Invasive Species
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This study documented a 30% increase in ventenata cover and 55% increase in frequency on the PNB over the past 15 yr, including areas that were not disturbed by fire or cattle grazing. We found only weak evidence that cattle grazing increased ventenata standing crop when compared with cattle-excluded paddocks, something that could be related to timing of use. There was no evidence that prescribed burning impacted the response of ventenata on its own. However, we found some evidence of interactions between cattle grazing and prescribed fire that suggests prescribed burning could help reduce the abundance of ventenata in areas grazed by livestock. These studies reinforce the important differences between ventenata and other invasive winter annuals in grasslands and clarify a need for research that focuses primarily on the dynamics between this relatively new exotic species in grasslands and the many ecosystems it now inhabits.
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Sampling seven taxa from the same sites allowed us to ask how trait–environment–performance associations differ among taxa and whether natural selection favors similar traits across multiple taxa and functional groups. All taxa showed trait–environment associations consistent with local adaptation, and both environment of origin and phenotypes predicted survival in competitive restoration settings, with some commonalities among taxa. Notably, rapid emergence and larger seeds increased survival for multiple taxa. Environmental factors at collection sites, including lower slopes (especially for grasses), greater mean annual temperatures (especially for shrubs and forbs), and greater precipitation seasonality were frequently associated with increased survival. We noted one collection site with high seedling survival across all seven taxa, suggesting that conditions within some sites may result in selection for traits that increase establishment for multiple species. Thus, choosing native plant sources with the most adaptive traits, along with matching climates, will likely improve the restoration of invaded communities.
We compared moderate grazing during the off season with not grazing in five Wyoming big sagebrush−bunchgrass communities in the northern Great Basin. Treatments were applied annually for 10 yr (2009−2010 through 2018−2019). Plant community characteristics were measured after treatments had been applied from 6 to 10 yr. Off-season grazing reduced exotic annual grass density and cover. After a decade, annual grass cover was twofold greater in ungrazed areas. Sandberg bluegrass density increased with off-season grazing, but large bunchgrass density was similar between off-season grazed and ungrazed areas. Perennial and annual forb density and cover were similar between off-season grazed and ungrazed treatments. Biological soil crust cover was also similar between off-season grazed and ungrazed areas.
We compared 1) burned and ungrazed (burned), 2) off-season, moderately grazed and unburned (grazed), and 3) ungrazed and unburned (control) treatments at five Wyoming big sagebrush sites in southeastern Oregon for half a decade. Fire, but not off-season grazing, substantially increased exotic annual grass cover and abundance. Vegetation cover and density were generally similar between grazed and control areas. In contrast, at the end of the study exotic annual grass cover and density were over fourfold greater in burned areas. Exotic annual grass became the dominant plant group in burned areas, but not in grazed and control areas. Cover and density of annual forbs, predominately non-native species, were generally greater in the burned compared with grazed and control treatments. Fire also decreased soil biological crust cover and sagebrush cover and density compared with grazed and control treatments. This study provides strong evidence that fire is a threat to the sustainability of Wyoming big sagebrush communities at risk of exotic annual grass dominance, but that off-season, moderate grazing poses little risk. However, considering the spatial extent of our study was limited, further evaluations are needed across a larger geographic area.
Webinar recording.
Invasive annual grasses pose ecological and economic challenges for invasive species managers and agricultural producers across the West. On this Working Lands, Working Communities Initiative webinar, speakers will examine management tools and strategies to effectively manage cheatgrass, medusahead, and ventenata.
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This study involved a review of available spatial products to assess advances in, and barriers to, applying contemporary model-based maps to support rangeland management. We found dozens of regional data products describing cheatgrass or annual herbaceous cover and few maps describing ventenata or medusahead. Over the past decade, IAG spatial data increased in spatial and temporal resolution and increasingly used response variables that indicate the severity of infestation such as percent cover. Despite improvements, use of such data is limited by the time required to find, compare, understand, and translate model-based maps into management strategy. There is also a need for products with higher spatial resolution and accuracy. In collaboration with a multipartner stakeholder group, we identified key considerations that guide selection of IAG spatial data products for use by land managers and other users. On the basis of these considerations, we discuss issues that contribute to a research-implementation gap between users and product developers and suggest future directions for improved development of management-ready spatial products.
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Research teams at the USGS Earth Resources Observation and Science (EROS) Center have released a satellite-derived dataset that maps the recent history of the fire-fueling invasive annual grasses spreading through the Western U.S. in greater detail than ever before.
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Oregon partners used new spatial data to develop a geographic strategy for management of invasive annual grasses at landscape scales across jurisdictional boundaries. The geographic strategy considers annual and perennial herbaceous cover along with site resilience and resistance in categorizing areas into intact core, transitioning, and degraded areas. The geographic strategy provides 1) a conceptual framework for proactive management, building upon similar work recently begun across the Great Basin, and 2) multi-scale spatial products for both policymakers and local managers to identify strategic areas for investment of limited resources.
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Minimizing vulnerability of rangeland cores to annual grass conversion includes reducing exposure to annual grass seed sources, improving resilience and resistance by promoting perennial plants, and building capacity of communities and partnerships to adapt to changing conditions and respond to the problem with appropriate actions in a timely manner.
Webinar recording.
In this deep dive webinar, Dr. Becky Kerns and collaborating scientists will present and synthesize results from a Joint Fire Science funded project aimed at understanding the current and future Ventenata dubia (ventenata) invasion in the Blue Mountains Ecoregion. Wildfires in 2014 and 2015 in the ecoregion reportedly spread in an unusual fashion owing to this invasive annual grass. Concern was raised that ventenata might be a “game-changer” for wildfire. Results from our studies show that ventenata has ecosystem transformation potential and influences landscape-scale fire across the ecoregion. In this webinar we report these findings and the management implications, as well as place our results in the context of other plant invasion research. The webinar includes 90 minutes of scientific presentations with short Q&A, and ends with a 30-minute wrap up and panel discussion. Talks will adhere to the following agenda to allow attendees to join and leave the meeting for specific talks, if desired.