The effects of logging and grazing on the insect community associated with a semi-arid chaco forest in central Argentina

The ground-dwelling insect community associated with semi-arid chaco forest in the ChancanmH Natural Park and Forest Reserve (CoH rdoba, central Argentina) was studied from pitfall trap collections. The taxonomic composition and functional structure of the community present in the natural climax forest was compared with that of a degraded forest (shrubland) resulting from heavy logging and grazing. The studied communities differed significantly in taxonomic composition, sharing less than half of the insect families and less than a third of the Coleoptera species. The shift in dominant families within the Coleoptera reflected the habitat changes imposed by disturbance, mainly the scarcity of litter and presence of cattle dung in the shrubland. Such effects were also reflected in changes in the relative size of insect feeding guilds within the two habitats, scavengers being remarkably under-represented in the shrub- land. Given the key role of scavenging insects as decomposers in arid systems, this observation could have profound implications for the functioning of this habitat type.