Increasing growth sensitivity of Pinus wallichiana to summer season maximum temperature – evidence from central Bhutan Himalaya

The impacts of global warming are pervasive across different forest biomes and are most pro­nounced in high mountain ecosystems such as the Himalayas. This study examines the growth response of Blue pine (Pinus wallichiana) to climate from Bumthang district in the central Bhutan Himalaya. Tree radial growth parameters (ring width index and basal area increment) were correlated with monthly and daily climate. Temporal changes in significant climate response were assessed using running correlations. Irrespective of tree growth parameters or temporal resolution of climatic variables, growth-climate re­sponse revealed maximum temperature during summer as the most significant climatic factor regulating the growth of P. wallichiana in central Bhutan. The strength and stability of the climate response improved when using daily climate, which is not restricted by non-biological calendar months. Around the turn of the 21st century, we observed a rapid rise in radial growth. Over the last ~30 years, blue pine from central Bhutan has benefited from warming summer season maximum temperatures. This study highlights the importance of considering daily climate variables for more accurate assessments of tree growth responses to climate. These findings have significant implications for understanding the impact of climate change on forests in the Himalayan region.