Ground-dwelling arthropod communities present in three types of Cantabrian (NW Spain) heathland grazed by sheep or goats

摘要

The abundance, diversity and community composition of ground-dwelling arthropods present in three different types of Cantabrian heathland grazed by small ruminants were studied. A factorial design of three vegetation types (heather-, gorse- or grassdominated) and two grazer species (sheep or goats) with two replicates was established in twelve 0.6 ha paddocks. Ground-dwelling arthropods (Araneae, Opiliones, Isopoda, Julida, Microcoryphia, Hemiptera, Coleoptera and Hymenoptera) were recorded using pitfall traps and plant cover and canopy height assessed in each paddock in 2005, 2006 and 2007. Higher abundances and more families of ground dwelling arthropods were recorded in areas dominated by heather, although certain species were more numerous in areas dominated by grass. The direct effects of the grazer species on arthropods were subtle compared to their great effect on the vegetation. Significant interactions between grazer species and vegetation were observed for some taxa and the overall arthropod community composition. Gradient analyses indicate that arthropod assemblages that include Lycosidae, Opiliones and Carabidae differed between vegetation types and years, but are not affected by the grazer species. Our study shows that areas dominated by shrubby and diverse heather had the highest diversity and abundance of arthropods. Species composition varied along a gradient in the structure of the vegetation, which in turn was modified by the grazer species.