Density-dependent survival in seedlings differs among woody life-forms in tropical wet forests of a Caribbean Island

Negative density dependence contributes to seedling dynamics in forested ecosystems, but the relative importance of this factor for different woody plant life-forms is not well-understood. We used 1 yr of seedling survivorship data for woody seedlings in 17 different plots of lower to mid-montane rain forests on the island of Dominica to examine how seedling height, abiotic factors, and biotic factors such as negative density dependence are related to seedling survival of five different life-forms (canopy, midstory, and understory trees; shrubs; and lianas). Across 64 species, taller seedlings in seedling plots with higher canopy openness, greater seedling density, lower relative abundance of conspecific seedlings, and lower relative abundance of conspecific adults generally had a greater probability of surviving. Height was the strongest predictor of seedling survival for all life-forms except lianas. Greater seedling density was positively related to survival for canopy and midstory trees but negatively related to survival for the other life-forms. For trees, the relative abundance of conspecific seedling and adult neighbors had weak and strong negative effects on survival respectively. Neither shrub nor liana seedling survival was affected by the relative abundance of conspecific neighbors. Thus, negative density dependence is confirmed as an important structuring mechanism for tree seedling communities but does not seem to be important for lianas and shrubs in Dominican rain forests. These results represent the first direct assessment of controls on seedling survival of all woody life-forms - an important step in understanding the dynamics and structure of the entire woody plant community.