Components of woody plant diversity in semi-arid Chaco forests with heterogeneous land use and disturbance histories A. Tálamo a, * , J. Lopez de Casenave b , S.M. Caziani a a Instituto de Bio y Geociencias (IBIGEO), Facultad de Ciencias Naturales, Universidad Nacional de Salta e Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Avda. Bolivia 5150, CP 4400 Salta, Argentina b Departamento de Ecología, Genética & Evolución, Facultad de Cs. Exactas y Naturales, Universidad de Buenos Aires, Piso 4, Pab. 2, Ciudad Universitaria, C1428EHA Buenos Aires, Argentina article info Article history: Received 5 July 2011 Received in revised form 12 May 2012 Accepted 29 May 2012 Available online xxx Keywords: Additive partitioning of diversity Alpha diversity Beta diversity Chaco forest Gamma diversity Woody plant diversity 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 parti- tioning 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. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction The Semi-arid Chaco of Argentina, a vast vegetation formation historically under pressure from various sources of degradation and now threatened by massive deforestation for soybean cultivation (Boletta et al., 2006; Gasparri and Grau, 2009; Zak et al., 2004), is a priority for biodiversity conservation on the regional scale (Dinerstein et al., 1995). Land use for livestock grazing and hard- wood logging, along with fire, have historically been the principal sources of degradation and continue to be so outside of regions converted to soybeans (TNC et al., 2005). Despite the ubiquity of these disturbances in the Chaco ecosystem, however, to date no study has dealt with their possible consequences to species diver- sity and its components. In general, human land use and associated disturbances such as fire have major impacts on local and global biodiversity (Chapin et al., 2000; Foley et al., 2005; Polasky et al., 2011). Under- standing the relationship between biodiversity and land use history is crucial to management, particularly of those ecosystems already extensively modified by human activities (Halffter et al., 1999). Species diversity is one aspect of biodiversity (Noss, 1990) and itself consists of various components. A half century ago Whittaker (1960, 1972) proposed partitioning gamma diversity (the diversity of a landscape or region) among alpha or local diversity and beta diversity (species turnover along an environmental gradient). Par- titioning diversity into these two components enables ecologists and managers to better understand the interaction of local and regional processes in determining the species diversity of a land- scape (Schluter and Ricklefs, 1993). In particular, the magnitude of species turnover from site to site may be critical to land use plan- ning and management of the elements making up said landscape, for example when designing a network of protected areas (Kattan et al., 2005; Wiersma and Urban, 2005; Wu et al., 2010). Analysis of diversity components also serves as a guide for regional conservation strategies (Chandy et al., 2006; Gering et al., 2003; Jost et al., 2010; Paknia and Pfeiffer, 2011; Summerville et al., 2003). Fewer studies have dealt with beta than with alpha diversity (Moreno et al., 2006), but the past decade has seen an increase in research on species turnover among sites at different spatial scales (Anderson et al., 2011; Colwell, 2010; Ricota, 2008). Definitions and * Corresponding author. Tel.: þ54 387 4255491; fax: þ54 387 4255483. E-mail address: andrestalamo@gmail.com (A. Tálamo). Contents lists available at SciVerse ScienceDirect Journal of Arid Environments journal homepage: www.elsevier.com/locate/jaridenv 0140-1963/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jaridenv.2012.05.008 Journal of Arid Environments 85 (2012) 79e85