Beck: Grazing impacts structure, composition of sagebrush biome
“Most people know livestock grazing is the single largest landscape use across the sagebrush biome consistently, across both public and private land,” said Jeff Beck of the University of Wyoming (UW) Department of Ecosystem Science and Management. “Some estimates say 90 percent of the sagebrush biome is grazed at some point in the year.”
Beck, who discussed grazing impacts on sagebrush during the Society of Range Management’s (SRM) annual meeting, noted much of SRM’s meeting focused around sage grouse and its interaction with grazing.
“How resistant and resilient is our system to change and to invasion of annual grasses?” asked Beck. “When we look at this system focused on sage grouse, there may be some direct impacts, but they’re hard to understand because of differences in diet selection and habitat use.”
However, indirect impacts may be larger.
“From four review articles, we know that grazing changes the composition, structure and productivity of the plants that sage grouse use during nesting and early brood rearing to protect themselves from predation,” Beck said.
Grazing, or herbivory, is a process whereby animals select nutritious forages based on their life stage and requirements to meet growth and production.
“Economically, grazing is highly important,” Beck said, also noting range managers and ecologist focus on increasing the productivity and efficiency of animals on rangelands.
“However, even though it may be an individual process or an animal, we really do incur a lot of management, whether it be herding or other practices, including fencing,” Beck said, “to achieve the goals that individual producers have.”
Season of use further tempers grazing, when snow and other seasonal factors are incorporated.
“Ultimately we have a sagebrush system that is variable across the entire range of sagebrush,” Beck said. “That sagebrush provides a number of functions.”
Primarily, sagebrush serves as wildlife habitat.
The diverse sagebrush habitat includes shrubs, grasses, forbs, bare ground and more, all of which are important for the life cycle of sage grouse and successful nesting.
Simply, Beck delineated desirable species from undesirable species, noting that perennial forbs, perennial grasses and Big sagebrush are important, whereas annual forbs, annual grasses and cool, short-statured perennial grasses as negative invaders.
State and transition models, which have been published, provide a layout of each ecological site and the species present, coupled with the traits of potential steps to restore the site to proper function, said Beck.
“There are quite a few examples where differences in strategy or management have led to different effects on sagebrush communities,” Beck explained.
As one example at the U.S. Sheep Experiment Station, a spring-grazed pasture limited forb production on the rangeland, whereas fall grazing allowed for forb production on the landscape, along with reduced sagebrush.
Improper livestock grazing, as defined by Chambers in 2017, is, “Grazing that impedes progress toward or maintenance of ecological process and the desired plant community composition and structure within a given set of site conditions and the natural range of variability, including climatic variability and nature disturbance regimes, expected within a management planning time horizon.”
“There’s a lot going on in that definition, but it’s about timing, how that might change species composition and sites,” he said.
Grazing management can be looked at in two ways – at midscale and local levels.
“With grazing management, the point is, in a field office situation, we have to look at many things,” he said.
Beck said three geospatial analyses are utilized to evaluate grazing management at a mid-scale level, including likely response of an area to disturbance, the capacity of an area to support target species and predominant threats.
The second scale to consider is the local scale.
“This is where we focus a lot,” Beck said. “Site level considerations are really important, but we have to start high before drilling down to the site level.”
Three things should be considered at the local scale, including identification of ecological sites, evaluate current ecological dynamics within those sites, as well as potential restoration pathways, and finally selection of grazing management practices.
“We want to select management practices that have the potential to increase the overall ecosystem’s function and habitat considerations,” he said.
Saige Albert is managing editor of the Wyoming Livestock Roundup and can be reached at firstname.lastname@example.org.