PARENT SESSION
Oral Session #30: Modeling.
Presiding: T. Day
Tuesday, August 6. 8:00 AM to 11:30 AM. Apache Meeting Room, TCC.
Life history tradeoffs among seedlings of four native Malagasy tree species.
de Gouvenain, Roland*,1, Kobe, Richard2, Silander, John1, 1 University of Connecticut, Storrs, CT2 Michigan State University, East Lansing, MI
ABSTRACT- Species-specific tradeoffs between survivorship and growth across resource gradients have been hypothesized to result in environmental niche partitioning among different tree species and have been found to explain some of the spatial variation in species composition observed in natural forest. However, few studies have examined potential tradeoffs due to species-specific responses to variables other than light, especially in African forest systems. The goal of this study was to investigate and model the regeneration responses of four native Madagascar tree species as a function of light, soil moisture, and soil type, and to evaluate the possible role of life history tradeoffs in the regeneration dynamics of these four species. We used data from 1200 seedlings transplanted in a natural lowland rainforest of Madagascar and maximum likelihood estimators to parameterize competing seedling mortality and growth models as a joint function of light and soil moisture. We modeled relative seedling performance as a joint function of both light and soil moisture to determine which species would likely dominate other species at the seedling and sapling stages of forest regeneration. The four species studied, Harungana madagascariensis, Ocotea cymosa, Stephanostegia capuronii and Uapaca ferruginea, exhibited significantly different mortality and growth responses to light and soil moisture. These relative performances suggest that there are species-specific tradeoffs that operate even at the seedling and sapling stage of a tree's life history, and that these life history tradeoffs can result in niche dissimilarity among tree species along light and soil moisture gradients in a tropical forest.
KEY WORDS: forest dynamics, life history tradeoffs, maximum likelihood, Madagascar