Resistance & Resilience

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Past management spurs differential plant communities with single aspen clone forest

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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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Using remote sensing products to predict recovery of vegetation after energy development

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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.

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Reproduction and dispersal of biological soil crust organisms

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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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Using remote sensing products to predict recovery of vegetation across space and time following energy development

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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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Human altered disturbance patterns and forest succession: Impacts of competition and ungulate herbivory

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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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Rethinking resilience to wildfire

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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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Bunchgrass root abundances and their relationship to resistance and resilience of burned shrub-steppe

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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.

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Successful vegetation management practices in the sagebrush-steppe

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This learning series responds to Section 7.b.iii, Action Item #5 within the Fuels section of the 2015 Integrated Rangeland Fire Management Strategy, which calls for a comprehensive knowledge transfer program to enhance the fuels management program’s role in sagebrush-steppe management. The Strategy is intended to improve the efficiency and efficacy of actions to address rangeland fire, to better prevent and suppress rangeland fire, and improve efforts to restore fire-impacted landscapes.
The learning modules synthesize the state of the science for six management topics:

  • Background and origins of the conservation problems facing the sagebrush steppe and greater sage-grouse
  • Understanding and applying the concepts of resistance and resilience
  • Management of sagebrush ecosystems experiencing conifer encroachment
  • Management of sagebrush ecosystems at risk of or invaded by invasive annual grasses
  • Restoration of sagebrush steppe ecosystems
  • Issues specific to the eastern range of greater sage-grouse
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The ecology and significance of below-ground bud banks in plants

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Vegetation responses to environmental change may be mediated through changes in bud bank dynamics and phenology. Environmental change that depletes the bud bank or prohibits its formation likely results in a loss of vegetation resilience and plant species diversity. Standardization of bud sampling, examination of bud banks in more ecosystems and their response to environmental variation and disturbance regimes, employment of stage-structured bud bank modelling and evaluation of the cost of bud bank construction and maintenance will benefit this expanding field of research.

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The history and value of National Grasslands

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The National Grassland Council prepared an audiovisual presentation about the history and value of USFS National Grasslands. Research Ecologist Jackie Ott narrates.

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