PARENT SESSION
Poster Session 2: Forest Ecology
Monday, August 8, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Leaf optical properties across vertical transects in tropical rain forest canopies.
Garcia-Guerrero, Andrea*,1, Oberbauer, Steven 1, Clark, David2, Olivas, Paulo3, Ordoñez, Harlyn3, 1 Florida International University, Miami, FL2 University of Missouri-St. Louis, St. Louis, MO3 La Selva Biological Station, Puerto Viejo, Sarapiqui, Costa Rica
ABSTRACT- Light is the dominant limiting factor for tropical rain forest plants. Consequently light absorption properties of leaves might be expected to be under strong selection. Leaves typically absorb 85-90% of light in the photosynthetically active range, but relatively few studies have investigated how leaf optical properties might differ with position in the forest canopy or how species of different growth forms growing under the same conditions compare. These questions are particularly relevant in the tropics where hundreds of species per hectare are present. The objective of this project was to evaluate variation of leaf optical properties with height and among plant functional groups in tropical rain forest canopy and to identify correlates of optical properties. Sampling was done in 11 vertical transects using scaffolding towers in old-growth forest at La Selva, Costa Rica. Plants were grouped into canopy trees, subcanopy trees, emergent trees, tree seedlings, palms, vines and lianas, epiphytes, ferns, shrubs, and herbs. All plants encountered at each level (1.9 m in height) along the transect were included. We found significant differences in optical properties among the functional groups (p < 0.0001); canopy trees absorbed the most and reflected the least, and epiphytes reflected the most and absorbed the least. When all functional groups were considered together, only reflectance was significantly related (positively, p < 0.001) to height in the canopy. Canopy tree absorptance decreased with increasing leaf area above and decreasing light level, a response opposite to that of the epiphytes. Vines had some properties that behaved similar to epiphytes (reflectance) and others that behaved more similarly to trees (transmittance and absorptance). We also found significant correlations between leaf optical properties and chlorophyll concentration, leaf thickness, specific leaf area, and leaf carbon concentration.
Key words: absorptance, la selva, par, canopy tower