Vegetation responses along edge-to-interior gradients in a high altitude tropical forest in peninsular India

Abstract

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. Species inventory was taken in 25 m 2 plots, established at 10 m intervals along edge to interior transects. The measured soil variables included pH, organic carbon, total nitrogen, available phosphorus, and soil moisture. Microenvironmental factors including light transmittance, relative humidity, and air and soil temperatures also were monitored. Both edaphic and microenvironmental factors exhibited strong patterns along the edge to interior gradient. Forest edges were characterized by higher light transmittance, higher air and soil temperatures, and lower relative humidity. Soil variables including pH, organic carbon, total nitrogen, available phosphorus, and moisture increased toward the forest interior. Significant increases in organic carbon (53.9%), total nitrogen (47%), and soil moisture (55%) indicated a relatively fertile forest interior compared with the forest edge. A definite floristic compositional pattern also was observed along the edge to interior gradient which was correlated to the edaphic and microenvironmental variables as revealed by canonical correspondence analysis. It appears that edge effects in these high altitude forests penetrate to a distance of 15–30 m. Further, edaphic factors have an important influence on woody species regeneration, perhaps much more than microenvironmental factors. This indicates that any disturbance that significantly exposes theforest floor, thus lowering soil moisture and altering soil nutrient status, can adversely affect the regeneration of many of the shola species.