Attenuated tree species diversity in human-impacted tropical evergreen forest sites at Kolli hills, Eastern Ghats, India

Tree diversity (greater than or equal to 30 cm gbh) in undisturbed and huma n-impacted tropical evergreen forest sites was investigated in the Kolli hi lls, Eastern Ghats, India. Four 2-ha contiguous permanent plots were erecte d, one each in Perumakkai shola (site PS), Vengodai shola (VS), Kuzhivalavu shola (KS) and Mottukkadu shola (MS) at 1000, 1050, 1200 and 1250 m elevat ion, with increasing human disturbance, to evaluate the difference in tree species composition, stand structure and dynamics. This paper discusses the results of the first survey. A total of 3825 individuals and 78 species fr om 61 genera and 36 families were enumerated in the 8 ha area. Among the fo ur 2-ha sites, species richness was greatest (58) in the undisturbed site P S and lowest (39) in the highly disturbed site MS. Shannon, Simpson, Hill d iversity and evenness indexes revealed a progressive reduction in diversity with increasing disturbance. The asymptote species-area curves imply adequ ate site sampling. Tree density (1151 to 651 trees ha(-2)) and basal area ( 106 to 46.6 m(2) ha(-2)) decreased from undisturbed to disturbed site, due to selective felling. Single species, Memecylon umbellatum dominated sites MS (39%) and VS (26%), while Nothopegia heyneana, Memecylon umbellatum and Diospyros ovalifolia were dominant in PS, and Meliosma simplicifolia, Myris tica dactyloides and Phoebe wightii in KS. Based on species abundance, we c lassify the study area as Memecylon-Phoebe-Beilschmiedia association with N eolitsea and Myristica as codominants. Tree population structure revealed a step-wise decline in girth frequencies with increasing size class in undis turbed site PS, whereas tree density fell sharp (> 50%) in medium girth cla ss in the disturbed site MS. Population of the dominant species varied wide ly. The diversity values of this inventory are compared with similar studie s in India and other tropical forests. Evidently, the reduction in species richness (by 52%), basal area (56%) and tree density (58%) in disturbed sit es, with 57.6% of species rarity of this tropical evergreen forest, in secl uded patches ('sholas') of Kolli hills, underlines conservation need to pre vent species loss.