Effects of logging and other forms of harvesting on genetic diversity in humid tropical forests.

Abstract

AbstractCommercial harvesting of timber through logging is a major form of disturbance in many areas, but the variety of products harvested from tropical forests is immense: wood, fruit and other foods, medicinal plants, construction materials and many more. Commercial logging has been separated from other types of human use to reflect the relative importance of logging in all types of forest. In a comprehensive study of logging in tropical forests, genetic diversity (expected heterozygosity, He, for isozyme data and Shannon Diversity Index, H, for RAPD data) was reduced by 5.0-23.4% after logging for five species with different life history strategies. Generally, the order of reduction in number of individuals corresponded with the order of reduction in genetic diversity. Daemonorops verticillaris exhibited the highest loss of alleles (13.8%) most probably due to death of individuals following logging damage to supporting trees and being trampled during extraction of felled trees. No significant differences in outcrossing rates were observed between logged and unlogged stands for Shorea leprosula and Dryobalanops aromatica. No adverse changes in genetic diversity measures of Parkia speciosa, Scaphium macropodum, Shorea leprosula, Garcinia malaccensis, Daemonorops verticillaris and Labisia pumila were detected in two regenerated stands (13.5% and 40.7% disturbances) compared to an unlogged stand in the mixed dipterocarp lowland forest indicating maintenance of genetic diversity in regenerated stands after a single low intensity logging event. In comprehensive studies on collection of non-timber forest products in the Biligiri Rangan Hills of south India, a significant effect on recruitment of Phyllanthus emblica, the fruits of which are harvested for food and as a base for numerous traditional medicines, was observed. Harvesting of fruits or flowers tend to have a more direct or dramatic effect on regeneration and genetic diversity than harvesting of leaves, bark or other non-reproductive parts of the plants.