Resistance & Resilience
A resilience-based approach to management can facilitate regional planning by guiding the allocation of management resources to where they will have optimal socioecological benefits. This type of approach requires a sound understanding of the environmental factors, ecosystem attributes and processes, and landscape components that influence ecological resilience of the focal system. Chambers et al. review and integrate resilience concepts to help inform natural resources management decisions for ecosystems and landscapes. They describe the six key components of a resilience-based approach, beginning with managing for adaptive capacity and selecting an appropriate spatial extent and grain. Additional components include developing an understanding of the factors influencing the general and ecological resilience of ecosystems and landscapes, the landscape context and spatial resilience, pattern and process interactions and their variability, and relationships among ecological and spatial resilience and the capacity to support habitats and species. They suggest that a spatially explicit approach that couples geospatial information on general and spatial resilience to disturbance with information on resources, habitats, or species provides the foundation for resilience-based management. A case study from the sagebrush biome is provided that is widely used by the management agencies.
Description: Severe wildfires threaten forests and communities of the northern Klamath Mountains. Historically these forests thrived with frequent, low-mixed severity fire. However, hotter, drier summers, a century of fire exclusion, and past destructive logging practices are increasing the likelihood of destructive fire. Insights from historical fire regimes and stand conditions have been integrated with contemporary evaluations of wildfire risk and habitat needs to inform the collaboratively derived Rogue Basin Cohesive Forest Restoration Strategy.
Presenter: Kerry Metlen, Forest Ecologist with The Nature Conservancy of Oregon
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The United States Forest Service 2012 Planning Rule prioritizes making lands resilient to climate change. Although researchers have investigated the history of “resilience” and its multiple interpretations, few have examined perceptions or experiences of resource staff tasked with implementing resilience. This study interviewed Forest Service staff in the Southwestern Region to evaluate how managers and planners interpret resilience as an agency strategy, execution of resilience in management, and climate change’s impact on perception of resilience. Interviewees identified resilience as a main driver of agency response to land management but, when applying the concept, experienced barriers including ambiguity; scale; management specificity versus broad, adaptive landscape approach; and lack of metrics or examples. Interviewees found restoring ecosystem function to promote resilience while planning for future changed landscapes difficult. They desired landscape-scale collaboration to understand how to operationalize the resilience directive. Our findings revealed obstacles and opportunities for resilience in a managerial context.
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This study found distinct evidence that within management group species composition was more similar than across groups for two of the three pairings. However, the other pairing, the most successfully protected area and the completely unprotected area, was not statistically distinct; likely a result a deteriorating overstorey in these two areas, whereas the third management type (2014 Fence) exhibited higher canopy cover. Indicator species analysis found that a small group of plant species had statistical allegiances to specific management groups, suggesting resource preference selection within Pando. Ordination analysis searching for causal factors reached two broad conclusions: (1) aspen regeneration, and therefore long-term resilience, is being negatively affected by chronic animal browsing and (2) current understorey species diversity is highest where forest canopy gaps are abundant.
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With remotely-sensed (Landsat) estimates of vegetation cover collected every 2–5 years from sw Wyoming (1985–2015), we modeled changes in sagebrush cover on 375 former oil and gas well pads in response to weather and site-level conditions. We then used modeled relationships to predict recovery time across the landscape as an indicator of resilience for vegetation after well pad disturbances, where faster recovery indicates a greater capacity to recover when similarly disturbed. Rate of change in sagebrush cover generally increased with moisture and temperature, particularly at higher elevations. Rate of change in sagebrush cover also increased and decreased with greater percent sand and larger well pads, respectively. We predicted 21% of the landscape would recover to pre-disturbance conditions within 60 years, whereas other areas may require >100 years for recovery.
Biological soil crusts (BSCs) consist of a diverse and highly integrated community of organisms that effectively colonize and collectively stabilize soil surfaces. BSCs vary in terms of soil chemistry and texture as well as the environmental parameters that combine to support unique combinations of organisms – including cyanobacteria dominated, lichen-dominated, and bryophyte-dominated crusts. The various BSC organismal groups demonstrate several common characteristics including – desiccation and extreme temperature tolerance, production of various soil binding chemistries, a near exclusive dependency on asexual reproduction, a pattern of aerial dispersal over impressive distances, and a universal vulnerability to a wide range of human-related perturbations. With this publication, we provide literature-based insights as to how each organismal group contributes to the formation and maintenance of the structural and functional attributes of BSCs, how they reproduce, and how they are dispersed. We also emphasize the importance of effective application of molecular and microenvironment sampling and assessment tools in order to provide cogent and essential answers that will allow scientists and land managers to better understand and manage the biodiversity and functional relationships of soil crust communities.
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With remotely-sensed (Landsat) estimates of vegetation cover collected every 2–5 years from southwestern Wyoming, USA, over nearly three decades (1985–2015), we modeled changes in sagebrush cover on 375 former oil and gas well pads in response to weather and site-level conditions. We then used modeled relationships to predict recovery time across the landscape as an indicator of resilience for vegetation after well pad disturbances, where faster recovery indicates a greater capacity to recover when similarly disturbed. We found the rate of change in sagebrush cover generally increased with moisture and temperature, particularly at higher elevations. Rate of change in sagebrush cover also increased and decreased with greater percent sand and larger well pads, respectively. We predicted 21% of the landscape would recover to pre-disturbance conditions within 60 years, whereas other areas may require >100 years for recovery. These predictions and maps could inform future restoration efforts as they reflect resilience. This approach also is applicable to other disturbance types (e.g., fires and vegetation removal treatments) across landscapes, which can further improve conservation efforts by characterizing past conditions and monitoring trends in subsequent years.
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Using a region-wide exclosure network across a broad gradient of aspen–conifer overstory abundance, we empirically tested the effects of ungulate herbivory and conifer competition (that increases with fire suppression), on the regeneration and recruitment of aspen forests over a 4-year period. The study results indicate that ungulate herbivory and increasing abundance of overstory conifers dramatically reduced aspen regeneration and recruitment success. The average height of aspen suckers exposed to ungulate herbivory was 72% shorter than aspen suckers in fenced plots and resulted in 24% less recruitment. There was a 9% decrease in aspen recruitment and 12% decrease in average aspen height with every 20% increase in overstory conifer density. Aspen suckers were most vulnerable to herbivory at 70 cm height, with the probability of herbivory decreasing under 50 cm or above 90 cm. Steep slope angles and higher winter precipitation increased aspen regeneration and recruitment success. Reduction in aspen recruitment in response to ungulate herbivory and competition by conifers may result in loss of biodiversity, altered forest function and loss of key ecosystem services because of the important role that aspen plays in facilitating forest succession and biodiversity.
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This study brought together ecologists and social scientists to confront this challenge and consider how to better promote both social and ecological resilience to a more flammable world. The result led to the new insights highlighted in the paper “Rethinking resilience to wildfire” – that catastrophic wildfires are forcing us to rethink what social–ecological resilience to wildfire means, and accept that more diverse approaches to resilience thinking are needed to facilitate human coexistence with wildfire.
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This study used a standardized protocol for root measurement across sagebrush steppe burned in the 2015 Soda fire in the Northern Great Basin, United States. Nearly all (99%) bunchgrasses, including seedlings, had deeper roots than the surrounding annual grasses (mean depth of annuals = 6.8 ± 3.3 cm), and 88% of seedlings remained rooted in response to the “tug test” (uprooting resistance to ~ 1 kg of upward pull on shoot), with smaller plants (mean height and basal diameters < 20 cm and < 2 cm, respectively) more likely to fail the test regardless of their root abundance. Lateral roots of bunchgrasses were scarcer in larger basal gaps (interspace between perennials) but were surprisingly not directly related to cover of surrounding exotic annual grasses (EAG). However, EAG cover increased with the size of basal gaps and decreased with greater basal diameter of bunchgrass (in addition to prefire EAG abundance). These results provide some support for 1) the importance of basal gaps and bunchgrass diameters as indicators of both vulnerability to annual grass invasion and bunchgrass root abundance and 2) the need for more detailed methods for root measurement than used here in order to substantiate their usefulness in understanding rangeland resistance and resilience.