PARENT SESSION
Oral Session #72: Herbivory: Herbivore Response to Plants.
Presiding: C. Mitchell
Wednesday, August 7. 1:00 PM to 4:45 PM. Mesquite Room, Radisson.
Response of trees and herbivores to relaxed nutrient availability constraints in secondary tropical dry forests.
CAMPO, JULIO*,1, DIRZO, RODOLFO1, 1 Universidad Nacional Autónoma de México, México, D.F., México
ABSTRACT- Leaf nutrients and leaf damage were studied in dominant tree species of secondary tropical dry forests in Yucatan, including a young forest (10 yr-old) and an old forest (~60 yr-old). Selected species at the young forest were Acacia gaumeri, Leucaena leucocephala and Lysiloma latisiliquum and A. gaumeri, Bursera simaruba and Pithecellobium dulce at the old forest. Four plots (12 x 12 m) at each forest were fertilized with N, with P, or with N plus P for 3 yr. Nitrogen was applied at 225 kg ha-1yr-1 and P at 75 kg ha-1yr-1. Leaf nitrogen and phosphorus concentrations and herbivory were measured in control and fertilized plots. When results from unfertilized plots of both sites were combined, we observed that leaf P concentration increased in the old forest while N remained constant. Relaxation of nutrient limitations at the young forest resulted in an increase of leaf P and herbivory in all species, but did not affect leaf N. In contrast, fertilization at the old forest increased leaf N and damage only in Bursera simaruba. Subsequent to nutrient addition, we observed that leaf-P concentration in the leguminous species increased at the young forest; leaf-N concentration in the non-leguminous species increased at the old forest. We conclude that the regulatory mechanisms of leaf quality and damage will vary, depending on the site nutrient limitations and on the identity of species.
KEY WORDS: herbivory, leaf nutrients, soil nutrient limitation