STRUCTURE, COMPOSITION AND SMALL LITTER DYNAMICS OF A SEMI-DECIDUOUS FOREST IN MATO-GROSSO, BRAZIL

Structure, floristic composition, and the dynamics of small litterfall and the litter layer were studied for one year in semi-deciduous fore st in Mate Grosso, Brazil. This vegetation type is rapidly disappearin g as its mesotrophic soils are much in demand for agricultural develop ment. The field site was located at 15 degrees 42' S, 56 degrees 06' W in the cerrado (savanna) region of the seasonal tropics not far from the southern limit of the Amazonian forest. The 0.25 ha study plot con tained 236 trees with a dbh greater than or equal to 5 cm and a maximu m height of over 20 m. Stand basal area was 21.8 +/- 2.0 m(2).ha(-1). Tabebuia impetiginosa, Dipteryx alata, and Astronium urundeuva were do minant among the 35 recorded tree species from 20 families. Structure and floristics of the study site were similar to semi-deciduous forest found elsewhere in Mate Grosso. Total small litterfall was 7.7 +/- 0. 3 t.ha(-1).year(-1) and fell within the range reported for semi-decidu ous and deciduous tropical forests. Leaf litter made up over 68% and w as five times higher in the dry season than in the wet season. Mean ma ss of small ground litter was 3.1 +/- 0.4 t.ha(-1) ranging from 1.6 +/ - 0.1 t to 6.1 +/- 0.2 t.ha(-1) for the wet and dry season, respective ly. Seasonality of litterfall and decomposition of leaf litter was ver y high compared with published data.