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The role of the cyanobacterium Microcoleus vaginatlls in cold-desert soil crusts is investigated using scanning electron microscopy. Crusts from sandstone-, limestone-, and gypsum-derived soils are examined. When dry, polysaccharide sheath material from this cyanobacterium can be seen winding through and across all three types of soil surfaces, attaching to and binding soil particles together. When wet, sheaths and living filaments can be seen absorbing water, swelling and covering soil surfaces even more extensively. Addition of negatively charged material, found both as sheath material and attached clay particles, may affect cation exchange capacity of these soils as well. As a result of these observations, we...
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Riparian grasslands dominated by big sacaton (Sporobolus wrightii) once covered floodplains across the southwest, but have been reduced to some 5% of their historical extent. Sacaton stands that remain provide key resources for watershed function, wildlife, and livestock—yet may need special management to sustain these benefits. This report describes mapping methods and management recommendations that can be applied to riparian grasslands throughout the region. By examining sacaton grasslands in the Las Cienegas National Conservation Area, this project also refines methods for evaluating ecological condition, and provides managers at this site with detailed maps of both high-quality habitat and restoration needs.
Wind erosion researchers need field equipment and techniques for ascertaining threshold wind velocities and the amount and vertical distribution of the eroded soil particles. To detect moving soil particles and field erosion, sensors and soil samplers to measure surface creep and airborne particles have been developed. A power expression will describe the variation in amounts of suspended material to a 2-m height. The quantity of material (f) and height of material (y) within the saltation zone can be explained by the expression f = f ~ ( l - ~ / o ) $ where "fo" is surface creep, o is height below which 50% of the total mass flow occurs in the saltation process, and is the slope of the line. With this equipment...
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Seasonal changes in soil phosphorus (P) availability are not yet known for many ecosystems. We report seasonal changes in several pools of soil phosphorus, including plant available P from the Mojave Desert and Colorado Plateau. In addition we show that cheatgrass changes soil P fractions in unexpected and ecologically significant ways. Monthly soil samples (0-10 cm) from four sites in Canyonlands National Park in southeast Utah, are analyzed for P with a modified Hedley P fractionation method. Labile P (plant available) peaks in spring and autumn with significant monthly variation. Surprisingly, HCl extractable P changes as well, with a pattern inverse to that of labile P. Each of these sites has considerable Bromus...
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NatureServe worked with several federal, state, and NGO partners in the United States and Mexico to conduct a climate change vulnerability assessment of major natural community types found within the Mojave and Sonoran Deserts. The project focused on ten major upland, riparian, and aquatic community types, including pinyon-juniper woodlands, Joshua tree-blackbrush scrub, creosote-bursage scrub, salt desert scrub, Paloverde-mixed cacti scrub, semi-desert grassland, desert riparian and stream, riparian mesquite bosque, and desert springs. This effort piloted a new Habitat Climate Change Vulnerability Index (HCCVI) approach being developed by NatureServe, as a companion to an existing index for species. The project...
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The human footprint map focuses on shrubland ecosystems and combines models of habitat use by synanthropic predators (“top-down” effects) and the risk of invasive plant presence (“bottom-up” effects) to estimate the total influence of human activities. Humans have dramatically altered wildlands in the western United States over the past 100 years by using these lands and the resources they provide. Anthropogenic changes to the landscape, such as urban expansion, construction of roads, power lines, and other networks and land uses necessary to maintain human populations influence the number and kinds of plants and wildlife that remain. We developed the map of the human footprint for the western United States from...
Shifts in plant community structure in shrub and grass-dominated ecosystems are occurring over large land areas in the western US. It is not clear what effect this vegetative change will have on rates of carbon and nitrogen cycling, and thus long-term ecosystem productivity. To study the effect of different plant species on the decomposability of soil organic substrates and rates of C- and N-cycling, we conducted laboratory incubations of soils from a 15-yr-old experimental plot where big sagebrush (Artemisia tridentata Nutt.) and crested wheatgrass (Agropyron desertorum [Fisch.] Schult.) plants had been planted in a grid pattern. Soil samples collected from beneath crested wheatgrass had significantly greater total...
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Many soils in southeastern Utah are protected from surface disturbance by biological soil crusts that stabilize soils and reduce erosion by wind and water. When these crusts are disturbed by land use, soils become susceptible to erosion. In this study, we compare a never-grazed grassland in Canyonlands National Park with two historically grazed sites with similar geologic, geomorphic, and geochemical characteristics that were grazed from the late 1800s until 1974. We show that, despite almost 30 years without livestock grazing, surface soils in the historically grazed sites have 38-43% less silt, as well as 14-51% less total elemental soil Mg, Na, P, and Mn content relative to soils never exposed to livestock disturbances....
The amount of carbon plants allocate to mycorrhizal symbionts exceeds that emitted by human activity annually. Senescent ectomycorrhizal roots represent a large input of carbon into soils, but their fate remains unknown. Here, we present the surprising result that, despite much higher nitrogen concentrations, roots colonized by ectomycorrhizal (EM) fungi lost only one-third as much carbon as non-mycorrhizal roots after 2 years of decomposition in a piñon pine (Pinus edulis) woodland. Experimentally excluding live mycorrhizal hyphae from litter, we found that live mycorrhizal hyphae may alter nitrogen dynamics, but the afterlife (litter-mediated) effects of EM fungi outweigh the influences of live fungi on root...
Whole air drawn from four heights within the high elevation (3,340 m asl), deep, winter snowpack at Niwot Ridge, Colorado, were sampled into stainless steel canisters, and subsequently analyzed by gas chromatography for 51 volatile inorganic and organic gases. Two adjacent plots with similar snow cover were sampled, one over bare soil and a second one from within a snow-filled chamber where Tedlar/Teflon-film covered the ground and isolated it from the soil. This comparison allowed for studying effects from processes in the snowpack itself versus soil influences on the gas concentrations and fluxes within and through the snowpack. Samples were also collected from ambient air above the snow surface for comparison...
Interest in the utilization of forest biomass for energy is growing. A search into existing forest biomass harvesting and regeneration guidelines was carried out to identify how biomass energy can be environmentally sustainable. Findings have shown that there are only a few guidelines that specifically address harvesting and regenerating biomass for bioenergy or other bio-based products. Of these few, there are guidelines developed for dedicated energy plantations such as the Scottish Agricultural College guidelines, as well as some Finnish and Swedish guidelines recommending management practices for both timber and biomass extraction. Most of the existing small woody material guidelines emphasize the retention,...
Cyanobacteria develop as large, cryptic populations in the topsoil of arid land, where plant cover is restricted, water is scarce and harsh microenvironmental conditions prevail. Here we show that some cyanobacteria can actively move in response to wetting or drying events by migrating to the soil surface or retreating to their refuge below. This ability to follow water, which to our knowledge has not been demonstrated before in microbes, may turn out to be important for microbial terrestrial populations in general. Published in Nature, volume 413, issue 6854, on pages 380 - 1, in 2001.
Physical ecosystem engineers are organisms that physically modify the abiotic environment. They can affect biogeochemical processing by changing the availability of resources for microbes (e.g., carbon, nutrients) or by changing abiotic conditions affecting microbial process rates (e.g., soil moisture or temperature). Physical ecosystem engineers can therefore create biogeochemical heterogeneity in soils and sediments. They do so via general mechanisms influencing the flows of materials (i.e., modification of fluid dynamic properties, fluid pumping, and material transport) or the transfer of heat (i.e., modification of heat transfer properties, direct heat transfer, and convective forcing). The consequences of physical...
We investigated the relationships between foliar stable carbon isotope discrimination (Delta), % foliar N, and predawn water potentials (psi(pd)) and midday stomatal conductance ( g(s)) of Larrea tridentata across five Mojave Desert soils with different age-specific surface and sub-surface horizon development and soil hydrologies. We wished to elucidate how this long-lived evergreen shrub optimizes leaf-level physiological performance across soils with physicochemical characteristics that affect the distribution of limiting water and nitrogen resources. We found that in young, coarse alluvial soils that permit water infiltration to deeper soil horizons, % foliar N was highest and Delta, g(s) and psi(pd) were lowest,...
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Emerging applications of ecosystem resilience and resistance concepts in sagebrush ecosystems allow managers to better predict and mitigate impacts of wildfire and invasive annual grasses. Soil temperature and moisture strongly influence the kind and amount of vegetation, and consequently, are closely tied to sagebrush ecosystem resilience and resistance (Chambers et al. 2014). Soil taxonomic temperature and moisture regimes can be used as indicators of resilience and resistance at landscape scales to depict environmental gradients in sagebrush ecosystems that range from cold/cool-moist sites to warm-dry sites. We aggregated soil survey spatial and tabular data to facilitate broad-scale analyses of resilience and...
Categories: Data, Publication; Types: Citation, Map Service, OGC WFS Layer, OGC WMS Layer, OGC WMS Service; Tags: California, Colorado, EARTH SCIENCE > LAND SURFACE > LANDSCAPE, Greater sage-grouse, Greater sage-grouse, All tags...
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This report is volume 2 of a two-volume ecological assessment of grassland ecosystems in the Southwestern United States. Broad-scale assessments are syntheses of current scientific knowledge, including a description of uncertainties and assumptions, to provide a characterization and comprehensive description of ecological, social, and economic components within an assessment area. Volume 1 of this assessment focused on the ecology, types, conditions, and management practices of Southwestern grasslands. Volume 2 (this volume) describes wildlife and fish species, their habitat requirements, and species-specific management concerns, in Southwestern grasslands. This assessment is regional in scale and pertains primarily...
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Information about the condition of the land and related natural resources is needed at many different scales to inform decision makers. The U.S. Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) gathers rangeland on-site data as part of the National Resources Inventory (NRI). This report focuses on information derived from NRI rangeland data collected on-site 2004 to 2011. The findings reported here focus on key issues in rangeland science, including rangeland health, non-native plant species, non-native and native invasive plant species, bare ground, inter-canopy gaps and soil surface aggregate stability. Future reports will provide monitoring results based on data collected at revisited...
The effect of snow cover on surface-atmosphere exchanges of nitrogen oxides (nitrogen oxide (NO) + nitrogen dioxide (NO2); note, here ?NO2? is used as surrogate for a series of oxidized nitrogen gases that were detected by the used monitor in this analysis mode) was investigated at the high elevation, subalpine (3,340 m asl) Soddie site, at Niwot Ridge, Colorado. Vertical (NO + NO2) concentration gradient measurements in interstitial air in the deep (up to ~2.5 m) snowpack were conducted with an automated sampling and analysis system that allowed for continuous observations throughout the snow-covered season. These measurements revealed sustained, highly elevated (NO + NO2) mixing ratios inside the snow. Nitrogen...
Drylands are considered a net sink for atmospheric methane and a main component of global inventories for greenhouse gas budgets. However, a significant portion of drylands occur over sedimentary basins hosting natural gas and oil reservoirs, with gas migration to the surface (named “microseepage”) producing positive atmospheric CH4 fluxes. In this overview, we summarize the outcomes of microseepage surveys performed in different petroleum basins, describe how the microseepage area is estimated and what are the emission factors that can be used for a preliminary global emission estimate. Microseepage frequently overcomes methanotrophic consumption occurring in dry soil throughout large areas, and it is enhanced...
Categories: Publication; Types: Citation; Tags: CH4, Methane, drylands, microseepage, soil
Soil treatment of wastewater has the potential to achieve high purification efficiency, yet the understanding and predictability of purification with respect to removal of viruses and other pathogens is limited. Research has been completed to quantify the removal of virus and bacteria through the use of microbial surrogates and conservative tracers during controlled experiments with three-dimensional pilot-scale soil treatment systems in the laboratory and during the testing of full-scale systems under field conditions. The surrogates and tracers employed included two viruses (MS-2 and PRD-1 bacteriophages), one bacterium (ice-nucleating active Pseudomonas), and one conservative tracer (bromide ion). Efforts have...
map background search result map search result map Multi-Decadal Impacts of Grazing on Soil Physical and Biogeochemical Properties in Southeast Utah Cheatgrass (Bromus tectorum L.) and seasonal patterns of soil phosphorus availability in arid ecosystems Journal Article: Soil Temperature and Moisture Regimes across Sage-Grouse Range The Human Footprint in the West Climate Change Vulnerability and Adaptation Strategies for Natural Communities Assessment of Grassland Ecosystem Conditions in the Southwestern United States: Wildlife and Fish, Volume 2 Sacaton Riparian Grasslands National Resources Inventory Rangeland Resource Assessment Sacaton Riparian Grasslands Multi-Decadal Impacts of Grazing on Soil Physical and Biogeochemical Properties in Southeast Utah Cheatgrass (Bromus tectorum L.) and seasonal patterns of soil phosphorus availability in arid ecosystems Climate Change Vulnerability and Adaptation Strategies for Natural Communities Assessment of Grassland Ecosystem Conditions in the Southwestern United States: Wildlife and Fish, Volume 2 Journal Article: Soil Temperature and Moisture Regimes across Sage-Grouse Range The Human Footprint in the West National Resources Inventory Rangeland Resource Assessment