Resistance & Resilience
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Our new indicators were based on climate and soil water availability variables derived from process-based ecohydrological models that allow predictions of future conditions. We asked: (1) Which variables best indicate resilience and resistance? (2) What are the relationships among the indicator variables and resilience and resistance categories? (3) How do patterns of resilience and resistance vary across the area? We assembled a large database (n = 24,045) of vegetation sample plots from regional monitoring programs and derived multiple climate and soil water availability variables for each plot from ecohydrological simulations. We used USDA Natural Resources Conservation Service National Soils Survey Information, Ecological Site Descriptions, and expert knowledge to develop and assign ecological types and resilience and resistance categories to each plot. We used random forest models to derive a set of 19 climate and water availability variables that best predicted resilience and resistance categories. Our models had relatively high multiclass accuracy (80% for resilience; 75% for resistance). Top indicator variables for both resilience and resistance included mean temperature, coldest month temperature, climatic water deficit, and summer and driest month precipitation. Variable relationships and patterns differed among ecoregions but reflected environmental gradients; low resilience and resistance were indicated by warm and dry conditions with high climatic water deficits, and moderately high to high resilience and resistance were characterized by cooler and moister conditions with low climatic water deficits. The new, ecologically-relevant indicators provide information on the vulnerability of resources and likely success of management actions, and can be used to develop new approaches and tools for prioritizing areas for conservation and restoration actions.
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This study expands on a 2011 tribal research needs assessment with a survey to identify tribal natural resource professionals’ research needs, access to research findings, and interest in participating in research. Information needs identified in our survey includes forest health, water quality, culturally significant species, workforce and tribal youth development, cultural importance of water, and invasive species. Additionally, postfire response and valuation, resilience and long-term forestry, protecting and curating tribal data, and Indigenous burning were more important research needs for tribal members than for nontribal members. This study can inform forestry research planning efforts and establish research priorities and collaborations that are aligned with needs identified by tribal natural resource managers.
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Field data from 460 sagebrush populations sampled across the Great Basin revealed several patterns. Sagebrush seedlings were uncommon in the first 1–2 years after fire, with none detected in 69% of plots, largely because most fires occurred in areas of low resistance to invasive species and resilience to disturbance (hereafter, R&R). Post-fire aerial seeding of sagebrush dramatically increased seedling occupancy, especially in low R&R areas, which exhibited a 3.4-fold increase in occupancy over similar unseeded locations. However, occupancy models and repeat surveys suggested exceptionally high mortality, as occupancy rates declined by as much as 50% between the first and second years after fire. We found the prevalence of “fertile island” microsites (patches beneath fire-consumed sagebrush) to be the best predictor of seedling occupancy, followed by aerial seeding status, native perennial grass cover, and years since fire. In populations where no sagebrush seeding occurred, seedlings were most likely to occur in locations with a combination of high fertile island microsite cover and close proximity to a remnant sagebrush plant. These important attributes were only present in 13% of post-fire locations, making them rare across the Great Basin.
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Past practices, such as fire suppression, have created densely packed forests with an overabundance of woody vegetation. Live or dead, this vegetation can fuel severe wildfire. Overcrowded growing conditions also prevent trees and other plants from obtaining sufficient nutrients, light, or water to bounce back and remain healthy following a stressful event. The warming climate further stresses vegetation and can foster tinderbox conditions on the landscape, especially under widespread persistent drought.
Webinar recording.
This presentation discusses the following topics as they relate to rangelands:
- Resistance and Resilience are commonly used terms in discussions about agriculture and preparing for the future.
- Provide a common understanding of these terms as they apply to the ecology of grazed systems.
- Relationships between ecological resistance and resilience, disturbances, and ecological processes will be discussed.
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Our findings suggest that all deserts exhibited vulnerability to increasing fire disturbance because relatively low soil seed densities may not provide enough propagules for revegetation. Therefore, seeding of these communities may be especially important. In the cold deserts, this susceptibility was further evidenced by the fact that aboveground community composition in fire-affected areas was significantly different from the nearby unburned community even 30 years after fire and burned communities were associated with non-native species. That said, native species did exist in seed banks of burned sites and some taxa, like Sporobolus sp., occurred in high densities. Therefore, caution may be needed when using herbicide treatments to control exotic species as there may be unintended consequences of decreasing desirable species. In contrast, our warm desert sites exhibited less change in terms of seed densities, species richness and aboveground community composition following fire. In the face of more frequent fires, the lack of shrub seeds in the seed bank of all deserts was notable and we found no evidence of greater seed densities or unique species assemblages associated with shrub microsites.
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Assessing the geomorphic sensitivity of streams and the ecological resilience of riparian ecosystems provides the basis for understanding how they have responded to disturbances and management actions and how they are expected to respond in the future.
A collaborative group of managers and scientists led by Jeanne Chambers, research ecologist and senior scientist (emeritus) with the USDA Forest Service Rocky Mountain Research Station, and geomorphologist Jerry Miller, a professor of environmental science at Western Carolina University, developed a multiscale approach to help land managers rapidly assess watersheds and categorize them based on resilience and sensitivity to disturbance. The project was built on the long-term work of Chambers and her collaborators on Great Basin riparian ecosystems.
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Results suggest that dry forest species are undergoing an active range shift driven by both changing recruitment and mortality, and that increasing temperatures and drought threaten the long-term viability of many of these species in their current range. While four of the five species examined were experiencing some declines, Pinus edulis is currently most vulnerable. Management actions such as reducing tree density may be able to mitigate some of these impacts. The framework we present to estimate range-wide demographic rates can be applied to other species to determine where range contractions are most likely.
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Although important to consider in land management planning, abiotic properties cannot be directly influenced with management. In contrast, biotic properties of the ecosystem can be readily influenced by management. The formula for robust biotic resilience to wildfire and resistance to invasive annual grasses in the northern Great Basin sagebrush ecosystem is about maintaining and promoting perennial bunchgrasses. The management system must be resilient if we hope to promote ecosystem resilience in an ever-changing risk, seedling recruitment, and recovery environment. A successful strategy for promoting ecosystem resilience will require securing a resilient management system, and a shift in paradigm from random acts of opportunistic restoration to a sustained, organized, process-based approach for promoting ecosystem resilience.
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We propose an integrated fire management approach in which all management activities before, during, and after wildfire are synergistic and improve long-term ecosystem response to fire. Harney County Wildfire Collaborative is adapting the Potential Operational Delineations (PODs) framework to improve fire outcomes and promote values at risk in the Stinkingwater Mountains pilot project area. The PODs framework serves to promote a broader geographic strategy for addressing the underlying causes of frequent and severe wildfires in the sagebrush ecosystem.