We are studying how herbicides sprayed onto soil to prevent the establishment of exotic annual grasses such as cheatgrass may impact the health, growth resources and microbiota of soils in sagebrush-steppe, where herbicide use is an important and common tool. Our findings will help make herbicide applications more successful.
Background
Land managers use herbicides in the sagebrush steppe to try to control populations of invasive annual grasses such as cheatgrass and medusahead. These invasive grasses complete their life cycle and dry out within a relatively short time in early spring, leaving behind a layer of highly flammable plant litter that has been linked to more frequent and more intense wildfires. These grasses are also quick to invade after fires, creating a cycle of more invasive annual grass and more fire. Herbicides are used to disrupt this annual grass-fire cycle. The effects of herbicides on vegetation are widely documented, but the effects of herbicides on soil are less known.
The Fire, Invasion, and Ecology in Sagebrush Steppe (FIREss) lab is studying the effects of several pre-emergent herbicides on soil. Pre-emergent herbicides prevent weeds from growing by inhibiting the germination of the weeds’ seeds. These differ from post-emergent herbicides which are designed to directly target and control existing weeds that are already established. We are working with partners from many other agencies to study the impact of the herbicides indaziflam, imazapic and rimsulfuron on soil resources, soil processes and soil communities.
Soil resources include readily available mineral forms of nitrogen, such as ammonium and nitrate, and organic forms of nitrogen and carbon. During soil processes, organic forms of nitrogen are converted into mineral forms, and organic carbon is converted into CO2. These soil processes are facilitated by micro-organisms like fungi and bacteria. The soil community consists of a diverse and interconnected group of organisms that inhabit and interact within the soil ecosystem. This community includes a wide range of life, from microorganisms like bacteria and fungi to larger organisms like invertebrates and small mammals. The soil community is essential for maintaining soil health, nutrient cycling, decomposition of organic matter, and overall ecosystem functioning. Invasive plants can alter soil resources, processes, and communities, and using herbicides to control invasive plants can cause further alterations that are not well understood.
Objectives
Our objectives are to use controlled and replicated field experiments to determine:
1) The influence of invasive grasses on soil microorganisms
2) The responses of soil resources, processes, and communities to herbicide treatments
3) The potential for innovative management strategies to minimize negative effects of herbicides on soils
4) The effects of all these factors on restoration outcomes
Methods
We collected over 500 soil samples from hundreds of plots in sites treated with herbicides in southwest Idaho. Soil resources are analyzed at the new FIREss Plant and Soil Laboratory. We are also collaborating with Boise State University and other agencies to extract and sequence DNA from soil samples to characterize soil microbial communities. This work will generate valuable information land managers can use to improve, predict, and set expectations for restoration treatment success.
- Overview
We are studying how herbicides sprayed onto soil to prevent the establishment of exotic annual grasses such as cheatgrass may impact the health, growth resources and microbiota of soils in sagebrush-steppe, where herbicide use is an important and common tool. Our findings will help make herbicide applications more successful.
Background
Sources/Usage: Public Domain. Visit Media to see details.Cheatgrass (Bromus tectorum) invasion of sagebrush habitats after a fire in northwestern Nevada, U.S.A. Land managers use herbicides in the sagebrush steppe to try to control populations of invasive annual grasses such as cheatgrass and medusahead. These invasive grasses complete their life cycle and dry out within a relatively short time in early spring, leaving behind a layer of highly flammable plant litter that has been linked to more frequent and more intense wildfires. These grasses are also quick to invade after fires, creating a cycle of more invasive annual grass and more fire. Herbicides are used to disrupt this annual grass-fire cycle. The effects of herbicides on vegetation are widely documented, but the effects of herbicides on soil are less known.
The Fire, Invasion, and Ecology in Sagebrush Steppe (FIREss) lab is studying the effects of several pre-emergent herbicides on soil. Pre-emergent herbicides prevent weeds from growing by inhibiting the germination of the weeds’ seeds. These differ from post-emergent herbicides which are designed to directly target and control existing weeds that are already established. We are working with partners from many other agencies to study the impact of the herbicides indaziflam, imazapic and rimsulfuron on soil resources, soil processes and soil communities.
Soil resources include readily available mineral forms of nitrogen, such as ammonium and nitrate, and organic forms of nitrogen and carbon. During soil processes, organic forms of nitrogen are converted into mineral forms, and organic carbon is converted into CO2. These soil processes are facilitated by micro-organisms like fungi and bacteria. The soil community consists of a diverse and interconnected group of organisms that inhabit and interact within the soil ecosystem. This community includes a wide range of life, from microorganisms like bacteria and fungi to larger organisms like invertebrates and small mammals. The soil community is essential for maintaining soil health, nutrient cycling, decomposition of organic matter, and overall ecosystem functioning. Invasive plants can alter soil resources, processes, and communities, and using herbicides to control invasive plants can cause further alterations that are not well understood.
Objectives
Our objectives are to use controlled and replicated field experiments to determine:
1) The influence of invasive grasses on soil microorganisms
2) The responses of soil resources, processes, and communities to herbicide treatments
3) The potential for innovative management strategies to minimize negative effects of herbicides on soils
4) The effects of all these factors on restoration outcomes
Methods
We collected over 500 soil samples from hundreds of plots in sites treated with herbicides in southwest Idaho. Soil resources are analyzed at the new FIREss Plant and Soil Laboratory. We are also collaborating with Boise State University and other agencies to extract and sequence DNA from soil samples to characterize soil microbial communities. This work will generate valuable information land managers can use to improve, predict, and set expectations for restoration treatment success.
Sources/Usage: Public Domain.The Wildcat experimental treatment site in southwest Idaho at the base of the Owyhee Mountains. The brown square was treated with pre-emergent herbicide and is free of cheatgrass, a few native perennial bunchgrasses were able to establish. This image was taken the first Spring after treatment.
Sources/Usage: Public Domain.A field technician taking a soil core sample. Scientists are studying the effects of herbicides used to control exotic annual grasses on soil.
Sources/Usage: Public Domain.A Berlese-Tullgren funnel system that is used for studying soil invertebrates. This laboratory technique causes soil invertebrates to move away from the soil surface as it is being warmed and dried by the lights above. The invertebrates are caught in jars of ethanol below the funnels, counted, and identified under a microscope. - Multimedia
- Partners