Document: DAV-3-83-13

Population-level effects of defoliation in the tropical understory palm Chamaedorea elegans.

ANTEN, N.P.R.* ¹, M.MARTINEZ-RAMOS ² and D.D.ACKERLY ¹

Stanford University, Stanford CA 94305 USA ¹
Universidad Nacional Autonoma de Mexico, Morelia, Michoacan, Mexico ²

Abstract:
At this moment, natural populations of palms in many areas are endangered due to overexploitation resulting from poorly designed harvest schemes. We therefore undertook to investigate the long-term effects of sustained leaf removal on the demographic parameters in natural populations of the understorey palm Chamaedorea elegans. In March 1997, individual C. elegans plants, growing in a natural population were subjected to either of five defoliation treatments: (0, 33, 50, 66 and 100% of the leaves removed). Survival, growth and reproduction were recorded at six months intervals for two years and population-level consequences of defoliation were analyzed using matrix models. Sustainable harvesting was defined as a defoliation level at which population growth (lambda) greater than 1 can be sustained for an extended time period. In the first year, reproduction decreased strongly with defoliation while the other demographic parameters were unaffected. Lambda was relatively unaffected by defoliation and lambda was greater than 1 for all levels of harvest levels except the 100% treatment (lambda = 0.967). This result indicates that lambda was relatively insensitive to changes in fecundity. In the second year, leaf removal negatively affected all demographic parameters and lambda declined strongly with defoliation. The condition lambda > 1 was only met for defoliation levels of 50% or less. These results show that multi-year experiments are essential in designing sustainable harvest schemes, for long-lived species such as C. elegans and most other palms.

Keywords: defoliation, matrix models, leaf harvesting, non-timber forest products, sustainable harvesting, tropical rain forest

This abstract is being presented at: 1:00 PM in session:
Oral Session #51: Disturbance Ecology: Harvesting, Grazing and Roads.