Northern pocket gopher (Thomomys talpoides) control of alpine plant community structure

We evaluated the importance of the northern pocket gopher (Thomomys talpoides) in controlling plant species composition and richness in two alpine tundra plant communities. We hypothesized that forb diversity and relative abundance is modified by gopher mounding activities in moist meadows of Niwot Ridge, Colorado, U.S.A., where both the pocket gopher and forbs are most concentrated. We tested this hypothesis with simulated gopher mounds. Forbs recovered faster following burial than graminoids or cushion plants, demonstrating a resilience that we propose confers a competitive advantage over other growth forms and favors forb dominance in moist meadows. Gopher effects on species richness varied according to spatial scale of measurement and community type. For one decade we monitored the responses of a sedge-dominated community to gopher activity in 1.5 m(2) plots that included both gopher mounds and intermound spaces and found that species richness was significantly positively correlated with recent disturbance. Species richness on the simulated gopher mounds (0.2 m(2)) immediately declined significantly after burial but recovered within a year. When evaluated in conjunction with studies of gopher diet preferences and effects on ecosystem biogeochemistry, our findings suggest that the northern pocket gopher is instrumental in constructing a locally diverse alpine plant community.