shuijin; Chen, Xin

    2010-08-24

    Negative or positive feedback between arbuscular mycorrhizal fungi (AMF) and host plants can contribute to plant species interactions, but how this feedback affects plant invasion or resistance to invasion is not well known. Here we tested how alterations in AMF community induced by an invasive plant species generate feedback to the invasive plant itself and affect subsequent interactions between the invasive species and its native neighbors. We first examined the effects of the invasive forb Solidago canadensis L. on AMF communities comprising five different AMF species. We then examined the effects of the altered AMF community on mutualisms formed with the native legume forb species Kummerowia striata (Thunb.) Schindl. and on the interaction between the invasive and native plants. The host preferences of the five AMF were also assessed to test whether the AMF form preferred mutualistic relations with the invasive and/or the native species. We found that S. canadensis altered AMF spore composition by increasing one AMF species (Glomus geosporum) while reducing Glomus mosseae, which is the dominant species in the field. The host preference test showed that S. canadensis had promoted the abundance of AMF species (G. geosporum) that most promoted its own growth. As a consequence, the altered AMF community enhanced the competitiveness of invasive S. canadensis at the expense of K. striata. Our results demonstrate that the invasive S. canadensis alters soil AMF community composition because of fungal-host preference. This change in the composition of the AMF community generates positive feedback to the invasive S. canadensis itself and decreases AM associations with native K. striata, thereby making the native K. striata less dominant.

  3. Positive feedback between mycorrhizal fungi and plants influences plant invasion success and resistance to invasion.

    Qian Zhang

    2010-08-01

    Full Text Available Negative or positive feedback between arbuscular mycorrhizal fungi (AMF and host plants can contribute to plant species interactions, but how this feedback affects plant invasion or resistance to invasion is not well known. Here we tested how alterations in AMF community induced by an invasive plant species generate feedback to the invasive plant itself and affect subsequent interactions between the invasive species and its native neighbors. We first examined the effects of the invasive forb Solidago canadensis L. on AMF communities comprising five different AMF species. We then examined the effects of the altered AMF community on mutualisms formed with the native legume forb species Kummerowia striata (Thunb. Schindl. and on the interaction between the invasive and native plants. The host preferences of the five AMF were also assessed to test whether the AMF form preferred mutualistic relations with the invasive and/or the native species. We found that S. canadensis altered AMF spore composition by increasing one AMF species (Glomus geosporum while reducing Glomus mosseae, which is the dominant species in the field. The host preference test showed that S. canadensis had promoted the abundance of AMF species (G. geosporum that most promoted its own growth. As a consequence, the altered AMF community enhanced the competitiveness of invasive S. canadensis at the expense of K. striata. Our results demonstrate that the invasive S. canadensis alters soil AMF community composition because of fungal-host preference. This change in the composition of the AMF community generates positive feedback to the invasive S. canadensis itself and decreases AM associations with native K. striata, thereby making the native K. striata less dominant.

  4. Decreasing Relative Risk Premium

    Hansen, Frank

    relative risk premium in the small implies decreasing relative risk premium in the large, and decreasing relative risk premium everywhere implies risk aversion. We finally show that preferences with decreasing relative risk premium may be equivalently expressed in terms of certain preferences on risky......We consider the risk premium demanded by a decision maker with wealth x in order to be indifferent between obtaining a new level of wealth y1 with certainty, or to participate in a lottery which either results in unchanged present wealth or a level of wealth y2 > y1. We define the relative risk...... premium as the quotient between the risk premium and the increase in wealth y1–x which the decision maker puts on the line by choosing the lottery in place of receiving y1 with certainty. We study preferences such that the relative risk premium is a decreasing function of present wealth, and we determine...

  5. To tilfaelde af invasive infektioner med Haemophilus influenzae type f

    Nielsen, Jette Dettmann; Lind, Jens Wentzel; Bruun, Britta

    2009-01-01

    Two cases of invasive Haemophilus influenzae type f infection are presented: a three-week-old boy with meningitis and a 62-year-old woman with arthritis and bacteremia. Since 1993 vaccination against H. influenzae type b (Hib) has been offered to Danish children. The result has been a remarkable...... decrease in invasive Hib disease. However, physicians need to be aware of the existence of non-type b invasive H. influenzae disease. Udgivelsesdato: 2009-Jan...

  6. To tilfaelde af invasive infektioner med Haemophilus influenzae type f

    Nielsen, Jette Dettmann; Lind, Jens; Bruun, Brita

    2009-01-01

    Two cases of invasive Haemophilus influenzae type f infection are presented: a three-week-old boy with meningitis and a 62-year-old woman with arthritis and bacteremia. Since 1993 vaccination against H. influenzae type b (Hib) has been offered to Danish children. The result has been a remarkable...... decrease in invasive Hib disease. However, physicians need to be aware of the existence of non-type b invasive H. influenzae disease. Udgivelsesdato: 2009-Jan-19...

  7. [Two cases of invasive Haemophilus influenzae type f infection

    Nielsen, J.D.; Lind, J.W.; Bruun, B.

    2009-01-01

    Two cases of invasive Haemophilus influenzae type f infection are presented: a three-week-old boy with meningitis and a 62-year-old woman with arthritis and bacteremia. Since 1993 vaccination against H. influenzae type b (Hib) has been offered to Danish children. The result has been a remarkable...... decrease in invasive Hib disease. However, physicians need to be aware of the existence of non-type b invasive H. influenzae disease Udgivelsesdato: 2009/1/19...

  8. Changes in rainfall amount and frequency do not affect the outcome of the interaction between the shrub Retama sphaerocarpa and its neighbouring grasses in two semiarid communities

    Soliveres, Santiago; García-Palacios, Pablo; Maestre, Fernando T.; Escudero, Adrián; Valladares, Fernando

    2015-01-01

    We evaluated the net outcome of the interaction between the shrub Retama sphaerocarpa, our target plant, and different herbaceous neighbours in response to changes in the magnitude and frequency of rainfall events during three years. The experiment was conducted in natural and anthropogenic grasslands dominated by a perennial stress-tolerator and ruderal annual species, respectively. In spite of the neutral or positive effects of neighbours on water availability, neighbouring plants reduced the performance of Retama juveniles, suggesting competition for resources other than water. The negative effects of grasses on the photochemical efficiency of Retama juveniles decreased with higher water availabilities or heavier irrigation pulses, depending on the grassland studied; however, these effects did not extent to the survival and growth of Retama juveniles. Our findings show the prevalence of competitive interactions among the studied plants, regardless of the water availability and its temporal pattern. These results suggest that positive interactions may not prevail under harsher conditions when shade-intolerant species are involved. This study could be used to further refine our predictions of how plant-plant interactions will respond to changes in rainfall, either natural or increased by the ongoing climatic change, in ecosystems where grass-shrubs interactions are prevalent. PMID:25914429

  9. Changes in rainfall amount and frequency do not affect the outcome of the interaction between the shrub Retama sphaerocarpa and its neighbouring grasses in two semiarid communities.

    Soliveres, Santiago; García-Palacios, Pablo; Maestre, Fernando T; Escudero, Adrián; Valladares, Fernando

    2013-04-01

    We evaluated the net outcome of the interaction between the shrub Retama sphaerocarpa , our target plant, and different herbaceous neighbours in response to changes in the magnitude and frequency of rainfall events during three years. The experiment was conducted in natural and anthropogenic grasslands dominated by a perennial stress-tolerator and ruderal annual species, respectively. In spite of the neutral or positive effects of neighbours on water availability, neighbouring plants reduced the performance of Retama juveniles, suggesting competition for resources other than water. The negative effects of grasses on the photochemical efficiency of Retama juveniles decreased with higher water availabilities or heavier irrigation pulses, depending on the grassland studied; however, these effects did not extent to the survival and growth of Retama juveniles. Our findings show the prevalence of competitive interactions among the studied plants, regardless of the water availability and its temporal pattern. These results suggest that positive interactions may not prevail under harsher conditions when shade-intolerant species are involved. This study could be used to further refine our predictions of how plant-plant interactions will respond to changes in rainfall, either natural or increased by the ongoing climatic change, in ecosystems where grass-shrubs interactions are prevalent.

  10. Effects of elevated root zone CO2 on xerophytic shrubs in re-vegetated sandy dunes at smaller spatial and temporal scales.

    Lei, Huang; Zhishan, Zhang

    2015-01-01

    The below-ground CO2 concentration in some crusted soils or flooded fields is usually ten or hundred times larger than the normal levels. Recently, a large number of studies have focused on elevated CO2 in the atmosphere; however, only few have examined the influence of elevated root zone CO2 on plant growth and vegetation succession. In the present study, a closed-air CO2 enrichment (CACE) system was designed to simulate elevated CO2 concentrations in the root zones. The physio-ecological characteristics of two typical xerophytic shrubs C. korshinskii and A. ordosica in re-vegetated desert areas were investigated at different soil CO2 concentrations from March 2011 to October 2013. Results showed that plant growth, phenophase, photosynthetic rate, stomatal conductance, transpiration rate, and water use efficiency for the two xerophytic shrubs were all increased at first and then decreased with increasing soil CO2 concentrations, and the optimal soil CO2 concentration thresholds for C. korshinskii and A. ordosica were 0.554 and 0.317%, respectively. And A. ordosica was more tolerate to root zone CO2 variation when compared with C. korshinskii, possible reasons and vegetation succession were also discussed.

  11. Decreasing Serial Cost Sharing

    Hougaard, Jens Leth; Østerdal, Lars Peter

    The increasing serial cost sharing rule of Moulin and Shenker [Econometrica 60 (1992) 1009] and the decreasing serial rule of de Frutos [Journal of Economic Theory 79 (1998) 245] have attracted attention due to their intuitive appeal and striking incentive properties. An axiomatic characterization...... of the increasing serial rule was provided by Moulin and Shenker [Journal of Economic Theory 64 (1994) 178]. This paper gives an axiomatic characterization of the decreasing serial rule...

  12. Decreasing serial cost sharing

    Hougaard, Jens Leth; Østerdal, Lars Peter Raahave

    2009-01-01

    The increasing serial cost sharing rule of Moulin and Shenker (Econometrica 60:1009-1037, 1992) and the decreasing serial rule of de Frutos (J Econ Theory 79:245-275, 1998) are known by their intuitive appeal and striking incentive properties. An axiomatic characterization of the increasing serial...... rule was provided by Moulin and Shenker (J Econ Theory 64:178-201, 1994). This paper gives an axiomatic characterization of the decreasing serial rule....

  13. Plant invasions in China: an emerging hot topic in invasion science

    Jian Liu

    2012-12-01

    Full Text Available China has shown a rapid economic development in recent decades, and several drivers of this change are known to enhance biological invasions, a major cause of biodiversity loss. Here we review the current state of research on plant invasions in China by analyzing papers referenced in the ISI Web of Knowledge. Since 2001, the number of papers has increased exponentially, indicating that plant invasions in China are an emerging hot topic in invasion science. The analyzed papers cover a broad range of methodological approaches and research topics. While more that 250 invasive plant species with negative impacts have been reported from China, only a few species have been considered in more than a handful of papers (in order of decreasing number of references: Spartina alterniflora, Ageratina adenophora, Mikania micrantha, Alternanthera philoxeroides, Solidago canadensis, Eichhornia crassipes. Yet this selection might rather reflect the location of research teams than the most invasive plant species in China. Considering the previous achievements in China found in our analysis research in plant invasions could be expanded by (1 compiling comprehensive lists of non-native plant species at the provincial and national scales and to include species that are native to one part of China but non-native to others in these lists; (2 strengthening pathways studies (primary introduction to the country, secondary releases within the country to enhance prevention and management; and (3 assessing impacts of invasive species at different spatial scales (habitats, regions and in relation to conservation resources.

  14. [Allelopathic effects of the humus soils from Betula platyphylla and Quercus liaotungensis pure plantations on 9 kinds of common shrubs and herbs].

    Huang, Liang-Jia; Liu, Zeng-wen; Zhu, Bo-Chao; Bing, Yuan-Hao; Zhang, Xiao-Xi; Lü, Chen

    2014-06-01

    The humus soils were collected from Betula platyphylla and Quercus liaotungensis pure plantations and woodless land separately where the site conditions were basically the same, and taken as medium for potting culture test of 9 kinds of shrubs or herbs in plastic greenhouse to assess the allelopathic effects of humus soils of pure plantations on shrubs or herbs. Humus soils from B. platyphylla plantation significantly inhibited the seed germinations of Medicago sativa and Melilotus officinalis, decreased the catalase (CAT) activity of M. officinalis, Coronilla varia, M. sativa and Lespedeza davurica, and improved malondialdehyde (MDA) contents in seedlings of Caragana kor-shinskii, C. varia and Astragalus adsurgens. The biomass growths of C. varia, Amorpha fruticosa, M. sativa, M. officinalis and A. adsurgens in humus soils from B. platyphylla plantation were significantly decreased by 48.2%, 45.1%, 44.3%, 37.3% and 36.0%, respectively. In addition, humus soil of Q. liaotungensis plantation significantly decreased the germination rates of M. sativa and A. adsurgens, the chlorophyll contents of Vicia villosa, A. fruticosa and M. sativa, and improved malondialdehyde (MDA) contents in seedlings of Lespedeza davurica, Caragana korshinskii, M. officinalis and A. adsurgens. The biomass growths of A. adsurgens, M. sativa, M. officinalis and A. fruticosa were significantly decreased by 52.6% , 43.8%, 35.5% and 34.6%, respective- ly. B. platyphylla plantation humus soil had obvious inhibition effects on M. sativa, M. officinalis and A. fruticosa, while Q. liaotungensis plantation humus soil had obvious inhibition effects on M. sativa, A. adsurgens and A. fruticosa.

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

    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

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

    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.

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

    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.

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

    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.

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

    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.

  20. Fire-driven alien invasion in a fire-adapted ecosystem.

    Keeley, Jon E; Brennan, Teresa J

    2012-08-01

    Disturbance plays a key role in many alien plant invasions. However, often the main driver of invasion is not disturbance per se but alterations in the disturbance regime. In some fire-adapted shrublands, the community is highly resilient to infrequent, high-intensity fires, but changes in the fire regime that result in shorter fire intervals may make these communities more susceptible to alien plant invasions. This study examines several wildfire events that resulted in short fire intervals in California chaparral shrublands. In one study, we compared postfire recovery patterns in sites with different prefire stand ages (3 and 24 years), and in another study we compared sites that had burned once in four years with sites that had burned twice in this period. The population size of the dominant native shrub Adenostoma fasciculatum was drastically reduced following fire in the 3-year sites relative to the 24-year sites. The 3-year sites had much greater alien plant cover and significantly lower plant diversity than the 24-year sites. In a separate study, repeat fires four years apart on the same sites showed that annual species increased significantly after the second fire, and alien annuals far outnumbered native annuals. Aliens included both annual grasses and annual forbs and were negatively correlated with woody plant cover. Native woody species regenerated well after the first fire but declined after the second fire, and one obligate seeding shrub was extirpated from two sites by the repeat fires. It is concluded that some fire-adapted shrublands are vulnerable to changes in fire regime, and this can lead to a loss of native diversity and put the community on a trajectory towards type conversion from a woody to an herbaceous system. Such changes result in alterations in the proportion of natives to non-natives, changes in functional types from deeply rooted shrubs to shallow rooted grasses and forbs, increased fire frequency due to the increase in fine fuels

  1. Fire-driven alien invasion in a fire-adapted ecosystem

    Keeley, Jon E.; Brennan, Teresa J.

    2012-01-01

    Disturbance plays a key role in many alien plant invasions. However, often the main driver of invasion is not disturbance per se but alterations in the disturbance regime. In some fire-adapted shrublands, the community is highly resilient to infrequent, high-intensity fires, but changes in the fire regime that result in shorter fire intervals may make these communities more susceptible to alien plant invasions. This study examines several wildfire events that resulted in short fire intervals in California chaparral shrublands. In one study, we compared postfire recovery patterns in sites with different prefire stand ages (3 and 24 years), and in another study we compared sites that had burned once in four years with sites that had burned twice in this period. The population size of the dominant native shrub Adenostoma fasciculatum was drastically reduced following fire in the 3-year sites relative to the 24-year sites. The 3-year sites had much greater alien plant cover and significantly lower plant diversity than the 24-year sites. In a separate study, repeat fires four years apart on the same sites showed that annual species increased significantly after the second fire, and alien annuals far outnumbered native annuals. Aliens included both annual grasses and annual forbs and were negatively correlated with woody plant cover. Native woody species regenerated well after the first fire but declined after the second fire, and one obligate seeding shrub was extirpated from two sites by the repeat fires. It is concluded that some fire-adapted shrublands are vulnerable to changes in fire regime, and this can lead to a loss of native diversity and put the community on a trajectory towards type conversion from a woody to an herbaceous system. Such changes result in alterations in the proportion of natives to non-natives, changes in functional types from deeply rooted shrubs to shallow rooted grasses and forbs, increased fire frequency due to the increase in fine fuels

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

    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.

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

    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

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

    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.

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

    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.

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

    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

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

    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.

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

    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.

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

    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....

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

    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.

  11. [Water parameters of desert xeric shrubs in west Erdos region].

    Li, Xiao; Wang, Ying-chun; Zheng, Rong

    2007-05-01

    By using PV technique, this paper studied the turgor pressure (psi P), cell elastic modulus (epsilon), and relative cell volume (RCV) of super xerophytes Potaninia mongolica, Reaumuria soongorica, Tetraena mongolica and Zygophyllum xanthoxylon in west Alashan, with the relationships among the parameters analyzed. The results showed that R. soongorica had the strongest ability to maintain maximum turgor pressure (a = 2.4593). The four plants maintained their turgor pressure by different ways, i.e., P. mongolica maintained it by elastic adjustment (epsilon max = 8.4005 MPa), R. soongorica by osmotic adjustment (psi pi100 = -3.1302 MPa; psi0 = -3.5074 MPa), T. mongolica by both osmotic and elastic adjustment, and Z. xanthoxylon by osmotic adjustment, which had weak adjustment ability. The cell wall of P. mongolica was soft and highly elastic, benefiting to the water absorption by root and stem and to the fast water transmission. T. mongolica also had relatively soft and high elastic cell wall, and its psi P, and epsilon changed slowly with decreasing RCV, suggesting that this plant had strong ability of holding water and resisting dehydration.

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

    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.

  13. Effects of sand burial on the survival and growth of two shrubs dominant in different habitats of northern China.

    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.

  14. Effect of coppicing height on the regeneration and productivity of certain firewood shrubs in alkaline soils of north Indian plains

    Misra, P.N.; Tewari, S.K.; Singh, Dheer; Katiyar, R.S. [National Botanical Research Inst., Lucknow (India)

    1995-12-31

    Four shrubs, viz. Hibiscus tiliaceus, Leucaena leucocephala, Vitex negundo and Sesbania sesban, were evaluated for their performance as firewood crops in coppiced stands of varying cutting heights (15, 30 and 45 cm) in repeated annual harvests (4) on alkaline soils of the North Indian plains. The dry wood yield of Leucaena and Sesbania ranged between 22.9-42.6 and 9.9-18.0 tonnes ha{sup -1} year{sup -1}, respectively. Leucaena showed progressive increases in yield from coppiced stumps up to the 4th harvest while Sesbania showed a reduction after the third harvest mainly due to the high degeneration (60%) of coppiced stumps. Degeneration was low (< 10%) in Leucaena and Vitex. The coppicing heights generally did not show any significant effect on the growth and productivity. The number of coppice shoots per stump increased with stump height and production of coppice shoots was maximum in Vitex and minimum in Leucaena. The average diameter of coppice shoots tended to decrease with increasing coppicing height of the stumps. (author)

  15. Population differentiation in a Mediterranean relict shrub: the potential role of local adaptation for coping with climate change.

    Lázaro-Nogal, Ana; Matesanz, Silvia; Hallik, Lea; Krasnova, Alisa; Traveset, Anna; Valladares, Fernando

    2016-04-01

    Plants can respond to climate change by either migrating, adapting to the new conditions or going extinct. Relict plant species of limited distribution can be especially vulnerable as they are usually composed of small and isolated populations, which may reduce their ability to cope with rapidly changing environmental conditions. The aim of this study was to assess the vulnerability of Cneorum tricoccon L. (Cneoraceae), a Mediterranean relict shrub of limited distribution, to a future drier climate. We evaluated population differentiation in functional traits related to drought tolerance across seven representative populations of the species' range. We measured morphological and physiological traits in both the field and the greenhouse under three water availability levels. Large phenotypic differences among populations were found under field conditions. All populations responded plastically to simulated drought, but they differed in mean trait values as well as in the slope of the phenotypic response. Particularly, dry-edge populations exhibited multiple functional traits that favored drought tolerance, such as more sclerophyllous leaves, strong stomatal control but high photosynthetic rates, which increases water use efficiency (iWUE), and an enhanced ability to accumulate sugars as osmolytes. Although drought decreased RGR in all populations, this reduction was smaller for populations from the dry edge. Our results suggest that dry-edge populations of this relict species are well adapted to drought, which could potentially mitigate the species' extinction risk under drier scenarios. Dry-edge populations not only have a great conservation value but can also change expectations from current species' distribution models.

  16. Post-fire environments are favourable for plant functioning of seeder and resprouter Mediterranean shrubs, even under drought.

    Parra, Antonio; Moreno, José M

    2017-05-01

    Understanding how drought affects seeder and resprouter plants during post-fire regeneration is important for the anticipation of Mediterranean vegetation vulnerability in a context of increasing drought and fire caused by climate change. A Mediterranean shrubland was subjected to various drought treatments (including 45% rainfall reduction, 7 months drought yr -1 ), before and after experimental burning, by means of a rainout-shelter system with an irrigation facility. Predawn shoot water potential (Ψ pd ), relative growth rate (RGR), specific leaf area (SLA) and bulk leaf carbon isotopic composition (δ 13 C) were monitored in the main woody species during the first 3 yr after fire. Cistus ladanifer seedlings showed higher Ψ pd , RGR and SLA, and lower δ 13 C, than unburned plants during the first two post-fire years. Seedlings under drought maintained relatively high Ψ pd , but suffered a decrease in Ψ pd and RGR, and an increase in δ 13 C, relative to control treatments. Erica arborea, E. scoparia and Phillyrea angustifolia resprouts had higher Ψ pd and RGR than unburned plants during the first post-fire year. Resprouters were largely unaffected by drought. Overall, despite marked differences between the two functional groups, post-fire environments were favourable for plant functioning of both seeder and resprouter shrubs, even under the most severe drought conditions implemented. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

  17. MicroRNA and protein profiles in invasive versus non-invasive oral tongue squamous cell carcinoma cells in vitro

    Korvala, Johanna, E-mail: johanna.korvala@oulu.fi [Cancer and Translational Medicine Research Unit, University of Oulu, The Medical Research Center Oulu, Oulu University Hospital, Aapistie 5A, 90014 Oulu (Finland); Jee, Kowan [Department of Pathology, University of Turku, Turku University Hospital, Turku (Finland); Department of Pathology, Haartman Institute, University of Helsinki, Helsinki (Finland); Porkola, Emmi [Cancer and Translational Medicine Research Unit, University of Oulu, The Medical Research Center Oulu, Oulu University Hospital, Aapistie 5A, 90014 Oulu (Finland); Almangush, Alhadi [Department of Pathology, Haartman Institute, University of Helsinki, Helsinki (Finland); Mosakhani, Neda [Department of Pathology, HUSLAB, Helsinki (Finland); Bitu, Carolina [Cancer and Translational Medicine Research Unit, University of Oulu, The Medical Research Center Oulu, Oulu University Hospital, Aapistie 5A, 90014 Oulu (Finland); Cervigne, Nilva K. [Department of Oral Diagnosis, School of Dentistry, University of Campinas (UNICAMP), Av. Limeira, 901 – Bairro Areião, CEP: 13414-903 Piracicaba, São Paulo (Brazil); Department of Clinical and Pathology, Faculty of Medicine of Jundiai - FMJ, Jundiai, SP (Brazil); Zandonadi, Flávia S.; Meirelles, Gabriela V.; Leme, Adriana Franco Paes [Laboratório Nacional de Biociências, LNBio, CNPEM, Rua Giuseppe Máximo Scolfaro, 10.000, Polo II de Alta Tecnologia de Campinas, Campinas/SP, P.O.Box 6192, CEP 13083-970 Campinas, São Paulo (Brazil); Coletta, Ricardo D. [Department of Oral Diagnosis, School of Dentistry, University of Campinas (UNICAMP), Av. Limeira, 901 – Bairro Areião, CEP: 13414-903 Piracicaba, São Paulo (Brazil); and others

    2017-01-01

    Complex molecular pathways regulate cancer invasion. This study overviewed proteins and microRNAs (miRNAs) involved in oral tongue squamous cell carcinoma (OTSCC) invasion. The human highly aggressive OTSCC cell line HSC-3 was examined in a 3D organotypic human leiomyoma model. Non-invasive and invasive cells were laser-captured and protein expression was analyzed using mass spectrometry-based proteomics and miRNA expression by microarray. In functional studies the 3D invasion assay was replicated after silencing candidate miRNAs, miR-498 and miR-940, in invasive OTSCC cell lines (HSC-3 and SCC-15). Cell migration, proliferation and viability were also studied in the silenced cells. In HSC-3 cells, 67 proteins and 53 miRNAs showed significant fold-changes between non-invasive vs. invasive cells. Pathway enrichment analyses allocated “Focal adhesion” and “ECM-receptor interaction” as most important for invasion. Significantly, in HSC-3 cells, miR-498 silencing decreased the invasion area and miR-940 silencing reduced invasion area and depth. Viability, proliferation and migration weren’t significantly affected. In SCC-15 cells, down-regulation of miR-498 significantly reduced invasion and migration. This study shows HSC-3 specific miRNA and protein expression in invasion, and suggests that miR-498 and miR-940 affect invasion in vitro, the process being more influenced by mir-940 silencing in aggressive HSC-3 cells than in the less invasive SCC-15.

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

    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. New invasive species of aphids (Hemiptera, Aphididae in Serbia and Montenegro

    Petrović-Obradović Olivera

    2010-01-01

    Full Text Available Three new invasive species of aphids have been found in Serbia: Chaitophorus populifolli Essig, Myzocallis walshii (Monell and Trichosiphonaphis polygonifoliae (Shinji and two have been found in Montenegro: Aphis illinoisensis Shimer and Tinocallis kahawaluokalani (Kirkaldy. A. illinoisensis is a pest of the grapevine, T. polygonifoliae, feeds on a decorative shrub (Lonicera and the other three feed on trees (Populus, Quercus and Lagerostroemia. Three of the species are American aphids and two are of Asian origin. Their morphology, illustrated by original drawings and data on the biology and distribution are given. .

  20. Epigenetic suppression of neprilysin regulates breast cancer invasion.

    Stephen, H M; Khoury, R J; Majmudar, P R; Blaylock, T; Hawkins, K; Salama, M S; Scott, M D; Cosminsky, B; Utreja, N K; Britt, J; Conway, R E

    2016-03-07

    In women, invasive breast cancer is the second most common cancer and the second cause of cancer-related death. Therefore, identifying novel regulators of breast cancer invasion could lead to additional biomarkers and therapeutic targets. Neprilysin, a cell-surface enzyme that cleaves and inactivates a number of substrates including endothelin-1 (ET1), has been implicated in breast cancer, but whether neprilysin promotes or inhibits breast cancer cell progression and metastasis is unclear. Here, we asked whether neprilysin expression predicts and functionally regulates breast cancer cell invasion. RT-PCR and flow cytometry analysis of MDA-MB-231 and MCF-7 breast cancer cell lines revealed decreased neprilysin expression compared with normal epithelial cells. Expression was also suppressed in invasive ductal carcinoma (IDC) compared with normal tissue. In addition, in vtro invasion assays demonstrated that neprilysin overexpression decreased breast cancer cell invasion, whereas neprilysin suppression augmented invasion. Furthermore, inhibiting neprilysin in MCF-7 breast cancer cells increased ET1 levels significantly, whereas overexpressing neprilysin decreased extracellular-signal related kinase (ERK) activation, indicating that neprilysin negatively regulates ET1-induced activation of mitogen-activated protein kinase (MAPK) signaling. To determine whether neprilysin was epigenetically suppressed in breast cancer, we performed bisulfite conversion analysis of breast cancer cells and clinical tumor samples. We found that the neprilysin promoter was hypermethylated in breast cancer; chemical reversal of methylation in MDA-MB-231 cells reactivated neprilysin expression and inhibited cancer cell invasion. Analysis of cancer databases revealed that neprilysin methylation significantly associates with survival in stage I IDC and estrogen receptor-negative breast cancer subtypes. These results demonstrate that neprilysin negatively regulates the ET axis in breast cancer

  1. Decreasing relative risk premium

    Hansen, Frank

    2007-01-01

    such that the corresponding relative risk premium is a decreasing function of present wealth, and we determine the set of associated utility functions. We find a new characterization of risk vulnerability and determine a large set of utility functions, closed under summation and composition, which are both risk vulnerable...

  2. Decreasing asthma morbidity

    1994-12-12

    Dec 12, 1994 ... Apart from the optimal use of drugs, various supplementary methods have been tested to decrease asthma morbidity, usually in patients from reiatively affluent socio-economic backgrounds. A study of additional measures taken in a group of moderate to severe adult asthmatics from very poor socio- ...

  3. Biology of Pink Hibiscus MealybugMaconellicoccushirsutus (Green on Chinese Hibiscus Shrubs in Khuzestan Province

    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

  4. Genomic comparison of invasive and rare non-invasive strains reveals Porphyromonas gingivalis genetic polymorphisms

    Svetlana Dolgilevich

    2011-03-01

    Full Text Available Porphyromonas gingivalis strains are shown to invade human cells in vitro with different invasion efficiencies, varying by up to three orders of magnitude.We tested the hypothesis that invasion-associated interstrain genomic polymorphisms are present in P. gingivalis and that putative invasion-associated genes can contribute to P. gingivalis invasion.Using an invasive (W83 and the only available non-invasive P. gingivalis strain (AJW4 and whole genome microarrays followed by two separate software tools, we carried out comparative genomic hybridization (CGH analysis.We identified 68 annotated and 51 hypothetical open reading frames (ORFs that are polymorphic between these strains. Among these are surface proteins, lipoproteins, capsular polysaccharide biosynthesis enzymes, regulatory and immunoreactive proteins, integrases, and transposases often with abnormal GC content and clustered on the chromosome. Amplification of selected ORFs was used to validate the approach and the selection. Eleven clinical strains were investigated for the presence of selected ORFs. The putative invasion-associated ORFs were present in 10 of the isolates. The invasion ability of three isogenic mutants, carrying deletions in PG0185, PG0186, and PG0982 was tested. The PG0185 (ragA and PG0186 (ragB mutants had 5.1×103-fold and 3.6×103-fold decreased in vitro invasion ability, respectively.The annotation of divergent ORFs suggests deficiency in multiple genes as a basis for P. gingivalis non-invasive phenotype. Access the supplementary material to this article: Supplement, table (see Supplementary files under Reading Tools online.

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

    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

  6. Minimally Invasive Surgery (MIS) Approaches to Thoracolumbar Trauma.

    Kaye, Ian David; Passias, Peter

    2018-03-01

    Minimally invasive surgical (MIS) techniques offer promising improvements in the management of thoracolumbar trauma. Recent advances in MIS techniques and instrumentation for degenerative conditions have heralded a growing interest in employing these techniques for thoracolumbar trauma. Specifically, surgeons have applied these techniques to help manage flexion- and extension-distraction injuries, neurologically intact burst fractures, and cases of damage control. Minimally invasive surgical techniques offer a means to decrease blood loss, shorten operative time, reduce infection risk, and shorten hospital stays. Herein, we review thoracolumbar minimally invasive surgery with an emphasis on thoracolumbar trauma classification, minimally invasive spinal stabilization, surgical indications, patient outcomes, technical considerations, and potential complications.

  7. Responses of the soil fungal communities to the co-invasion of two invasive species with different cover classes.

    Wang, C; Zhou, J; Liu, J; Jiang, K; Xiao, H; Du, D

    2018-01-01

    Soil fungal communities play an important role in the successful invasion of non-native species. It is common for two or more invasive plant species to co-occur in invaded ecosystems. This study aimed to determine the effects of co-invasion of two invasive species (Erigeron annuus and Solidago canadensis) with different cover classes on soil fungal communities using high-throughput sequencing. Invasion of E. annuus and/or S. canadensis had positive effects on the sequence number, operational taxonomic unit (OTU) richness, Shannon diversity, abundance-based cover estimator (ACE index) and Chao1 index of soil fungal communities, but negative effects on the Simpson index. Thus, invasion of E. annuus and/or S. canadensis could increase diversity and richness of soil fungal communities but decrease dominance of some members of these communities, in part to facilitate plant further invasion, because high soil microbial diversity could increase soil functions and plant nutrient acquisition. Some soil fungal species grow well, whereas others tend to extinction after non-native plant invasion with increasing invasion degree and presumably time. The sequence number, OTU richness, Shannon diversity, ACE index and Chao1 index of soil fungal communities were higher under co-invasion of E. annuus and S. canadensis than under independent invasion of either individual species. The co-invasion of the two invasive species had a positive synergistic effect on diversity and abundance of soil fungal communities, partly to build a soil microenvironment to enhance competitiveness of the invaders. The changed diversity and community under co-invasion could modify resource availability and niche differentiation within the soil fungal communities, mediated by differences in leaf litter quality and quantity, which can support different fungal/microbial species in the soil. © 2017 German Society for Plant Sciences and The Royal Botanical Society of the Netherlands.

  8. Environmental Adaptations, Ecological Filtering, and Dispersal Central to Insect Invasions.

    Renault, David; Laparie, Mathieu; McCauley, Shannon J; Bonte, Dries

    2018-01-07

    Insect invasions, the establishment and spread of nonnative insects in new regions, can have extensive economic and environmental consequences. Increased global connectivity accelerates rates of introductions, while climate change may decrease the barriers to invader species' spread. We follow an individual-level insect- and arachnid-centered perspective to assess how the process of invasion is influenced by phenotypic heterogeneity associated with dispersal and stress resistance, and their coupling, across the multiple steps of the invasion process. We also provide an overview and synthesis on the importance of environmental filters during the entire invasion process for the facilitation or inhibition of invasive insect population spread. Finally, we highlight important research gaps and the relevance and applicability of ongoing natural range expansions in the context of climate change to gain essential mechanistic insights into insect invasions.

  9. Comparing soil organic carbon dynamics in perennial grasses and shrubs in a saline-alkaline arid region, northwestern China.

    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.

    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. Herbivore-induced volatiles in the perennial shrub, Vaccinium corymbosum, and their role in inter-branch signaling.

    Rodriguez-Saona, Cesar R; Rodriguez-Saona, Luis E; Frost, Christopher J

    2009-02-01

    Herbivore feeding activates plant defenses at the site of damage as well as systemically. Systemic defenses can be induced internally by signals transported via phloem or xylem, or externally transmitted by volatiles emitted from the damaged tissues. We investigated the role of herbivore-induced plant volatiles (HIPVs) in activating a defense response between branches in blueberry plants. Blueberries are perennial shrubs that grow by initiating adventitious shoots from a basal crown, which produce new lateral branches. This type of growth constrains vascular connections between shoots and branches within plants. While we found that leaves within a branch were highly connected, vascular connectivity was limited between branches within shoots and absent between branches from different shoots. Larval feeding by gypsy moth, exogenous methyl jasmonate, and mechanical damage differentially induced volatile emissions in blueberry plants, and there was a positive correlation between amount of insect damage and volatile emission rates. Herbivore damage did not affect systemic defense induction when we isolated systemic branches from external exposure to HIPVs. Thus, internal signals were not capable of triggering systemic defenses among branches. However, exposure of branches to HIPVs from an adjacent branch decreased larval consumption by 70% compared to those exposed to volatiles from undamaged branches. This reduction in leaf consumption did not result in decreased volatile emissions, indicating that leaves became more responsive to herbivory (or "primed") after being exposed to HIPVs. Chemical profiles of leaves damaged by gypsy moth caterpillars, exposed to HIPVs, or non-damaged controls revealed that HIPV-exposed leaves had greater chemical similarities to damaged leaves than to control leaves. Insect-damaged leaves and young HIPV-exposed leaves had higher amounts of endogenous cis-jasmonic acid compared to undamaged and non-exposed leaves, respectively. Our results

  12. Homeostasis in leaf water potentials on leeward and windward sides of desert shrub crowns: water loss control vs. high hydraulic efficiency.

    Iogna, Patricia A; Bucci, Sandra J; Scholz, Fabián G; Goldstein, Guillermo

    2013-11-01

    Phenotypic plasticity in morphophysiological leaf traits in response to wind was studied in two dominant shrub species of the Patagonian steppe, used as model systems for understanding effects of high wind speed on leaf water relations and hydraulic properties of small woody plants. Morpho-anatomical traits, hydraulic conductance and conductivity and water relations in leaves of wind-exposed and protected crown sides were examined during the summer with nearly continuous high winds. Although exposed sides of the crowns were subjected to higher wind speeds and air saturation deficits than the protected sides, leaves throughout the crown had similar minimum leaf water potential (ΨL). The two species were able to maintain homeostasis in minimum ΨL using different physiological mechanisms. Berberis microphylla avoided a decrease in the minimum ΨL in the exposed side of the crown by reducing water loss by stomatal control, loss of cell turgor and low epidermal conductance. Colliguaja integerrima increased leaf water transport efficiency to maintain transpiration rates without increasing the driving force for water loss in the wind-exposed crown side. Leaf physiological changes within the crown help to prevent the decrease of minimum ΨL and thus contribute to the maintenance of homeostasis, assuring the hydraulic integrity of the plant under unfavorable conditions. The responses of leaf traits that contribute to mechanical resistance (leaf mass per area and thickness) differed from those of large physiological traits by exhibiting low phenotypic plasticity. The results of this study help us to understand the unique properties of shrubs which have different hydraulic architecture compared to trees.

  13. Seedling responses to water pulses in shrubs with contrasting histories of grassland encroachment.

    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.

  14. Bird communities of the arctic shrub tundra of Yamal: habitat specialists and generalists.

    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.

  15. Freezing resistance in Patagonian woody shrubs: the role of cell wall elasticity and stem vessel size.

    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.

  16. Ecophysiological aspects of the interactions between Bromus kopetdaghensis and two nurse shrubs, Astragalus meschedensis and Acantholimon raddeanam in a semiarid rangeland.

    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.

  17. Development of Microsatellite Markers for the Coastal Shrub Scaevola taccada (Goodeniaceae

    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.

  18. Tall shrub expansion facilitated by patterned ground in the northwest Siberian Low Arctic

    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

  19. Allometric equations for estimating aboveground biomass for common shrubs in northeastern California

    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...

  20. [Soil moisture dynamics and water balance of Salix psammophila shrubs in south edge of Mu Us Sandy Land].

    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).

  1. Models of invasion and establishment of African Mustard (Brassica tournefortii)

    Berry, Kristin H.; Gowan, Timothy A.; Miller, David M.; Brooks, Matthew L.

    2015-01-01

    Introduced exotic plants can drive ecosystem change. We studied invasion and establishment ofBrassica tournefortii (African mustard), a noxious weed, in the Chemehuevi Valley, western Sonoran Desert, California. We used long-term data sets of photographs, transects for biomass of annual plants, and densities of African mustard collected at irregular intervals between 1979 and 2009. We suggest that African mustard may have been present in low numbers along the main route of travel, a highway, in the late 1970s; invaded the valley along a major axial valley ephemeral stream channel and the highway; and by 2009, colonized 22 km into the eastern part of the valley. We developed predictive models for invasibility and establishment of African mustard. Both during the initial invasion and after establishment, significant predictor variables of African mustard densities were surficial geology, proximity to the highway and axial valley ephemeral stream channel, and number of small ephemeral stream channels. The axial valley ephemeral stream channel was the most vulnerable of the variables to invasions. Overall, African mustard rapidly colonized and quickly became established in naturally disturbed areas, such as stream channels, where geological surfaces were young and soils were weakly developed. Older geological surfaces (e.g., desert pavements with soils 140,000 to 300,000 years old) were less vulnerable. Microhabitats also influenced densities of African mustard, with densities higher under shrubs than in the interspaces. As African mustard became established, the proportional biomass of native winter annual plants declined. Early control is important because African mustard can colonize and become well established across a valley in 20 yr.

  2. Checklist of invasive alien species in CSIR-NBRI Botanic Garden, Lucknow, India

    Shilpi Singh

    2015-08-01

    Full Text Available The invasive alien species of CSIR-NBRI Botanic Garden are enumerated and their impact on the surrounding ecosystem are discussed. This study deals with the information on habit, nativity and family of plant species occurring in the area of study. A total of 103 invasive alien species under 86 genera and 36 families were recorded. Among these, the eudicotyledons represent 85 species, 69 genera and 32 families; monocotyledons represent 18 species, 17 genera and 4 families. In terms of nativity, species from Tropical America are the most dominant group with 34 species. In addition, based on life forms, herbs are dominant (88 species, followed by shrubs (8 species, climbers (4 species and trees (3 species.

  3. Response of the Fine Root Production, Phenology, and Turnover Rate of Six Shrub Species from a Subtropical Forest to a Soil Moisture Gradient and Shading

    Fu, X.; Dai, X.; Wang, H.

    2015-12-01

    Knowledge of the fine root dynamics of different life forms in forest ecosystems is critical to understanding how the overall belowground carbon cycling is affected by climate change. However, our current knowledge regarding how endogenous or exogenous factors regulate the root dynamics of understory vegetation is limited. We selected a suite of study sites representing different habitats with gradients of soil moisture and solar radiation (shading or no shading). We assessed the fine root production phenology, the total fine root production, and the turnover among six understory shrub species in a subtropical climate, and examined the responses of the fine root dynamics to gradients in the soil moisture and solar radiation. The shrubs included three evergreen species, Loropetalum chinense, Vaccinium bracteatum, and Adinandra millettii, and three deciduous species, Serissa serissoides, Rubus corchorifolius, and Lespedeza davidii. We observed that variations in the annual fine root production and turnover among species were significant in the deciduous group but not in the evergreen group. Notably, V. bracteatum and S. serissoides presented the greatest responses in terms of root phenology to gradients in the soil moisture and shading: high-moisture habitat led to a decrease and shade led to an increase in fine root production during spring. Species with smaller fine roots of the 1st+2nd-order diameter presented more sensitive responses in terms of fine root phenology to a soil moisture gradient. Species with a higher fine root nitrogen-to -carbon ratio exhibited more sensitive responses in terms of fine root annual production to shading. Soil moisture and shading did not change the annual fine root production as much as the turnover rate. The fine root dynamics of some understory shrubs varied significantly with soil moisture and solar radiation status and may be different from tree species. Our results emphasize the need to study the understory fine root dynamics

  4. Alterations in integrin expression modulates invasion of pancreatic cancer cells.

    Walsh, Naomi

    2009-01-01

    BACKGROUND: Factors mediating the invasion of pancreatic cancer cells through the extracellular matrix (ECM) are not fully understood. METHODS: In this study, sub-populations of the human pancreatic cancer cell line, MiaPaCa-2 were established which displayed differences in invasion, adhesion, anoikis, anchorage-independent growth and integrin expression. RESULTS: Clone #3 displayed higher invasion with less adhesion, while Clone #8 was less invasive with increased adhesion to ECM proteins compared to MiaPaCa-2. Clone #8 was more sensitive to anoikis than Clone #3 and MiaPaCa-2, and displayed low colony-forming efficiency in an anchorage-independent growth assay. Integrins beta 1, alpha 5 and alpha 6 were over-expressed in Clone #8. Using small interfering RNA (siRNA), integrin beta1 knockdown in Clone #8 cells increased invasion through matrigel and fibronectin, increased motility, decreased adhesion and anoikis. Integrin alpha 5 and alpha 6 knockdown also resulted in increased motility, invasion through matrigel and decreased adhesion. CONCLUSION: Our results suggest that altered expression of integrins interacting with different extracellular matrixes may play a significant role in suppressing the aggressive invasive phenotype. Analysis of these clonal populations of MiaPaCa-2 provides a model for investigations into the invasive properties of pancreatic carcinoma.

  5. [Models for biomass estimation of four shrub species planted in urban area of Xi'an city, Northwest China].

    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.

  6. Functional groups in North Chilean desert shrub species, based on the water sources used

    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

  7. Intraspecific Variation in Armillaria Species from Shrubs and Trees in Northwestern Spain

    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.

  8. Energy evaluation of forest residues originated from shrub species in Galicia

    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)

  9. Desert Perennial Shrubs Shape the Microbial-Community Miscellany in Laimosphere and Phyllosphere Space.

    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.

  10. Growth responses of low-alpine dwarf-shrub heath species to nitrogen deposition and management

    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

  11. Shrubs tracing sea surface temperature--Calluna vulgaris on the Faroe Islands.

    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.

  12. Regeneration potential and growth of two indigenous shrubs in the desert of Saudi Arabia

    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)

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

    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.

  14. Study of Tree and Shrub Species Diversity in Forestry Plans with Different Forest Management

    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.

  15. Multiple mechanisms enable invasive species to suppress native species.

    Bennett, Alison E; Thomsen, Meredith; Strauss, Sharon Y

    2011-07-01

    Invasive plants represent a significant threat to ecosystem biodiversity. To decrease the impacts of invasive species, a major scientific undertaking of the last few decades has been aimed at understanding the mechanisms that drive invasive plant success. Most studies and theories have focused on a single mechanism for predicting the success of invasive plants and therefore cannot provide insight as to the relative importance of multiple interactions in predicting invasive species' success. We examine four mechanisms that potentially contribute to the success of invasive velvetgrass Holcus lanatus: direct competition, indirect competition mediated by mammalian herbivores, interference competition via allelopathy, and indirect competition mediated by changes in the soil community. Using a combination of field and greenhouse approaches, we focus on the effects of H. lanatus on a common species in California coastal prairies, Erigeron glaucus, where the invasion is most intense. We found that H. lanatus had the strongest effects on E. glaucus via direct competition, but it also influenced the soil community in ways that feed back to negatively influence E. glaucus and other native species after H. lanatus removal. This approach provided evidence for multiple mechanisms contributing to negative effects of invasive species, and it identified when particular strategies were most likely to be important. These mechanisms can be applied to eradication of H. lanatus and conservation of California coastal prairie systems, and they illustrate the utility of an integrated set of experiments for determining the potential mechanisms of invasive species' success.

  16. Exotic invasive plants

    Carolyn Hull Sieg; Barbara G. Phillips; Laura P. Moser

    2003-01-01

    Ecosystems worldwide are threatened by nonnative plant invasions that can cause undesirable, irreversible changes. They can displace native plants and animals, out-cross with native flora, alter nutrient cycling and other ecosystem functions, and even change an ecosystem's flammability (Walker and Smith 1997). After habitat loss, the spread of exotic species is...

  17. Minimally invasive distal pancreatectomy

    Røsok, Bård I.; de Rooij, Thijs; van Hilst, Jony; Diener, Markus K.; Allen, Peter J.; Vollmer, Charles M.; Kooby, David A.; Shrikhande, Shailesh V.; Asbun, Horacio J.; Barkun, Jeffrey; Besselink, Marc G.; Boggi, Ugo; Conlon, Kevin; Han, Ho Seong; Hansen, Paul; Kendrick, Michael L.; Kooby, David; Montagnini, Andre L.; Palanivelu, Chinnasamy; Wakabayashi, Go; Zeh, Herbert J.

    2017-01-01

    The first International conference on Minimally Invasive Pancreas Resection was arranged in conjunction with the annual meeting of the International Hepato-Pancreato-Biliary Association (IHPBA), in Sao Paulo, Brazil on April 19th 2016. The presented evidence and outcomes resulting from the session

  18. Pathogenesis of invasive candidiasis.

    Veerdonk, F.L. van de; Kullberg, B.J.; Netea, M.G.

    2010-01-01

    PURPOSE OF REVIEW: Disseminated candidiasis remains a life-threatening disease in the ICU. The development of invasive disease with Candida albicans is dependent on multiple factors, such as colonization and efficient host defense at the mucosa. In the present review, we describe the host defense

  19. Facilitation by a Spiny Shrub on a Rhizomatous Clonal Herbaceous in Thicketization-Grassland in Northern China: Increased Soil Resources or Shelter from Herbivores

    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.

  20. Plant Invasions Associated with Change in Root-Zone Microbial Community Structure and Diversity.

    Richard R Rodrigues

    Full Text Available The importance of plant-microbe associations for the invasion of plant species have not been often tested under field conditions. The research sought to determine patterns of change in microbial communities associated with the establishment of invasive plants with different taxonomic and phenetic traits. Three independent locations in Virginia, USA were selected. One site was invaded by a grass (Microstegium vimineum, another by a shrub (Rhamnus davurica, and the third by a tree (Ailanthus altissima. The native vegetation from these sites was used as reference. 16S rRNA and ITS regions were sequenced to study root-zone bacterial and fungal communities, respectively, in invaded and non-invaded samples and analyzed using Quantitative Insights Into Microbial Ecology (QIIME. Though root-zone microbial community structure initially differed across locations, plant invasion shifted communities in similar ways. Indicator species analysis revealed that Operational Taxonomic Units (OTUs closely related to Proteobacteria, Acidobacteria, Actinobacteria, and Ascomycota increased in abundance due to plant invasions. The Hyphomonadaceae family in the Rhodobacterales order and ammonia-oxidizing Nitrospirae phylum showed greater relative abundance in the invaded root-zone soils. Hyphomicrobiaceae, another bacterial family within the phyla Proteobacteria increased as a result of plant invasion, but the effect associated most strongly with root-zones of M. vimineum and R. davurica. Functional analysis using Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt showed bacteria responsible for nitrogen cycling in soil increased in relative abundance in association with plant invasion. In agreement with phylogenetic and functional analyses, greater turnover of ammonium and nitrate was associated with plant invasion. Overall, bacterial and fungal communities changed congruently across plant invaders, and support the hypothesis that

  1. Where to Combat Shrub Encroachment in Alpine Timberline Ecosystems: Combining Remotely-Sensed Vegetation Information with Species Habitat Modelling.

    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

  2. Annual increments of juniper dwarf shrubs above the tree line on the central Tibetan Plateau: a useful climatic proxy

    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

  3. Endemic shrubs in temperate arid and semiarid regions of northern China and their potentials for rangeland restoration.

    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

  4. Evaluation of Air Pollution Tolerance Index of Plants and Ornamental Shrubs in Enugu City: Implications for Urban Heat Island Effect

    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.

  5. Annual increments of juniper dwarf shrubs above the tree line on the central Tibetan Plateau: a useful climatic proxy.

    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.

  6. Where to Combat Shrub Encroachment in Alpine Timberline Ecosystems: Combining Remotely-Sensed Vegetation Information with Species Habitat Modelling.

    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

  7. Resource competition in plant invasions: emerging patterns and research needs.

    Gioria, Margherita; Osborne, Bruce A

    2014-01-01

    Invasions by alien plants provide a unique opportunity to examine competitive interactions among plants. While resource competition has long been regarded as a major mechanism responsible for successful invasions, given a well-known capacity for many invaders to become dominant and reduce plant diversity in the invaded communities, few studies have measured resource competition directly or have assessed its importance relative to that of other mechanisms, at different stages of an invasion process. Here, we review evidence comparing the competitive ability of invasive species vs. that of co-occurring native plants, along a range of environmental gradients, showing that many invasive species have a superior competitive ability over native species, although invasive congeners are not necessarily competitively superior over native congeners, nor are alien dominants are better competitors than native dominants. We discuss how the outcomes of competition depend on a number of factors, such as the heterogeneous distribution of resources, the stage of the invasion process, as well as phenotypic plasticity and evolutionary adaptation, which may result in increased or decreased competitive ability in both invasive and native species. Competitive advantages of invasive species over natives are often transient and only important at the early stages of an invasion process. It remains unclear how important resource competition is relative to other mechanisms (competition avoidance via phenological differences, niche differentiation in space associated with phylogenetic distance, recruitment and dispersal limitation, indirect competition, and allelopathy). Finally, we identify the conceptual and methodological issues characterizing competition studies in plant invasions, and we discuss future research needs, including examination of resource competition dynamics and the impact of global environmental change on competitive interactions between invasive and native species.

  8. Resource competition in plant invasions: emerging patterns and research needs

    Gioria, Margherita; Osborne, Bruce A.

    2014-01-01

    Invasions by alien plants provide a unique opportunity to examine competitive interactions among plants. While resource competition has long been regarded as a major mechanism responsible for successful invasions, given a well-known capacity for many invaders to become dominant and reduce plant diversity in the invaded communities, few studies have measured resource competition directly or have assessed its importance relative to that of other mechanisms, at different stages of an invasion process. Here, we review evidence comparing the competitive ability of invasive species vs. that of co-occurring native plants, along a range of environmental gradients, showing that many invasive species have a superior competitive ability over native species, although invasive congeners are not necessarily competitively superior over native congeners, nor are alien dominants are better competitors than native dominants. We discuss how the outcomes of competition depend on a number of factors, such as the heterogeneous distribution of resources, the stage of the invasion process, as well as phenotypic plasticity and evolutionary adaptation, which may result in increased or decreased competitive ability in both invasive and native species. Competitive advantages of invasive species over natives are often transient and only important at the early stages of an invasion process. It remains unclear how important resource competition is relative to other mechanisms (competition avoidance via phenological differences, niche differentiation in space associated with phylogenetic distance, recruitment and dispersal limitation, indirect competition, and allelopathy). Finally, we identify the conceptual and methodological issues characterizing competition studies in plant invasions, and we discuss future research needs, including examination of resource competition dynamics and the impact of global environmental change on competitive interactions between invasive and native species. PMID

  9. Animal ecosystem engineers modulate the diversity-invasibility relationship.

    Nico Eisenhauer

    Full Text Available Invasions of natural communities by non-indigenous species are currently rated as one of the most important global-scale threats to biodiversity. Biodiversity itself is known to reduce invasions and increase stability. Disturbances by ecosystem engineers affect the distribution, establishment, and abundance of species but this has been ignored in studies on diversity-invasibility relationships.We determined natural plant invasion into 46 plots varying in the number of plant species (1, 4, and 16 and plant functional groups (1, 2, 3, and 4 for three years beginning two years after the establishment of the Jena Experiment. We sampled subplots where earthworms were artificially added and others where earthworm abundance was reduced. We also performed a seed-dummy experiment to investigate the role of earthworms as secondary seed dispersers along a plant diversity gradient. Horizontal dispersal and burial of seed dummies were significantly reduced in subplots where earthworms were reduced in abundance. Seed dispersal by earthworms decreased with increasing plant species richness and presence of grasses but increased in presence of small herbs. These results suggest that dense vegetation inhibits the surface activity of earthworms. Further, there was a positive relationship between the number of earthworms and the number and diversity of invasive plants. Hence, earthworms decreased the stability of grassland communities against plant invasion.Invasibility decreased and stability increased with increasing plant diversity and, most remarkably, earthworms modulated the diversity-invasibility relationship. While the impacts of earthworms were unimportant in low diverse (low earthworm densities and high diverse (high floral structural complexity plant communities, earthworms decreased the stability of intermediate diverse plant communities against plant invasion. Overall, the results document that fundamental processes in plant communities like plant seed

  10. Stress in biological invasions: Introduced invasive grey squirrels increase physiological stress in native Eurasian red squirrels.

    Santicchia, Francesca; Dantzer, Ben; van Kesteren, Freya; Palme, Rupert; Martinoli, Adriano; Ferrari, Nicola; Wauters, Lucas Armand

    2018-05-23

    Invasive alien species can cause extinction of native species through processes including predation, interspecific competition for resources or disease-mediated competition. Increases in stress hormones in vertebrates may be associated with these processes and contribute to the decline in survival or reproduction of the native species. Eurasian red squirrels (Sciurus vulgaris) have gone extinct across much of the British Isles and parts of Northern Italy following the introduction of North American invasive grey squirrels (Sciurus carolinensis). We extracted glucocorticoid metabolites from faecal samples to measure whether the presence of the invasive species causes an increase in physiological stress in individuals of the native species. We show that native red squirrels in seven sites where they co-occurred with invasive grey squirrels had glucocorticoid concentrations that were three times higher than those in five sites without the invasive species. Moreover, in a longitudinal study, stress hormones in native red squirrels increased after colonisation by grey squirrels. When we experimentally reduced the abundance of the invasive grey squirrels, the concentration of faecal glucocorticoid metabolites in co-occurring red squirrels decreased significantly between pre- and postremoval periods. Hence, we found that the invasive species acts as a stressor which significantly increases the concentrations of glucocorticoids in the native species. Given that sustained elevations in glucocorticoids could reduce body growth and reproductive rate, our results are consistent with previous studies where the co-occurrence of the invasive grey squirrel was associated with smaller size and lower reproductive output in red squirrels. © 2018 The Authors. Journal of Animal Ecology © 2018 British Ecological Society.

  11. Effects of Mechanical Properties on Tumor Invasion: Insights from a Cellular Model

    Li, YZ

    2014-08-01

    Understanding the regulating mechanism of tumor invasion is of crucial importance for both fundamental cancer research and clinical applications. Previous in vivo experiments have shown that invasive cancer cells dissociate from the primary tumor and invade into the stroma, forming an irregular invasive morphology. Although cell movements involved in tumor invasion are ultimately driven by mechanical forces of cell-cell interactions and tumor-host interactions, how these mechanical properties affect tumor invasion is still poorly understood. In this study, we use a recently developed two-dimensional cellular model to study the effects of mechanical properties on tumor invasion. We study the effects of cell-cell adhesions as well as the degree of degradation and stiffness of extracellular matrix (ECM). Our simulation results show that cell-cell adhesion relationship must be satisfied for tumor invasion. Increased adhesion to ECM and decreased adhesion among tumor cells result in invasive tumor behaviors. When this invasive behavior occurs, ECM plays an important role for both tumor morphology and the shape of invasive cancer cells. Increased stiffness and stronger degree of degradation of ECM promote tumor invasion, generating more aggressive tumor invasive morphologies. It can also generate irregular shape of invasive cancer cells, protruding towards ECM. The capability of our model suggests it a useful tool to study tumor invasion and might be used to propose optimal treatment in clinical applications.

  12. Mapping the Flowering of an Invasive Plant Using Unmanned Aerial Vehicles: Is There Potential for Biocontrol Monitoring?

    Nuno C. de Sá

    2018-03-01

    Full Text Available Invasion by alien species is a worldwide phenomenon with negative consequences at both natural and production areas. Acacia longifolia is an invasive shrub/small tree well known for its negative ecological impacts in several places around the world. The recent introduction of a biocontrol agent (Trichilogaster acaciaelongifoliae, an Australian bud-galling wasp which decreases flowering of A. longifolia, in Portugal, demands the development of a cost-efficient method to monitor its establishment. We tested how unmanned aerial vehicles (UAV can be used to map A. longifolia flowering. Our core assumption is as the population of the biocontrol agent increases, its impacts on the reduction of A. longifolia flowering will be increasingly visible. Additionally, we tested if there is a simple linear correlation between the number of flowers of A. longifolia counted in field and the area covered by flowers in the UAV imagery. UAV imagery was acquired over seven coastal areas including frontal dunes, interior sand dunes and pine forests considering two phenological stages: peak and off-peak flowering season. The number of flowers of A. longifolia was counted, in a minimum of 60 1 m2 quadrats per study area. For each study area, flower presence/absence maps were obtained using supervised Random Forest. The correlation between the number of flowers and the area covered by flowering plants could then be tested. The flowering of A. longifolia was mapped using UAV mounted with RGB and CIR Cannon IXUS/ELPH cameras (Overall Accuracy > 0.96; Cohen’s Kappa > 0.85 varying according to habitat type and flowering season. The correlation between the number of flowers counted and the area covered by flowering was weak (r2 between 0.0134 and 0.156. This is probably explained, at least partially, by the high variability of A. longifolia in what regards flowering morphology and distribution. The very high accuracy of our approach to map A. longifolia flowering proved to

  13. Long-term experimental warming, shading and nutrient addition affect the concentration of phenolic compounds in arctic-alpine deciduous and evergreen dwarf shrubs

    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...

  14. 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

    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...

  15. Physiological, morphological and allocation plasticity of a semi-deciduous shrub

    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

  16. Deepened winter snow increases stem growth and alters stem δ13C and δ15N in evergreen dwarf shrub Cassiope tetragona in high-arctic Svalbard tundra

    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...

  17. Management of invasive species

    Schou, Jesper Sølver; Jensen, Frank

    impact of the establishment of this invasive species is a substantial increase in the number of allergy cases, which we use as a measure of the physical damage. As valuation methods, we use both the cost-of-illness method and the benefit transfer method to quantify the total gross benefits of the two...... policy actions. Based on the idea of an invasion function, we identify the total and average net benefit under both prevention and mitigation. For both policy actions, the total and average net benefits are significantly positive irrespective of the valuation method used; therefore, both prevention...... and mitigation are beneficial policy actions. However, the total and average net benefits under mitigation are larger than the benefits under prevention, implying that the former policy action is more beneficial. Despite this result, we conclude that prevention, not mitigation, shall be used because...

  18. [Invasive nosocomial pulmonary aspergillosis].

    Germaud, P; Haloun, A

    2001-04-01

    Immunodepressed patients, particularly those with neutropenia or bone marrow or organ grafts, are at risk of developing nosocomial invasive pulmonary aspergilosis. The favoring factors, early diagnostic criteria and curative treatment protocols are well known. Prognosis remains however quite severe with a death rate above 50%. Preventive measures are required for the treatment of these high-risk patients and epidemiology surveillance is needed in case of aspergillosis acquired in the hospital.

  19. Fuel buildup and potential fire behavior after stand-replacing fires, logging fire-killed trees and herbicide shrub removal in Sierra Nevada forests

    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.

  20. Plant invasions: Merging the concepts of species invasiveness and community invasibility

    Richardson, D. M.; Pyšek, Petr

    2006-01-01

    Roč. 30, č. 3 (2006), s. 409-431 ISSN 0309-1333 Institutional research plan: CEZ:AV0Z60050516 Keywords : plant invasions * species invasiveness * community invasibility Subject RIV: EF - Botanics Impact factor: 1.278, year: 2006

  1. Vegetation monitoring to detect and predict vegetation change: Connecting historical and future shrub/steppe data in Yellowstone National Park

    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...

  2. The impact of aging on laboratory fire behaviour in masticated shrub fuelbeds of California and Oregon, USA

    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...

  3. Experimental study and large eddy simulation of effect of terrain slope on marginal burning in shrub fuel beds

    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...

  4. Influence of canopy closure and shrub coverage on travel along coarse woody debris by Eastern chipmunks (Tamias striatus)

    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...

  5. Seasonal changes and vertical distribution of root standing biomass of graminoids and shrubs at a Siberian tundra site

    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

  6. Testing aggregation hypotheses among Neotropical trees and shrubs: results from a 50-ha plot over 20 years of sampling.

    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.

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

    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...

  8. Insect Pests of Shade Trees and Shrubs: A Guide for Commercial Nurserymen and Arborists. Publication E-41.

    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.…

  9. Shrub seed banks in mixed conifer forests of northern California and the role of fire in regulating abundance

    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...

  10. Both gas chromatography and an electronic nose reflect chemical polymorphism of juniper shrubs browsed or avoided by sheep.

    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.

  11. Investigation on the sensitivity of trees and shrubs for air pollution

    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.

  12. THE ROLE OF POLYPLOIDY IN ADAPTATION AND SETTLING OF STEPPE SHRUBS IN CENTRAL ASIA

    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.

  13. SNAI2/Slug promotes growth and invasion in human gliomas

    Yang, Hong Wei; Menon, Lata G; Black, Peter M; Carroll, Rona S; Johnson, Mark D

    2010-01-01

    Numerous factors that contribute to malignant glioma invasion have been identified, but the upstream genes coordinating this process are poorly known. To identify genes controlling glioma invasion, we used genome-wide mRNA expression profiles of primary human glioblastomas to develop an expression-based rank ordering of 30 transcription factors that have previously been implicated in the regulation of invasion and metastasis in cancer. Using this approach, we identified the oncogenic transcriptional repressor, SNAI2/Slug, among the upper tenth percentile of invasion-related transcription factors overexpressed in glioblastomas. SNAI2 mRNA expression correlated with histologic grade and invasive phenotype in primary human glioma specimens, and was induced by EGF receptor activation in human glioblastoma cells. Overexpression of SNAI2/Slug increased glioblastoma cell proliferation and invasion in vitro and promoted angiogenesis and glioblastoma growth in vivo. Importantly, knockdown of endogenous SNAI2/Slug in glioblastoma cells decreased invasion and increased survival in a mouse intracranial human glioblastoma transplantation model. This genome-scale approach has thus identified SNAI2/Slug as a regulator of growth and invasion in human gliomas

  14. Dendrochronological potential of the alpine shrub Rhododendron nivale on the south-eastern Tibetan Plateau.

    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.

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

    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.

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

    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

  17. Water use patterns of co-occurring C3 and C4 shrubs in the Gurbantonggut desert in northwestern China.

    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

  18. Sonomammographic characteristics of invasive lobular carcinoma

    El-Damshety O

    2012-07-01

    Full Text Available Osama R Kombar,1,3 Dalia M Fahmy,1 Mary V Brown,3 Omar Farouk,2 Osama El-Damshety21Diagnostic Radiology Department, 2Surgical Oncology Department, Oncology Center, Mansoura University, Mansoura, Egypt; 3Diagnostic Radiology Department, Al-Amiri Hospital, Safat, KuwaitObjective: The objective of our study was to identify characteristic features of invasive lobular carcinoma on mammography and ultrasound examinationsMaterials and methods: This is a retrospective multicenter study of women with biopsy-proven invasive lobular carcinoma. All patients had undergone diagnostic sonomammography. The imaging findings were identified by experienced breast imagers. Final surgical pathology results were used as the reference standard.Results: Thirty-two women ranging in age from 42 to 63 years old (mean age, 53 years, All had biopsy-proven invasive lobular carcinomas. Common features on mammogram included dense mass followed by architectural distortion; three cases showed breast asymmetry and one case was reported as normal. On ultrasound, common features included solid mass with spiculated margins, posterior shadowing, and perpendicular to the skin.Conclusion: Although no specific features could be linked to invasive lobular carcinoma, care should be directed to subtle signs such as architectural distortion and breast asymmetry in order not to miss any lesions. The combination of mammographic and sonographic helps to decrease the relatively high false negative diagnosis of this type of breast cancer.Keywords: mammography, ultrasound, cancer, breast

  19. Nonmotorized recreation and motorized recreation in shrub-steppe habitats affects behavior and reproduction of golden eagles (Aquila chrysaetos).

    Spaul, Robert J; Heath, Julie A

    2016-11-01

    Different forms of outdoor recreation have different spatiotemporal activity patterns that may have interactive or cumulative effects on wildlife through human disturbance, physical habitat change, or both. In western North America, shrub-steppe habitats near urban areas are popular sites for motorized recreation and nonmotorized recreation and can provide important habitat for protected species, including golden eagles. Our objective was to determine whether recreation use (i.e., number of recreationists) or recreation features (e.g., trails or campsites) predicted golden eagle territory occupancy, egg-laying, or the probability a breeding attempt resulted in ≥1 offspring (nest survival). We monitored egg-laying, hatching and fledging success, eagle behavior, and recreation activity within 23 eagle territories near Boise, Idaho, USA. Territories with more off-road vehicle (ORV) use were less likely to be occupied than territories with less ORV use (β = -1.6, 85% CI: -2.8 to -0.8). At occupied territories, early season pedestrian use (β = -1.6, 85% CI: -3.8 to -0.2) and other nonmotorized use (β = -3.6, 85% CI: -10.7 to -0.3) reduced the probability of egg-laying. At territories where eagles laid eggs, short, interval-specific peaks in ORV use were associated with decreased nest survival (β = -0.5, 85% CI: -0.8 to -0.2). Pedestrians, who often arrived near eagle nests via motorized vehicles, were associated with reduced nest attendance (β = -11.9, 85% CI: -19.2 to -4.5), an important predictor of nest survival. Multiple forms of recreation may have cumulative effects on local populations by reducing occupancy at otherwise suitable territories, decreasing breeding attempts, and causing nesting failure. Seasonal no-stopping zones for motorized vehicles may be an alternative to trail closures for managing disturbance. This study demonstrates the importance of considering human disturbance across different parts of the annual cycle, particularly where

  20. Communities of Putative Ericoid Mycorrhizal Fungi Isolated from Alpine Dwarf Shrubs in Japan: Effects of Host Identity and Microhabitat.

    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.

  1. Potential of fodder tree/shrub legumes as a feed resource for dry season supplementation of smallholder ruminant animals

    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)

  2. Fire feedbacks facilitate invasion of pine savannas by Brazilian pepper (Schinus terebinthifolius).

    Stevens, Jens T; Beckage, Brian

    2009-10-01

    * Fire disturbance can mediate the invasion of ecological communities by nonnative species. Nonnative plants that modify existing fire regimes may initiate a positive feedback that can facilitate their continued invasion. Fire-sensitive plants may successfully invade pyrogenic landscapes if they can inhibit fire in the landscape. * Here, we investigated whether the invasive shrub Brazilian pepper (Schinus terebinthifolius) can initiate a fire-suppression feedback in a fire-dependent pine savanna ecosystem in the southeastern USA. * We found that prescribed burns caused significant (30-45%) mortality of Brazilian pepper at low densities and that savannas with more frequent fires contained less Brazilian pepper. However, high densities of Brazilian pepper reduced fire temperature by up to 200 degrees C, and experienced as much as 80% lower mortality. * A cellular automaton model was used to demonstrate that frequent fire may control low-density populations, but that Brazilian pepper may reach a sufficient density during fire-free periods to initiate a positive feedback that reduces the frequency of fire and converts the savanna to an invasive-dominated forest.

  3. Invasive plant species alters consumer behavior by providing refuge from predation.

    Dutra, Humberto P; Barnett, Kirk; Reinhardt, Jason R; Marquis, Robert J; Orrock, John L

    2011-07-01

    Understanding the effects of invasive plants on native consumers is important because consumer-mediated indirect effects have the potential to alter the dynamics of coexistence in native communities. Invasive plants may promote changes in consumer pressure due to changes in protective cover (i.e., the architectural complexity of the invaded habitat) and in food availability (i.e., subsidies of fruits and seeds). No experimental studies have evaluated the relative interplay of these two effects. In a factorial experiment, we manipulated cover and food provided by the invasive shrub Amur honeysuckle (Lonicera maackii) to evaluate whether this plant alters the foraging activity of native mammals. Using tracking plates to quantify mammalian foraging activity, we found that removal of honeysuckle cover, rather than changes in the fruit resources it provides, reduced the activity of important seed consumers, mice in the genus Peromyscus. Two mesopredators, Procyon lotor and Didelphis virginiana, were also affected. Moreover, we found rodents used L. maackii for cover only on cloudless nights, indicating that the effect of honeysuckle was weather-dependent. Our work provides experimental evidence that this invasive plant species changes habitat characteristics, and in so doing alters the behavior of small- and medium-sized mammals. Changes in seed predator behavior may lead to cascading effects on the seeds that mice consume.

  4. When landscaping goes bad: The incipient invasion of Mahonia bealei in the southeastern United States

    Allen, Craig R.; Garmestani, A.S.; LaBram, J.A.; Peck, A.E.; Prevost, L.B.

    2006-01-01

    Woodlots are forest islands embedded within an urban matrix, and often represent the only natural areas remaining in suburban areas. Woodlots represent critical conservation areas for native plants, and are important habitat for wildlife in urban areas. Invasion by non-indigenous (NIS) plants can alter ecological structure and function, and may be especially severe in remnant forests where NIS propagule pressure is high. Woody shrubs in the Family Berberidaceae have been well documented as invaders of the forest-urban matrix in North America. Mahonia bealei (Berberidaceae) is a clonal shrub native to China, and is a popular ornamental in the Southeastern United States. Mahoni bealei is listed as "present" on some local and state floras, but almost nothing is known regarding its invasion potential in the United States. We sampled 15 woodlots in Clemson, South Carolina, to assess the invasion of M. bealei and other woody non-indigenous species (NIS). M. bealei invaded 87% of the woodlots surveyed and species richness of NIS on these woodlots varied from 5 to 14. Stepwise-multiple regression indicated that less canopy cover and older M. bealei predicted greater abundance of M. bealei , and that not all subdivisions were equally invaded (P < 0.0001; r 2 = 0.88). The impact of M. bealei on native flora and fauna may be considerable, and it is likely to continue to spread in the Southeastern United States. M. bealei should be recognized as an aggressive invader in the Southeastern United States, with the potential for negative impacts on native flora and fauna. ?? Springer 2006.

  5. Sparrow nest survival in relation to prescribed fire and woody plant invasion in a northern mixed-grass prairie

    Murphy, Robert K.; Shaffer, Terry L.; Grant, Todd A.; Derrig, James L.; Rubin, Cory S.; Kerns, Courtney K.

    2017-01-01

    Prescribed fire is used to reverse invasion by woody vegetation on grasslands, but managers often are uncertain whether influences of shrub and tree reduction outweigh potential effects of fire on nest survival of grassland birds. During the 2001–2003 breeding seasons, we examined relationships of prescribed fire and woody vegetation to nest survival of clay-colored sparrow (Spizella pallida) and Savannah sparrow (Passerculus sandwichensis) in mixed-grass prairie at Des Lacs National Wildlife Refuge in northwestern North Dakota, USA. We assessed relationships of nest survival to 1) recent fire history, in terms of number of breeding seasons (2, 3, or 4–5) since the last prescribed fire, and 2) prevalence of trees and tall (>1.5 m) shrubs in the landscape and of low (≤1.5 m) shrubs within 5 m of nests. Nest survival of both species exhibited distinct patterns related to age of the nest and day of year, but bore no relationship to fire history. Survival of clay-colored sparrow nests declined as the amount of trees and tall shrubs within 100 m increased, but we found no relationship to suggest nest parasitism by brown-headed cowbirds (Molothrus ater) as an underlying mechanism. We found little evidence linking nest survival of Savannah sparrow to woody vegetation. Our results suggest that fire can be used to restore northern mixed-grass prairies without adversely affecting nest survival of ≥2 widespread passerine species. Survival of nests of clay-colored sparrow may increase when tall woody cover is reduced by fire. Our data lend support to the use of fire for reducing scattered patches of tall woody cover to enhance survival of nests of ≥1 grassland bird species in northern mixed-grass prairies, but further study is needed that incorporates experimental approaches and assessments of shorter term effects of fire on survival of nests of grassland passerines.

  6. Radiative transfer in shrub savanna sites in Niger: preliminary results from HAPEX-Sahel. 2. Photosynthetically active radiation interception of the woody layer

    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)

  7. [Dynamics and modeling of water content of ten shrub species in their growth period in Maoershan Mountain region of Northeast China].

    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%.

  8. Invasive mammals and habitat modification interact to generate unforeseen outcomes for indigenous fauna.

    Norbury, Grant; Byrom, Andrea; Pech, Roger; Smith, James; Clarke, Dean; Anderson, Dean; Forrester, Guy

    2013-10-01

    Biotic invasions and habitat modification are two drivers of global change predicted to have detrimental impacts on the persistence of indigenous biota worldwide. Few studies have investigated how they operate synergistically to alter trophic interactions among indigenous and nonindigenous species in invaded ecosystems. We experimentally manipulated a suite of interacting invasive mammals, including top predators (cat Felis catus, ferret Mustela furo, stoat M. erminea), herbivores (rabbit Oryctolagus cuniculus, hare Lepus europaeus), and an insectivore (hedgehog Erinaceus europaeus occidentalis), and measured their effects on indigenous lizards and invertebrates and on an invasive mesopredator (house mouse Mus musculus). The work was carried out in a grassland/shrubland ecosystem that had been subjected to two types of habitat modification (widespread introduction of high-seed-producing pasture species, and areas of land use intensification by fertilization and livestock grazing). We also quantified food productivity for indigenous and invasive fauna by measuring pasture biomass, as well as seed and fruit production by grasses and shrubs. Indigenous fauna did not always increase following top-predator suppression: lizards increased on one of two sites; invertebrates did not increase on either site. Mesopredator release of mice was evident at the site where lizards did not increase, suggesting negative effects of mice on lizard populations. High mouse abundance occurred only on the predator-suppression site with regular production of pasture seed, indicating that this food resource was the main driver of mouse populations. Removal of herbivores increased pasture and seed production, which further enhanced ecological release of mice, particularly where pasture swards were overtopped by shrubs. An effect of landscape supplementation was also evident where nearby fertilized pastures boosted rabbit numbers and the associated top predators. Other studies have shown that

  9. Quantifying the invasiveness of species

    Robert Colautti

    2014-04-01

    Full Text Available The success of invasive species has been explained by two contrasting but non-exclusive views: (i intrinsic factors make some species inherently good invaders; (ii species become invasive as a result of extrinsic ecological and genetic influences such as release from natural enemies, hybridization or other novel ecological and evolutionary interactions. These viewpoints are rarely distinguished but hinge on distinct mechanisms leading to different management scenarios. To improve tests of these hypotheses of invasion success we introduce a simple mathematical framework to quantify the invasiveness of species along two axes: (i interspecific differences in performance among native and introduced species within a region, and (ii intraspecific differences between populations of a species in its native and introduced ranges. Applying these equations to a sample dataset of occurrences of 1,416 plant species across Europe, Argentina, and South Africa, we found that many species are common in their native range but become rare following introduction; only a few introduced species become more common. Biogeographical factors limiting spread (e.g. biotic resistance, time of invasion therefore appear more common than those promoting invasion (e.g. enemy release. Invasiveness, as measured by occurrence data, is better explained by inter-specific variation in invasion potential than biogeographical changes in performance. We discuss how applying these comparisons to more detailed performance data would improve hypothesis testing in invasion biology and potentially lead to more efficient management strategies.

  10. Intraspecific variation in stomatal traits, leaf traits and physiology reflects adaptation along aridity gradients in a South African shrub.

    Carlson, Jane E; Adams, Christopher A; Holsinger, Kent E

    2016-01-01

    Trait-environment relationships are commonly interpreted as evidence for local adaptation in plants. However, even when selection analyses support this interpretation, the mechanisms underlying differential benefits are often unknown. This study addresses this gap in knowledge using the broadly distributed South African shrub Protea repens. Specifically, the study examines whether broad-scale patterns of trait variation are consistent with spatial differences in selection and ecophysiology in the wild. In a common garden study of plants sourced from 19 populations, associations were measured between five morphological traits and three axes describing source climates. Trait-trait and trait-environment associations were analysed in a multi-response model. Within two focal populations in the wild, selection and path analyses were used to test associations between traits, fecundity and physiological performance. Across 19 populations in a common garden, stomatal density increased with the source population's mean annual temperature and decreased with its average amount of rainfall in midsummer. Concordantly, selection analysis in two natural populations revealed positive selection on stomatal density at the hotter, drier site, while failing to detect selection at the cooler, moister site. Dry-site plants with high stomatal density also had higher stomatal conductances, cooler leaf temperatures and higher light-saturated photosynthetic rates than those with low stomatal density, but no such relationships were present among wet-site plants. Leaf area, stomatal pore index and specific leaf area in the garden also co-varied with climate, but within-population differences were not associated with fitness in either wild population. The parallel patterns of broad-scale variation, differences in selection and differences in trait-ecophysiology relationships suggest a mechanism for adaptive differentiation in stomatal density. Densely packed stomata may improve performance by

  11. A comparison of non-invasive versus invasive methods of ...

    Puneet Khanna

    for Hb estimation from the laboratory [total haemoglobin mass (tHb)] and arterial blood gas (ABG) machine (aHb), using ... A comparison of non-invasive versus invasive methods of haemoglobin estimation in patients undergoing intracranial surgery. 161 .... making decisions for blood transfusions based on these results.

  12. Testing the discrimination and detection limits of WorldView-2 imagery on a challenging invasive plant target

    Robinson, T. P.; Wardell-Johnson, G. W.; Pracilio, G.; Brown, C.; Corner, R.; van Klinken, R. D.

    2016-02-01

    Invasive plants pose significant threats to biodiversity and ecosystem function globally, leading to costly monitoring and management effort. While remote sensing promises cost-effective, robust and repeatable monitoring tools to support intervention, it has been largely restricted to airborne platforms that have higher spatial and spectral resolutions, but which lack the coverage and versatility of satellite-based platforms. This study tests the ability of the WorldView-2 (WV2) eight-band satellite sensor for detecting the invasive shrub mesquite (Prosopis spp.) in the north-west Pilbara region of Australia. Detectability was challenged by the target taxa being largely defoliated by a leaf-tying biological control agent (Gelechiidae: Evippe sp. #1) and the presence of other shrubs and trees. Variable importance in the projection (VIP) scores identified bands offering greatest capacity for discrimination were those covering the near-infrared, red, and red-edge wavelengths. Wavelengths between 400 nm and 630 nm (coastal blue, blue, green, yellow) were not useful for species level discrimination in this case. Classification accuracy was tested on three band sets (simulated standard multispectral, all bands, and bands with VIP scores ≥1). Overall accuracies were comparable amongst all band-sets (Kappa = 0.71-0.77). However, mesquite omission rates were unacceptably high (21.3%) when using all eight bands relative to the simulated standard multispectral band-set (9.5%) and the band-set informed by VIP scores (11.9%). An incremental cover evaluation on the latter identified most omissions to be for objects high mapping accuracy of objects >16 m2 allows application for mapping mesquite shrubs and coalesced stands, the former not previously possible, even with 3 m resolution hyperspectral imagery. WV2 imagery offers excellent portability potential for detecting other species where spectral/spatial resolution or coverage has been an impediment. New generation satellite

  13. Synergistic impacts by an invasive amphipod and an invasive fish explain native gammarid extinction.

    Beggel, S; Brandner, J; Cerwenka, A F; Geist, J

    2016-07-14

    Worldwide freshwater ecosystems are increasingly affected by invasive alien species. In particular, Ponto-Caspian gobiid fishes and amphipods are suspected to have pronounced effects on aquatic food webs. However, there is a lack of systematic studies mechanistically testing the potential synergistic effects of invasive species on native fauna. In this study we investigated the interrelations between the invasive amphipod Dikerogammarus villosus and the invasive fish species Neogobius melanostomus in their effects on the native amphipod Gammarus pulex. We hypothesized selective predation by the fish as a driver for displacement of native species resulting in potential extinction of G. pulex. The survival of G. pulex in the presence of N. melanostomus in relation to the presence of D. villosus and availability of shelter was analyzed in the context of behavioural differences between the amphipod species. Gammarus pulex had a significantly higher susceptibility to predation by N. melanostomus compared to D. villosus in all experiments, suggesting preferential predation by this fish on native gammarids. Furthermore, the presence of D. villosus significantly increased the vulnerability of G. pulex to fish predation. Habitat structure was an important factor for swimming activity of amphipods and their mortality, resulting in a threefold decrease in amphipods consumed with shelter habitat structures provided. Behavioral differences in swimming activity were additionally responsible for higher predation rates on G. pulex. Intraguild predation could be neglected within short experimental durations. The results of this study provide evidence for synergistic effects of the two invasive Ponto-Caspian species on the native amphipod as an underlying process of species displacements during invasion processes. Prey behaviour and monotonous habitat structures additionally contribute to the decline of the native gammarid fauna in the upper Danube River and elsewhere.

  14. Klebsiella pneumoniae Invasive Syndrome

    Vasco Evangelista

    2018-01-01

    Full Text Available Klebsiella pneumoniae invasive syndrome (KPIS is a rare clinical condition characterized by primary liver abscess associated with metastatic infection. Most case reports are from Southeast Asia, with only one case described in Portugal. The Authors present the case of a 44-year-old man with a history of fever, dry cough and cervicalgia. A thoracic computed tomography (CT scan showed multiple pulmonary and hepatic nodules, suggestive of metastatic malignancy. Both blood cultures and bronchoalveolar lavage were positive for Klebsiella pneumoniae. Imaging studies were repeated during his hospital stay, showing a reduction in both number and volume of identified lesions, thus revealing their infectious nature. This case illustrates how much this entity can mimic other illnesses.

  15. Dietary Flexibility Aids Asian Earthworm Invasion in North American Forests

    On a local scale, invasiveness of introduced species and invasibility of habitats together determine invasion success. A key issue in invasion ecology has been how to quantify the contribution of species invasiveness and habitat invasibility separately. Conventional approaches, s...

  16. Comparisons of invasive plants in southern Africa originating from southern temperate, northern temperate and tropical regions

    L. Henderson

    2006-08-01

    Full Text Available A subset of invasive alien plant species in southern Africa was analysed in terms of their history of introduction, rate of spread, countries/region of origin, taxonomy, growth forms, cultivated uses, weed status and current distribution in southern Africa, and comparisons made of those originating from south of the tropic of Capricorn, north of the tropic of Cancer and from the tropics. The subset of 233 species, belonging to 58 families, includes all important declared species and some potentially important species. Almost as many species originate from temperate regions (112 as from the tropics (121. Most southern temperate species came from Australia (28/36, most tropical species from tropical America (92/121 and most northern temperate species from Europe (including the Mediterranean and Asia (58/76. Transformers account for 33% of  all species. More transformers are of tropical origin (36 than of northern temperate (24 and southern temperate origin (18. However. 50% of southern temperate species are transformers, compared to 32% of northern temperate and 29% of tropical species. Southern temperate transformer species are mainly woody trees and shrubs that were established on a grand scale as silvicultural crops, barriers (hedges, windbreaks and screens and cover/binders. Most aquatics, herbs, climbers and succulent shrubs an. trom the tropics. Ornamentals are the single largest category of plants from all three regions, the tropics having contributed twice as many species as temperate regions.

  17. Report and recommendations of the task force on tree and shrub planting on active oil sands tailings dams

    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.

  18. Pathogenicity of the bioherbicide fungus chondrostereum purpureum to some trees and shrubs of southern Vancouver Island. FRDA report No. 246

    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.

  19. Microbial ecology of biological invasions

    Van der Putten, W.H.; Klironomos, J.N.; Wardle, D.A.

    2007-01-01

    Invasive microbes, plants and animals are a major threat to the composition and functioning of ecosystems; however, the mechanistic basis of why exotic species can be so abundant and disruptive is not well understood. Most studies have focused on invasive plants and animals, although few have

  20. MSX2 Induces Trophoblast Invasion in Human Placenta.

    Hao Liang

    Full Text Available Normal implantation depends on appropriate trophoblast growth and invasion. Inadequate trophoblast invasion results in pregnancy-related disorders, such as early miscarriage and pre-eclampsia, which are dangerous to both the mother and fetus. Msh Homeobox 2 (MSX2, a member of the MSX family of homeobox proteins, plays a significant role in the proliferation and differentiation of various cells and tissues, including ectodermal organs, teeth, and chondrocytes. Recently, MSX2 was found to play important roles in the invasion of cancer cells into adjacent tissues via the epithelial-mesenchymal transition (EMT. However, the role of MSX2 in trophoblastic invasion during placental development has yet to be explored. In the present study, we detected MSX2 expression in cytotrophoblast, syncytiotrophoblast, and extravillous cytotrophoblast cells of first or third trimester human placentas via immunohistochemistry analysis. Furthermore, we found that the in vitro invasive ability of HTR8/SVneo cells was enhanced by exogenous overexpression of MSX2, and that this effect was accompanied by increased protein expression of matrix metalloproteinase-2 (MMP-2, vimentin, and β-catenin. Conversely, treatment of HTR8/SVneo cells with MSX2-specific siRNAs resulted in decreased protein expression of MMP-2, vimentin, and β-catenin, and reduced invasion levels in a Matrigel invasion test. Notably, however, treatment with the MSX2 overexpression plasmid and the MSX2 siRNAs had no effect on the mRNA expression levels of β-catenin. Meanwhile, overexpression of MSX2 and treatment with the MSX2-specific siRNA resulted in decreased and increased E-cadherin expression, respectively, in JEG-3 cells. Lastly, the protein expression levels of MSX2 were significantly lower in human pre-eclamptic placental villi than in the matched control placentas. Collectively, our results suggest that MSX2 may induce human trophoblast cell invasion, and dysregulation of MSX2 expression may