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Title: Small Mammal and Plant Community Responses to Mechanical Disturbance and Rest in Wyoming Big Sagebrush Grassland

item Borchgrevink, Matt
item Derner, Justin
item Weston, Terrill
item Olson, Richard
item Schuman, Gerald
item Hess, Bret

Submitted to: Arid Land Research and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/7/2009
Publication Date: 1/22/2010
Citation: Borchgrevink, M.B., Derner, J.D., Weston, T.R., Olson, R.A., Schuman, G.E., Hess, B.W. 2010. Small mammal and plant community responses to mechanical disturbance and rest in Wyoming big sagebrush grassland. Arid Land Research and Management. 24:57-67.

Interpretive Summary: The improvement practice of interseeding legumes (e.g., alfalfa) into rangelands has been widely evaluated in grass-dominated systems for increased forage production, higher nutritive quality of the forage and greater soil carbon and nitrogen. Effects of this improvement practice in sagebrush-dominated systems, however, are less known. Here, we evaluated small mammal and plant community responses to interseeding yellow-flowered alfalfa into a sagebrush grassland in southeastern Wyoming. Establishment of the yellow-flowered alfalfa was minimal due to drought conditions. The interseeding disturbed about 1/10 of the ground surface area. Interseeding did not influence species richness of small mammals, but species diversity was enhanced. Plant community responses (production, species richness, species diversity) were not affected by interseeding. Although the implementation of this improvement practice directly affected about 10% of the ground area, interseeding of yellow-flowered alfalfa into this sagebrush grassland had little influence on initial small mammal population or plant community dynamics.

Technical Abstract: Small mammal and plant community dynamics were evaluated in a native Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis)-grassland following disturbance from interseeding yellow-flowered alfalfa (Medicago sativa ssp. falcata) in April 2003. Small mammal live trapping and vegetation sampling were conducted in 2004 and 2005 on replicated 1 ha study plots for 1) interseeded grassland rested from grazing during the study (interseeded), 2) non-interseeded grassland and rested from grazing (rested), and 3) non-interseeded grassland moderately grazed by cattle (control). Few yellow-flowered alfalfa plants survived due to low precipitation. Deer mice (Peromyscus maniculatus), northern grasshopper mouse (Onychomys leucogaster) and sagebrush vole (Lemmiscus curtatus) were the primary small mammal species captured during 7,776 trap nights in 2004 and 2005. Substantially more small mammals were captured across treatments in 2004 (192) compared to 2005 (39). Small mammal species richness did not differ between treatments in either year, but richness was higher among treatments in 2004 than 2005. Across years, small mammal diversity was greater for the interseeded (H’ = 1.22) than the rested (H’= 0.85) treatment with the control grazed treatment intermediate. Plant community variables of species richness, diversity, similarity and aboveground biomass production did not differ among treatments. Canopy cover of the dominant species, Wyoming big sagebrush, was reduced 20-34% by the disturbance in the interseeded plots (6.9% ± 1.0) compared to rested (8.6% ± 0.6) and control grazed (10.4% ± 1.0) plots. The disturbance associated with interseeding yellow-flowered alfalfa affected 10.5% of the ground surface area but this had little impact on short-term small mammal or plant community dynamics in this rangeland ecosystem.