Effects of prairie vole runways on tallgrass prairie

Disturbances by large mammals influence plant populations and ecosystem processes. In contrast, impacts on ecosystem processes at local scales by small herbivorous rodents are relatively unknown. To examine effects of the runways of prairie voles (Microtus ochrogaster) on soil nitrogen, we collected soil cores from under runways, along the runway edges and at 0.25 and 2 m away from runways. Plant samples (both current and previous year's growth) were clipped from microsites at edges of runways and at 0.25 and 2 m away from runways. Concentrations of soil nitrate were highest along runway edges and lowest 2 m away, whereas those of ammonium were highest 0.25 m away from runways and lowest under runways and along runway edges. Biomass of plants from previous growth (litter) was higher along edges of runways than at 0.25 and 2 m from runway edges. In contrast to differences in soil nitrate and ammonium concentrations and in litter biomass among microsites, carbon: nitrogen (C:N) ratios of big bluestem and live plant biomass were similar among the three microsites. Our data suggest that prairie voles do affect nutrient dynamics and plant litter at a local scale in tallgrass prairie.