EFFECTS OF POCKET GOPHERS (GEOMYS BURSARIUS) ON MICROTOPOGRAPHIC VARIATION

Mounds of soil created by pocket gophers during the process of constru ction of burrows represent small-scale variation in topography and res ources that may influence vegetation by creating a broader range of mi crosites for germination and growth. We mapped gopher mounds and measu red microtopographic variation on 4 by 4-m plots that had been fertili zed annually with four levels of nitrogen addition for 11 years. Ferti lized plots had more mounds and greater topographic variation than unf ertilized plots, and greater mean height of soil than unfertilized plo ts and adjacent unfertilized aisles. These changes in microtopography and height of soil, caused by the cumulative effects of locally greate r activity by pocket gophers over more than a decade, illustrate one w ay in which burrowing animals can affect heterogeneity in soils.