Causes and consequences of monodominance in tropical lowland forests

Tropical canopy dominance in lowland, well-drained forests by one plant spe cies is a long-standing conundrum in tropical biology. Research now shows t hat dominance is not the result of one trait or mechanism. We suggest that the striking dominance of Gilbertiodendron dewevrei in the Ituri Forest of northeastern Congo is the result of a number of traits in adult trees that significantly modify the understory environment, making it difficult for ot her species to regenerate there. Adults cast deep shade that reduces light levels in the understory of the Gilbertiodendron forest to levels significa ntly lower than in the mixed-species forest. Moreover, the monodominant for est has deep leaf litter that could inhibit the establishment of small-seed ed species, and the leaf litter is slow to decompose, potentially causing t he low availability of nitrogen. We expect that juveniles of Gilbertiodendr on may have an advantage in this environment over other species. In general , it appears that all tropical monodominant species share a similar suite o f traits.