VEGETATIVE EDGE EFFECTS AND POCKET GOPHER TUNNELS

Abstract

Herbivory and soil movement by subterranean mammals influences structure and species composition of plant communities they inhabit. Tunnels constructed by pocket gophers (Geomys bursarius) in Kansas produced an edge effect wherein biomass of the dominant plant species, big bluestem (Andropogon gerardii), increased adjacent to tunnels, then decreased, before increasing again. This wave-like phenomenon was attributed to reduction of biomass of big bluestem above tunnels releasing plants adjacent to tunnels from intraspecific competition. We tested for edge effects on vegetation over tunnels of Attwater's pocket gopher (Geomys attwateri) in a floristically diverse (>10 species of monocots, >30 species of dicots) prairie in coastal Texas. No community-level edge effect was detected; neither biomass, species richness, nor diversity of all plants, monocots alone, or dicots alone over tunnels differed significantly from that in quadrats 0 to 10, 10 to 20, 20 to 30, or 30 to 40 cm away from tunnels. Biomass of 4 individual species of plants prominent in the diet of G. attwateri did not show an edge effect. We conclude that tunnels of pocket gophers have a minor impact on plant biomass or community structure in the floristically diverse coastal prairie of Texas. This result contrasts to the negative effect of deposition of mounds above ground on plant biomass in prairies elsewhere in Texas and Kansas.