Remote sensing of alpine treeline ecotone dynamics and phenology in Arunachal Pradesh Himalaya

ABSTRACT

Global warming is inducing the elevational alpine treeline ecotone (ATE) to migrate to higher elevations in the Himalaya. Prior research on ATE dynamics has been primarily based on field inventory and studied at the community level. The potential of using remote sensing and geographic information system for the delineation of the treeline ecotone has been explored. In this study, we used satellite-derived Normalized Difference Vegetation Index (NDVI) data from Landsat-1/2 Multispectral Scanner (MSS), Resourcesat-1/2 Linear Imaging Self Scanning Sensor (LISS-III), and National Oceanographic and Atmospheric Administration-Advanced Very High-Resolution Radiometer (NOAA-AVHRR) to investigate long-term ATE dynamics. Satellite remote sensing of treeline in Arunachal Pradesh Himalaya revealed an upward shift over the past four decades. The ATE has shifted c. 452 m ± 74 m upward in vertical dimension at a rate c. 113 m decade⁻¹. Furthermore, the land surface phenology along ATE and forest area has changed significantly over the past 33 years. The significant positive trend in length of the growing season (LOS; p < 0.05) and delay in the end of the growing season (EOS) was observed. The start of the growing season (SOS) had a negative tendency with non-significant linear trend. The treeline upward shift and significant lengthening of the growing season at ATE and forest area indicate changing climatic patterns and processes.

Acknowledgements

The authors gratefully acknowledge Shri. Tapan Misra, Director, Space Applications Centre (SAC); Dr Raj Kumar, Deputy Director, EPSA; and Dr Prakash Chauhan, Group Director, BPSG, SAC, Indian Space Research Organisation (ISRO), Ahmedabad for their support and encouragement. Authors are thankful to Dr B.K. Bhattacharya, Head, AED and Dr R.P. Singh, Project Director (PRACRITI-II) and Head, Land Hydrology Division (LHD) for their guidance. The project has been carried out under ‘Alpine Ecosystem Dynamics and Impact of Climate Change in Indian Himalaya’ under PRACRITI-II program of ISRO. The GIMMS NDVI_3g data facility of NOAA; GHCN gridded V2 data provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA; and Landsat data of National Aeronautics and Space Administration (NASA) and the United States Geological Survey (USGS) are duly acknowledged. The authors would also like to thank the anonymous reviewers for their insightful and critical comments, which make this paper be improved largely.

Disclosure statement

No potential conflict of interest was reported by the authors.