Forest edge and diversity: carabids along forest-grassland transects

Diversity relationships of carabids in forest edges and the neighbouring fo rest interior and the surrounding grassland are studied. Samples were taken along three replicated forest-grassland transects using pitfall traps in t he Aggtelek National Park in Hungary during 2 years. The study revealed sig nificant edge effect on the carabids. The Shannon diversity of carabids wer e significantly higher in the forest edge and the grassland than in the for est interior. Carabids of the forest interior, forest edge and grassland ca n be separated from each other by ordinations, both on the species composit ion and abundance, suggesting that all three habitats have a distinct speci es assemblage. Moreover, indicator species analysis detected significant ed ge associated species; based on the specificity and fidelity of the carabid s we have distinguished five groups of species: habitat generalists, grassl and-associated species, forest generalists, forest specialists, and edge-as sociated species. Multiple linear regression analyses showed that relative air moisture, temperature of the ground and cover of the herbs are the most important Factors determining the diversity of carabids along the transect s. Our results show that the high diversity of carabids in forest edges is due to the edge-associated species and the presence of species characterist ic to the adjacent habitats. The significance of forest edges in nature con servation, serving as a source habitat for dispersal processes, contributin g to the recolonization of carabids after habitat destruction or other dist urbance is emphasized.