PARENT SESSION
Organized Oral Session 22: Comparative ecology of tropical trees: Linking physiology to dynamics and distribution
Organizer(s): SC Thomas and KE Harms
Tuesday, August 9, 1:30 PM - 5:00 PM, Meeting Room 511 B, Level 5, Palais des congrès de Montréal

Phylogenetic inertia and functional relationships constrain the evolution of leaf traits of tropical savanna and forest trees.

Hoffmann, William^*,1, ¹ North Carolina State University, Raleigh, NC

ABSTRACT- Savanna and evergreen forest are the two most important biomes in terms of area, biodiversity, use by humans, and total carbon stocks. However we know little about the differences in functional traits that govern savanna-forest dynamics and determine distribution of savanna and forest. To improve our understanding of the ecological and physiological differences of savanna and forest trees, we compared leaf traits of species native to savanna and gallery (riparian) forests in the Cerrado region of central Brazil. Congeneric species pairs from fourteen different taxonomic families were studied, each with a savanna species and a forest species present at the study site. Only individuals growing in savanna conditions under full sun were studied. We measured foliar nutrients, 13C, 15N, and specific leaf area (SLA, leaf area per unit leaf mass). Overall, leaves of forest species had 21% greater N concentration, 41% greater P concentration, and 49% greater K concentration, despite growing in similar soils. Concentrations of all three of these elements were strongly and positively correlated to SLA. Forest species had 60% greater SLA on average than savanna species, which accounts for the higher foliar nutrient content of these species. Savanna species had greater values 13C than forest species, indicating greater water use efficiency. SLA was negatively correlated with 13C, indicating that SLA may account for the higher water use efficiency of savanna species. These results contribute to recent studies showing that tropical savanna and forest species represent two distinct functional types with large differences in resource utilization that likely have important consequences for the dynamics of savanna-forest boundaries.

Key words: Tropical Savanna, Tropical Forest, Comparative ecology, Nutrient relations