Understanding Spatio-temporal Pattern of Grassland Phenology in the western Indian Himalayan State
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RESEARCH ARTICLE
Understanding Spatio-temporal Pattern of Grassland Phenology in the western Indian Himalayan State Harshit Rajan1 • C. Jeganathan1 Received: 9 August 2018 / Accepted: 19 March 2019 Ó Indian Society of Remote Sensing 2019
Abstract The present study has analysed grassland phenology: start of greening (SOG), end of greening (EOG) and length of greening (LOG), and their rate of change in the western Himalaya in India (Himachal Pradesh) using MODIS NDVI time series data (2001–2015). These metrics were inspected at different stratification levels: state, elevation, climatic zones and bio-geographic provinces. Delayed SOG was observed over 44.87% (P \ 0.1), and delayed EOG over 63.3% (P \ 0.1) of grassland grids. LOG was shortened in 24.37% (P \ 0.1) and extended in 58.04% (P \ 0.1) of the grids. At the state level, when statistically significant pixels (SSP) and all the pixels (AP) are used (given as SSP:AP), SOG is delayed by 20.27:6.28 days year-15, while EOG is delayed by 38.02:14.97 days year-15 and LOG is extended by 35.07:8.70 year-15 days. Extended LOG is observed over the temperate and cold arid regions, and shortened LOG is observed over sub-alpine and alpine regions. Variations in SOG and EOG are not uniform across different climatic and bio-geographic regions. However, in the sub-alpine and alpine zones, SOG and EOG followed elevation gradients, i.e. late SOG with early EOG over higher elevations, and early SOG with late EOG over lower elevations. Our study has revealed an interesting pattern of translational phenology (i.e. late SOG and late EOG) of grasslands which hints towards shifting winter period. Overall, it is observed that variations in timing of snowfall and snow cover extent are the reasons for inter-annual variations in the grassland phenology. Keywords Grasslands Phenology Western Himalaya Bio-geographic zones Climatic zones India
Introduction Himalaya is the most remarkable geographic structure of India and perceived for its magnificent ecosystem services for all the eight adjoining countries (Tewari and Kapoor 2013). It represents a profoundly intricate and diversified system in terms of both biological and physical characteristics (Palni and Rawal 2010). In recent years there has been an increasing realization about the sensitivity of vegetation of mountainous areas to climate change, and Himalayan ecosystem is considered as delicate and Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12524-019-00976-w) contains supplementary material, which is available to authorized users. & Harshit Rajan [email protected] 1
Department of Remote Sensing, Birla Institute of Technology (BIT), Mesra, Ranchi, Jharkhand, India
susceptible to radical changes because of the anthropogenic development-induced climate change (Chawla et al. 2012; Tiwari and Joshi 2013). Grasslands of Western Himalaya not only provide employment to countless local and transitory pastoral communities (Kumar et al. 2015), but are also home to several biodiver
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