Multivariate Analyses of Tropical Grassland Communities in Mato Grosso, Brazil

Abstract

Variations in the floristic composition and environmental conditions of an area of grassland from the northeastern Mato Grosso are described. The grassland, including a range from dry grassland to the moister campo types, occurs as a narrow strip between gallery forest and savanna woodland (cerrado), and is subjectively classified into eight main divisions: 1, cerrado/campo transitional areas; 2, dry grassland on lateritic hills; 3, white sand areas at heads of campos; 4, dry campo; 5, campo of intermediate wetness; 6, wet campo; 7, very wet campo flushes; 8, gallery forest/campo transitional areas. An intensive survey was made of part of one campo area using a grid of 108 quadrats, each 4 m x 4 m in size. Presence/absence data for all plant species within this have been analysed using association analysis and principal components analysis, and the resultant groupings ofquadrats compared with values of soil moisture, organic content, pH, levels of extractable sodium, potassium, calcium, magnesium andphosphate. Although the campo is sharply defined at its boundaries with cerrado and gallery forest, the vegetational variation within it proved to be continuous andgradual. The distribution of most species in this campo is most closely correlated with soil moisture differences. Most species are restricted to a narrow range within the soil moisture gradient and appear to be independently distributed. It is concluded that the species composition of the vegetation is determined by a combination of the range of water table fluctuations and by burning.