Experimental Analysis of the Effects of Pocket Gopher Mounds on Texas Coastal Prairie

Abstract

The effect of pocket gopher ( Geomys attwateri ) mounds on Texas coastal prairie was investigated by depositing simulated mounds at locations where vegetation had previously been quantified. Mounds were constructed in March 1984 and vegetation on mounds and random sites was sampled in May and October 1984. Most plant biomass was negatively impacted by mounds in May, but dicot shoot biomass increased. Species diversity was also higher on mounds in May than in March. By October, neither plant biomass nor species diversity was significantly different between mound and random samples. There was an initial selection for dicot shoots due to a negative initial effect by pocket gopher mounds on monocots, but biomass and species diversity differences were reduced as monocots grew through mounds by the October sample. Growth of perennial plant species was less affected than that of annual species. Our findings differed somewhat from those in other pocket gopher systems because gopher mounds are short-lived in south Texas. Deposition of gopher mounds may be instrumental in maintenance of a dicot assemblage in this coastal grassland. Recovery of sites buried by pocket gopher mounds depends on location-specific interrelationships between biotic and abiotic factors.