Palm harvesting affects seed predation of Euterpe edulis, a threatened palm of the Brazilian Atlantic Forest

M A Pizo,E M Vieira

doi:10.1590/s1519-69842004000400015

Abstract

The palm tree Euterpe edulis is endemic to the Atlantic Forest, where it constitutes an economically important forest product. The often unplanned and illegal harvesting of palm hearts has led to drastic reductions in the populations of E. edulis in many areas where this palm used to be the dominant understorey tree species. We investigated the effects of harvesting on seed and seedling predation of E. edulis. We tested the predictions of the dominance-predation hypothesis according to which predator satiation leads to an inverse relationship between the amount of predation and the dominance of a tree species. During two consecutive years, seeds were set experimentally on an unharvested (> 250 adult palms/ha) and a neighboring harvested site (few, if any, adult palms) located in the Atlantic Forest of SE Brazil. Seedling mortality was studied at both sites for a six-month period in each of two consecutive years. Seed predation caused by rodents was higher at the harvested site, while insects caused more damage to seeds placed at the unharvested site. The proportion of seeds preyed upon by rodents varied annually, while insect predation did not. Seedling mortality did not differ between harvested and unharvested sites. The dominance-predation hypothesis was confirmed for generalist rodent seed predators, but not for specialist insect predators. This result shows that density-dependent mortality, not only at the individual level but also at the population-level scale, is a function of the class of predators and their types of foraging behavior.

Highlights

The palm Euterpe edulis Martius is endemic to the Atlantic Forest (Henderson et al, 1995) and constitutes an economically important forest product (Galetti & Fernandez, 1998)
Unlike the multistemmed E. oleracea from the Amazon basin, which permits the extraction of selected stems year after year, the harvesting of the palm heart from the single-stemmed E. edulis results in the death of the plant
Seed predation The effects of palm harvesting on post-dispersal seed predation of E. edulis were investigated in JuneJuly of 1996 and 1997 by setting seeds on two parallel, 300 m long transects established at the harvested and unharvested sites, and recording the number of seeds that had been preyed upon by rodents and insects one month later

Summary

Introduction

The palm Euterpe edulis Martius is endemic to the Atlantic Forest (Henderson et al, 1995) and constitutes an economically important forest product (Galetti & Fernandez, 1998). Unlike the multistemmed E. oleracea from the Amazon basin, which permits the extraction of selected stems year after year, the harvesting of the palm heart (i.e., the edible apical meristem) from the single-stemmed E. edulis results in the death of the plant. This is because, once cut, it is unable to sprout. Over a great part of its range, E. edulis is found only in protected reserves which are, frequently invaded by illegal poachers (Galetti & Chivers, 1995). All of these put the once abundant E. edulis in a vulnerable position (Dransfield et al, 1988)

Methods

Results

Conclusion