Structure, physiognomy and floristic composition of a Schinopsis balansae (Anacardiaceae) forest in the southern Chaco, Argentina

Amazonia and the Gran Chaco are the largest phytogeographic units of tropical and subtropical South America. The Santa Fe Forest Wedge is the southernmost portion of the Eastern Chaco, where the Schinopsis balansae forest (Quebrachal) is the most widespread and characteristic community. A detailed analysis of the floristic composition, physiognomy and vegetation structure was carried out in 32 10 x 10 m contiguous plots sampled along two transects in one of these forests near Vera, Province of Santa Fe, Argentina. All woody individuals higher than 0.6 m present in the plots were recorded, identified and their height and crown diameter measured. With these data, cartographic diagrams and vegetation profiles were drawn. Woody species were classified according to leaf size, leaf texture, presence of spines and phenology. This quebrachal is an open forest with very complex structure and heterogeneous floristic composition. Most woody species of this forest are deciduous, with small leaves and frequently with spiny structures. It has two higher tree layers of S. balansae and Acacia praecox. and a lower tree layer of Achatocarpus praecox with younger individuals of the higher strata species and some large shrubs. There is as well a 2 m high shrub layer. The tree canopy is discontinuous, with gaps that can be rather large, where the soil is covered by a dense grass layer. This forest is much like other S. balansae forests of the Santa Fe Forest Wedge, but quite different from most other forest areas of the Gran Chaco.