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Sofaer, HR, CS Jarnevich, EK Buchholtz, BS Cade, JT Abatzoglou, CL Aldridge, PJ Comer, D Manier, LE Parker, and JA Heinrichs. 2022. Potential cheatgrass abundance within lightly invaded areas of the Great Basin. Landscape Ecology 37, 2607–2618. doi.org/10.1007/s10980-022-01487-9
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Abstract
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Publisher Website
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October 2022
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<b>Context: </b>Anticipating where an invasive species could become abundant can help guide prevention and control efforts aimed at reducing invasion impacts. Information on potential abundance can be combined with information on the current status of an invasion to guide management towards currently uninvaded locations where the threat of invasion is high.<br><b>Objectives: </b>We aimed to support management by developing predictive maps of potential cover for cheatgrass (<i>Bromus tectorum</i>), a problematic invader that can transform plant communities. We integrated our predictions of potential abundance with mapped estimates of current cover to quantify invasion potential within lightly invaded areas.<br><b>Methods: </b>We used quantile regression to model cheatgrass abundance as a function of climate, weather, and disturbance, treating outputs as low to high invasion scenarios. We developed a species-specific set of covariates and validated model performance using spatially and temporally independent data.<br><b>Results: </b>Potential cheatgrass abundance was higher in areas that had burned, at low elevations, and when fall germination conditions were more favorable. Our results highlight the extensive areas across the Great Basin where cheatgrass abundance could increase to levels that can alter fire behavior and cause other ecological impacts.<br><b>Conclusions:</b> We predict potential cheatgrass abundance to quantify relative invasion risk. Our model results provide high and low scenarios of cheatgrass abundance to guide resource allocation and planning efforts across shrubland ecosystems of the Great Basin that remain relatively uninvaded. Combining information on an invasive species’ current and potential abundance can yield spatial predictions to guide resource allocation and management action.
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Roche, M.D., D.J. Saher, E.K. Buchholtz, M.R. Crist, D.J. Shinneman, C.L. Aldridge, B.E. Brussee, P.S. Coates, C.L. Weise, J.A. Heinrichs. 2024. Ecological trade-offs associated with fuel breaks in the sagebrush ecosystem. Fire Ecology. 107. https://doi.org/10.1186/s42408-024-00334-3
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Abstract
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December 2024
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Background: Unprecedented wildfire frequency, fueled by invasive annual grasses, threatens sagebrush ecosystems. To suppress wildfire and conserve sagebrush, land management agencies have installed fuel breaks across the sagebrush biome. However, despite the potential reduction in wildfire, fuel breaks may have ecological costs. Determining an acceptable balance between risks and benefits of fuel breaks is needed to avoid accelerating sagebrush loss, annual grass invasion, and habitat degradation. To evaluate the potential for ecological trade-offs to occur, we characterized the contexts in which known fuel breaks currently exist. We synthesized spatial data on all known fuel breaks and a suite of variables that may contribute to fuel break risks and benefits, including burn probabilities, predicted fuel break effectiveness, linear infrastructure, invasive annual grass cover, soil moisture conditions that confer resistance to invasion and resilience to disturbance, and priority wildlife habitats across the sagebrush biome. Results: We found that within the sagebrush biome, fuel breaks are generally located in areas with high burn probability and are thus positioned well to intercept potential wildfires. However, fuel breaks are also frequently positioned in areas with lower predicted fuel break effectiveness relative to the sagebrush biome overall. Fuel breaks also are spatially associated with high invasive grass cover, indicating the need to better understand the causal relationship between fuel breaks and annual invasive grasses. We also show that the fuel break network is dense within priority wildlife habitats. Dense fuel breaks within wildlife habitats may trade off wildfire protection for decreased integrity of such habitats. Conclusions: Our analyses describe the potential for fuel breaks to invoke ecological trade-offs and show that the balance of risks and benefits differs across sagebrush ecosystems. Strategic research and actions are needed to evaluate which factors tip the balance towards maximizing wildfire suppression while minimizing risk to sensitive ecological resources.
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Buchholtz, E.K., J. Kreitler, D. Shinneman, M. Crist, & J. Heinrichs (2023). Assessing large landscape patterns of potential fire connectivity using circuit methods. Landscape Ecology. https://doi.org/10.1007/s10980-022-01581-y.
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Abstract
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April 2023
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Minimizing negative impacts of wildfire is a major societal objective in fire-prone landscapes. Models of fire connectivity can aid in understanding and managing wildfires by analyzing potential fire spread and conductance patterns. We define ‘fire connectivity’ as the landscape’s capacity to facilitate fire transmission from one point on the landscape to another. Our objective was to develop an approach for modeling fire connectivity patterns representing potential fire spread and relative flow across a broad landscape extent, particularly in the management-relevant context of fuel breaks. We applied an omnidirectional circuit theory algorithm to model fire connectivity in the Great Basin of the western United States. We used predicted rates of fire spread to approximate conductance and calculated current densities to identify connections among areas with high spread rates. We compared existing and planned fuel breaks with fire connectivity patterns. Fire connectivity and relative flow outputs were characterized by spatial heterogeneity in the landscape’s capacity to transmit fire. We found that existing fuel break networks were denser in areas with relatively diffuse and impeded flow patterns, rather than in locations with channelized flow. This approach could be paired with traditional fire behavior and risk analyses to better understand wildfire spread as well as direct strategic placement of individual fuel breaks within larger networks to constrain fire spread. Thus, our findings may offer local- to landscape-level support for management actions that aim to disrupt fire spread and mitigate the costs of fire on the landscape.
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Buchholtz, E.K., J. Heinrichs, & M. Crist (2023). Landscape and connectivity metrics as a spatial tool to support invasive annual grass management decisions. Biological Invasions. doi.org/10.1007/s10530-022-02945-w
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Abstract
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Publisher Website
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January 2023
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The spatial context of invasions is increasingly recognized as important for the success and efficiency of management actions. This information can be key for managing invasive grasses that threaten native ecosystems. While methods for quantifying invasive grass presence and abundance advance, few options have been explored in characterizing and comparing spatial patterns of extent and connectivity. We calculated landscape metrics and circuit-based centrality for invasive grasses using a weighted-average product (30m resolution) in the Great Basin, USA. We found variation among extent metrics (mean class and patch area, number of patches, largest patch index) and connectivity metrics (nearest neighbor, contiguity, aggregation index, centrality); most of the extent and connectivity metrics were not strongly correlated with dominant abundance class and so provided additional information at the sampled grid and local scales. We also illustrated how thresholding relevant metrics could be used to identify areas needing different management strategies, for example, where strategies could proactively protect uninvaded cores, disconnect fine fuel patches, or contain established invasions. The landscape metric approach can be applied across scales to spatially target patches locally, provide broader context within a single region, as well as to compare metrics and spatial variation in patterns among different regions.
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