This work extends our earlier, chronosequence-based study of mound succession to address effects at larger spatial scales and to assess the role of winter castings (figure, right)—largely ignored in previous studies of gopher disturbance and plant community structure.

• greater disturbance would reduce plant cover, graminoid dominance, and species richness, but increase heterogeneity (spatial variation in species composition)
• both mounds and castings would contribute to these effects, but castings less so, due to their smaller size and ephemeral nature

Sampling. Four plots (5 x 20 m) were established in three meadows of differing composition. All plots had moderate but variable levels of gopher disturbance. Each plot was sampled with twenty 5 m transects; each transect consisted of 25 contiguous 20 x 20 cm quadrats (see photos, below).

Following snowmelt we estimated cover (%) of mounds (>1 yr old) and castings. Several weeks later, we estimated cover of forb and graminoid species.

Analyses. Mixed-effects models were used to assess the relationships between disturbance (cover of mounds, castings, or their sum) and three measures of community structure:

• Plant cover. Total, forbs, graminoids, and forb:graminoid ratio
• Richness. Number of species per transect
• Heterogeneity. Mean Bray-Curtis dissimilarity between pairs of quadrats