Vegetation types of the Arid Chaco in Central-Western Argentina

Aims : We address the following questions: 1) Which are main vegetation types that currently occur in Arid Chaco? 2) Do those differ terms of floristic composition, endemism, chorotypes and life forms? 3) Is there any spatial association between environmental heterogeneity Study area The southwestern extreme Gran Chaco, Central-Western Argentina. Methods survey was based on a dataset comprising 654 relevés collected according to Braun-Blanquet method. Data were classified by hierarchical ISOmetric feature mapping Partition Around Medoids (ISOPAM), ordinated through isometric (ISOMAP). Bioclimatic edaphic variables related ISOMAP ordination. Results recorded 439 vascular plant species, 62 endemic at national level 22 species restricted study surrounding environments A total nine types, belonging four major clusters, identified. most prominent included distributed Chaco region Chaco/Monte phytogeographic units. predominant forms micro- nano-phanerophytes, followed hemicryptophytes, chamaephytes mesophanerophytes. Conclusions Major results highlighted xerophytic shrublands common this as result historical present use, while old growth forests constrained areas with low anthropogenic disturbance last decades or protected areas. Most (with exception halophytic environments) poorly differentiated from point view; however, they clearly physiognomy. composition described revealed numerous other sectors northern Argentina, Bolivia Paraguay. Although number quite low, relevant chorotype Western Eastern distribution, conferring clear Chaquenian identity discriminating it Taxonomic reference Catálogo de las Plantas Vasculares del Cono Sur (Zuloaga et al. 2008) its online update (http://www.darwin.edu.ar). Abbreviations = mapping; ISOPAM partitioning around medoids.