Timberline and Climate in the Indian Western Himalayan Region: Changes and Impact on Timberline Elevations

Abstract

In Himalayas, the high-elevational mountains have warmed more rapidly in recent decades than other areas of the globe. Himalayan timberline is climate dependent and sensitive to changes, thus can provide biological proof of global warming. The present analysis changes in timberline elevations over four decades and corresponding climatic parameters (temperature and precipitation) in the Western Himalayan region (Himachal Pradesh). Landsat-2 Multispectral Scanner (MSS) and Landsat-8 were used to evaluate the long-term (1976–2015) timberline dynamics. The climate data APHRODITE was used to calculate the annual mean temperature and annual precipitation along the spatially distinct timberline locations. The mean elevation of timberline position has shifted vertically 145 m with a rate of ~37 m per decade (@ 3.7 m per year) over the past four decades, however majority of timberline remained stationary (no shift). The annual mean temperature in timberline elevations of outer Himalayan ranges (away from permanent snowline) and locations of inner Himalayan ranges (near to permanent snowline) has increased at the rate of 0.32 °C decade⁻¹ and 0.23 °C decade⁻¹, respectively. The annual precipitation in timberline elevations of outer Himalayan ranges decreased and at timberline elevations of inner Himalayan ranges increased at the rate of 38 mm decade⁻¹ and 21 mm decade⁻¹, respectively. The study concludes that temperature and precipitation at timberline elevations are one of the main drivers to respond by the timberline vegetation, and yet to better understand and predict timberline response to changing climate.