Components of woody plant diversity in semi-arid Chaco forests with heterogeneous land use and disturbance histories

Abstract

We assessed components of woody plant diversity within and between 16 sites dispersed across the nearly 200,000 ha of the Semi-arid Chaco vegetation of the Copo Conservation Unit, northern Argentina. Argentina's Semi-arid Chaco is an object of international conservation concern, as it is under pressure from conversion to agroindustry supplanting long-standing practices of logging and livestock grazing. We recorded from 16 (shrubby grassland following forest fire) to 27 (selectively logged forest) woody plant species per site and 37 species in total (gamma diversity). Additive partitioning showed that alpha diversity contributed 59% to gamma diversity and beta diversity only 41%. A separate additive partitioning of gamma diversity of the 13 forested sites alone showed that beta diversity attributable to logging history was considerably lower than remaining beta diversity and alpha diversity. Ordination analyses confirmed this finding: species composition of unlogged, selectively logged and intensively logged forest sites was quite similar. Results suggest that (1) woody vegetation, at least, of the Semi-arid Chaco is quite tolerant to traditional modes of land use and that (2) conservation of this vegetation as a whole must include not only “pristine” sites varying in edaphic conditions but also sites varying in land use and management histories.