Impact of selective logging on the dynamics of a low elevation dense moist evergreen forest in the Western Ghats (South India)
Résumé
Within the framework of a programme on the functioning of dense moist evergreen forests of the Western Ghats, the French Institute of Pondicherry, in collaboration with the Karnataka Forest Department, installed permanent plots to monitor the dynamics of a low elevation forest. The preliminary results of the comparison of the demographic processes in two compartments are presented: one compartment had never been harvested, while the other was selectively felled in 1979–1980. They are compared in terms of species composition, recruitment, mortality and individual growth, in order to describe the natural forest dynamics and evaluate the impact of selective felling. In both compartments, the mortality rate, around 0.9% yr−1, is lower than in other tropical moist evergreen forests, while the average diameter increment, at 2.1 (unlogged stand) and 2.9 mm yr−1 (logged stand), is higher. The impact of selective felling, 10 to 15 years after the harvest, is mainly noticeable: (i) on mortality of trees with dbh>40 cm belonging to lower canopy and intermediate stratum species which died about four times more in the logged compartment; and (ii) on diameter increment of emergent and upper canopy tree species whose growth is still stimulated by about 50%. Despite the general trend of a reduction in the difference between the density and the basal area of the two compartments, medium-term modification of the demographic processes among the various structural ensembles in the logged compartment, indicates that selective felling may not be sustainable in the long-term without consequences on the forest structure and composition.