Research and Publications
The book, Exotic brome-grasses in arid and semiarid ecosystems of the western US: causes, consequences, and management implications, is presented in several chapters.
Access is provided for the following chapters -
Chapter 1 - Introduction: Exotic annual Bromus in the western USA
Chapter 2 - Exotic annual Bromus invasions: comparisons among species and ecoregions in the western US
Chapter 3 - Ecosystem impacts of exotic annual invaders in the genus Bromus
Chapter 7 - Community ecology of fungal pathogens on Bromus tectorum
Chapter 8 - Soil moisture and biogeochemical factors influence the distribution of annual Bromus species
Chapter 9 - Bromus response to climate and projected changes with climate change
Chapter 10 - Plant community resistance to invasion by Bromus species: The roles of community attributes, Bromus interactions with plant communities, and Bromus traits
Chapter 11 - Land uses, fire, and invasion: Exotic annual Bromus and human dimensions
Chapter 12 - Assessing restoration and management needs for ecosystems invaded by exotic annual Bromus species
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It is likely that increasing temperatures will stress native sagebrush steppe species in the lowest, hottest basins more than in cooler and wetter upland habitats. Second, the effect of climate change on cheatgrass and fire is critical but uncertain. Regional warming will increase the frequency of hot, dry conditions that promote fire, but droughts could dampen the fire cycle by limiting the production of fine fuels. Third, the adaptive capacity of sagebrush is unknown and research on the potential for sagebrush to adapt to climate change should be a high priority.
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Big sagebrush cover decreased significantly in response to spring temperatures. On the other hand, cheatgrass cover and Sandberg’s bluegrass cover increased mostly in wetter years. Three other species analyzed, three-tip sagebrush, needle-and-thread grass and bluebunch wheatgrass, showed very weak responses to annual climate. This analysis shows that species commonly found together may differ in how they respond to annual climate variation. The weak response to annual climate variation we observed is in contrast to the strong sensitivity to climate predicted by species distribution models. Our analysis suggests that species’ responses to climate may require long-term changes in climate or may be driven by other indirect effects of climate, such as fire frequency.
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The primary goal of this project was to assess the effect of climate change on carbon cycling in mature sagebrush ecosystems. We used initial soil characteristics and carbon values for three location and modeled future climate at those locations for four different climate scenarios. We found that mature sagebrush ecosystems continued to act as carbon sinks into the future under all different climate change scenarios. The magnitude of carbon storage differed depending on initial conditions and soil characteristics at each site. Climate change may affect the potential for sequestration by increasing carbon loss through respiration, but we found that increased losses were offset by increased gains through greater primary production.
Forecasts of sagebrush distribution across western land management agencies: Who owns the sagebrush?
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Species distribution models were used to predict how sagebrush distribution could change in response to climate change across land management agencies in the West. Models predict that sagebrush habitats will shift northward and upward in elevation and decrease greatly in extent. Mountainous higher elevation areas were predicted to maintain more sagebrush. U.S. Forest Service lands were predicted to lose proportionally less sagebrush area than non-federal land or the BLM. Analysis suggests that some agencies such as the BLM with the most experience managing sagebrush will lose much of this habitat, while other agencies such as the USFS may have new sagebrush habitats to manage.
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In the future, areas where sagebrush will expand, the leading edge, are predicted to be on the northern edge of its current range—predominately northeast Montana. Conversely, areas where the current sagebrush distribution is predicted to contract, the trailing edge, reside at the southern edge of the current distribution, including the Great Basin. Both of these projected shifts are most likely in response to predicted increased minimum temperature and changes in precipitation amount and seasonality. Climate and hydrological factors have the potential to strongly affect sagebrush regeneration because sagebrush does not reproduce asexually and depends solely on germination rates and seedling survival. By exploring these relationships using an ecohydrologic simulation model, we found that sagebrush germination is not expected to be limiting at either the leading or trailing edge. However, seedling survival was expected to decrease at the trailing edge while increasing at the leading edge.
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Paleovegetation studies show that even prior to anthropogenic influence, sage steppe communities were dynamic, and in some cases, susceptible to replacement by other vegetation communities (including forests) under changing climatic conditions.
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Public land management agencies are under increasing pressure to consider climate change impacts in their land-use planning process. As a first step, many agencies are conducting vulnerability assessments to identify the components of an ecosystem, or conservation targets, most at-risk from climate change. Vulnerability assessment is the first step towards a climate change adaptation plan.
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This study found evidence of a gap between risk perceptions of WUI residents and wildfire professionals. On average, residents underestimated the overall risk of their property. One third of the study participants reported having a neighbor that they think is increasing their risk. Perceived likelihood of fire reaching the property and causing damages was positively correlated with perceiving a neighbor is not taking action. The only consistent predictor of defensible space was the level of defensible space on neighboring properties. Our results suggest that programs that are effective in getting single homeowners to mitigate risk may have benefits that spillover to neighboring properties, and risk neutral/tolerant individuals lived on parcels that were rated by the professional as having less defensible space and more ignitable structure materials.
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Smoke is challenging. It can be lofted high into the atmosphere to interact with cloud processes. It can smolder near the ground, depositing emissions. The combination of aerosols and trace gases create their own chemical mix, with reactions that are as yet unidentified. Temperature and atmospheric water content interact with the smoke plume and fog processes. Smoke also blocks the transmission of solar radiation, hindering photolysis reactions. Many of the trace gases emitted from wildland fires have yet to be identified, as do the intermediary products produced in a plume. With the outlook for more wildfires in the future, especially in a changing climate—and with tighter health standards—understanding these processes will become more critical in the years to come.