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Sample records for banderita bouteloua curtipendula

  1. Efecto de la composición de una mezcla de hidrocarburos en la respuesta fenotípica y la acumulación de azúcares por Bouteloua curtipendula Michx. Torr. en cultivos in vitro

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    Marianela Orozco-Soto

    2015-07-01

    Full Text Available Bouteloua curtipendulaMichx Torr. es un pasto originario de México con gran capacidad de adaptación a condiciones climáticas adversas, ha sido reportado con potencial para fitorremediar suelos contaminados con hidrocarburos (HC. En el presente estudio, se hicieron cultivos in vitro de B. curtipendula con una concentración de 1 500 mg HC·L-1 de medio de cultivo, y distintas mezclas de fenantreno (PHE, pireno (PYR y hexadecano (HXD. En todos los casos, tanto la longitud de brotes y raíces, así como la producción de biomasa disminuyeron signifi cativamente con respecto al control. El 100% de las semillas germinaron en el medio sin HC, mientras que en las mezclas con mayor proporción de HDX (1 100 mg HC·L-1 germinó alrededor del 75% de las semillas. La mayor acumulación de azúcares totales en el medio de cultivo, después de 35 días (40 mg de azúcares totales acumulados en el medio·mg-1 de raíz seca, equivalentes a 200 mg de azúcares totales·tubo se registró en la mezcla con menor concentración de HXD; por otro lado, en los cultivos donde no se adicionó HC se observó un consumo en los azúcares totales (225.7 ± 3 mg azúcares totales·tubo. Los resultados obtenidos sugieren que una mayor proporción de HXD en las mezclas incrementa el efecto tóxico a las plantas. Aunque hay estudios en donde se han cuantificado los azúcares exudados por las raíces, en nuestro conocimiento éste es el primer reporte de cultivos in vitro en donde se observa la producción de azúcares como respuesta de un pasto al estrés por HC.

  2. MORFOLOGÍA Y MORFOMETRÍA DE DOS ESPECIES DE BANDERITAS (ORCHIDACEAE: MASDEVALLIA EN COLOMBIA Morphology and Morphometry of Two Banderitas Species (Orchidaceae: Masdevallia in Colombia

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    MÓNICA ADRIANA CUERVO MARTÍNEZ

    2012-12-01

    Full Text Available Masdevallia coccinea y Masdevallia ignea (Orchidaceae conocidas como "banderitas", son orquídeas ornamentales muy apreciadas por cultivadores aficionados y coleccionistas. En Colombia, la presión de colecta sobre estas especies ha sido enorme y pocas poblaciones naturales sobreviven en los departamentos de Boyacá (Arcabuco, Páramo de Berlín, Duitama y Santander (entre Málaga y Bucaramanga, estas poblaciones son reducidas y de difícil acceso; razón por la cual se encuentran en el apéndice II de CITES. Poco se sabe sobre su biología reproductiva, sistema reproductivo y polinización y parte de lo que consta en la literatura es incompleto. En este marco el objetivo general del trabajo fue estudiar la morfología y morfometría floral de M. coccinea y M. ignea en condiciones de semicultivo al aire libre en la finca Villa Rosa ubicada en el municipio de Guasca, Cundinamarca, para lo cual se realizó fotografía digital, pruebas histoquímicas, morfometría y Microscopía Electrónica de Barrido. Los resultados principales de la morfometría mostraron que los sépalos dorsal y lateral fueron más largos en M. coccinea (X= 53,0 mm σ = 7,4 mm y X = 44,4 mm y σ = 8,3 mm en comparación a M. ignea (X = 34 mm σ = 7,7 mm y X = 31,5 mm y σ = 6,1 mm, pero las coloraciones de las partes florales de esta última fueron más intensas y su labelo fue más largo (X = 7,1 mm y σ = 0,6 mm. En las dos especies el labelo estuvo articulado a la columna y no se encontró presencia de glándulas con estructuras secretoras como nectarios ni osmóforos.Masdevallia coccinea and the Masdevallia ignea "banderitas" are ornamental orchids which are very prized by amateur farmers and collectors. In Colombia, the harvest pressure on these species has been enormous and few natural populations survive in the departments of Boyacá (Arcabuco of Berlin Páramo, Duitama and Santander (between Málaga and Bucaramanga, in which these populations are reduced and of

  3. Morphology and morphometry of two banderitas species (Orchidaceae: masdevallia) in Colombia

    International Nuclear Information System (INIS)

    Masdevallia coccinea and the Masdevallia ignea (Banderitas) are ornamental orchids which are very prized by amateur farmers and collectors. In Colombia, the harvest pressure on these species has been enormous and few natural populations survive in the departments of Boyaca (Arcabuco of Berlin Paramo, Duitama) and Santander (between Malaga and Bucaramanga), in which these populations are reduced and of difficult access. For this reason these species are in the II appendix of cites. However, little is known on their reproductive biology, floral biology and pollination and the literature about this is incomplete. Under this framework, the goal of the project was to study the morphology and morphometry of m. coccinea and m. ignea (pleurothallidinae) under semicultivation conditions in the Villa Rosa Farm located in the municipality of Guasca, Cundinamarca (Colombia). The floral morphology was analyzed by digital photography, morphometry and scanning electron microscope. The main results were differences in color and length of dorsal and lateral sepals between m. coccinea (x = 53.0 mm Sigma = 7.4 mm and x = 44.4 mm and Sigma = 8.3 mm) and m. ignea (x = 34 mm Sigma = 7.7 mm and x = 31.5 mm and Sigma = 6.1 mm). These parts were longest in m. coccinea in contrast to m. ignea. However the lip was longest in m. ignea (x = 7.1 mm y Sigma = 0.6 mm). On the other hand both species had lip articulated to the column but without rewards as nectar and osmophores.

  4. Soil sterilization alters interactions between the native grass Bouteloua gracilis and invasive Bromus tectorum

    Science.gov (United States)

    Aims: The invasive grass Bromus tectorum negatively impacts grassland communities throughout the western U.S. We asked whether soil biota growing in association with a native grass (Bouteloua gracilis) increase growth and competitive ability of Bromus, and whether responses vary between soils collec...

  5. Rediscovery of Bouteloua vaneedenii (Gramineae: Chloridoideae: endemic species from the West Indies Redescubrimiento de Bouteloua vaneedenii (Gramineae: Chloridoideae: especie endémica de las Indias Occidentales

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    María Elena Siqueiros-Delgado

    2011-12-01

    Full Text Available Bouteloua vaneedenii is an endemic and extremely rare grass of the West Indies. Very few collections are known, and the most recent collection is from 1922. With the aim of finding the species, a team of Mexican and Cuban agrostologists conducted a field trip and found B. vaneedenii in the same locality where it was collected in 1922 on dry limestone rocks. Although it was stated that B. vaneedenii probably was extinct from Cuba, vigorous populations remain in at least 2 localities in Pastelillo. Further exploration may lead to the discovery of additional populations and the reevaluation of its current conservation status.Bouteloua vaneedenii es un pasto extremadamente raro, nativo de Las Indias Occidentales y del que muy pocas recolectas se conocen hasta ahora, la última se realizó en 1922. Con el objetivo de encontrar la especie, un equipo de agrostólogos mexicanos y cubanos condujeron un viaje de campo en busca de B. vaneedenii , la cual fue hallada en la misma localidad donde se recolectó sobre rocas calizas en 1922, a pesar de que se había señalado como probable extinta para Cuba. Se ubicaron 2 poblaciones en buenas condiciones; no obstante, es necesaria una exploración más intensa confirmar su estado actual de conservación.

  6. Rooting depths of plants on low-level waste disposal sites

    International Nuclear Information System (INIS)

    In 1981-1982 an extensive bibliographic study was done to reference rooting depths of native plants in the United States. The data base presently contains 1034 different rooting citations with approximately 12,000 data elements. For this report, data were analyzed for rooting depths related to species found on low-level waste (LLW) sites at Los Alamos National Laboratory. Average rooting depth and rooting frequencies were determined and related to present LLW maintenance. The data base was searched for information on rooting depths of 53 species found on LLW sites at Los Alamos National Laboratory. The study indicates 12 out of 13 grasses found on LLW sites root below 91 cm. June grass [Koeleria cristata (L.) Pers.] (76 cm) was the shallowest rooting grass and side-oats grama [Bouteloua curtipendula (Michx.) Torr.] was the deepest rooting grass (396 cm). Forbs were more variable in rooting depths. Indian paintbrush (Castelleja spp.) (30 cm) was the shallowest rooting forb and alfalfa (Medicago sativa L.) was the deepest (>3900 cm). Trees and shrubs commonly rooted below 457 cm. The shallowest rooting tree was elm (Ulmus pumila L.) (127 cm) and the deepest was one-seed juniper [Juniperus monosperma (Engelm) Sarg.] (>6000 cm). Apache plume [Fallugia paradoxa (D. Don) Endl.] rooted to 140 cm, whereas fourwing saltbush [Atriplex canecens (Pursh) Nutt.] rooted to 762 cm

  7. Characteristics of a ringtail (Bassariscus astutus) population in Trans Pecos, Texas

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    Ackerson, B.K.; Harveson, L.A.

    2006-01-01

    Despite the common occurrence of ringtails (Bassariscus astutus) few studies have been conducted to assess population characteristics. The objectives of this study were to determine (1) habitat selection, (2) home range, (3) denning characteristics, and (4) food habits of ringtails in the Trans Pecos region of west Texas. Seventeen ringtails were captured between November 1999 and January 2001 using Havahart live box traps. Second- and third-order habitat selection was determined for a ringtail population using range sites, slope, elevation, and vegetation communities. Diets were determined from volumetric scat analysis. The mean summer and winter range sizes (100% Minimum Convex Polygon [MCP]) for ringtails (n = 5) were 0.28 ?? 0.163 km2 and 0.63 ?? 0.219 km2, respectively. Overlap between ringtail ranges averaged 33.3%. Ringtails preferred catclaw (Mimosa biuncifera), persimmon (Diospyros texana), oak (Quercus sp.) bottom and catclaw/goldeneye (Viguiera stenoloba), sideoats (Bouteloua curtipendula) slope communities. Rock dens were used exclusively by ringtails, with 80.6% of dens found on slopes between 30-60%. Plant (seeds and miscellaneous vegetation) and animal material were found in 74.6 and 86.6% of scats, respectively. Findings suggest that ringtails in Trans Pecos, Texas, are an important component of the ecosystem and that management practices should conserve canyon habitats and adjacent slopes for ringtails.

  8. Soil Respiration Responses to Variation in Temperature Treatment and Vegetation Type

    Science.gov (United States)

    Liu, S.; Pavao-zuckerman, M.

    2013-12-01

    Complex linkages exist between terrestrial vegetation, soil moisture, soil organic matter (SOM), local climate, and soil microorganisms. Thus, large-scale changes in vegetation, such as the woody plant encroachment observed in many historically semiarid and arid grasslands worldwide, could potentially alter the flux of carbon from soil reserves to the atmosphere. Mathematical models that attempt to project the long-term impact of vegetative shifts on soil fluxes largely rely on assumptions such as first-order donor control rather than incorporate the biological aspects of soil respiration such as microbial activity. To examine the impact of vegetation type on soil physicochemical properties and soil microbial respiration and provide experimental data to refine existing predictive models, we compared soil (ground basalt from northern Arizona) in mesocosms established with no vegetation, velvet mesquites (Prosopis velutina; woody shrub), or sideoats gramas (Bouteloua curtipendula; grass) for 2 years, The temperature sensitivity of soil respiration was examined by incubating soil (0-10 and 10-30 cm depth fractions) from each vegetation treatment at 10, 20, 30, and 40 °C for 24 hours. Vegetated soils contained more SOM (~0.1% for mesquite and grass mesocosms) than non-vegetated soils (~0.02%). Respiration rates were generally highest from grass-established soils, intermediate from mesquite-established soils, and lowest from non-vegetated soils. Respiration rates of samples incubated without the addition of substrate peaked at approximately 30 °C, whereas respiration rates of samples incubated with dextrose were highest at 40 °C. Further, the respiration assays suggest that while respiration rates are overall higher in grass-established soils, mesquite-established soils are more temperature sensitive which may have significant implications in the context of global warming and current fire management practices.

  9. Effect of woody and herbaceous plants on chemical weathering of basalt material

    Science.gov (United States)

    Mark, N.; Dontsova, K.; Barron-Gafford, G. A.

    2011-12-01

    Worldwide, semi-arid landscapes are transitioning from shallow-rooted grasslands to mixed vegetation savannas composed of deeper-rooted shrubs. These contrasting growth forms differentially drive below-ground processes because they occupy different soil horizons, are differentially stressed by periods of drought, and unequally stimulate soil weathering. Our study aims to determine the effect of woody and herbaceous plants on weathering of granular basalt serving as a model for soil. We established pots with velvet mesquite (Prosopis veluntina), sideoats grama (Bouteloua curtipendula), and bare-soil pots within two temperature treatments in University of Arizona Biosphere 2. The Desert biome served as the ambient temperature treatment, while the Savanna biome was maintained 4°C warmer to simulate projected air temperatures if climate change continues unabated. Rhizon water samplers were installed at a depth of one inch from the soil surface to monitor root zone exudates (total dissolved carbon and nitrogen), dissolved inorganic carbon, and lithogenic elements resulting from basalt weathering. Soil leachates were collected through the course of the experiment. The anion content of the leachates was determined using the ICS-5000 Reagent-Free ion chromatography system. Dissolved carbon and nitrogen were analyzed by combustion using the Shimadzu TOC-VCSH with TN module. Metals and metalloids were measured using inductively coupled plasma mass spectrometry. Irrigation of the pots was varied in time to simulate periods of drought and determine the effect of stress on root exudation. Leachates from all treatments displayed higher pH and electrical conductivity than water used for irrigation indicating weathering. On average, leachates from the potted grasses displayed higher pH and electrical conductivity than mesquites. This agreed with higher concentrations of organic carbon, a measure of root exudation, and inorganic carbon, measure of soil respiration. Both organic

  10. Fire in Chihuahuan Desert grassland: Short-term effects on vegetation, small mammal populations, and faunal pedoturbation

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    A prescribed burn resulted in significant decreases in canopy cover of the grasses: Bouteloua eriopoda, Sporobolus flexuosus, and Aristida purpurea. One year post-burn, basal cover of B. eriopoda remained significantly lower in burned patches than in unburned areas but there were no differences in b...

  11. Small mammal herbivory: Feedbacks that help maintain desertified ecosystems

    Science.gov (United States)

    We tested the hypothesis that herbivores contribute to feedbacks maintaining arid ecosystems in a degraded state. We studied small mammal herbivory on a subshrub, broom snakeweed (Gutierrezia sarothrae), and perennial grasses at three sites: (1) ungrazed black grama (Bouteloua eriopoda) grassland; (...

  12. Patchiness in wind erosion-deposition patterns in response to a recent state change reversal in the Chihuahuan Desert

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    Shifts from shrub-dominated states to grasslands are believed to be irreversible as a result of positive feedbacks between woody plants and soil properties. In the Chihuahuan Desert, mesquite (Prosopis glandulosa) expansion into black grama (Bouteloua eriopoda) grasslands is maintained by wind redis...

  13. Differential nutrient uptake responses to CO{sub 2} enrichment in three desert species

    Energy Technology Data Exchange (ETDEWEB)

    BassiriRad, H.; Tremmel, D.C. [Duke Univ., Durham, NC (United States)]|[Dartmouth College, Hanover, NH (United States)] [and others

    1995-09-01

    Differences in species capacity to absorb nutrients may be a crucial factor determining species and ecosystem responses to CO{sub 2} enrichment. In a phytotron study, we examined responses of three dominant species from the Chihuahuan Desert-Prosopis glandolusa and Larrea tridentata (C{sub 3} shrubs) and Bouteloua gracilis (a C{sub 4} perennial grass)-to a doubling of atmospheric CO{sub 2}, with special emphasis on rates of root NO and PO, uptake. Seedlings were grown in pots at CO{sub 2} partial pressure of either 35 or 70 pa. Rates of root NO{sup {minus}}{sub 3} and PO{sup 3{minus}}{sub 4} uptake were determined on three month old individual seedlings or tussocks using depletion rates of these ions from {1/4} strength Hoagland solutions over a 4h period. Root uptake rates of both NO{sup {minus}}{sub 3} and PO{sup 3{minus}}{sub 4} more than doubled in response to CO{sub 2} enrichment in Bouteloua but did not significantly respond in Prosopis. High CO{sub 2} also did not significantly affect rate of PO{sup 3{minus}}{sub 4} uptake in Larrea but inhibited NO{sup {minus}}{sub 3} uptake rate. Biomass increased an average of 36% in the shrubs and 25% in the grass. A positive biomass response to CO{sub 2} in C{sub 4} species has been observed in several other studies but the potential mechanism for such an enhancement is still nuclear. Our data suggests that such an enhancement may result from improved root nutrient uptake capacity.

  14. Establishment and performance of an experimental green roof under extreme climatic conditions

    Energy Technology Data Exchange (ETDEWEB)

    Klein, Petra M., E-mail: pkklein@ou.edu [School of Meteorology, University of Oklahoma, Norman, OK (United States); Coffman, Reid, E-mail: rcoffma4@kent.edu [College of Architecture and Environmental Design, Kent State University, Kent, OH (United States)

    2015-04-15

    Green roofs alter the surface energy balance and can help in mitigating urban heat islands. However, the cooling of green roofs due to evapotranspiration strongly depends on the climatic conditions, and vegetation type and density. In the Southern Central Plains of the United States, extreme weather events, such as high winds, heat waves and drought conditions pose challenges for successful implementation of green roofs, and likely alter their standard performance. The National Weather Center Experimental Green Roof, an interdisciplinary research site established in 2010 in Norman, OK, aimed to investigate the ecological performance and surface energy balance of green roof systems. Starting in May 2010, 26 months of vegetation studies were conducted and the radiation balance, air temperature, relative humidity, and buoyancy fluxes were monitored at two meteorological stations during April–October 2011. The establishment of a vegetative community trended towards prairie plant dominance. High mortality of succulents and low germination of grasses and herbaceous plants contributed to low vegetative coverage. In this condition succulent diversity declined. Bouteloua gracilis and Delosperma cooperi showed typological dominance in harsh climatic conditions, while Sedum species experienced high mortality. The plant community diversified through volunteers such as Euphorbia maculate and Portulaca maculate. Net radiation measured at a green-roof meteorological station was higher than at a control station over the original, light-colored roofing material. These findings indicate that the albedo of the green roof was lower than the albedo of the original roofing material. The low vegetative coverage during the heat and drought conditions in 2011, which resulted in the dark substrate used in the green roof containers being exposed, likely contributed to the low albedo values. Nevertheless, air temperatures and buoyancy fluxes were often lower over the green roof indicating

  15. Establishment and performance of an experimental green roof under extreme climatic conditions

    International Nuclear Information System (INIS)

    Green roofs alter the surface energy balance and can help in mitigating urban heat islands. However, the cooling of green roofs due to evapotranspiration strongly depends on the climatic conditions, and vegetation type and density. In the Southern Central Plains of the United States, extreme weather events, such as high winds, heat waves and drought conditions pose challenges for successful implementation of green roofs, and likely alter their standard performance. The National Weather Center Experimental Green Roof, an interdisciplinary research site established in 2010 in Norman, OK, aimed to investigate the ecological performance and surface energy balance of green roof systems. Starting in May 2010, 26 months of vegetation studies were conducted and the radiation balance, air temperature, relative humidity, and buoyancy fluxes were monitored at two meteorological stations during April–October 2011. The establishment of a vegetative community trended towards prairie plant dominance. High mortality of succulents and low germination of grasses and herbaceous plants contributed to low vegetative coverage. In this condition succulent diversity declined. Bouteloua gracilis and Delosperma cooperi showed typological dominance in harsh climatic conditions, while Sedum species experienced high mortality. The plant community diversified through volunteers such as Euphorbia maculate and Portulaca maculate. Net radiation measured at a green-roof meteorological station was higher than at a control station over the original, light-colored roofing material. These findings indicate that the albedo of the green roof was lower than the albedo of the original roofing material. The low vegetative coverage during the heat and drought conditions in 2011, which resulted in the dark substrate used in the green roof containers being exposed, likely contributed to the low albedo values. Nevertheless, air temperatures and buoyancy fluxes were often lower over the green roof indicating

  16. Conservation and yield aspects of old European aspen Populus tremula L. in Swedish forestry

    Energy Technology Data Exchange (ETDEWEB)

    Hazell, Per [Swedish Univ. of Agricultural Sciences, Uppsala (Sweden). Dept. of Forest Management and Products

    1999-06-01

    Biodiversity issues are becoming integrated parts of Swedish forest management. In this context, the amount and distribution of broadleaved species, including aspen, are important. This thesis summarises results of two studies in which species from the rich epiphytic flora on aspen were used to evaluate important features of aspens, and two studies relating these features to production losses due to retention of aspen. The presence and abundance of four epiphytic, bark-living bryophytes in relation to stand and host-tree characteristics, were investigated in four mixed forest stands in central Sweden. There was no general and consistent relation between aspen density and bryophyte presence. Large diameter and rough bark of the aspen host, together with site factors and stand density around the host, were important. On 35 clearfelled areas, the bryophyte Antitrichia curtipendula (Hedw.) Brid. and the lichen Lobaria pulmonaria (L.) Hoffm., species considered sensitive to clearfelling, were transplanted on retained aspen stems. As a reference, transplants were made on aspens in adjacent old stands. After two years the bryophyte showed its highest vitality in the forest, but was also vigorous on the north side of retained trees. The lichen thrived best on the clearfelled areas, on the north side of trees retained in groups. For conservation purposes, aspen are best retained in groups. Qualitative and quantitative aspects of retained large aspens (diameter 49.6{+-}7.0 cm and height 29.4{+-}1.0 m) were studied in a 110-year-old aspen stand. Twelve trees were destructively analysed to establish allometric equations relating stem, bark and branch biomass and current annual stem increment (CAI{sub s}) to diameter at breast height. Biomass of the mean tree was 1172 kg, of which 80% was stemwood. CAI{sub s} was 1.5% of total stem biomass. Finally, the yield of a 44-year-old Norway spruce stand under an aspen overstorey was compared with that of pure Norway spruce, estimated

  17. Cervus elaphus Foraging Impacts on Plants and Soils at an Ungrazed Desert Grass/Shrubland in Northwestern New Mexico, USA

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    Louis C. Bender

    2015-01-01

    Full Text Available We evaluated Cervus elaphus herbivory and trampling impacts on plants and soils on Chaco Culture National Historical Park (Chaco, a desert grass/shrubland in northwestern New Mexico, USA, most (63% of which has been protected from grazing by domestic livestock since 1948. We conducted grazing, browse, and water infiltration surveys in areas which received different amounts of C. elaphus use (use and control, 2004–2007. Browse utilization was <32% on monitored species and Odocoileus hemionus use accounted for the majority of browsing. Live plant cover was greater on areas receiving more C. elaphus use, and no grass species were used above recommended levels. Stubble heights of Bouteloua spp. were positively related to relative C. elaphus use on some areas, suggesting possible stimulation of grassland productivity by C. elaphus grazing. Water infiltration rates either did not differ among use or control sites or were faster in use sites, indicating no impacts of C. elaphus use on soil compaction. At current C. elaphus densities (0.2–0.4/km2, negative impacts to plants and soils were not seen on Chaco, and some evidence suggests that light grazing is optimizing desert grasslands of Chaco.

  18. Competition, resources, and vegetation during 10 years in native grassland.

    Science.gov (United States)

    Wilson, Scott D

    2007-12-01

    A 10-year experiment tested for variation in competition intensity over time in a natural grassland at the northern edge of the Great Plains. Growing-season precipitation varied fivefold during the study. All ecosystem-level variables varied significantly among years, and most covaried in expected ways. The covers of all common grasses possessing the C3 photosynthetic pathway varied significantly among years; in contrast, all common species with traits associated with drought tolerance (a C4 grass, a lichen, a spikemoss, and a subshrub) did not vary. Annual transplant experiments measured the competitive effects of neighbors on the growth of individuals of the native grass Bouteloua gracilis. A significant interaction between year and competition showed that competition intensity varied among years. The size of this effect, however, was small (eta2 = 0.074) relative to the size of the direct effect of competition (eta2 = 0.20) or the year in which the experiment was conducted (eta2 = 0.51). Further, competition intensity was not significantly related to any variable describing standing crop or resources, or species richness. Species richness was highest in years with high precipitation, standing crop, and individual growth, due to the recruitment of rare species that were absent from dry years. In summary, variation in competition intensity was statistically significant but had small effects relative to the direct effects of climate. PMID:18229830

  19. Establishment of Native Grasses with Biosolids on Abandoned Croplands in Chihuahua, Mexico

    Directory of Open Access Journals (Sweden)

    Pedro Jurado-Guerra

    2013-01-01

    Full Text Available The objective of the work was to evaluate establishment and forage production of native grasses with application of biosolids, a byproduct of waste-water treatment, at an abandoned field, in Ejido Nuevo Delicias, Chihuahua, Mexico. Four biosolids rates from 0 (control to 30 dry Mg ha−1 and two methods of application, surface applied (BioSur and soil incorporated (BioInc, were evaluated. Seedbed preparation included plowing and harrowing before rainfall. Field plots of 5 × 5 m were manually sown with a mix of blue grama (Bouteloua gracilis (50% and green sprangletop (Leptochloa dubia (50% in early August 2005. Experimental design was a randomized block with a split plot arrangement. Grass density, height, and forage production were estimated for three years. Data were analyzed with mixed linear models and repeated measures. Green sprangletop density increased under all biosolids rates regardless of method of application, while blue grama density slightly decreased. Biosolids were more beneficial for green sprangletop height than for blue grama height. Blue grama forage production slightly increased, while green sprangletop forage production increased the most at 10 Mg ha−1 biosolids rate under BioSur method. It was concluded that BioSur application at 10 and 20 Mg ha−1 rates had positive effects on the establishment and forage production of native grasses, especially green sprangletop.

  20. Scale-dependent feedbacks between patch size and plant reproduction in desert grassland

    Science.gov (United States)

    Svejcar, Lauren N.; Bestelmeyer, Brandon T.; Duniway, Michael C.; James, Darren K.

    2015-01-01

    Theoretical models suggest that scale-dependent feedbacks between plant reproductive success and plant patch size govern transitions from highly to sparsely vegetated states in drylands, yet there is scant empirical evidence for these mechanisms. Scale-dependent feedback models suggest that an optimal patch size exists for growth and reproduction of plants and that a threshold patch organization exists below which positive feedbacks between vegetation and resources can break down, leading to critical transitions. We examined the relationship between patch size and plant reproduction using an experiment in a Chihuahuan Desert grassland. We tested the hypothesis that reproductive effort and success of a dominant grass (Bouteloua eriopoda) would vary predictably with patch size. We found that focal plants in medium-sized patches featured higher rates of grass reproductive success than when plants occupied either large patch interiors or small patches. These patterns support the existence of scale-dependent feedbacks in Chihuahuan Desert grasslands and indicate an optimal patch size for reproductive effort and success in B. eriopoda. We discuss the implications of these results for detecting ecological thresholds in desert grasslands.

  1. Prospects for optimizing soil microbial functioning to improve plant nutrient uptake and soil carbon sequestration under elevated CO2

    Science.gov (United States)

    Nie, M.; Pendall, E. G.

    2013-12-01

    Potential to mitigate climate change through increasing plant productivity and its carbon (C) input to soil may be limited by soil nitrogen (N) availability. Using a novel 13C-CO2 and 15N-soil dual labeling method, we investigated whether plant growth-promoting bacteria would interact with atmospheric CO2 concentration to alter plant productivity and soil C storage. We grew Bouteloua gracilis under ambient (380 ppm) or elevated CO2 (700 ppm) in climate-controlled chambers, and plant individuals were grown with or without Pseudomonas fluorescens inoculum, which can produce N catabolic enzymes. We observed that both eCO2 and P. fluorescens increased plant productivity and its C allocation to soil. P. fluorescens relative to eCO2 enhanced plant N uptake from soil organic matter, which highly correlated with soil N enzyme activities and rhizosphere exudate C. More importantly, P. fluorescens increased microbial biomass and deceased specific microbial respiration in comparison with eCO2. These results indicate that application of plant growth-promoting bacteria can increase microbial C utilization efficiency with subsequent N mineralization from soil organic matter, and may improve plant N availability and soil C sequestration. Together, our findings highlight the potential of plant growth-promoting bacteria for global change mitigation by terrestrial ecosystems.

  2. Microbial response to drought in a Texas highplains shortgrass prairie.

    Science.gov (United States)

    Thayer, D W

    1974-10-01

    The population of the microbial flora of a mixed blue gramma grass (Bouteloua gracilis H. B. K.) and prickly pear (Opuntia polyacantha Haw.) prairie near Amarillo, Texas, was studied during 1971 after a severe drought. Bacteria, fungi, and algae were estimated by plate count and terminal dilution procedures. Rates of grass and paper decomposition were determined. The microbial flora of soil associated with bovine-grazed grass did not differ significantly from the flora associated with ungrazed grass, either qualitatively or quantitatively. During drought, a greater number of fungi were found in soil associated with prickly pear than in that associated with blue gramma grass. The microbial biomass decreased one full log between the surface and a depth of 50 cm, and the percentage of anaerobes increased with depth. The maximum numbers of fungi and algae detected were 8 x 10 and 6 x 10/g respectively. A linear relationship existed between the microbial biomass and soil moisture. The maximum number of aerobic, heterotrophic bacteria detected was 1.5 x 10 viable cells per g of soil.

  3. Composición y abundancia del banco de semillas en una región semiárida del trópico mexicano: patrones de variación espacial y temporal Composition and abundance of the seed bank in a semiaridregion in tropical Mexico: spatial and temporal patterns

    Directory of Open Access Journals (Sweden)

    Adriana Cano-Salgado

    2012-06-01

    Full Text Available Se estudió la estructura del banco de semillas en el valle semiárido de Zapotitlán, Puebla. El registro de la composición y abundancia del banco de semillas se realizó en 2 tipos de vegetación (tetechera y matorral espinoso en los microhábitats (bajo arbustos, espacio abierto y basureros de la hormiga granívora Pogonomyrmex barbatus. Las semillas se recolectaron en las épocas de secas, lluvias y finales de lluvias durante 2 años. No se encontraron diferencias en la densidad de semillas entre las épocas y años, pero sí hubo diferencias entre los microhábitats evaluados. El microhábitat del hormiguero presentó la mayor abundancia de semillas, lo que resalta la importancia de las hormigas en la conformación espacial de la estructura de las comunidades en estos ecosistemas. Se registraron semillas de 38 especies de plantas. La densidad promedio varió de 23 800 a 28 000 semillas m-2, concordando con otros registros de regiones semiáridas y áridas. Las especies más frecuentes fueron las anuales Eragrostis mexicana, Bouteloua barbata, Kallstroemia rosei y Portulaca pilosa. Los resultados muestran que la heterogeneidad de sitios y de microhábitats en esta zona es alta. Es necesaria la realización de más estudios sobre patrones espacio-temporales en los bancos de semillas y su relación con la vegetación en pie en zonas áridas y semiáridas en México.The seed bank structure in the semiarid valley of Zapotitlán, Puebla was studied. The record of the composition and abundance of the seed bank was conducted in 2 types of vegetation (tetechera and thorny scrub in the microhabitats (under shrubs, open space and refuse- dumps of granivorous ants Pogonomyrmex barbatus. Seed collection was carried out in dry, rainy and late rainy seasons for 2 years. There were no differences in seed density between seasons and years, but there were differences between microhabitats evaluated. The microhabitat of the ant refuse-dumps had the highest

  4. Competitive effects of introduced annual weeds on some native and reclamation species in the Powder River Basin, Wyoming

    Energy Technology Data Exchange (ETDEWEB)

    Allen, E.B.; Knight, D.H.

    1980-01-01

    Four experiments were conducted to examine the competitive effects of introduced annual weeds on certain native and reclamation species. The first experiment was initiated by discing three sites in the Powder River Basin, Wyoming, at three distances from introduced weed seed sources. Introduced weed colonization was greatest when a seed source was located nearby. Higher weed cover resulted in reductions of percent cover, density, and richness of the native species. The second experiment was conducted in the greenhouse and was designed to determine if there are changes in response of S. kali and the native grasses Agropyron smithii and Bouteloua gracilis to competition and water regime. Both grass species had lower biomass and higher stomatal resistance when growing in mixed culture with S. kali than in pure culture in the dry regime, but there were no significant differences in the wet regime. In general, the difference in plant response between mixed and pure cultures was more pronounced in the dry than in the wet regime. The third study was a greenhouse experiment on germination and competition of S. kali (a C/sub 4/ species) with native species Lepidium densiflorum (C/sub 3/), Chenopodium pratericola (C/sub 3/), A. smithii (C/sub 3/), and B. gracilis (C/sub 4/) under May, June, and July temperature regimes. Salsola kali germinated equally well in all three regimes, but the other C/sub 4/ species had highest germination in the July regime and the C/sub 3/ species in the May and June regimes. The fourth study was designed to examine the effect of weed colonization on the success of mine reclamation. Little effect was observed, but colonization by introduced annuals was very low. (ERB)

  5. Establishment and performance of an experimental green roof under extreme climatic conditions.

    Science.gov (United States)

    Klein, Petra M; Coffman, Reid

    2015-04-15

    Green roofs alter the surface energy balance and can help in mitigating urban heat islands. However, the cooling of green roofs due to evapotranspiration strongly depends on the climatic conditions, and vegetation type and density. In the Southern Central Plains of the United States, extreme weather events, such as high winds, heat waves and drought conditions pose challenges for successful implementation of green roofs, and likely alter their standard performance. The National Weather Center Experimental Green Roof, an interdisciplinary research site established in 2010 in Norman, OK, aimed to investigate the ecological performance and surface energy balance of green roof systems. Starting in May 2010, 26 months of vegetation studies were conducted and the radiation balance, air temperature, relative humidity, and buoyancy fluxes were monitored at two meteorological stations during April-October 2011. The establishment of a vegetative community trended towards prairie plant dominance. High mortality of succulents and low germination of grasses and herbaceous plants contributed to low vegetative coverage. In this condition succulent diversity declined. Bouteloua gracilis and Delosperma cooperi showed typological dominance in harsh climatic conditions, while Sedum species experienced high mortality. The plant community diversified through volunteers such as Euphorbia maculate and Portulaca maculate. Net radiation measured at a green-roof meteorological station was higher than at a control station over the original, light-colored roofing material. These findings indicate that the albedo of the green roof was lower than the albedo of the original roofing material. The low vegetative coverage during the heat and drought conditions in 2011, which resulted in the dark substrate used in the green roof containers being exposed, likely contributed to the low albedo values. Nevertheless, air temperatures and buoyancy fluxes were often lower over the green roof indicating

  6. Root development during soil genesis: effects of root-root interactions, mycorrhizae, and substrate

    Science.gov (United States)

    Salinas, A.; Zaharescu, D. G.

    2015-12-01

    A major driver of soil formation is the colonization and transformation of rock by plants and associated microbiota. In turn, substrate chemical composition can also influence the capacity for plant colonization and development. In order to better define these relationships, a mesocosm study was set up to analyze the effect mycorrhizal fungi, plant density and rock have on root development, and to determine the effect of root morphology on weathering and soil formation. We hypothesized that plant-plant and plant-fungi interactions have a stronger influence on root architecture and rock weathering than the substrate composition alone. Buffalo grass (Bouteloua dactyloides) was grown in a controlled environment in columns filled with either granular granite, schist, rhyolite or basalt. Each substrate was given two different treatments, including grass-microbes and grass-microbes-mycorrhizae and incubated for 120, 240, and 480 days. Columns were then extracted and analyzed for root morphology, fine fraction, and pore water major element content. Preliminary results showed that plants produced more biomass in rhyolite, followed by schist, basalt, and granite, indicating that substrate composition is an important driver of root development. In support of our hypothesis, mycorrhizae was a strong driver of root development by stimulating length growth, biomass production, and branching. However, average root length and branching also appeared to decrease in response to high plant density, though this trend was only present among roots with mycorrhizal fungi. Interestingly, fine fraction production was negatively correlated with average root thickness and volume. There is also slight evidence indicating that fine fraction production is more related to substrate composition than root morphology, though this data needs to be further analyzed. Our hope is that the results of this study can one day be applied to agricultural research in order to promote the production of crops

  7. Establishment and performance of an experimental green roof under extreme climatic conditions.

    Science.gov (United States)

    Klein, Petra M; Coffman, Reid

    2015-04-15

    Green roofs alter the surface energy balance and can help in mitigating urban heat islands. However, the cooling of green roofs due to evapotranspiration strongly depends on the climatic conditions, and vegetation type and density. In the Southern Central Plains of the United States, extreme weather events, such as high winds, heat waves and drought conditions pose challenges for successful implementation of green roofs, and likely alter their standard performance. The National Weather Center Experimental Green Roof, an interdisciplinary research site established in 2010 in Norman, OK, aimed to investigate the ecological performance and surface energy balance of green roof systems. Starting in May 2010, 26 months of vegetation studies were conducted and the radiation balance, air temperature, relative humidity, and buoyancy fluxes were monitored at two meteorological stations during April-October 2011. The establishment of a vegetative community trended towards prairie plant dominance. High mortality of succulents and low germination of grasses and herbaceous plants contributed to low vegetative coverage. In this condition succulent diversity declined. Bouteloua gracilis and Delosperma cooperi showed typological dominance in harsh climatic conditions, while Sedum species experienced high mortality. The plant community diversified through volunteers such as Euphorbia maculate and Portulaca maculate. Net radiation measured at a green-roof meteorological station was higher than at a control station over the original, light-colored roofing material. These findings indicate that the albedo of the green roof was lower than the albedo of the original roofing material. The low vegetative coverage during the heat and drought conditions in 2011, which resulted in the dark substrate used in the green roof containers being exposed, likely contributed to the low albedo values. Nevertheless, air temperatures and buoyancy fluxes were often lower over the green roof indicating

  8. Regional signatures of plant response to drought and elevated temperature across a desert ecosystem.

    Science.gov (United States)

    Munson, Seth M; Muldavin, Esteban H; Belnap, Jayne; Peters, Debra P C; Anderson, John P; Reiser, M Hildegard; Gallo, Kirsten; Melgoza-Castillo, Alicia; Herrick, Jeffrey E; Christiansen, Tim A

    2013-09-01

    The performance of many desert plant species in North America may decline with the warmer and drier conditions predicted by climate change models, thereby accelerating land degradation and reducing ecosystem productivity. We paired repeat measurements of plant canopy cover with climate at multiple sites across the Chihuahuan Desert over the last century to determine which plant species and functional types may be the most sensitive to climate change. We found that the dominant perennial grass, Bouteloua eriopoda, and species richness had nonlinear responses to summer precipitation, decreasing more in dry summers than increasing with wet summers. Dominant shrub species responded differently to the seasonality of precipitation and drought, but winter precipitation best explained changes in the cover of woody vegetation in upland grasslands and may contribute to woody-plant encroachment that is widespread throughout the southwestern United States and northern Mexico. Temperature explained additional variability of changes in cover of dominant and subdominant plant species. Using a novel empirically based approach we identified "climate pivot points" that were indicative of shifts from increasing to decreasing plant cover over a range of climatic conditions. Reductions in cover of annual and several perennial plant species, in addition to declines in species richness below the long-term summer precipitation mean across plant communities, indicate a decrease in the productivity for all but the most drought-tolerant perennial grasses and shrubs in the Chihuahuan Desert. Overall, our regional synthesis of long-term data provides a robust foundation for forecasting future shifts in the composition and structure of plant assemblages in the largest North American warm desert.

  9. A test of catastrophic transition mechanisms in the Chihuahuan Desert Grassland

    Science.gov (United States)

    Svejcar, L.; Bestelmeyer, B.; Duniway, M.

    2012-12-01

    Dryland ecosystems are known to undergo transitions from grassland or savanna states to shrub-dominated and/or eroded states with persistent loss of herbaceous vegetation. Theoretical models for predicting critical thresholds between states have been examined in drylands to search for early warning indicators, yet there is scant empirical evidence for the mechanisms. The models postulate that larger patches are favorable environments for plant growth in arid ecosystems due to short-range facilitation. The breakdown of large patches is thought to trigger catastrophic transitions. We tested assumptions underpinning these models using an experiment in black grama grassland (Bouteloua eriopoda Torr.) of the Chihuahuan Desert in which variable grazing intensities produced a wide range of patch sizes in plots with differing mesquite shrub (Prosopis glandulosa Torr.) densities. We tested the hypothesis that growth, reproductive capability, and reproductive success of black grama plants would be greater in larger plant patches than in smaller patches. From 2010-2012 we measured numbers of stolons, ramets, rooted ramets and young individual plants associated with focal black grama plants and fixed areas within each patch. We found that the largest patches did not always feature the highest rates of grass reproduction across years, suggesting that patch size does not consistently indicate the patch persistence mechanisms proposed in catastrophic transition models. Other factors, such as resource competition within patches, may play important roles in black grama grasslands. When assessing rangeland conditions in the Chihuahuan desert grasslands, theoretical models of critical thresholds and early warning indicators should be applied with caution.

  10. Effects of ungulates and prairie dogs on seed banks and vegetation in a North American mixed-grass prairie

    Science.gov (United States)

    Fahnestock, J.T.; Larson, D.L.; Plumb, G.E.; Detling, J.K.

    2003-01-01

    The relationship between vegetation cover and soil seed banks was studied in five different ungulate herbivoreprairie dog treatment combinations at three northern mixed-grass prairie sites in Badlands National Park, South Dakota. There were distinct differences in both the seed bank composition and the aboveground vegetation between the off-prairie dog colony treatments and the on-colony treatments. The three on-colony treatments were similar to each other at all three sites with vegetation dominated by the forbs Dyssodia papposa, Hedeoma spp., Sphaeralcea coccinea, Conyza canadensis, and Plantago patagonica and seed banks dominated by the forbs Verbena bracteata and Dyssodia papposa. The two off-colony treatments were also similar to each other at all three sites. Vegetation at these sites was dominated by the grasses Pascopyrum smithii, Bromus tectorum and Bouteloua gracilis and the seed banks were dominated by several grasses including Bromus tectorum, Monroa squarrosa, Panicum capillare, Sporobolus cryptandra and Stipa viridula. A total of 146 seedlings representing 21 species germinated and emerged from off-colony treatments while 3069 seedlings comprising 33 species germinated from on-colony treatments. Fifteen of the forty species found in soil seed banks were not present in the vegetation, and 57 of the 82 species represented in the vegetation were not found in the seed banks. Few dominant species typical of mixed-grass prairie vegetation germinated and emerged from seed banks collected from prairie dog colony treatments suggesting that removal of prairie dogs will not result in the rapid reestablishment of representative mixed-grass prairie unless steps are taken to restore the soil seed bank.

  11. Effects of VA mycorrhiza formation on plant nitrogen uptake and rhizosphere bacteria

    Energy Technology Data Exchange (ETDEWEB)

    Ames, R.N.

    1983-01-01

    Mycorrhizal and nonmycorrhizal sorghum plants were grown in pots at three levels of fertilizer nitrogen ((NH/sub 4/)/sub 2/SO/sub 4/) which had been enriched with /sup 15/N. Root colonization by Glomus mosseae did not affect plant growth or total N uptake, but significant reductions in mycorrhizal plant /sup 15/N:/sup 14/N ratios and increased 'A' values were found. This suggested that mycorrhizal plants had access to an N source which was less available to nonmycorrhizal plants. In two additional experiments, mycorrhizal and nonmycorrhizal celery plants were grown in pots which allowed VAM fungal hyphae, but not roots, to have direct access to /sup 15/N-enriched organic or inorganic N sources. Root dry weight was significantly reduced in mycorrhizal plants. Mycorrhizal plants had significantly greater shoot and root /sup 15/N content than nonmycorrhizal plants. Number and length of VAM fungal hyphae crossing into the area of /sup 15/N placement were positively correlated with mycorrhizal plant /sup 15/N content in the inorganic-N but not organic-N treatment. In a fourth experiment, the effect of G. mosseae on the rhizosphere populations of five bacterial isolates associated with blue grama (Bouteloua gracilis) was examined. No significant differences in bacterial populations were found in nonrhizosphere soil samples from pots of mycorrhizal and nonmycorrhizal plants. One bacterial isolate was significantly increased in number, while a different isolate and total bacterial populations were significantly reduced by the presence of the mycorrhizal fungus. The results suggest that root colonization by VAM fungi can alter rhizosphere bacterial populations.

  12. Regional signatures of plant response to drought and elevated temperature across a desert ecosystem

    Science.gov (United States)

    Munson, Seth M.; Muldavin, Esteban H.; Belnap, Jayne; Peters, Debra P.C.; Anderson, John P.; Reiser, M. Hildegard; Gallo, Kirsten; Melgoza-Castillo, Alicia; Herrick, Jeffrey E.; Christiansen, Tim A.

    2013-01-01

    The performance of many desert plant species in North America may decline with the warmer and drier conditions predicted by climate change models, thereby accelerating land degradation and reducing ecosystem productivity. We paired repeat measurements of plant canopy cover with climate at multiple sites across the Chihuahuan Desert over the last century to determine which plant species and functional types may be the most sensitive to climate change. We found that the dominant perennial grass, Bouteloua eriopoda, and species richness had nonlinear responses to summer precipitation, decreasing more in dry summers than increasing with wet summers. Dominant shrub species responded differently to the seasonality of precipitation and drought, but winter precipitation best explained changes in the cover of woody vegetation in upland grasslands and may contribute to woody-plant encroachment that is widespread throughout the southwestern United States and northern Mexico. Temperature explained additional variability of changes in cover of dominant and subdominant plant species. Using a novel empirically based approach we identified ‘‘climate pivot points’’ that were indicative of shifts from increasing to decreasing plant cover over a range of climatic conditions. Reductions in cover of annual and several perennial plant species, in addition to declines in species richness below the long-term summer precipitation mean across plant communities, indicate a decrease in the productivity for all but the most drought-tolerant perennial grasses and shrubs in the Chihuahuan Desert. Overall, our regional synthesis of long-term data provides a robust foundation for forecasting future shifts in the composition and structure of plant assemblages in the largest North American warm desert.

  13. Spatial partitioning of water use by herbaceous and woody lifeforms in semiarid woodlands

    International Nuclear Information System (INIS)

    Ecological studies of soil moisture, plant water uptake, and community composition in semiarid regions have focused on differences with depth in the soil profile, yet there are many reasons to expect that moisture also varies with the presence or absence of woody vegetation. Plant and soil moisture relationships for three dominant species in a semiarid woodland, Bouteloua gracilis, Juniperus monosperma, and Pinus edulis, were studied for 1.5 years. Soil moisture varied by type of plant cover as well as by depth. Plant water potential and conductance differed among species and was related to spatial variability in soil moisture. Water potential for blue grama was most correlated with soil moisture in the 0-15 cm layer of intercanopies; juniper water potential was highly correlated with soil moisture in the 0-15 cm layer beneath tree canopies of either species, and pinyon water potential was only weakly correlated with soil moisture in the 15-30 cm depth interval beneath pinyons. Pinyons had consistently greater maximum conductance rates than junipers, even though pinyon conductance was more sensitive to reductions in soil moisture. The results from this study indicate that horizontal differences in the soil moisture profile associated with type of plant cover may be as important as differences in depth for predicting plant-water relationships. A simple model was hypothesized for predicting community composition of three lifeforms: Herbaceous plants, shallow-rooted woody plants, and deeper-rooted woody plants. Distributions of roots of each lifeform and plant-available water were defined with respect to four soil compartments that distinguish upper vs. lower and canopy vs. intercanopy soil regions. The model predicts that multiple combinations of herbaceous and woody biomass can exist at a site and was qualitatively consistent with field data from a climatic gradient

  14. Efficient breakdown of lignocellulose using mixed-microbe populations for bioethanol production.

    Energy Technology Data Exchange (ETDEWEB)

    Murton, Jaclyn K.; Ricken, James Bryce; Powell, Amy Jo

    2009-11-01

    (DoE) Joint Genome Institute (JGI) to perform metatranscriptomic functional profiling of eukaryotic microbial communities of blue grama grass (Bouteloua gracilis) rhizosphere (RHZ) soils and (2) isolated and provided initial genotypic and phenotypic characterization data for thermophilic fungi. Our preliminary results show that many strains in our collection of thermophilic fungi frequently outperform industry standards in key assays; we also demonstrated that this collection is taxonomically diverse and phenotypically compelling. The studies summarized here are being performed in collaboration with University of New Mexico and are based at the Sevilleta LTER research site.

  15. Assessing vegetation structure and ANPP dynamics in a grassland-shrubland Chihuahuan ecotone using NDVI-rainfall relationships

    Science.gov (United States)

    Moreno-de las Heras, M.; Diaz-Sierra, R.; Turnbull, L.; Wainwright, J.

    2015-01-01

    Climate change and the widespread alteration of natural habitats are major drivers of vegetation change in drylands. A classic case of vegetation change is the shrub-encroachment process that has been taking place over the last 150 years in the Chihuahuan Desert, where large areas of grasslands dominated by perennial grass species (black grama, Bouteloua eriopoda, and blue grama, B. gracilis) have transitioned to shrublands dominated by woody species (creosotebush, Larrea tridentata, and mesquite, Prosopis glandulosa), accompanied by accelerated water and wind erosion. Multiple mechanisms drive the shrub-encroachment process, including exogenous triggering factors such as precipitation variations and land-use change, and endogenous amplifying mechanisms brought about by soil erosion-vegetation feedbacks. In this study, simulations of plant biomass dynamics with a simple modelling framework indicate that herbaceous (grasses and forbs) and shrub vegetation in drylands have different responses to antecedent precipitation due to functional differences in plant growth and water-use patterns, and therefore shrub encroachment may be reflected in the analysis of landscape-scale vegetation-rainfall relationships. We analyze the structure and dynamics of vegetation at an 18 km2 grassland-shrubland ecotone in the northern edge of the Chihuahuan Desert (McKenzie Flats, Sevilleta National Wildlife Refuge, NM, USA) by investigating the relationship between decade-scale (2000-2013) records of medium-resolution remote sensing of vegetation greenness (MODIS NDVI) and precipitation. Spatial evaluation of NDVI-rainfall relationship at the studied ecotone indicates that herbaceous vegetation shows quick growth pulses associated with short-term (previous 2 months) precipitation, while shrubs show a slow response to medium-term (previous 5 months) precipitation. We use these relationships to (a) classify landscape types as a function of the spatial distribution of dominant vegetation

  16. Vegetation change in dryland environments: understanding changes in fluvial fluxes via changes in hydrological connectivity

    Science.gov (United States)

    Puttock, A.; Brazier, R. E.; Dungait, J. A. J.; Bol, R.; Macleod, C. J. A.

    2012-04-01

    Dryland environments are estimated to cover around 40% of the global land surface (Okin et al, 2009) and are home to approximately 2.5 billion people (Reynolds et al. 2007). Many of these areas have recently experienced extensive land degradation. One such area and the focus of this project is the semi-arid US Southwest, where degradation over the past 150 years has been characterised by the invasion of woody vegetation into grasslands. The transition from grass to woody vegetation results in a change in ecosystem structure and function (Turnbull et al, 2008). Structural change is typically characterised by an increased heterogeneity of soil and vegetation resources, associated with reduced vegetation coverage. Functional change is characterised by an increased vulnerability to soil erosion and the potential loss of key nutrients to adjacent fluvial systems. Such loss of resources may impact heavily upon the amount of carbon that is sequestered by these environments and the amount of carbon that is lost as the land becomes more degraded. Therefore, understanding these vegetation transitions is significant for sustainable land use and global biogeochemical cycling. Connectivity is a key concept in understanding the hydrological response to this vegetation change, with reduced vegetation coverage in woody environments being associated with longer and more connected overland flow pathways. This increase in hydrological connectivity results in an accentuated rainfall-runoff response and increased fluvial fluxes of eroded sediment and associated soil organic carbon and other nutrients. This project uses an ecohydrological approach, characterising ecological structure and monitoring natural rainfall-runoff events over bounded plots with different vegetation covering the transitions from C4 pure-grass (Bouteloua eriopoda) to C3 creosote (Larrea tridentate) shrubland and C3 piñon-juniper (Pinus edulis-Juniperus monosperma) mixed stand woodland. Data collected quantifies

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

    Science.gov (United States)

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

    2009-04-01

    The degradation of grasslands is a common problem across semi-arid areas worldwide. Over the last 150 years much of the South-Western USA has experienced significant land degradation, with desert grasslands becoming dominated by shrubs and concurrent changes in runoff and erosion which are thought to propagate further the process of degradation. Field-based experiments were carried out to determine how runoff and erosion vary at stages over a transition from a black grama (Bouteloua eriopoda) grassland to creosotebush (Larrea tridentata) shrubland at the Sevilleta NWR LTER site in New Mexico. 14C and δ13C analyses were carried out to investigate the age and potential provenance of eroded sediment. Results show an overall increase in runoff and erosion over the transition from grassland to shrubland, associated with an increase in connectivity of bare, runoff-generating areas, although these increases do not appear to follow a linear trajectory. Erosion rates increased over the transition from grassland to shrubland, related in part to changes in runoff characteristics and the increased capacity of the runoff to detach, entrain and transport sediment. Over all plots fine material was preferentially eroded which has potential implications for nutrient cycling since nutrients tend to be associated with fine sediment. There are significant differences in the isotopic signatures of eroded sediment between the grass- and shrub-dominated plots. The positive correlation between event runoff and δ13C signatures of eroded sediment that is consistent over plots 1, 3 and 4 suggests that the δ13C signatures can be used to distinguish between changes in erosion dynamics over events of different magnitudes and over different vegetation types. 14C analysis of sediment revealed that sediment eroded from all plots is considerably younger than the surface soils over all plots, which is likely to indicate that eroded sediments tend to source form very near surface areas that are

  18. Developing an Understanding of Vegetation Change and Fluvial Carbon Fluxes in Semi-Arid Environments

    Science.gov (United States)

    Puttock, A.; Brazier, R. E.; Dungait, J. A. J.; Bol, R.; Macleod, C. J. A.

    2012-04-01

    Dryland environments are estimated to cover around 40% of the global land surface (Okin et al, 2009) and are home to approximately 2.5 billion people (Reynolds et al. 2007). Many of these areas have recently experienced extensive land degradation. One such area and the focus of this project is the semi-arid US Southwest, where degradation over the past 150 years has been characterised by the invasion of woody vegetation into grasslands. Transition from grass to woody vegetation results in a change in ecosystem structure and function (Turnbull et al, 2008). Structural change is typically characterised by an increased heterogeneity of soil and vegetation resources, associated with reduced vegetation coverage and an increased vulnerability to soil erosion and the potential loss of key nutrients to adjacent fluvial systems. Such loss of resources may impact heavily upon the amount of carbon that is sequestered by these environments and the amount of carbon that is lost as the land becomes more degraded. Therefore, understanding these vegetation transitions is significant for sustainable land use and global biogeochemical cycling. This project uses an ecohydrological approach, monitoring natural rainfall-runoff events over six bounded plots with different vegetation coverage. The experiment takes advantage of a natural abundance stable 13C isotope shift from C3 piñon-juniper (Pinus edulis-Juniperus monosperma) mixed stand through a C4 pure-grass (Bouteloua eriopoda) to C3 shrub (Larrea tridentata). Data collected quantify fluvial fluxes of sediment and associated soil organic matter and carbon that is lost from across the grass-to-shrub and grass-to-woodland transition (where change in space is taken to indicate a similar change through time). Results collected during the 2010 and 2011 monsoon seasons will be presented, illustrating that soil and carbon losses are greater as the ecosystem becomes more dominated by woody plants. Additionally this project utilises novel

  19. Bridging Estimates of Greenness in an Arid Grassland Using Field Observations, Phenocams, and Time Series Unmanned Aerial System (UAS) Imagery

    Science.gov (United States)

    Browning, D. M.; Tweedie, C. E.; Rango, A.

    2013-12-01

    Spatially extensive grasslands and savannas in arid and semi-arid ecosystems (i.e., rangelands) require cost-effective, accurate, and consistent approaches for monitoring plant phenology. Remotely sensed imagery offers these capabilities; however contributions of exposed soil due to modest vegetation cover, susceptibility of vegetation to drought, and lack of robust scaling relationships challenge biophysical retrievals using moderate- and coarse-resolution satellite imagery. To evaluate methods for characterizing plant phenology of common rangeland species and to link field measurements to remotely sensed metrics of land surface phenology, we devised a hierarchical study spanning multiple spatial scales. We collect data using weekly standardized field observations on focal plants, daily phenocam estimates of vegetation greenness, and very high spatial resolution imagery from an Unmanned Aerial System (UAS) throughout the growing season. Field observations of phenological condition and vegetation cover serve to verify phenocam greenness indices along with indices derived from time series UAS imagery. UAS imagery is classified using object-oriented image analysis to identify species-specific image objects for which greenness indices are derived. Species-specific image objects facilitate comparisons with phenocam greenness indices and scaling spectral responses to footprints of Landsat and MODIS pixels. Phenocam greenness curves indicated rapid canopy development for the widespread deciduous shrub Prosopis glandulosa over 14 (in April 2012) to 16 (in May 2013) days. The modest peak in greenness for the dominant perennial grass Bouteloua eriopoda occurred in October 2012 following peak summer rainfall. Weekly field estimates of canopy development closely coincided with daily patterns in initial growth and senescence for both species. Field observations improve the precision of the timing of phenophase transitions relative to inflection points calculated from phenocam

  20. Biophysical drivers of net ecosystem exchange in shrublands of the northern Chihuahuan Desert

    Science.gov (United States)

    Jaimes, A.; Laney, C.; Tweedie, C. E.

    2013-12-01

    In the northern Chihuahuan Desert, large areas of southern New Mexico that were formerly dominated by perennial grasses, including black grama (Bouteloua eriopa) and mesa dropseed (Sporobolus flexus) have been replaced by desert shrubland species, in particular creosote bush (Larrea tridentata) and honey mesquite (Prosopis glandulosa). Recent studies suggest that these changes in land cover have the ability to modify near surface microclimate such as soil water holding capacity, albedo, carbon dioxide sequestration, and increases in local air temperature, respiration, sensible heat and evapotranspiration. Despite the recognized importance of the consequences of land cover change in the ecosystem, the rates and tipping points at which these changes occur are not well understood. This knowledge is key to improve predictions in regional and global models, as the region is expected to go through an imminent transition from warm to warmer climate in this century. This study analyze three years of data (2010-2012) from our multi sensor platform situated on the USDA ARS Jornada Experimental Range (JER), about 25 km northeast of Las Cruces, New Mexico, USA. A robust data set that combines high frequency micrometeorological data, plot phenology estimates and spectral indices was used. A combination of statistical analyses based on clustering methods (self-organizing maps) and simple nonparametric regression techniques (regression trees) were used to identify factors controlling fluxes and likely biophysical thresholds and tipping points indicative of different functional system states. Both analyses were implemented through the use of Neural Network Toolbox and Statistics toolbox within MATLAB 7.0. During the period of study the shrubland acted as a carbon sink ranging between -105 to -134 gCO2 m-2 y-1. The largest variation between years in the annual estimated fluxes was the slight decrease of total annual net ecosystem exchange during 2011 (-105 g m-2 s-1) in comparison

  1. Evaluating channel morphology in small watersheds of oak savannas Southeastern New Mexico, USA: Do seasonal prescribed burn treatments have a significant impact on sediment processes?

    Science.gov (United States)

    Koestner, Karen; Neary, Daniel; Gottfried, Gerald; Tecle, Aregai

    2010-05-01

    Oak-savannas comprise over 80,000 km2 of the southwestern United States and northern Mexico. However, there is a paucity of data to assist in the management of this vast ecotype. Fire, which was once the most important natural disturbance in this system, has been excluded due to over-grazing and fire suppression practices. This has resulted in ecosystem changes and fuel accumulations. Prescribed fire is one management technique to restore natural processes within southwestern oak-savannas by reducing woody species density, increasing herbaceous plant production, and creating vegetative mosaics on the landscape. However, questions concerning the seasonality of burn treatments and the overall effects of these treatments on physical and ecological processes need to be addressed prior to broad management application. The Cascabel Watershed Study is a collaborative effort between multiple government agencies, universities, local land managers, and environmental interest groups to evaluate the impacts of warm and cool season burn treatments on an array of ecosystem processes. Established in 2000, the Cascabel Watershed study takes an "ecosystem approach" to watershed research by examining an array of physical and biological components, including geomorphologic, climatologic, hydrologic, and biologic (flora and fauna) data to determine ecosystem response to prescribed fire. The 182.6 ha study area is located in the eastern Peloncillo Mountains, New Mexico at about the 1,640 m elevation. It consists of 12 small watersheds dominated by an oak (Quercus spp.) overstory and bunch-grass (Bouteloua spp.), savanna component. The parent material is fine-grained Tertiary rhyolite that is part of an extensive lava field that was formed about 25 to 27 M ybp. A US Forest Service soil survey in the area classified 45% of the soils as Typic Haplustolls, coarse-loamy, mixed, mesic, 25% as Typic Haplustalfs, and 15% rock outcrops. Here, we evaluate within-channel processes to establish

  2. Seasonal Soil Nitrogen Mineralization within an Integrated Crop and Livestock System in Western North Dakota, USA

    Science.gov (United States)

    Landblom, Douglas; Senturklu, Songul; Cihacek, Larry; Pfenning, Lauren; Brevik, Eric C.

    2015-04-01

    pipes were pressed into the soil as enclosures to restrict root access to soil nitrogen. Soil samples were taken as close to 2-week intervals as possible from both inside and outside the enclosures. The crop rotation N values were also compared to triple replicated perennial native grassland plot areas (predominate sp. Western wheatgrass - Pascopyrum smithii, Blue grama - Bouteloua gracilis, Little bluestem - Schizachyrium scoparium, Switchgrass - Panicum virgatum). Trends identified for both NH4-N and NO3-N indicate that the values are relatively similar with respect to seasonal change over time. There was a greater amount of soil nitrogen accumulation inside the enclosures indicating that outside the enclosures roots scavenge nitrogen for plant growth and production. Seasonally, comparing the cropping system crops, NO3-N declined mid-July and then rebounded by mid-August and continued to increase until leveling off in September. Corn NO3-N, however, did not follow this pattern, but increased from early June to the end of June and remained high until the first of September. We will present the results of bulk density data and seasonal N fertility data providing evidence for the impact of previous CC on corn production. Probable explanation for the mid-summer nitrogen decline will be presented and justification for reduced fertilizer application will be discussed.

  3. Plant phenological responses to extreme events - A long term perspective from the Chihuahuan Desert

    Science.gov (United States)

    Browning, D. M.; Peters, D. P.; Anderson, J.; Yao, J.

    2011-12-01

    Arid and semi-arid regions of the southwestern USA are especially sensitive to changes in temperature as well as drought frequency and intensity. Timing of periodic life cycle events (i.e., phenology) is an integrated and salient indicator of plant responses to climate change. We examine an 18-year dataset of monthly observations of plant phenology for two species of perennial grasses and a deciduous shrub (honey mesquite) distributed across three upland grassland sites and three mesquite-dominated sites on the Jornada Basin USDA-LTER in southern New Mexico, USA. Precipitation is highly variable between years and across space. Long-term phenology data collection spanned a multi-year drought (1994-2003) followed by a sequence of years with average to very high rainfall (2004 - 2008). Our objective was to compare and contrast responses to extreme dry and wet cycles in the timing and duration of first leaf and fruit production for two grasses (Bouteloua eriopoda [black grama], Sporobolus flexuosus [mesa dropseed]) with one co-existing shrub that has displaced grasses in this system (Prosopis glandulosa [honey mesquite]). Monthly field observations yield estimates of phenological status and abundance for 18 growing seasons from 1993 to 2010. All three species most commonly initiated new growth prior to onset of the monsoon rains (March or April). Timing of first growth for mesquite was less variable (standard deviation = 0.47) than for black grama (SD = 1.42) and mesa dropseed (SD = 1.22) grasses. Initial growth for grasses was delayed to September in 2006 following twelve months of deficit values for PDSI. The appearance of first fruit for grasses occurred consistently in August or September, although the number of plants producing fruit was highly variable from year to year. The largest numbers of fruit-bearing grasses were observed in late fall 2008 in response to heavy monsoon rains in 2006 and 2008. Mesquite demonstrated remarkable synchrony in the production of