Mammal mounds stimulate microbial activity in a semiarid shrubland

This study was conducted to determine the influence of animal disturbance, in the form of banner-tailed kangaroo rat (Dipodomys spectabilis) mounds, o n soil microbial abundance and activities in a Chihuahuan Desert shrubland. Total organic carbon (TOC), microbial biomass C (C-mic), and basal respira tion were quantified in soils from beneath and between creosote bush (Larre a tridentata) in three zones: directly on the mounds, immediately surroundi ng the mounds, and between mounds. TOC, C-mic, and respiration were enhance d both in soils beneath the canopies of the shrubs and on the mammal mounds . Thus, mammals as well as shrubs contribute to spatial heterogeneity. Rati os of respiration to C-mic (metabolic quotient) were highest on the mammal mounds; however, the ratio of C-mic:TOC was not affected by shrub canopy co ver or location relative to mammal mounds. The higher metabolic quotients i n the vicinities of the mounds reflect physical disturbance by mammals and suggest higher proportions of relatively easily metabolized organic carbon than in soils more distant from mounds.