Impact of human extraction on tropical humid forests in the Western Ghats Uttara Kannada, South India

Abstract

1. Thirty strip transects of 2400 m2 each, in the evergreen forest tract of the district of Uttara Kannada in South India; were clustered into two groups with high and low levels of disturbance on the basis of the density of perennial flowering plants and the fraction of deciduous species. 2. The set of 20 transects corresponding to low disturbance localities harboured 48 ± 6 (mean ± SD) species and 694 ± 135 individuals per transect, while the other 10 transects affected by high levels of disturbance supported 36 ± 12 species and 379 ± 135 individuals. 3. Eighty-four of the total of 200 species (operational taxonomic units) were exclusive to sites of low disturbance, and 28 to those of high disturbance; 88 species were shared by sites of high and low disturbance. This number of shared species was significantly less than expected on the basis of chance alone. 4. The differences in species richness, as well as those in species turnover (0.73 ± 0.07 for high and 0.65 ± 0.01 for low disturbance sites) were significant at the 1% level, but were as expected given the lower plant densities at sites of high disturbance. 5. Lack of coppicing ability in conjunction with their use in the plywood/matchwood industry has led to the disappearance of several evergreen species such as Syzigium gardneri and Myristica malabarica at sites with high levels of disturbance. 6. With villagers concentrating on harvests of trees in the height class of 4-8 m as poles, and commercial interests mostly extracting trees > 16 m in height, there was a reduction of around 45% across all height classes between sites of low and high levels of disturbance.