PARENT SESSION
Oral Session #107: Forest Ecology: Disturbance.
Presiding: H. Regan
Friday, August 9. 9:00 AM to 12:00 PM. Mesquite Room, Radisson.

Comparative ecology of congeneric savanna and forest tree to understand to dynamics of tropical ecotones.

Hoffmann, William^*,1, ¹ Departamento de Engenharia Florestal, Brasília, DF, Brazil

ABSTRACT- Understanding the factors that determine the location and dynamics of savanna-forest boundaries is necessary for predicting the distribution of these biomes under future climate and land use. However there has been virtually no work to understand the ecological differences between savanna and forest species. To fill this gap and to understand adaptations to the savanna environment, I used congeneric species pairs as a basis for ecological comparisons of these two plant type. Savanna species exhibit higher root:shoot ratios and thicker bark, resulting in much greater capacity to survive fire. They also exhibit greater capacity to germinate under water stress and, as seedlings, maintain higher pre-dawn water potential during the dry season. Growth analysis of seedlings revealed that savanna species have lower leaf-area ratio, lower specific leaf area, higher net assimilation rate, and greater phenotypic plasticity in response to light intensity. Despite clear differences between savanna an forest species, more of the overall variation in these plant traits is explained by differences among genera than by the differnce between these two plant types. This points to a high degree of phylogenetic inertia which has constrained the evolution of these plant traits.

KEY WORDS: Savanna, Tropical Forest, Growth analysis, Comparative Ecology