Geospatial assessment of treeline shift in response to climate change in Langtang National Park, central Nepal

Abstract

The Himalayan region harbors diverse treeline species but remains highly sensitive to even minor climate fluctuations, leading to shifts in forest distribution and recruitment patterns. This study examines treeline dynamics in response to climate change in Langtang National Park (LNP), Nepal, using remote sensing data, GIS techniques, and field observations. We assessed changes in Normalized Difference Vegetation Index (NDVI), forest coverage, and treeline positions from 2000 AD to 2018 AD. Statistical analyses, including regression modeling, Pearson correlation, and the Mann-Kendall trend test, were employed to quantify trends and relationships between climate variables and treeline shifts. Results indicate a significant upward advancement of the treeline at a rate of 3.73 m/year, with the average treeline elevation rising from 3,609.60 m during 2000 AD to 3,680.34 m during 2018 AD. Forest cover expanded accompanied by a notable increase in NDVI. Climate data revealed a significant warming trend, particularly in winter minimum temperatures (0.060°C/year). Treeline positions exhibited strong positive correlations with both maximum and minimum temperatures, while pre-monsoon rainfall showed a declining trend (-4.322 mm/year). These findings highlight climate warming, especially winter warming, as a primary driver of treeline advancement in LNP, with potential consequences for high-altitude ecosystems and biodiversity. This study provides insights into climate-induced vegetation shifts in the Himalayan region, offering valuable information for conservation planning and climate adaptation strategies. By quantifying treeline shifting rates and associated climatic influences, our research establishes a baseline for predicting future ecological changes in fragile mountain environments.