Invasive Species
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Our data revealed that ventenata frequency and cover increased on all plots. However, there was not significantly higher abundance in burned plots in any of the sampling years. In addition, ventenata abundance did not increase more in burned plots over time. Our findings suggest that, unlike cheatgrass, fire may not be a driving factor in the spread and increase of ventenata across the PNB Prairie. This finding has important implications for the management and control of ventenata, as well as the conservation of the PNB Prairie.
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A review of United States Fish and Wildlife Service listing documents for 282 threatened and endangered species in California reveals a complex and varied relationship between grazing and conservation. According to these documents, 51% or 143 of the federally listed animal and plant species are found in habitats with grazing. While livestock grazing is a stated threat to 73% (104) of the species sharing habitat with livestock, 59% (85) of the species are said to be positively influenced, with considerable overlap between species both threatened and benefitting from grazing. Grazing is credited with benefiting flowering plants, mammals, insects, reptiles, amphibians, fish, crustaceans, and bird species by managing the state’s novel vegetation and providing and maintaining habitat structure and ecosystem functions. Benefits are noted for species across all of California’s terrestrial habitats, except alpine, and for some aquatic habitats, including riparian, wetlands, and temporary pools. Managed grazing can combat anthropomorphic threats, such as invasive species and nitrogen deposition, supporting conservation-reliant species as part of land sharing.
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Workshop purpose: Identify fire science and management needs and discuss tools and approaches to natural resource assessments and adaptation strategies for fire dynamics in future climates in Southwest (DOI Regions 8 & 10 [CA, NV, AZ]) bioregions.
Take-Aways:
Provide awareness of tools needed for decision-making in an uncertain future
Generate a list of new science actions to meet fire needs for practitioners/planners in future, non-analog landscapes and communities
Suggest how we might address and accomplish these identified needs going forward
Exchange Information
Make connections
This four-hour, virtual Summit was an abbreviated, rescheduled version of ‘Building Bridges and Solutions: Partners in Facing Fire-Science Challenges’ that was cancelled in April due to COVID-19. We assembled scientists and fire practitioners/leaders in an interagency effort to identify fire science and management needs and to discuss decision-making tools and approaches that address resource assessments and adaptation strategies for fire dynamics in future climates in the Southwest (Department of Interior [DOI] Regions 8 and 10 [CA, NV, AZ]). This overriding goal threaded together the Summit’s talks, Q&A, and break-out sessions. Speakers from various agencies, institutes, and academia focused on fire management and planning in future non-analog landscapes and climate-fire-ecosystem impact relationships in western forest (e.g., mixed-conifer, subalpine), desert (hot and cold, grassland, pinyon-juniper, sage-steppe), and Mediterranean/chaparral bioregions. Syntheses from talks, Mentimeter-conducted discussions, and break-out groups on management and actionable-science needs will be summarized in a white paper and posted on the Southwest, Great Basin, and California Fire Science Exchange websites. Let’s work together to address fire science and management in an uncertain future!
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Severity of fungal disease did not result in measurable reductions of populations of a non‐native, invasive host species, cheatgrass, which suggests that natural enemies may not strongly regulate cheatgrass in its introduced range. Landscape heterogeneity associated with disturbance and weather limited population‐level infection of hosts by the fungal pathogen. Disturbance (specifically wildfire) and variable weather are key components of this and similar invasion systems, and likely need to be considered when evaluating disease dynamics and potential for natural enemies to influence invasion potential.
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Top-down and bottom-up factors affecting invasive populations are rarely considered simultaneously, yet their interactive responses to disturbances and management interventions can be essential to understanding invasion patterns. We evaluated post-fire responses of the exotic perennial forb Chondrilla juncea (rush skeletonweed) and its biocontrol agents to landscape factors and a post-fire combined herbicide (imazapic) and bacteria (Pseudomonas fluorescens strain MB906) treatment that targeted invasive annual grasses in a sagebrush steppe ecosystem. Biocontrol agents released against C. juncea in previous decades included Cystiphora schmidti (gall midge), Aceria chondrillae (gall mite), and Puccinia chondrillina (rust fungus). C. juncea abundance was greater in sprayed than unsprayed plots, and where soils were coarser, slopes faced southwest, solar heat loads and topographic water accumulation were greater, and cover of deep-rooted native perennials was lower. Mite infestation was greater in unsprayed plots, midge infestation was greater at higher elevations on steeper slopes, and midges were more abundant while rust was less abundant on gravelly soils. Biocontrol infestation levels varied considerably between years and could not be predicted in 2019 from 2018 infestation levels. Multiple biocontrol species were often present at the same plots but were rarely present on the same C. juncea individuals. These results suggest that spatial patterns of invasion by C. juncea are related to deep-soil water availability, warmer conditions, and alleviation of competition. Treatments designed to reduce invasive annual grasses may inadvertently release C. juncea by both reducing plant competition for soil resources and affecting biocontrol agent (mite) abundance.
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A treatment targeting a single plant functional group did not achieve lasting success in these diversely invaded communities. Spraying alone did not release native perennials sufficiently to counteract the simultaneous release of secondary invaders and the return of target invaders. Planting or seeding may also be needed to achieve management goals.
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Cheatgrass invasion decreases biodiversity and rangeland productivity and alters fire regimes. Our findings indicate cheatgrass invasion also results in persistent biomass carbon (C) losses that occur with sagebrush replacement. We estimate that conversion from native sagebrush to cheatgrass leads to a net reduction of C storage in biomass and litter of 76 g C/m2, or 16 Tg C across the Great Basin without management practices like native sagebrush restoration or cheatgrass removal.
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Invasive Species in Forests and Rangelands of the United States is a sector-wide scientific assessment of the current state of invasive species science and research in the United States. Leading experts on invasive pests, climate change, social sciences, and forest and rangeland management contributed to highlighting the science and identifying knowledge gaps on a diverse array of topics related to invasive species. Stakeholders from nongovernmental organizations, academic institutions, professional organizations, private corporations, and state and federal agencies representing public, private, and tribal interests also provided input to the assessment. Input from these stakeholders helped to frame the subject matter content and management options presented in this report, ensuring relevance for decision-makers and resource managers.
Webinar recording.
The following topics and presenters are included:
Cheatgrass Impacts and Management Options in Western U.S. Ecosystems, presented by Ali Urza and Brice Hanberry
Impacts of Invasive Cogongrass on Private and Public land: Prevention and Control Strategies, presented by Rima Lucardi
Ventenata Invasion in the Western U.S.: Using Remote Sensing & Model Output to Understand Invasion Risk, presented by Becky K. Kerns