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The Grand Staircase—Escalante National Monument (GSENM) contains a rich diversity of native plant communities. However, many exotic plant species have become established, potentially threatening native plant diversity. We sought to quantify patterns of native and exotic plant species and cryptobiotic crusts (mats of lichens, algae, and mosses on the soil surface), and to examine soil characteristics that may indicate or predict exotic species establishment and success. We established 97 modified-Whittaker vegetation plots in 11 vegetation types over a 29,000 ha area in the Monument. Canonical correspondence analysis (CCA) and multiple linear regressions were used to quantify relationships between soil characteristics...
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Invasion by the C3 annual grass Bromus tectorum has significantly increased the amount of relatively low quality (high lignin:nitrogen) plant litter deposited in arid Colorado Plateau grasslands. Our objectives were to determine what effects these changes have on microbial utilization of carbon (C) and nitrogen (N). We measured net C and N mineralization, and the δ13C of bulk organic matter, mineralized C, and bacterial fatty acids from soils of invaded and non-invaded C3 (Stipa hymenoides) and C4 (Hilaria jamesii) native grasslands. Carbon mineralization was greater in invaded compared to non-invaded sites (1.25 +/- 0.09 and 1.52 +/- 0.18 g CO2-C kg-1 soil h-1 respectively). Rates of net inorganic N mineralization...
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Invasions of the annual species cheatgrass (Bromus tectorum) in North American ecosystems present a threat to the population viability of native plant and animal species. In the interest of curtailing B. tectorum success, we manipulated the biogeochemistry of Canyonlands National Park soils in greenhouse and germination experiments. We compared growth parameters of B. tectorum and a native perennial, Hilaria jamesii, in greenhouse experiments utilizing 10 soil additives. Biomass of B. tectorum growing in conjuction with H. jamesii was greater than that growing in monocultures, suggesting facilitation of Bromus growth by H. jamesii. The opposite trend was true for H. jamesii, indicating that Bromus inhibits H. jamesii...
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In dryland ecosystems, the timing and magnitude of precipitation pulses drive many key ecological processes, notably soil water availability for plants and soil microbiota. Plant available water has frequently been viewed simply as incoming precipitation, yet processes at larger scales drive precipitation pulses, and the subsequent transformation of precipitation pulses to plant available water are complex. We provide an overview of the factors that influence the spatial and temporal availability of water to plants and soil biota using examples from western USA drylands. Large spatial- and temporal-scale drivers of regional precipitation patterns include the position of the jet streams and frontal boundaries, the...
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MOAB, Utah — Drier conditions projected to result from climate change in the Southwest will likely reduce perennial vegetation cover and result in increased dust storm activity in the future, according to a new study by scientists with the U.S. Geological Survey and the University of California, Los Angeles. The research team examined climate, vegetation and soil measurements collected over a 20-year period in Arches and Canyonlands National Parks in southeastern Utah. Long-term data indicated that perennial vegetation in grasslands and some shrublands declined with temperature increases. The study then used these soil and vegetation measurements in a model to project future wind erosion. The findings strongly...
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