PARENT SESSION
Poster Session #71: Plant Ecology: Physiology and Function.
Friday, August 9. Presentation from 8:00 AM to 9:30 AM. Exhibit Hall B & C, TCC

Leaf morphological and chemical traits from geographically distant populations of Trachypogon plumosus, a dominant C4 grass from the neotropical savannas.

Baruch, Zdravko^*,1, ¹ Universidad Simon Bolivar, Caracas, Venezuela

ABSTRACT- Northern South American savannas are seasonally wet, unfertile, and frequently burnt but include diverse local climatic, edaphic and disturbance patterns. We determined several important leaf traits of T. plumosus and related them to water and nutrient availability. From 1998 to 2001, specific leaf area (SLA, cm² g^-1), width (LW), and nutrient and fibre content were measured yearly in 9 populations using standard methods. ANOVAS were done among populations and years and regressions were performed between plant and environmental variables. SLA is positivelly related to growth potential and to efficient resource use whereas LW affects leaf temperature and transpiration thorugh the energy balance. SLA ranged from 100 - 200 cm2 g-1 and LW from 0.5 - 1.0 cm, with statistically significant interpopulational differences. The thinnest and lowest SLA leaves correspond to the populations from the dryest savannas acting as a response to the local drought. Leaf nutrients and fiber reflect soil fertility and antiherbivory defence. Leaf N and P were low but with significant (100 - 300 %) interannual and population differences. Populations from the most fertile sites had the highest leaf nutrient and the lowest fibre content. This large populational variability partially explains the ability of T. plumosus to adapt locally to widely different environments and to dominate in these savannas. The recognition of this intraspecific diversity is crucial for restoration programs in degraded Neotropical savannas

KEY WORDS: Neotropical savannas, C4 grasses, Specific leaf area, Leaf nutrients