Invasive Species

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Westwide Fuel Assessment: June 2022 (S3 E3 of Reading the Tea Leaves)

Webinar recording.

The cool wet spring across much of the northwestern US has created a sea of cheatgrass that has improved fuelbed continuity and fuel loading, often exceeding 200 percent of normal. As a result we expect the potential for grass driven wildfires, especially in the Snake River Plain, eastern Washington, northwestern Nevada and northeastern California to be at least average to considerably above average.

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Framework for understanding and predicting animal responses to plant invasion

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This study propose a trait-based framework for understanding how invasive plants afect native fauna, which draws on community assembly, niche, and trait theories to define the mechanisms by which invasive plants alter ecological conditions relevant to native animals. This approach moves beyond prior frameworks by explicitly accounting for the context dependency that defines most ecological interactions and invasion outcomes.

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Short- vs medium-term effects of pre-emergent herbicides on target and non-target species after fire

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While short-term effects of chemical herbicides that target exotic annual grasses were relatively consistent and predictable, longer-term effects were specific to the herbicide and plant community. The “spray-and-release”  strategy may confer resistance to re-invasion by exotic annual grasses if herbicides prevent re-invasion for an extended period.

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Ventenata response to grazing and Rx fire on PNW bunchgrass prairie

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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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Phenotypes and environment predict seedling survival with invasive grass

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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.

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Cal-Pac Section Society for Range Management’s 2022 Spring Meeting

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Event registration.

The meeting will be in Alturas, CA. Cost for full day is $70 for members, $75 for non-members. Cost for morning only is $40 for all, $25 for students. Full registration includes morning presentations, tour, snacks, lunch and BBQ Dinner. Morning includes snacks, lunch and morning presentations.

Student lodging available: Camping at Howard’s Gulch $15/night or Hotel Niles.

Regular lodging available: Hotel Niles or the Trailside Inn.

 

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Moderate grazing in fall-winter reduces exotic annual grasses in sagebrush-bunchgrass steppe

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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.

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What’s driving the proliferation of exotic annual grasses in sagebrush? Comparing fire with off-season grazing

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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.

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Invasive annual grasses management

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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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Bridging the gap between spatial modeling and management of invasive annual grasses in sagebrush

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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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