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Few studies have examined plant?soil relationships in competitive arenas between exotic and native plants in the western United States. A pair-wise competitive design was used to evaluate plant?soil relationships between seedlings of the exotic annual grasses Bromus tectorum and Taeniatherium caput-medusae and the native perennial grasses Elymus elymoides and Pseudoroegneria spicata. Two soils were tested: an arid soil (argid) occupied by E. elymoides and presently invaded by B. tectorum and a high elevation, high organic matter, soil (aquept) where none of the tested species would typically occur. Plant growth proceeded for 85 days at which time above-ground biomass and tissue nutrient concentrations were quantified....
Eddy covariance measures net ecosystem exchange of CO2 (NEE) at a scale between chamber-based measurements of CO2 exchange processes and large-scale models of CO2 flux dynamics. As the intermediate, it represents a link between small and large-scale estimates of NEE. Accuracy is therefore critical. However, estimates of nighttime ecosystem respiration based on scaled-up measurements of soil and leaf CO2 exchange are most often larger than from eddy covariance. Identifying the source of the discrepancy is difficult due to large measurement uncertainties associated with high variability of fluxes in complex ecosystems. This study compared measurements in a simple system that allowed for minimal uncertainty. We compared...
Biological soil crusts can affect seed germination and seedling establishment. We have investigated the effect of biological soil crusts on seed water status as a potential mechanism affecting seed germination. The seed water potential of two annual grasses, one exotic Bromus tectorum L. and another native Vulpia microstachys Nutt., were analyzed after placing the seeds on bare soil, on a crust that contains various lichens and mosses (mixed crust), or on a crust dominated by the crustose lichen Diploschistes muscorum (Scop.) R. Sant. (Diploschistes crust). Seed water potential and germination were similar on the bare soil and the mixed crust, except for the initial germination of V. microstachys, which was higher...
The effects of salt stress on growth and development of cheatgrass (Bromus tectorum L.) were investigated in 2 greenhouse studies. The first study assessed developmental and physiological responses of this grass to 4 salinity levels. Salinity stunted growth through reduced leaf initiation and expansion, and reduced photosynthetic rates. Reduction of photosynthetic rates appeared to be primarily due to stomatal limitation. Salinity also reduced carbon isotope discrimination, indicating long-term effects on conductance and carbon gain. Root growth was severely inhibited by high salinity, resulting in a shift in the root to shoot allocation pattern. The second study investigated growth patterns of cheatgrass in relation...
Ecosystem susceptibility to invasion by nonnative species is poorly understood, but evidence is increasing that spatial and temporal variability in resources has large-scale effects. We conducted a study in Artemisia tridentata ecosystems at two Great Basin locations examining differences in resource availability and invasibility of Bromus tectorum over elevation gradients and in response to direct and interacting effects of removal of perennial herbaceous vegetation and fire. We monitored environmental conditions, soil variables, and B. tectorum establishment and reproduction over two years. Soil water (measured as the number of days soil matric potential was >?1.5 MPa) and nitrate availability (measured as micromoles...
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This dataset provides a near-real-time estimate of 2017 herbaceous annual cover with an emphasis on annual grass (Boyte and Wylie. 2016. Near-real-time cheatrass percent cover in the Northern Great Basin, USA, 2015. Rangelands 38:278-284.) This estimate was based on remotely sensed enhanced Moderate Resolution Imaging Spectroradiometer (eMODIS) Normalized Difference Vegetation Index (NDVI) data gathered through June 19, 2017. This is the second iteration of an early estimate of herbaceous annual cover for 2017 over the same geographic area. The previous dataset used eMODIS NDVI data gathered through May 1 (https://doi.org/10.5066/F7445JZ9). The pixel values for this most recent estimate ranged from 0 to100% with...
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The dataset provides an estimate of 2017 herbaceous annual percent cover predicted on May 1st with an emphasis on annual grasses. The pixel values range from 0 to100 with an overall mean value of 7.1 and a standard deviation of +/-10.5. The model's test mean error rate (n = 1670), based on nine different randomizations, equals 4.9% with a standard deviation of +/- 0.15. This dataset was generated by integrating ground-truth measurements of annual herbaceous percent cover with 250-m spatial resolution eMODIS NDVI satellite derived data and geophysical variables into regression-tree software. The geographic coverage includes the Great Basin, the Snake River Plain, the state of Wyoming, and contiguous areas. We applied...
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Among threats to the sagebrush ecosystem in the Great Basin and elsewhere (BLM 1999, 2002; Nachlinger et al. 2001; Wisdom et al. 2003) is the threat of displacement of native habitats by cheatgrass (Bromus tectorum). Mapping these threats in the sagebrush ecosystem will allow managers to identify areas of native vegetation at high risk of displacement, where active restoration may be required, versus areas at low risk, where conservation of existing habitats may be preferable. A draft model of risk of displacement of sagebrush and other native vegetation cover types by cheatgrass was applied to the 14 ecological provinces that intersect the Great Basin. The model was applied to sagebrush cover and other vegetation...
map background search result map search result map Risk of Cheatgrass Displacement of Sagebrush and other Native Vegetation Early Estimates of Herbaceous Annual Cover in the Sagebrush Ecosystem (May 1, 2017) Near-real-time Herbaceous Annual Cover in the Sagebrush Ecosystem (June 19, 2017) Species distribution model of the invasive annual grass Bromus rubens (red brome) in the Mojave Desert Species distribution model of the invasive annual grass Bromus tectorum (cheatgrass) in the Mojave Desert Species distribution model of the invasive annual grass Bromus rubens (red brome) in the Mojave Desert Species distribution model of the invasive annual grass Bromus tectorum (cheatgrass) in the Mojave Desert Early Estimates of Herbaceous Annual Cover in the Sagebrush Ecosystem (May 1, 2017) Near-real-time Herbaceous Annual Cover in the Sagebrush Ecosystem (June 19, 2017) Risk of Cheatgrass Displacement of Sagebrush and other Native Vegetation