Effects of Forest Fragmentation on Recruitment Patterns in Amazonian Tree Communities

Fragmentation can alter the ecology of rain forest remnants in many ways, but its long-term effects on tree communities are poorly understood. One phenomenon that has received little attention is tree regeneration in fragmented forests (Janzen 1983; Viana et al. 1997). Patterns of regeneration are important because they will ultimately determine the floristic composition of the remnant. Janzen (1983) suggested that fragments of tropical dry forest in Costa Rica are prone to invasions of weedy, generalist plant species from the surrounding modified matrix, which could progressively alter the floristic composition of remnants. Laurance (1991, 1997) proposed that fragments in some tropical regions are chronically disturbed by winds and other factors and may exhibit a general shift toward successional trees, lianas, and vines adapted for recurring disturbance. Using data collected over 13 years, we describe patterns of tree recruitment in a fragmented landscape in central Amazonia. We ask three questions: (1) Do rates of tree recruitment differ between fragmented and continuous forests? (2) Are recruitment rates influenced by fragment area, age, and proximity of forest edge? (3) Are regenerating trees in fragments biased toward successional species or against old-growth species?