Structure and regeneration of a Chaco semi-arid forest in ?Los Colorados? Biological Station, Salta, Argentina

Abstract

The structure and natural regeneration of a Chaco semi-arid forest was analyzed in detail in a 0.5 ha plot at The Colorados Biological Station (24°40?S, 63°18?0), Province of Salta, Argentina. All the plants with DBH > 5 cm were identified, and their diameter and canopy height were measured. A total of 729 individuals (basal areal = 9,83 m2) belonging to 20 species, 14 genera and 11 families were recorded. Free-climbing lianes were absent. Physiognomically the Colorado forest is a lowland subtropical dry forest. Schinopsis quebracho-colorado and Aspidosperma quebracho-blanco were the emergent tree species, and rarely exceed 16,5 m in heigh. The forest is dominated by five species: Acacia praecox, A. furcatispina, Capparis retusa, Ziziphus mistol y Aspidosperma quebracho-blanco, which account for the 64% of importance value (IVI). The Fabaceae and Capparaceae were the most species-rich families and they aecaunt for the 59% of the total family importance values (FIV). The 91% of the individuals measured < 20 cm DBH and have less of seven meters of height. The diversity of species of the Colorado forest (16 species/0.05 ha, plants DBH 2 2,5 cm) was comparable to that from other well-preserved Argentinean Chaco forests, but very low compared to other dry tropical forests. Excluding A. quebracho-blanco, the remaining tree species were poorly represented through the different diameter category, and their regeneration were scarce or nule. The 68% of the young plants belonged to A. praecox. Succession trends and possibilities of forest management are discussed.