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

The ground-dwelling insect community associated with semi-arid chaco forest in the Chancani Natural Park and Forest Reserve (Cordoba, central Argentin a) 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 hea vy logging and grazing. The studied communities differed significantly in t axonomic composition, sharing less than half of the insect families and les s than a third of the Coleoptera species. The shift in dominant families wi thin the Coleoptera reflected the habitat changes imposed by disturbance, m ainly 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-r epresented in the shrubland. Given the key role of scavenging insects as de composers in arid systems, this observation could have profound implication s for the functioning of this habitat type. (C) 1999 Academic Press.