Spatial and temporal variability in relative abundance and foraging behavior of subterranean termites in deserti®ed and relatively intact Chihuahuan Desert ecosystems

The annual feeding activity on paper baits of subterranean termites in deserti®ed (degraded-shrub dominated ecosystems) and relatively undegraded black-grama (Bouteloua eriopoda) grasslands was measured over six years on 12 sites. There were no signi®cant differences in mass losses from termite baits among the deserti®ed and undeserti®ed sites. Mass of paper consumed by termites on two sites dominated by creosotebush, Larea tridentata, was higher than on the other 10 sites. These sites were characterized by shallow, coarse soils and shrubs that did not retain a below-canopy litter layer. The spatial locations of the highest termite bait removal remained relatively constant over the duration of the study. Interannual variations in mass losses from termite baits were highly correlated with winter±spring rainfall (r between 0.60 and 0.95) except at one site on shallow soils. The relationship between annual rainfall and termite activity was less signi®cant (r between 0.48 and 0.83). Frequency of attack as measured by percent of bait rolls `̀ hit'' were not different among sites indicating no differences in densities of subterranean termites. Degradation of Chihuahuan desert grasslands and associated vegetation change has had minimal effect on the activity of subterranean termites. Subterranean termites continue to affect soil properties and processes in both degraded (deserti®ed) and undeserti®ed ecosystems. # 1999 Elsevier Science B.V. All rights reserved.