LOW-LEVEL FOREST DISTURBANCE EFFECTS ON PRIMARY PRODUCTION, LEAF CHEMISTRY, AND LEMUR POPULATIONS

This study quantifies the effects of low-intensity logging (affecting <10% of the forest surface) on leaf chemistry, leaf and fruit production, and their effects on lemurs in a dry deciduous forest in western Madagascar. Logging exposed the remaining trees to more sunlight. Within a single tree and among trees, this resulted in higher protein concentrations in sun-exposed leaves, while fiber content remained constant. Concentrations of condensed tannins were also higher at higher sun exposure, but they leveled off at lower light intensities before protein and sugar concentrations. Within the 2-yr study period, crown extension due to higher availability of sunlight could compensate only for parts of the crown area lost due to logging. Thus, the biomass of leaves available was reduced, while average leaf quality (measured as the ratio of protein to fiber) increased. Fruit production was also positively correlated with sun exposure of the tree crown. Since fruits of the main timber trees (Commiphora spp.) are rarely consumed by frugivorous lemurs, removal of these trees increases sun exposure of other potential food trees for frugivores. At the described level of logging intensity, sightings of all lemur species increased (significantly in three out of seven species at P less than or equal to 0.05) compared to the pre-logging state and two control plots. This increase was attributed to increased fruit production and higher protein concentration in sun-exposed leaves. In natural forests, treefall gaps may have effects similar to those of logging in the present study. Low level disturbances, in general, may be important for the carrying capacity for folivorous and frugivorous lemurs and possibly for most primates.