TROPICAL RAIN FORESTS OF KWAKWANI-GUYANA. PART1: PEDOSPHERE, SEDIMENTS AND VEGETATION STRUCTURE

Resumo

Soils in Kwakwani (northeastern Guyana) were identified and characterized to establish the patterns of spatial distribution of soil and vegetation and their relationships. The sludy área is located between 5° 21' 46" - 5° 20' 18" N and 58° 2' 24" - 58° 1' 44" W. Climate is rainy tropical with 2280-2540 mm of annual rainfall and udic soil humidity regime. Thirty observations of soil detail were done in five permanent plots established in Guyana by the Biodiversity Program SI/MAB, and simultaneously the characteristics of thc vegetation structure were determined. Data were analyzed by principal component analysis and canonical correlation analysis. In the sandy sediments, Aquoxic Quartzipsamments excessively drained were identified, with Haplorthods inclusions in the more depressed sites. In the loam sediments there was a dominance of Typic Paleudults with Aquic Paleudults inclusions. Thc forest associated to sandy soils had a similar structure to caatinga forest, presenting a low height and high density of trees (DBH> 10 cm), whereas forests associated to loam soils were characterized by high forests, with a low density (DBH> 10 cm). Soils were acidic with low nutrient levéis in the mineral fraction. Nutrient concentration was not related to the mineral fraction characteristic of soils, such as texture and exchangeable aluminum, but it was to organic matter content. Soil variability was related to texture, complex exchangc, A horizon thickness, and structure. which also had an influence on the water retention capacity of the soils; these characteristics were associated to forest type.