Grazing Effects on the Annual Grass Fire-Cycle after Post Fire Management
In order to break the annual grass fire-cycle in the sagebrush steppe, land managers use pre-emergent herbicides to reduce annual grass populations and seeding to increase fire-tolerant perennials. These tools must be applied to the same soils in ways that are not counterproductive, and their application must therefore be staggered in time, which we refer to as layering. Livestock grazing can also have counterproductive effects on active restoration investments if not reintroduced carefully after fire. We are evaluating the effectiveness of the many different sequences in which herbicides, seeding, and grazing can be applied to restore recently burned sagebrush steppe.
Background
Application of pre-emergent herbicides to reduce exotic annual grasses, seeding to increase perennials, and temporary withholding of livestock grazing to alleviate stress on recovering plant communities are the most common restoration tools used after fires in sagebrush steppe. However, pre-emergent herbicides can inhibit emergence of desirable native plants from sowed seed, and newly established perennials may be vulnerable to grazing stress. Land managers can implement the treatments at different times to prevent the negative impacts of herbicides on seeding treatment. The staggering of seeding and herbicide treatments is called layering. The final layer occurs after perennials start to establish and managers have to decide when it is safe to reintroduce livestock grazing.
Unbiased information about the effects of grazing is needed to determine when grazing can resume without reducing the resistance to annual grass invasion and resilience to disturbance that perennial bunchgrasses provide. However, grazing impacts are complex and challenging to study due to variability in where and how grazing actually occurs on landscapes. To determine the benefits or impacts of layering and grazing, The FIREss (Fire, Invasion, and Ecology in Sagebrush Steppe) team is working with the Bureau of Land Management to conduct two controlled experiments using fencing and grazing simulations. The experiments are located in areas that have been already treated after fires, with grazing layered on top of drill seeding, and also herbicide in some cases.
The first experiment is located in the 2012 Stout fire burn area. In 2012, the BLM seeded over 10,000 acres with native or introduced perennial grasses in strips of land, and in 2014 teamed with USGS to fence out livestock from a 5-acre exclosure. The FIREss team mowed portions of that plot to simulate grazing, applied in different seasons and at different intensities. We measured the plant community's response for five years then resumed the evaluation in June of 2023.
The second experiment is located in the 2015 Soda Fire burn area. In 2016, the BLM and the FIREss lab created five sites which replicated the Stout study, except they used mixed species when seeding instead of monocultural seedings. Each site has a different climate, soil condition and plant community. The FIREss team again used mowing to simulate grazing and is comparing the results to control plots. Actual grazing is also occurring at this site.
Phase two of this project will evaluate how the treatments have affected the relative abundance of perennial grasses, exotic annual grasses, and biocrusts. Biocrusts are soil-surface communities composed of moss, lichen, algae, and other microorganisms. They have been shown to reduce the spread of exotic annual grasses, and their responses to herbicides, drill seeding, and grazing are important to know for increasing the effectiveness of restoration. Analyzing data collected during phase one, as well as new data collected during phase two, will generate a valuable dataset on the impacts of layering strategies. This information could help managers determine how long to wait after treatment before resuming grazing to achieve restoration goals and maximize post-fire restoration investments.
Objective
We are using these two experiments to look at the incremental benefits or impacts of layering different post-fire herbicide and seeding treatments or grazing strategies on the relative abundances of exotic annual or perennial grasses.
In order to break the annual grass fire-cycle in the sagebrush steppe, land managers use pre-emergent herbicides to reduce annual grass populations and seeding to increase fire-tolerant perennials. These tools must be applied to the same soils in ways that are not counterproductive, and their application must therefore be staggered in time, which we refer to as layering. Livestock grazing can also have counterproductive effects on active restoration investments if not reintroduced carefully after fire. We are evaluating the effectiveness of the many different sequences in which herbicides, seeding, and grazing can be applied to restore recently burned sagebrush steppe.
Background
Application of pre-emergent herbicides to reduce exotic annual grasses, seeding to increase perennials, and temporary withholding of livestock grazing to alleviate stress on recovering plant communities are the most common restoration tools used after fires in sagebrush steppe. However, pre-emergent herbicides can inhibit emergence of desirable native plants from sowed seed, and newly established perennials may be vulnerable to grazing stress. Land managers can implement the treatments at different times to prevent the negative impacts of herbicides on seeding treatment. The staggering of seeding and herbicide treatments is called layering. The final layer occurs after perennials start to establish and managers have to decide when it is safe to reintroduce livestock grazing.
Unbiased information about the effects of grazing is needed to determine when grazing can resume without reducing the resistance to annual grass invasion and resilience to disturbance that perennial bunchgrasses provide. However, grazing impacts are complex and challenging to study due to variability in where and how grazing actually occurs on landscapes. To determine the benefits or impacts of layering and grazing, The FIREss (Fire, Invasion, and Ecology in Sagebrush Steppe) team is working with the Bureau of Land Management to conduct two controlled experiments using fencing and grazing simulations. The experiments are located in areas that have been already treated after fires, with grazing layered on top of drill seeding, and also herbicide in some cases.
The first experiment is located in the 2012 Stout fire burn area. In 2012, the BLM seeded over 10,000 acres with native or introduced perennial grasses in strips of land, and in 2014 teamed with USGS to fence out livestock from a 5-acre exclosure. The FIREss team mowed portions of that plot to simulate grazing, applied in different seasons and at different intensities. We measured the plant community's response for five years then resumed the evaluation in June of 2023.
The second experiment is located in the 2015 Soda Fire burn area. In 2016, the BLM and the FIREss lab created five sites which replicated the Stout study, except they used mixed species when seeding instead of monocultural seedings. Each site has a different climate, soil condition and plant community. The FIREss team again used mowing to simulate grazing and is comparing the results to control plots. Actual grazing is also occurring at this site.
Phase two of this project will evaluate how the treatments have affected the relative abundance of perennial grasses, exotic annual grasses, and biocrusts. Biocrusts are soil-surface communities composed of moss, lichen, algae, and other microorganisms. They have been shown to reduce the spread of exotic annual grasses, and their responses to herbicides, drill seeding, and grazing are important to know for increasing the effectiveness of restoration. Analyzing data collected during phase one, as well as new data collected during phase two, will generate a valuable dataset on the impacts of layering strategies. This information could help managers determine how long to wait after treatment before resuming grazing to achieve restoration goals and maximize post-fire restoration investments.
Objective
We are using these two experiments to look at the incremental benefits or impacts of layering different post-fire herbicide and seeding treatments or grazing strategies on the relative abundances of exotic annual or perennial grasses.