PARENT SESSION
Oral Session #3: Plant Population Ecology. Presiding: N. Fetcher.
Monday, August 6, 2001. 8:00 AM to 11:30 AM. Hall of Ideas L&M.
Consequences of variable seed production for seedling recruitment in three neotropical tree species.
DE STEVEN*, DIANE1, WRIGHT, S. JOSEPH2, 1 2
ABSTRACT- Over an 11-year period, we investigated the consequences of variable seed production for seedling recruitment in three neotropical tree species (Quararibea asterolepis, Tetragastris panamensis, and Trichilia tuberculata) in the semi-deciduous forest of Barro Colorado Island, Panama. Using a focal-tree transect design and a permanent sample of trees, we asked how individual contributions to population patterns varied temporally (across years) and spatially (across dispersal neighborhoods of individual trees). Quararibea and Tetragastris had a fluctuating pattern of productive and poor seeding years, whereas Trichilia had more consistent seed production across years. In each species, trees were synchronized in seed production, and synchrony appeared partly influenced by El Nino climatic events. Both temporal and spatial variation influenced seedling recruitment. At the population scale, more seedlings established in productive seed years than in poor seed years in all three species, whereas at the individual tree scale, patterns varied among species. Quararibea and Tetragastris trees with higher average seed production recruited more seedlings in their dispersal neighborhoods than less fecund trees. However, Trichilia seedling recruitment was not higher at trees with larger average seed crops and thus was spatially density-dependent. In all species, the number of seedlings surviving one year later was highly correlated with the number initially recruited, with no evident density-dependent mortality at the tree neighborhood scale. Overall, Quararibea and Tetragastris recruitment appeared to be partly seed-limited, whereas Trichilia recruitment was more establishment-limited.
KEY WORDS: tree seedling demography, variable seed production, recruitment limitation