Research and Publications
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The sagebrush (Artemisia spp.) biome, its wildlife, and the services and benefits it provides people and local communities are at risk. Development in the sagebrush biome, for many purposes, has resulted in multiple and often cumulative negative impacts. These impacts, ranging from simple habitat loss to complex, interactive changes in ecosystem function, continue to accelerate even as the need grows for the resources provided by this biome. This “Sagebrush Conservation Strategy—Challenges to Sagebrush Conservation,” is an overview and assessment of the challenges facing land managers and landowners in conserving sagebrush ecosystems. This strategy is intended to provide guidance so that the unparalleled collaborative efforts to conserve the iconic greater sage-grouse (Centrocercus urophasianus) by State and Federal agencies, Tribes, academia, nongovernmental organizations, and stakeholders can be expanded to the entire sagebrush biome to benefit the people and wildlife that depend on this ecosystem. This report is organized into 3 parts.
“Part I. Importance of the Sagebrush Biome to People and Wildlife” introduces the biome and a subset of the more than 350 species of plants and animals associated with sagebrush for which there is some level of conservation concern. These include several sagebrush obligates that have been petitioned for listing under the Endangered Species Act of 1973 (16 U.S.C. 1531 et seq.), including greater sage-grouse, Gunnison sage-grouse (C. minimus; listed as threatened), and pygmy rabbit (Brachylagus idahoensis). Other sagebrush-dependent species, such as pronghorn (Antilocapra americana) and mule deer (Odocoileus hemionus), have experienced significant population declines.
“Part II. Change Agents in the Sagebrush Biome—Extent, Impacts, and Effort to Address Them” is an overview of the variety of change agents that are causing the continued loss and degradation of sagebrush. Topics covered include altered fire regimes, invasive plant species, conifer expansion, overabundant free-roaming equids, and human land uses, including energy development, cropland conversion, infrastructure, and improper livestock grazing. Climate changes, including warmer temperatures and altered amounts and timing of precipitation, have and will likely increasingly compound negative effects to sagebrush ecosystems from all these threats.
“Part III. Current Conservation Paradigm and Other Conservation Needs for Sagebrush” begins with an overview of how sage-grouse conservation, and the associated efforts and collaborations, may be able to address threats to and restoring degraded sagebrush and habitat for other sagebrush-dependent and -associated species. Meeting conservation goals for sage-grouse, mule deer, pygmy rabbits, and other sagebrush-associated wildlife will require extensive restoration of sagebrush communities already converted or degraded by the change agents outlined in Part II of this report. Concepts, considerations, techniques for restoration, and adaptive management and monitoring are discussed to help set the stage for potential strategies to improve conditions throughout the sagebrush biome. Communication, outreach, and engagement can enhance grassroots conservation efforts and build the next generation of managers, practitioners, scientists, and communicators who will care for the sagebrush ecosystem and stimulate or sustain public participation in sagebrush conservation issues.
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Invasive Species in Forests and Rangelands of the United States is a sector-wide scientific assessment of the current state of invasive species science and research in the United States. Leading experts on invasive pests, climate change, social sciences, and forest and rangeland management contributed to highlighting the science and identifying knowledge gaps on a diverse array of topics related to invasive species. Stakeholders from nongovernmental organizations, academic institutions, professional organizations, private corporations, and state and federal agencies representing public, private, and tribal interests also provided input to the assessment. Input from these stakeholders helped to frame the subject matter content and management options presented in this report, ensuring relevance for decision-makers and resource managers.
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Widespread, rapid aspen (Populus tremuloides) mortality since the beginning of the 21st century, sometimes called sudden aspen decline (SAD), has been documented in many locations across North America, but it has been particularly pronounced in the southwestern U.S. We investigated the relationship between aspen growth, mortality, and climate across three forest types in northern Arizona using crossdated tree-ring samples from 126 live and 132 dead aspen. Aspen growth was negatively correlated with warm temperatures and positively associated with higher precipitation. Using survival analysis techniques to investigate the links between aspen mortality, tree traits, and climatic conditions, we found that tree traits played a larger role in mortality risk than climate factors. Trees with larger diameters, older trees, and trees with faster growth rates over the past 50 years had a reduced risk of mortality. Management actions aimed at maintaining the most vigorous, fastest growing aspen in the region could help mitigate the impacts of a warmer, drier future.
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California’s high density, fire-excluded forests experienced an extreme drought accompanied by warmer than normal temperatures from 2012 to 2015, resulting in the deaths of millions of trees. We examined tree mortality
and growth of mixed-conifer stands that had been experimentally treated between 2011 and 2013 with two different thinning treatments, one with more structural variability (HighV) and one with less structural variability (LowV), applied alone or in combination with prescribed burning. Tree mortality between 2014 and 2018 varied by species ranging from 42% of white fir (Abies concolor) to 18% of sugar pine (Pinus lambertiana), 12% of
incense cedar (Calocedrus decurrens) and 10% of yellow pine (P. ponderosa and P. jeffreyi). Lower overall tree mortality rates at this location relative to drier locations in the southern Sierra Nevada suggested that drought
effects may have been ameliorated by lower water deficits due to our site’s more northerly location and deep, productive soils in combination with reductions in tree competition following thinning and burning. Averaged
across burn treatments, thinning reduced the overall mortality rate between 2014 and 2018 from 34% to 11%. A total of 23% of the basal area was lost in the unthinned control treatments during this time period, while basal
area was unchanged in the thinned treatments, with growth offsetting mortality. There was no significant difference in mortality or basal area change between LowV and HighV, suggesting that leaving trees at variable spacing may not compromise growth or resilience of the stand during a drought. Overall tree mortality was greater in the prescribed burn treatments, most pronounced in the smaller tree size classes, and varied by species, with burning having a significant effect on incense cedar and all pines, but not white fir. Trees with greater competition (Hegyi index) were more likely to die, particularly when also burned. Burning, however, consumed surface fuels and lowered fire hazard. With predictions of warmer droughts and greater weather variability, reducing forest density (basal area) and keeping surface fuel loads low will be important for building greater resilience to future drought stress and wildfire.
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The need for basic information on spatial distribution and abundance of plant species for research and management in semiarid ecosystems is frequently unmet. This need is particularly acute in the large areas impacted by megafires in sagebrush steppe ecosystems, which require frequently updated information about increases in exotic annual invaders or recovery of desirable perennials. Remote sensing provides one avenue for obtaining this information. We considered how a vegetation model based on Landsat satellite imagery (30 m pixel resolution; annual images from 1985 to 2018) known as the National Land Cover Database (NLCD) “Back-in-Time” fractional component time-series, compared with field-based vegetation measurements. The comparisons focused on detection thresholds of post-fire emergence of fire-intolerant Artemisia L. species, primarily A. tridentata Nutt. (big sagebrush). Sagebrushes are scarce after fire and their paucity over vast burn areas creates challenges for detection by remote sensing. Measurements were made extensively across the Great Basin, USA, on eight burn scars encompassing ~500 000 ha with 80 plots sampled, and intensively on a single 113 000 ha burned area where we sampled 1454 plots.
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Today, American conservation confronts the climate crisis, the biodiversity crisis, a global pandemic, skeptics of these threats, a massive federal deficit, economic hardship, social injustice, and political divisions that threaten our democracy. Yet, at the same time, people continue to explore new ways to work together to use science, collaboration, and innovation to advance efforts to protect our environment, conserve our natural resource legacy, and broaden its benefits for all Americans.
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The researchers report on creating an unburned area data set for the Inland Northwest from 1984 – 2014 and subsequent analyses using this dataset. Here are some of the key findings for this JFSP project:
- Unburned area occurrence is consistent or stabilized to-date, with no evidence of increasing or decreasing trends under current climate conditions
- Unburned areas are utilized by sage grouse and help maintain viable populations when these fire refugia are present
- Persistent unburned islands are ecologically important areas and are related to specific topography and fuel type characteristics
- Persistent unburned area attributes differ between forests and rangelands
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In 2009, at the behest of Congress, the Council on Environmental Quality (CEQ) and the US Department of the Interior (DOI) were asked to develop a national, government-wide climate adaptation strategy for fish, wildlife, plants, and ecosystems. In doing so, the Federal Government recognized the immensity of climate change impacts on the Nation’s vital natural resources, as well as the critical need for partnership among federal, state, and tribal fish and wildlife agencies. More than 90 diverse technical, scientific, and management experts from across the country participated in the development and, in 2012, the National Fish, Wildlife, and Plants Climate Adaptation Strategy (Strategy) was published. Designed to “inspire and enable natural resource managers, legislators, and other decision makers to take effective steps towards climate change adaptation over the next five to ten years,” the time has come for the natural resource community to consider the impact of the Strategy, while identifying the necessary evolution of it, to continue to effectively safeguard the Nation’s natural resources in a changing climate.
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Extreme wildfires are increasing in frequency globally, prompting new efforts to mitigate risk. The ecological appropriateness of risk mitigation strategies, however, depends on what factors are driving these increases. While regional syntheses attribute increases in fire activity to both climate change and fuel accumulation through fire exclusion, they have not disaggregated causal drivers at scales where land management is implemented. Recent advances in fire regime modeling can help us understand which drivers dominate at management-relevant scales. We conducted fire regime simulations using historical climate and fire exclusion scenarios across two watersheds in the Inland Northwestern U.S., which occur at different positions along an aridity continuum. In one watershed, climate change was the key driver increasing burn probability and the frequency of large fires; in the other, fire exclusion dominated in some locations. We also demonstrate that some areas become more fuel-limited as fire-season aridity increases due to climate change. Thus, even within watersheds, fuel management must be spatially and temporally explicit to optimize effectiveness. To guide management, we show that spatial estimates of soil aridity (or temporally averaged soil moisture) can provide a relatively simple, first-order indicator of where in a watershed fire regime is climate vs. fuel-limited and where fire regimes are most vulnerable to change.
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The Sagebrush Treatment Evaluation Project (SageSTEP) evaluated the ecological effects of prescribed fire and cut‐and‐leave treatments in sagebrush communities experiencing tree expansion in North American cold desert shrublands. We used 10 yr of data from the SageSTEP network to test how treatments interacted with pre‐treatment tree dominance, soil climate, and time since treatment to affect plant functional groups and dominant species. Non‐sprouting shrub (Artemisia spp.), sprouting shrub, perennial graminoid, and annual grass responses depended on tree dominance and soil climate, and responses were related to the dominant species’ life‐history traits. Sites with warm and dry soils showed increased perennial graminoid but reduced Artemisia shrub cover across the tree dominance gradient after prescribed burning, while sites with cool and moist soils showed favorable post‐burn responses for both functional types, particularly at low to moderate tree dominance. Cut‐and‐leave treatments sustained or increased native perennial plant functional groups and experienced smaller increases in exotic annual plants in both soil climates across the tree dominance gradient. Both treatments reduced biocrust cover. Selecting appropriate tree‐reduction treatments to achieve desired long‐term outcomes requires consideration of dominant species, site environmental conditions, and the degree of woodland expansion. Careful selection of management treatments will reduce the likelihood of undesirable consequences to the ecosystem.