Background： Wildlife and livestock grazing are important products of forest ecosystems, but can be controversial. Herbivory by North American elk and domestic cattle is a contentious management issue throughout weste...Background： Wildlife and livestock grazing are important products of forest ecosystems, but can be controversial. Herbivory by North American elk and domestic cattle is a contentious management issue throughout western North America, often driving management proposals to decrease cattle and elk numbers based on perceived overutilization of forages. Such observations are often site level rather than landscape, and may confuse ecological sustainability with desired conditions. Methods： We used line transects to document vegetation composition, structure, and grazing and browsing utilization for 4 key habitat types： mountain meadows, aspen, thinned conifer, and burned conifer on Lincoln National Forest, New Mexico, USA. We documented relative habitat use of these types by elk, mule deer, and cattle and modeled relative use on residual grass biomass of mountain meadows and browse utilization of forested types. We determined diets and diet quality of elk and cattle to assess degree of competition. Results： Use of grasses in meadows was below management thresholds, and combined elk, cattle, and deer relative habitat use accounted for 〈 14 % of the variance in residual stubble height of Poa protensis, the most abundant grass. Palatable browse was limited in habitat types （〈 107 stems.ha^-1）, use was generally high, and elk presence was correlated with the majority of browsing. Elk and cattle diets did not significantly overlap （Schoener＇s index 0.54-0.57）; elk fed primarily on deciduous shrubs （34 %-55 % of annual diets） and cattle on grass （72 %-77 %）. Digestibility and crude protein levels of cattle diets and body condition of elk indicated high quality diets for cattle and marginal-good quality diets for elk. Conclusions： At observed stocking levels and densities, cattle and elk were not competing for forage based on diet similarity, nor were key habitat types being used beyond sustainable levels. Low browse availability indicates that opportunity exists to increase forage availability on Lincoln National Forest, and thus maintain or increase populations without increasing impacts to plant communities. Management actions that address increased stand densities and forest encroachment of meadows, a result of altered historical disturbance regimes, could increase distribution, quantity, and quality of forage.展开更多
基金the U.S.Forest Service,Rocky Mountain Elk Foundation,New Mexico Department of Game and Fish,and several private entities for funding this projectThe New Mexico State University,Agricultural Experiment Station provided additional financial support
文摘Background： Wildlife and livestock grazing are important products of forest ecosystems, but can be controversial. Herbivory by North American elk and domestic cattle is a contentious management issue throughout western North America, often driving management proposals to decrease cattle and elk numbers based on perceived overutilization of forages. Such observations are often site level rather than landscape, and may confuse ecological sustainability with desired conditions. Methods： We used line transects to document vegetation composition, structure, and grazing and browsing utilization for 4 key habitat types： mountain meadows, aspen, thinned conifer, and burned conifer on Lincoln National Forest, New Mexico, USA. We documented relative habitat use of these types by elk, mule deer, and cattle and modeled relative use on residual grass biomass of mountain meadows and browse utilization of forested types. We determined diets and diet quality of elk and cattle to assess degree of competition. Results： Use of grasses in meadows was below management thresholds, and combined elk, cattle, and deer relative habitat use accounted for 〈 14 % of the variance in residual stubble height of Poa protensis, the most abundant grass. Palatable browse was limited in habitat types （〈 107 stems.ha^-1）, use was generally high, and elk presence was correlated with the majority of browsing. Elk and cattle diets did not significantly overlap （Schoener＇s index 0.54-0.57）; elk fed primarily on deciduous shrubs （34 %-55 % of annual diets） and cattle on grass （72 %-77 %）. Digestibility and crude protein levels of cattle diets and body condition of elk indicated high quality diets for cattle and marginal-good quality diets for elk. Conclusions： At observed stocking levels and densities, cattle and elk were not competing for forage based on diet similarity, nor were key habitat types being used beyond sustainable levels. Low browse availability indicates that opportunity exists to increase forage availability on Lincoln National Forest, and thus maintain or increase populations without increasing impacts to plant communities. Management actions that address increased stand densities and forest encroachment of meadows, a result of altered historical disturbance regimes, could increase distribution, quantity, and quality of forage.
