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The alien grass Bromus tectorum dominates stable annual-plant communities that have replaced native shrub-perennial grass communities over much of the semi-arid western United States. We conducted field competition experiments between B. tectorum and a native grass, Elymus elymoides, on two sites to determine the effects of B. tectorum competition on perennial grasses, and the role of B. tectorum competition in the stability of B. tectorum-dominated communities. B. tectorum competition acting on seedling-stage E. elymoides plants greatly reduced first-year relative growth rates and biomass which, in turn, reduced second-year survival, biomass, and flowering. However, B. tectorum competition acting on older E. elymoides...
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This map depicts the distribution of sagebrush and associated shrubsteppe habitat types using readily available data from a variety of source maps from WA, OR, CA, UT, NV, CO, WY, MT, ND, SD, AZ, NM, AB, and BC. Habitat was grouped from map sources that were classified with detailed information on specific sagebrush types, as well as coarse-scale maps that classified vegetation as only "shrub" in the case of ND and the Canadian provinces. This map is a 90-meter grid, but source material included 30 to 90-meter grids, and 1:24,000 and 1:100,000 polygon coverages.
Beaver (Castor canadensis) populations have declined or failed to recover in heavily browsed envi­ronments. I suggest that intense browsing by livestock or ungulates can disrupt beaver-willow (Salix spp.) mutu­alisms that likely evolved under relatively low herbivory in a more predator-rich environment, and that this inter­ action may explain beaver and willow declines. Field experiments in Rocky Mountain National Park, Colorado, USA, found the interaction of beaver and elk (Cervus elaphus) herbivory suppressed compensatory growth in wil­low. Intense elk browsing of simulated beaver-cut willow produced plants which were small and hedged with a high percentage of dead stems, whereas protected plants were large...
* 1 Abandoned agricultural (AA) fields are often invaded by exotic plants. This observation has been difficult to explain because agricultural practices change nearly every aspect of an ecosystem. Restoring native plants to AA fields is likely to require a prioritized understanding of the many mechanisms through which agriculture encourages exotic and discourages native plant growth. * 2 Using 660 experimental plots in three sites in Methow Valley, Washington, USA, we determined the relative role of neighbour removal, propagule addition, plant?soil feedback, soil disturbance and fungal restriction to explain why exotics cover 38% of the ground in AA fields and 3% of the ground in non-agricultural (NA) fields. *...


    map background search result map search result map Distribution of Sagebrush and Associated Shrub-steppe Habitats in Western North America Distribution of Sagebrush and Associated Shrub-steppe Habitats in Western North America