VEGETATION RESPONSES ALONG EDGE-TO-INTERIOR GRADIENTS IN A HIGH-ALTITUDE TROPICAL FOREST IN PENINSULAR INDIA

A study was conducted in a high altitude tropical forest (shola forest ) in peninsular India to examine the changes in floristic composition (mainly woody species regeneration) along an edge to interior gradient in relation to changes in edaphic and microenvironmental factors. Spe cies inventory was taken in 25 m(2) plots, established at 10 m interva ls along edge to interior transects. The measured soil variables inclu ded pH, organic carbon, total nitrogen, available phosphorus, and soil moisture, Microenvironmental factors including light transmittance, r elative humidity, and air and soil temperatures also were monitored. B oth edaphic and microenvironmental factors exhibited strong patterns a long the edge to interior gradient, Forest edges were characterized by higher light transmittance, higher air and soil temperatures, and low er relative humidity. Soil variables including pH, organic carbon, tot al nitrogen, available phosphorus, and moisture increased toward the f orest interior. Significant increases in organic carbon (53.9%), total nitrogen (47%), and soil moisture (55%) indicated a relatively fertil e forest interior compared with the forest edge. A definite floristic compositional pattern also was observed along the edge to interior gra dient which was correlated to the edaphic and microenvironmental varia bles as revealed by canonical correspondence analysis. It appears that edge effects in these high altitude forests penetrate to a distance o f 15-30 m. Further, edaphic factors have an important influence on woo dy species regeneration, perhaps much more than microenvironmental fac tors, This indicates that any disturbance that significantly exposes t he forest floor, thus lowering soil moisture and altering soil nutrien t status, can adversely affect the regeneration of many of the shola s pecies.