Abstract
This study investigated the structure, diversity and composition of the regenerating shrub-tree species community along a stretch of riparian vegetation in relation to environmental heterogeneity. In the Environmental Protection Area of Pandeiros River, southeastern Brazil, the regenerating stratum on 70 plots (25 m2) divided into four groups according to their soil characteristics and natural barriers was sampled. For each plot observations were made of variables related to several soil properties, canopy openness and flooding regime. In addition to the traditional calculation of phytosociological parameters and diversity, a canonical correspondence analysis (CCA) to examine the existing relationships between environmental variables and species distribution was performed. The families with the highest species richness were Fabaceae and Myrtaceae and the species with the highest importance value indices were Zygia latifolia, Tapirira guianensis, Butia capitata, Bauhinia rufa and Hirtella gracilipes. The CCA largely confirmed the groups that were originally proposed. The stretch of riparian vegetation studied was highly heterogeneous with regard to both the abiotic variables tested and floristic structure and composition.
Highlights
The Brazilian semi-arid region occupies an area of approximately 1 million km2 that is mainly characterised by an average annual rainfall of less than 800 mm, high potential evapotranspiration and an aridity index of 0.5 or a drought risk of more than 60% (Sampaio, 1995; Brasil, 2005)
The species with the highest importance values (IV) were Zygia latifolia (23.56), Tapirira guianensis (20.52), Butia capitata (19.91), Bauhinia rufa (14.76), Hirtella gracilipes (13.70), Averrhoidium gardnerianum (13.06), Myrcia guianensis (11.74), Astronium fraxinifolium (9.80), Dilodendron bipinnatum (9.34) and Cordiera concolor (9.21), which was related to high densities of Z. latifolia, T. guianensis, M. guianensis and A. gardnerianum, dominance by B. capitata and A. fraxinifolium, and a high frequency of B. rufa, H. gracilipes, C. concolor and D. bipinnatum
The floristic composition of the regenerating stratum of the riparian vegetation of the Pandeiros River showed some similarities to other Brazilian riparian forests and to the tree stratum sampled in the same area
Summary
The Brazilian semi-arid region occupies an area of approximately 1 million km that is mainly characterised by an average annual rainfall of less than 800 mm, high potential evapotranspiration and an aridity index of 0.5 or a drought risk of more than 60% (Sampaio, 1995; Brasil, 2005). Cerrado is a Brazilian savanna biome covering 23% of the country, and is one of the least-studied biomes in the world (Furley, 1999; Machado et al, 2008) It has a significant number of endemic species and is considered a hotspot for the conservation of biodiversity in Brazil (Myers et al, 2000). Caatinga occupies 11% of the national territory and, despite being the only exclusively Brazilian biome, it is among the most degraded (Castelletti et al, 2003). This biome, represented by scrub and dry forests (Sampaio, 1995), has a considerable number of endemic species, about which there is currently little zoological and botanical knowledge (Castelletti et al, 2003)
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