Abstract
AbstractIn response to increasing fire, fuel‐reduction treatments are being used to minimize large fire risk. Although biocrusts are associated with reduced cover of fire‐promoting, invasive grasses, the impact of fuel‐reduction treatments on biocrusts is poorly understood. We use data from a long‐term experiment, the Sagebrush Steppe Treatment Evaluation Project, testing the following fuel‐reduction treatments: mowing, prescribed fire, and the use of two herbicides: one commonly used to reduce shrub cover, tebuthiuron, and one commonly used to combat cheatgrass, imazapic. Looking at sites with high cover of biocrusts prior to treatments, we demonstrate positive effects of the herbicide, tebuthiuron on lichens with an increase in cover of 10% and trending towards slightly negative effects on moss cover. Across plots, imazapic trended towards a decrease in lichen and moss cover without being statistically significant. Mowing and prescribed fire reduced cover of mosses, with the latter leading to greater declines across sites (declines of 18% vs. 32%). Reductions in moss cover mirrored gains in cover of bare soil, which is associated with increased risk of invasion by grasses responsible for increasing fire risk. We demonstrate that the use of herbicides simultaneously reduces fuels and maintains greater cover of lichens and mosses compared with other fuel‐reduction treatments, possibly reducing risk of invasion by annual grasses that are responsible for increasing fire risk.
Highlights
| INTRODUCTIONThe SageSTEP study looked at three common land management techniques employed by land management agencies: prescribed fire, mowing, and herbicide application
In the sagebrush steppe, wildfires have become increasingly severe and more frequent as early Euro-American settlement, grazing, and fire suppression have altered vegetation and land use patterns (Knick, 1999)
Mosses, and algae including cyanobacteria vary in their susceptibility to disturbances such as high-temperature wildfires, trampling by livestock or humans, compression by vehicle tires, and changing precipitation patterns induced by climate change (Condon & Pyke, 2018a, 2018b; Ponzetti, McCune, & Pyke, 2007; Weber, Budel, & Belnap, 2016)
Summary
The SageSTEP study looked at three common land management techniques employed by land management agencies: prescribed fire, mowing, and herbicide application. All of these treatments were intended to reduce fuels and release native herbaceous vegetation from competition with woody vegetation (i.e., sagebrush). Imazapic is transported through the xylem and phloem It is an acetolactate synthase inhibitor, which is a key enzyme in the biosynthesis of some amino acids (http:// herbicidesymptoms.ipm.ucanr.edu/MOA/ALS_or_AHAS_inhibitors/, accessed October 21, 2019). We ask two main questions: (a) what is the posttreatment response of biocrusts (as assessed by cover) to prescribed fire, mowing, and herbicide and (b) how do the two recorded biocrust components (cover of lichens and mosses) and soil differ in their response to the fuel-reduction treatments? Findings from this study will provide managers with documented effects of fuel-reduction treatments on biocrusts
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