Abstract
The soils are seasonally or permanently saturated in the moist grassland savanna, locally known as Campo Limpo Umido. Soil moisture variation seems to determine spatial distribution of communities. The objective of this study is to analyse the relationship between environmental variables and the patterns of spatial distribution of species in the herbaceous-subshrub layer of an area of moist grassland at the Agua Limpa Farm, Brasília, DF (15 degrees 56' to 15 degrees 59' S and 47 degrees 55' to 47 degrees 58' W Gr.). An area of 400 x 400 m was divided into four sections of 200 x 200 m where four transects were randomly sampled. A line intercept method was adopted for the phytossociological study. Superficial soils samples (0-20 cm) were collected for chemical and textural analyses. Gravimetric soil moisture was measured quarterly during the study-year. A total of 85 species in 67 genera and 24 families were found. The diversity was high, Shannon's index, H', was 2.60 nats.cover(-1). Floristic composition of the transects in soils with a high gravimetric soil moisture and high content of organic matter and sand differed from those transects in soils with a lower gravimetric soil moisture indicating seasonal variation. A Canonical Correspondence Analysis (CCA) showed significant correlations between soil texture and soil moisture features and species distribution. Gravimetric soil moisture, organic matter, clay, silt and sand were significantly correlated to species distribution in the moist grassland determining mosaics in the vegetation.
Highlights
The Cerrado Biome originally occupied 23% of Brazil’s land area (Ratter et al, 1997) covering the Brazilian Central Pateaux and presenting a wide physiognomic range, from grassland to tall woodlands where most physiognomies fit the definition of tropical savanna (Sarmiento, 1983).Campos limpos are savanna grassland vegetation with less than 10% tree cover (Ribeiro and Walter, 1998)
According to Reatto et al (1998) 2.3% of the c. 2 million ha of the Cerrado is occupied by moist grasslands on hydromorphic soils plus 0.2% of this formation growing on humic gleys soils
The herbaceous subshrub layer is an important component in all physiognomies of the Cerrado vegetation, from Grasslands (Campo Limpo) to Woodlands (Cerrado sensu stricto and Cerradão)
Summary
The Cerrado Biome originally occupied 23% of Brazil’s land area (Ratter et al, 1997) covering the Brazilian Central Pateaux and presenting a wide physiognomic range, from grassland to tall woodlands where most physiognomies fit the definition of tropical savanna (Sarmiento, 1983).Campos limpos are savanna grassland vegetation with less than 10% tree cover (Ribeiro and Walter, 1998). The herbaceous subshrub layer is an important component in all physiognomies of the Cerrado vegetation, from Grasslands (Campo Limpo) to Woodlands (Cerrado sensu stricto and Cerradão) (see Eiten, 1972 for a description of those physiognomies). It is the layer richest in species (Felfili et al, 1994; Mendonça et al, 1998), with more than 90 million ha of native vegetation used for pasture (Haridasan, 1996). Little is known about the nutrient contents, growth patterns and the natural distribution of the species, floristics, structure and dynamics of this ecosystem as well as the effect of disturbances such as fire, logging, clear-cutting, herbivory and extractivism, to guide conservation and management policies (Guimarães et al, 2002; Finlayson and van der Valk, 1995; Naranjo, 1995)
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