Invasive Species
Webinar recording.
In this webinar, a panel of scientists and practitioners will discuss a number of management techniques and research questions being utilized or tested in an effort to reduce the presence of introduced grasses and restore the historic fire regime. These include:
- Researching whether fire historically maintained the clumpy pattern of native vegetation in a self-perpetuating cycle.
- Reducing the risk of wildfire severity and extent, retaining native plant communities, and maintaining ecological processes in dry desert systems through a variety of invasive species removal techniques.
- Producing fire breaks, or strips of treatment intended to repress the forward progress of wildfires, through restoration of native vegetation patchiness and pruning of native woody species.
- Utilizing new technologies to detect invasive grasses and monitor their spread, assess treatment and cost-effectiveness, and present results from a networked experiment that tests vegetation management practices across the southwestern US.
View article.
More frequent, larger, and severe wildfires necessitate greater resources for fire-prevention, fire-suppression, and postfire restoration activities, while decreasing critical ecosystem services, economic and recreational opportunities, and cultural traditions. Increased flexibility and better prioritization of management activities based on ecological needs, including commitment to long-term prefire and postfire management, are needed to achieve notable reductions in uncharacteristic wildfire activity and associated negative impacts. Collaboration and partnerships across jurisdictional boundaries, agencies, and disciplines can improve consistency in sagebrush-management approaches and thereby contribute to this effort. Here, we provide a synthesis on sagebrush wildfire trends and the impacts of uncharacteristic fire regimes on sagebrush plant communities, dependent wildlife species, fire-suppression costs, and ecosystem services. We also provide an overview of wildland fire coordination efforts among federal, state, and tribal entities.
View brief.
Wildfires burned more area on non-forested lands than forested lands over the past 20 years. This was true for all land ownerships in CONUS and the western US. Burned area increased over the 20-year time period for both non-forest and forest. Across CONUS, annual area burned was higher on non-forest than forests for 14 of the past 21 years (Fig. 1), and total area burned was almost 3,000,000 ha more in non-forest than in forest. For the western US, total burned area was almost 1,500,000 ha more in non-forest than in forest. From a federal agency perspective, approximately 74% of the burned area on Department of the Interior (DOI) lands occurred in non-forest and 78% of the burned area on US Forest Service (FS) lands occurred in the forest.
Human population growth and accessibility from cities shape rangeland condition in the American West
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Human population growth contributes to the decline of sagebrush-steppe rangelands. More accessible rangelands from population centers have higher quality. Open space preservation provides opportunities for rangeland conservation in cities. Coordinated conservation strategies are necessary to protect rangeland ecosystems.
Pre-fire grazing and herbicide treatments can affect post-fire vegetation in a Great Basin rangeland
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This study found grazing and herbicide effects were consistent across cheatgrass biomass, count, and cover. Spring grazing reduced cheatgrass more effectively than fall grazing; however, this effect was detected primarily outside of the seeding treatments. Herbicide overall and in conjunction with grazing reduced cheatgrass and fuel loads. Among seeding treatments, seed mixtures proved more effective than monocultures for reducing both cheatgrass count and cover, particularly when combined with low seed rate. However, many seeding approaches resulted in higher cheatgrass dominance, and thus higher fuel loads.
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Black gravel increased mean temperatures of the surface soil by 1.6 and 2.6 °C compared to white gravel in Cheyenne and Boise, respectively, causing 21–24 more days with soil temperatures > 0 °C, earlier cheatgrass germination, and up to 2.8-fold increases in cheatgrass height. Higher seeding density of cheatgrass led to 1.4-fold taller plants on black gravel plots at both sites, but not white gravel at the Boise site, indicating a possible thermal benefit or reduction of water demand due to plant clustering in warmer treatments.
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Here, we examine how the ventenata invasion alters simulated fire across forest-mosaic landscapes of the 7 million ha Blue Mountains Ecoregion using the large fire simulator (FSim) with custom fuel landscapes: present-day invaded versus historic uninvaded. Invasion increased simulated mean fire size, burn probability, and flame lengths throughout the ecoregion, and the strength of these impacts varied by location and scale. Changes at the ecoregion scale were relatively modest given that fine fuels increased in only 2.8% of the ecoregion where ventenata invaded historically fuel-limited vegetation types. However, strong localized changes were simulated
within invaded patches (primarily dwarf-shrublands) and where invasion facilitated fire spread into nearby forests.
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Interactions among species can strongly affect how plant communities reassemble after disturbances, and variability among native and invasive species across environmental gradients must be known in order to manage plant-community recovery. The stress-gradient hypothesis (SGH) predicts species interactions will be more positive in abiotically stressful conditions and conversely, more negative in benign conditions, and the resistance-resilience concept (RRC) may predict where and when invasions will complicate ecosystem recovery. We evaluated how abiotic stress and biotic interactions determine native bunchgrass abundances across environmental gradients using additive models of cover data from over 500 plots re-measured annually for 5 years as they recovered naturally (untreated) after a megafire (>100,000 ha) in sagebrush steppe threated by the invasive-grass and fire cycle.
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Thus, to understand the effects of removing contemporary grazing, we compared contemporary grazed areas to long-term (+10 yrs.) grazing exclusion areas in three common Wyoming big sagebrush community types: intact, degraded, and exotic annual grass-dominated types. Plant community characteristics (cover, density, diversity, richness, dissimilarity) were measured in 2020 and 2021 in five grazed and grazing excluded areas within each community type. Most plant community characteristics were not influenced by grazing exclusion, suggesting that the removal of contemporary grazing has little effect on Wyoming big sagebrush plant communities. The effect of grazing exclusion on Sandberg bluegrass abundance and litter cover varied among community types, suggesting that grazing exclusion effects slightly varied among community types. In contrast, most plant community characteristics varied among community types and between years, suggesting that grazing management plans need to account for the spatial and temporal variability among Wyoming big sagebrush communities. Furthermore, our results suggest that contemporary grazing exclusion has negligible effects compared to contemporary grazing on plant communities, and that exclusion of contemporary grazing (passive restoration) does not promote the recovery of degraded and annual grass invaded plant communities.