Invasive grasses: A new perfect storm for forested ecosystems?

Kerns, Becky K.; Tortorelli, Claire M.; Day, Michelle A.; Nietupski, Ty C.; Barros, Ana M. G.; Kim, John B.; Krawchuk, Meg A.

doi:10.1016/j.foreco.2020.117985

Cited by 82 publications

(58 citation statements)

References 156 publications

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“…Prior to invasion, fuel‐limited forest scablands served as natural fire breaks, increasing burn heterogeneity throughout the larger forested landscape. Increased fine fuel cover in these historically fuel‐limited communities could allow fire to spread into and between adjacent forests more easily, potentially increasing forest fire activity (Kerns et al ., 2020). The increasing loss of forest canopy from stand‐replacing fire in these dry forest ecosystems (Odion et al ., 2010; Reilly et al ., 2020), and reduced competition from understorey species may promote the further expansion of V .…”

Section: Discussionmentioning

confidence: 99%

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Expanding the invasion footprint:Ventenata dubiaand relationships to wildfire, environment, and plant communities in the Blue Mountains of the Inland Northwest, USA

Tortorelli

Krawchuk

Kerns

2020

Applied Vegetation Science

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Questions: A recently introduced non-native annual grass, Ventenata dubia, is challenging previous conceptions of community resistance in forest mosaic communities in the Inland Northwest. However, little is known of the drivers and potential ecological impacts of this rapidly expanding species. Here we (1 identify abiotic and biotic habitat characteristics associated with the V. dubia invasion and examine how these differ between V. dubia and other problematic non-native annual grasses, Bromus tectorum and Taeniatherum caput-medusae; and (2) determine how burning influences relationships between V. dubia and plant community composition and structure to address potential impacts on Inland Northwest forest mosaic communities. Location: Blue Mountains of the Inland Northwest, USA. Methods: We measured environmental and plant community characteristics in 110 recently burned and nearby unburned plots. Plots were stratified to capture a range of V. dubia cover, elevations, biophysical classes, and fire severities. We investigated relationships between V. dubia, wildfire, environmental, and plant community characteristics using non-metric multidimensional scaling and linear regressions. Results: Ventenata dubia was most abundant in sparsely vegetated, basalt-derived rocky scablands interspersed throughout the forested landscape. Plant communities most heavily invaded by V. dubia were largely uninvaded by other non-native annual grasses. Ventenata dubia was abundant in both unburned and burned areas, but negative relationships between V. dubia cover and community diversity were stronger in burned plots, where keystone sagebrush species were largely absent after fire. Conclusions: Ventenata dubia is expanding the overall invasion footprint into previously uninvaded communities. Burning may exacerbate negative relationships between V. dubia and species richness, evenness, and functional diversity, including in communities that historically rarely burned. Understanding the drivers and impacts of the V. dubia invasion and recognizing how these differ from other annual grass invasions may provide insight into mechanisms of community invasibility, grass-fire feedbacks, and aid the development of species-specific management plans. | 563 Applied Vegetation Science TORTORELLI ET aL.

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Section: Discussionmentioning

confidence: 99%

“…dubia into recently burned dry mixed‐conifer forests, further exacerbating the invasion. Such shifts have the potential to alter landscape‐scale disturbance regimes and ecological processes in open and forested ecosystems across the Intermountain West (Kerns et al ., 2020).…”

Section: Discussionmentioning

confidence: 99%

Expanding the invasion footprint:Ventenata dubiaand relationships to wildfire, environment, and plant communities in the Blue Mountains of the Inland Northwest, USA

Tortorelli

Krawchuk

Kerns

2020

Applied Vegetation Science

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“…In all of the fires categorized as having mixed fuels, the invasive species cheatgrass was a component of the fuels in the burned area perimeter (24% Williams Flats, 12% North Hills, and 4% Ridgetop). Cheatgrass enhances fire size and frequency in the Western United States and can outcompete native vegetation after fire, which induces a vicious cycle where future wildfires propagate cheatgrass expansion (Balch et al, 2013; Kerns et al, 2020; Menakis et al, 2003).…”

Section: Methodsmentioning

confidence: 99%

High Temporal Resolution Satellite Observations of Fire Radiative Power Reveal Link Between Fire Behavior and Aerosol and Gas Emissions

Wiggins

Soja

Gargulinski

et al. 2020

Geophysical Research Letters

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Wildfire smoke influences on air quality and atmospheric chemistry have been underscored by the increasing fire prevalence in recent years, and yet, the connection between fire, smoke emissions, and the subsequent transformation of this smoke in the atmosphere remains poorly constrained. Toward improving these linkages, we present a new method for coupling high time-resolution satellite observations of fire radiative power with in situ observations of smoke aerosols and trace gases. We apply this technique to 13 fire plumes comprehensively characterized during the recent FIREX-AQ mission and show that changes in fire radiative power directly translate into changes in conserved smoke tracers (CO 2 , CO, and black carbon aerosol) observed in the downwind smoke plume. The correlation is particularly strong for CO 2 (mean r > 0.9). This method is important for untangling the competing effects of changing fire behavior versus the influence of dilution and atmospheric processing on the downwind evolution of measured smoke properties.

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“…Restoration targets should not be informed strictly by historical conditions because of changing climate, different land use practices, spread of invasive species, and other considerations (Keane et al 2009, Kerns et al 2020). However, future climatic conditions in eastern Oregon are projected to be even less conducive to extensive shade‐tolerant tree cover than the historical past (Kerns et al 2018).…”

Section: Discussionmentioning

confidence: 99%

Diameter limits impede restoration of historical conditions in dry mixed‐conifer forests of eastern Oregon, USA

et al. 2021

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The U.S. Forest Service is reconsidering policies that limit the size of trees that can be removed in the course of restoration treatments in dry forests of eastern Oregon. To evaluate the effects of diameter limits on the ability of managers to meet restoration objectives, we used an existing network of long-term research plots to summarize historical and contemporary structure and composition of mixed-conifer forests within a one million-ha study area in eastern Oregon. Then, we used a novel thinning simulation procedure to quantify the degree to which thinning using different diameter limits restored stands to historical conditions. Contemporary mixed-conifer forests within the study area are significantly denser, have more basal area, and have a greater proportion of shade-tolerant species than historical conditions. Our simulations of thinning under current policy that prohibits cutting of trees ≥53 cm show that a quarter of mixed-conifer stands cannot be restored to within the historical range of basal area or density. Those stands that could be restored to within historical basal area ranges still had a substantially higher component of shade-tolerant trees than historical stands. Permitting larger shade-tolerant trees to be removed allowed restoration of all or most of stands to within historical structural and compositional ranges. Forest conditions in the late 1800s may not necessarily provide the best template for management because climate and disturbance projections suggest that eastern Oregon forests will be less well suited to shade-tolerant species in the future. Adapting stands to future conditions will require robust monitoring of forest structural and compositional response to restoration treatments.

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Invasive grasses: A new perfect storm for forested ecosystems?

Cited by 82 publications

References 156 publications

Expanding the invasion footprint:Ventenata dubiaand relationships to wildfire, environment, and plant communities in the Blue Mountains of the Inland Northwest, USA

Expanding the invasion footprint:Ventenata dubiaand relationships to wildfire, environment, and plant communities in the Blue Mountains of the Inland Northwest, USA

High Temporal Resolution Satellite Observations of Fire Radiative Power Reveal Link Between Fire Behavior and Aerosol and Gas Emissions

Diameter limits impede restoration of historical conditions in dry mixed‐conifer forests of eastern Oregon, USA

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