Contrasting impacts of climate warming on Himalayan hemlock (Tsuga dumosa) growth: seasonal and elevational variations

Ongoing climate change can have varying impacts on tree growth within the growing season and across their elevation ranges, with important implications for forest ecosystem functions and services. However, our knowledge of these effects on climate-sensitive Himalayan forests is still limited. Here, we explore the elevational changes in climatic factors driving long-term changes in the radial growth of Himalayan hemlock (Tsuga dumosa), including recent responses to unprecedented climate warming in the central Himalayas. We evaluated several growth parameters, including total ring width, earlywood width, adjusted latewood width, and maximum latewood density, in unique old-growth forests at around 3000 m near Kangchenjunga and along an elevational gradient of 2500–3100 m on the southern slopes of Dhaulagiri, Nepal. Our findings show that the growth of Tsuga trees is influenced by multiple climatic factors that vary within the growing season and across different parts of its elevation range. Moreover, changing climatic conditions, characterized by increasing temperatures and variable precipitation patterns, had a more detrimental effect on Tsuga growth at the edge of its elevation range compared to the optimal mid-elevation zone.