Shrub-dwelling arthropod assemblages respond differently to grazing disturbance in the southern Monte, Argentina

Abstract

Grazing disturbance affects an extensive area of the Monte desert (Argentina). Arthropods are the main faunistic component of the Monte and play key roles in ecosystem processes. The aim of this study was to analyse the effect of grazing on the canopy arthropod assemblages that inhabit three representative shrub species of the southern Monte (Chuquiraga avellanedae, Schinus johnstonii and Larrea divaricata). Three sampling sites were established in three paddocks grazed by sheep and another three sites in a grazing exclosure. Five specimens of each shrub species were selected per site. Canopy arthropods were sampled using the beating method. The response of arthropod assemblages to grazing was found to vary among shrub species and between seasons. The assemblages associated with two shrub species (L. divaricata and C. avellanedae) were modified significantly by grazing. The most marked response was a general decrease in arthropod diversity in disturbed sites. The abundance of sap-sucking arthropods increased with grazing. These results could be related, in part, to differences in canopy architecture between grazed and ungrazed sites. This study contribute to understanding the ecological impacts of grazing on biological communities of the southern Monte and will aid in developing management strategies that improve regional biodiversity outcomes.