Secondary succession and indigenous management in semideciduous forest fallows of the Amazon Basin
To the discussion on secondary succession in tropical forests, we bring data on three under-addressed issues: understory as well as overstory changes, continuous as opposed to phase changes, and integration of forest succession with indigenous fallow management and plant uses. Changes in vegetation structure and species composition were analyzed in secondary forests following swidden agriculture in a semideciduous forest of Bolivian lowlands. Twenty-eight fallows, stratified by four successional stages (early = 1-5 yr, intermediate = 6-10 yr, advanced = 12-20 yr, and older = 22-36 yr), and ten stands of mature forests were sampled. The overstory (plants >=5 cm diameter at breast height [DBH]) was sampled using a 20 x 50 m plot and the understory (plants <5 cm DBH) in three nested 2 x 5 m subplots. Semistructured interviews provided information on fallow management. Canopy height, basal area, and liana density of the overstory increased with secondary forest age. The early stage had the lowest species density and diversity in the overstory, but the highest diversity in the understory. Species composition and abundance differentiated mature forests and early successional stage from other successional stages; however, species showed individualistic responses across the temporal gradient. A total of 123 of 280 species were useful with edible, medicinal, and construction plants being the most abundant for both over- and understories. Most of Los Gwarayo preferred mature forests for making new swidden, while fallows were valuable for crops, useful species, and regenerating timber species.