Research and Publications
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This study investigated the complex relationships among weather, fine fuels, and fire in the Great Basin, USA. It found that cheatgrass cover increased in years with higher precipitation and especially when one of the previous 3 years also was particularly wet. Area burned in a given year was mostly associated with native herb and non-native forb cover, whereas cheatgrass mainly influenced area burned in the form of litter derived from previous years’ growth. Results suggest that the region’s precipitation pattern of consecutive wet years followed by consecutive dry years results in a cycle of fuel accumulation followed by weather conditions that increase the probability of wildfire events in the year when the cycle transitions from wet to dry. These patterns varied regionally but were strong enough to allow us to model annual wildfire risk across the Great Basin based on precipitation alone.
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Fuel treatments decreased intrinsic water use efficiency relative to the control in Arizona although the differences were not sufficiently large to reach the threshold of statistical significance. Very dry conditions characterized post-treatment climate in Arizona and treatment decreased competition among trees for water. Decreased competition appears to have led to higher stomatal conductance in surviving trees and thus lower intrinsic water use efficiency, even with post-treatment growth increases as measured by basal area index. The treatment response supports our hypothesis of the expected treatment response.
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Results suggest that herbicide protection pods (HPPs) can be used to allow desired species to be seeded simultaneously with imazapic application. This will allow seeded species a longer window to become established before experiencing pressure from exotic annuals and enable a single-entry approach compared with multiple entries currently employed to revegetate annual grass − invaded rangelands. Though further field testing is needed, in particular with multiple species and higher herbicide applications rates, these results suggest that HPPs could improve our ability to restore and revegetate exotic annual grass − invaded rangelands.
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This paper defines the term ecological drought as an episodic deficit in water availability that drives ecosystems beyond thresholds of vulnerability, impacts ecosystem services, and triggers feedbacks in natural and/or human systems. We support this definition with a novel, integrated framework for ecological drought that is organized along two dimensions—the components of vulnerability (exposure + sensitivity/adaptive capacity) and a continuum from human to natural factors. The purpose of this framework is to help guide drought researchers and decision-makers to understand 1) the roles that both people and nature play as drivers of ecosystem vulnerability, 2) that ecological drought’s impacts are transferred to human communities via ecosystem services, and 3) these ecological and ecosystem service impacts will feed back to both natural and human systems. In addition, our framework will help identify important trade-offs and strategies for reducing the ecological drought risks facing both human and natural systems in the 21st century.
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This brief summarizes work by researchers who modeled exactly how problematic the grass-fire cycle could be for non-fire-adapted desert shrublands under three sets of climate conditions. Specifically, three different degrees of inter-annual precipitation variability (i.e., none, medium, and extreme climate change variability; sigma = 0 to 0.8) and related invasive grass cover biomass was modeled to theoretically induce land degradation.
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In this study, spectrophotometry was used to quantify chemical differences in the water-soluble compound, coumarin. Ultraviolet (UV) absorbance of A. tridentata subsp. vaseyana showed distinct differences among A.t. tridentata and wyomingensis. Use of spectrophotometry to acquire UV absorbance provides empirical results that can be used in seed testing laboratories using the seed chaff present with the seed to certify A. tridentata subspecies composition.
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Study results from this project suggest that treatments over a 70-year period on public lands in the southwestern United States are shifting toward restoration practices that are increasingly large, expensive, and related to fire and invasive species control.
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Skillful seasonal climate forecasts could greatly improve the cost efficiency of management treatments by limiting revegetation activities to time periods where forecasts suggest higher probabilities of successful seedling establishment. Climate-change projections are key to the application of current environmental models for development of mitigation and adaptation strategies and for management practices that require a multidecadal planning horizon. Adoption of new weather technology will require collaboration between land managers and revegetation specialists and modifications to the way we currently plan and conduct rangeland rehabilitation and restoration in the Intermountain West.
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This study showed higher levels of resilience to fire than is typically discussed in the sagebrush steppe, in part because the studied ecosystems were in good condition before the fire, but also because the longer post-fire monitoring time (17 years) may be more appropriate to capture patterns of succession in these ecosystems.
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Abstracts of Recent Papers on Range Management in the West. Prepared by Charlie Clements, Rangeland Scientist, USDA Agricultural Research Service, Reno, NV