Geomorphology, soil texture and tree density in a seasonal savanna in eastern Venezuela

Abstract

We studied the relationship between geomorphology, tree density, and soil texture in a seasonal savanna from eastern Venezuela. Six landforms were identified and mapped. Using a regular design, we sampled soils at depths of 0-20 and 20-40 cm, and determined textural fractions. Alternatively, using a stratified procedure, we measured tree densities by counting and identifying all woody individuals disregarding their size in 5x5 m plots. Contrary to our expectations, results showed that total tree density was positively linked to sand content that assures better drainage but lower water retention capacity. Moreover, tree density was also linked to the more stable landforms, suggesting that surface stability is more influential on tree population growth than water availability in the topsoil. Although most species are present in all landforms, the results also showed that three species (Curatella americana, Byrsonima coccolobifolia and Casearia sylvestris) were associated to the more stable depositional surfaces with sandy soils and other three (Byrsonima crassifolia, Roupala complicata and Bowdichia virgilioides) were associated to surfaces undergoing active morphogenesis with clayish top soil.