Relationship Between Field-Based Plant Species Richness and Satellite-Derived Biophysical Proxies in the Western Ghats, India

Abstract

Remote sensing offers fast and reliable technique to map the variation in plant diversity and distribution at different scales. Using 891 geo-tagged ground sampled point collected for the Western Ghats, India from a national level study on biodiversity characterization. We analyzed the distribution of plant species with respect to the satellite derived vegetation indices. The moderate resolution imaging spectroradiometer derived vegetation products, i.e., normalized difference vegetation index (NDVI), enhanced vegetation index (EVI), fraction of absorbed photosynthetically active radiation (fPAR), leaf area index (LAI), and surface reflectance (SR-645nm and SR-858nm) were fitted to suitable regression curves with respect to plant species richness where NDVI demonstrated the best fit (R2 = 0.07); while fPAR showed (R2 = 0.08) better relation with woody species richness. We observed positive but weak correlation for all the biophysiological proxies with species richness in the forests of Western Ghats. The annual pattern of correlation faired than seasonal (i.e., post-monsoon) between biophysical variables and species richness, while the woody subset of the species richness demonstrated marginally better relation at annual scale. The range of each biophysical proxy varied from medium to high, indicating higher vegetation strength. The species richness trend increased linearly for NDVI and EVI. The positive correlation showed by fPAR and LAI could be due to varied canopy architecture of the Western Ghats forests. Utility of fine resolution spatio-temporal data could render better understanding of species richness pattern using biophysical proxies, and thereby, help in long-term biodiversity monitoring.