Population Dynamics of the Meadow Vole (Microtus pennsylvanicus) in Nutrient-Enriched Old-Field Communities

Abstract

We examined effects of changes in structure of old-field plant-communities on population dynamics of the meadow vole (Microtus pennsylvanicus) following nutrient enrichment for 9 years. Population densities, recruitment, body mass, and survivorship of meadow voles were compared between nutrient-enriched (sludge- or fertilizer-treated) and control treatments in old-field communities established 9 years earlier. Eight 0.1-ha plots (two control and three each sludge- and fertilizer-treated) were stocked with meadow voles during early summer 1986. Population densities, rates of recruitment, and survivorship for voles were higher on control plots than on the other two treatments. Population-growth rates were positive on the control plots, whereas they were negative on nutrient-enriched plots. No significant differences in sex ratios or body mass of voles were detected between treatments. Although aboveground plant biomass was significantly higher on fertilizer-treated plots, edible biomass (plant species known to be consumed by voles) was significantly greater on control plots. Control plots also were more diverse and contained better vegetative cover in the form of grasses and forbs. Population dynamics of voles appeared to be regulated by plant-community structure, vegetative cover, plant diversity, and food quality, especially the diversity of edible plant species.