Pre-monsoon precipitation signal in tree rings of timberline Betula utilis in the central Himalayas

摘要

Himalayan birch {Betula utilis D. Don) is a long-lived, broadleaf tree species native to the Himalayas. However, it has received limited attention for dendroclimatological studies. Based on 49 tree-ring cores from 41 Himalayan birch trees at two sites in the Langtang National Park, central Nepal, a 458-year chronology (back to AD 1552) was developed. To date, this is the longest for this species in the Himalayas despite a low sample depth before AD 1785. The chronology statistics show the potential of Himalayan birch for dendroclimatology, as indicated by a positive correlation with precipitation in May and March-May (p < 0.001) and an inverse relationship with temperature in May and precipitation in August (p < 0.05). The Himalayan birch ring-width chronology is thus an indicator for pre-monsoon precipitation variations in the central Himalayas. The wide distribution of Himalayan birch in High Asia presents an outstanding opportunity for developing a large-scale, single-species tree-ring network.