Edge-interior differences in vegetation structure and composition in a Chaco semi-arid forest, Argentina

The differences in species composition and horizontal and vertical vegetation structure between a natural forest edge and the adjacent forest interior were analyzed in an old-growth Chaco forest of Argentina. Total basal area in the shrub stratum was slightly greater at the edge, whereas total basal area in the arboreal strata was slightly greater in the forest interior. The abundance of trees and thick stems were significantly greater in the interior, and total stem density, species richness and abundance of thin stems were significantly greater at the forest edge. Compared with the interior, the edge showed greater cover at low heights in the shrub layer and lower cover in the canopy. Edge-interior differences are similar to those reported for both tropical and temperate forests, and appear to be related mainly to the environmental conditions at edges and perhaps to vertebrate-related dispersion mechanisms associated with edges. The similarity of this forest edge with other modified areas elsewhere in the Chaco forest and the relationship with fragmentation processes are discussed.