FUNCTIONAL ECOLOGY DURING SECONDARY SUCCESSION IN TROPICAL FORESTS

Abstract

This thesis examines the effects of plant functional groups and traits on the productivity and compositional dynamics of secondary succession in Panama and Singapore. In Panama, lianas reduce the stand biomass recovery and such an effect becomes more negative as succession progresses, while N2-fixing trees neither facilitate nor competitively reduce stand biomass recovery rates. In the wind-disturbed secondary forests in Singapore, functional compositions remain similar between affected and unaffected sites despite their taxonomic divergence, indicating that gap-colonising species are functionally similar to unaffected-site colonisers. Wood density, seed dry mass, and adult stature are traits that moderated tree recruitment along the wind-generated light, leaf litter depth, and soil phosphorus gradients. The “pioneer” population dynamics arise from higher photosynthetic capacity, shorter adult stature, and lighter seeds, transitioning to “long-lived pioneers” as species become taller in stature or heavier in seed mass, and then finally to the “late successional” with lower photosynthetic capacities.