Effects of slash and burn agriculture on species abundance and composition of a tropical deciduous forest

We identified and mapped 869 woody plants to describe community composition of 2.4 ha of tropical deciduous forest near Chamela, Jalisco, Mexico and to document the response of woody vegetation to slash and burn agriculture. in the uncut forest. 87% of the individuals > 2.5 cm dbh were alive, and 24% had multiple trunks, indicating previous coppicing. Before slashing, burning, and cultivation, we encountered 104 species (> dbh 1 cm); only 13 species had a relative abundance > 4%, and 52 species were represented by only one or two individuals. The Five most abundant species also had the most multi-trunked individuals. Nine plots were slashed during January and February, 1993. Only 13% of the woody individuals that sprouted during the 57 to 111 day interval between slashing and burning survived burning. Remeasurements 15 months later. after burning, cultivation, and grazing, indicated that only four species retained their relative abundances of > 4%. The number of species < 1% relative abundance was reduced significantly by disturbance (P < 0.02. The Shannon-Weaver diversity index was similar for the uncut forest. after-slashing, and after disturbance, but after three burns during a 10-year period. woody species diversity was significantly lower in the adjacent pasture (P < 0.002). Slashing, burning, cultivation, and grazing thinned the tropical deciduous forest through mortality, altered the relative abundance of species, and simplified the community by eliminating similar to 29% of sprouting species encountered before burning. The disturbance reduced species diversity principally by reducing the presence of woody species with relative abundances of < 1% and by favoring a few species with high relative abundances(> 7%). Repeated burning to maintain the adjacent pasture conversion promoted the dominance of two species with relative abundances of 25.6 and 12.6%. (C) 1998 Elsevier Science B.V.