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Tom Dilts

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Understanding the Causes and Consequences of Cheatgrass Die-offs in the Great Basin
FY2013Cheatgrass die-offs are unexplained instances of stand failure observed in areas of Nevada and Utah, where cheatgrass fails to grow even though it has been a dominant component of plant communities in the past. The goals of this project are to:1) provide information on the size and extent of historic (1985 - 2012) die-offs in the Winnemucca area using satellite imagery, and 2) determine if die-offs are restoration opportunities by planting and monitoring local and commercially available native grasses in die-off areas.Support is requested to fund monitoring of the restoration project through a second growing season and to develop predictive spatial models of die-off from analysis of satellite imagery and GIS...
Content Changing aspen distribution in response to climate change and fire is a major focus of biodiversity conservation, yet little is known about the potential response of aspen to these two driving forces along topoclimatic gradients. Objective This study is set to evaluate how aspen distribution might shift in response to different climate-fire scenarios in a semi-arid montane landscape, and quantify the influence of fire regime along topoclimatic gradients. Methods We used a novel integration of a forest landscape succession and disturbance model (LANDIS-II) with a fine-scale climatic water deficit approach to simulate dynamics of aspen and associated conifer and shrub species over the next 150 years under...
The phenomenon of cheatgrass die-off is a common and naturally- occurring stand failure that can eliminate the presence of this annual grass for a year or more, affecting tens to hundreds of thousands of acres in some years. We designed a study to determine if the temporary lack of cheatgrass caused by die-offs is a restoration opportunity. We seeded native perennial species at three die-offs in the Winnemucca, Nevada area. Native grass establishment in die-offs was almost three times higher in the first season at all sites, relative to adjacent areas without die-off. In the second season, establishment was five times higher in the die-off at two sites, and plants were notably larger in the die-off at the third...
The exotic annual grass Bromus tectorum (cheatgrass) dominates vast acreages of rangeland in the western USA, leading to increased fire frequency and ecosystem degradation that is often irreversible. Episodic regeneration failure (“die-off”) has been observed in cheatgrass monocultures and can have negative ecosystem consequences, but can also provide an opportunity for restoration of native species and ecological function within the imperiled sagebrush steppe ecosystem. Proximate causes of cheatgrass die-off are uncertain, although several taxa of fungal soil pathogens have been implicated. Die-off occurrence is stochastic and can occur in remote areas. Thus, developing remote sensing indicators that are repeatable...
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Quantifying vulnerability of quaking aspen woodlands and associate bird communities to global climate change in the northern Great Basin
FY2011Aspen populations are in decline across western North America due to altered fire regimes, herbivory, drought, pathogens, and competition with conifers. Aspen stands typically support higher avian biodiversity than surrounding habitats, and maintaining current distributions of several avian species is likely tied to persistence of aspen on the landscape. We are examining effects of climate change on aspen and associated avian communities in isolated mountain ranges of the northern Great Basin, by coupling empirical models of avian-habitat relationships with spatially-explicit landscape simulations of vegetation and disturbance dynamics (using LANDIS-II) under various climate change scenarios. We are addressing...
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