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Patterns of Selective Herbivory on Five Prairie Legume Species

Nisi, Anna C., Hernández, Daniel L., English, Lydia P., Rogers, Emily S.
The American midland naturalist 2015 v.173 no.1 pp. 110-121
Amorpha canescens, Dalea purpurea, Desmodium, Lespedeza, Microtus pennsylvanicus, Odocoileus virginianus, Sylvilagus floridanus, agricultural land, bison, carbon, ecosystems, herbivores, landscapes, legumes, nitrogen content, prairies, prescribed burning, rabbits, small mammals, stems, Minnesota
Historic, wide-spread destruction of native prairies in Minnesota was caused by conversion to agricultural land, disruption of disturbance regimes, and loss of key species. Attempts to restore tall-grass prairies have resulted in a new ecosystem type on the Midwestern landscape, with novel assemblages of both plant and animal species. The mammalian herbivore community, once dominated by bison, is now primarily comprised of white-tailed deer (Odocoileus virginianus), Eastern cottontail rabbits (Sylvilagus floridanus), and small mammals such as meadow voles (Microtus pennsylvanicus). The role of this assemblage of herbivores in restored prairies is not well understood. This study characterizes patterns of mammalian herbivory on five legume species in restored prairie in southern Minnesota. Legumes were sampled along transects that varied in their distance from the prairie-forest boundary and time since prescribed burning. Herbivore selectivity was determined for each legume species using an electivity index based on the total number of stems of each species and the percent of stems grazed. Herbivory was highly variable among legume species: Desmodium canadense was strongly preferred, Dalea candida and Dalea purpurea were moderately preferred, and Amorpha canescens and Lespedeza capitata were avoided. Both Dalea species and Lespedeza experienced increased rates of herbivory in burned sites. Avoided species were characterized by either low tissue nitrogen content or a high proportion of recalcitrant carbon relative to preferred species. These results suggest mammalian herbivores have an important functional role in prairie communities with potential consequences for community dynamics and the success of prairie restorations.