Seedling Mortality by Litterfall in Amazonian Forest Fragments1

Abstract

ABSTRACTPhysical damage caused by litterfall is a source of seedling mortality that can be influenced by environmental disturbances, such as the isolation of forest fragments due to habitat destruction. The impact of physical damage in seedling mortality was evaluated in forest fragments and continuous forests in central Amazonia using artificial seedlings. A total of 11 reserves distributed among three sites were studied: three 1–ha, three 10–ha, two 100–ha, and three continuous forest reserves. In each reserve, ten transects each comprised of ten artificial seedlings were monitored for one year at four–week intervals. Survival curves were compared using failure time analysis, and the effect of reserve size on artificial seedling mortality after one year was analyzed with a categorical model. In the analysis of survival curves, artificial seedling survival was significantly greater in the continuous forest than in the 10–ha reserve at one site only, a result that may have occurred by chance. After one year, artificial seedlings suffered similar mortality due to litterfall among the reserves sampled. Physical damage by litterfall varied from 28 to 35 percent annually in the 1–and 10–ha forest fragments compared to 20 to 24 percent in the continuous forest. Mortality of artificial seedlings in the continuous forest was similar to other tropical sites in which the same method has been used, and may indicate that litterfall plays an important role in seedling mortality in the terra firme tropical forests of central Amazonia.