Assessment of biological richness in different altitudinal zones in the Eastern Himalayas, Arunachal Pradesh, India

Abstract

This article evaluates an approach for biological richness assessment at landscape level using satellite remote sensing, phytosociological data and knowledge base in a GIS domain at a test site in the Eastern Himalayan region. An attempt is made to establish the relationship existing between biological richness and biotic disturbances across an altitudinal gradient, divided into six zones based on different vegetation types. Biological richness was determined as a function of ecosystem uniqueness, species diversity, biodiversity value, terrain complexity and disturbance index. Satellite images of IRS 1C/1D LISS III are used to stratify different vegetation types following a hybrid approach supplemented with biogeographic and altitude zone maps. The number of economically important species, medicinal species and endemic species decreases with altitude. High level of disturbance was observed across settlements and road networks and the areas having simpler and easily accessible terrains. A declining trend in species richness and plant endemism is noticed with increase in altitude. Habitats with low disturbance, highly complex terrain, high degree of species richness, plant endemism and species uniqueness show high level of biological richness. In general, the disturbance decreased with increase in altitude, whereas biological richness shows a hump-shaped pattern for Arunachal Pradesh. It was observed that high biological richness and high disturbance occurred in lower altitudes, whereas high-altitude areas showed low biological richness and low level of disturbance. The study demonstrates integration of remote sensing and GIS for landscape ecological modelling and thereby contributes to the understanding of biodiversity distribution in the Eastern Himalayas, Arunachal Pradesh.