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Tests of the Janzen-Connell and Gap hypotheses in tropical forests in Panama: confirming the predictions of two long-standing hypotheses.
Carson, Walter1, Schnitzer, Stefan2, Stevens, Henry3, 1 2 3
ABSTRACT- Both gaps and seed and seedling predation may play critical roles in the maintenance of diversity and mode of regeneration in tropical forests. To test these hypotheses, we have been excluding ground-dwelling mammals with exclosures for 8-years in the understory at two old-growth forest sites in Panama. Additionally, we have been monitoring the fate of all woody species in a series of gap and non-gaps sites. Our results suggest that both gaps and seed and seedling predation can promote the maintenance of high woody species diversity in tropical forests. Data from both observational and experimental studies demonstrate that gaps promote the diversity of lianas and pioneer species while seed and seedling predation promotes diversity of shade-tolerant species by preventing a small number of these tree species from becoming extremely abundant in forest understories. Our results suggest that very different life-history trade-offs may allow numerous species to coexist in tropical forest understories.
KEY WORDS: tropical forest, herbivory, seed predation, gaps