Paleoclimatic studies from the tree-ring of Himalayan birch from Langtang National park, central Nepal

Abstract

Himalayan birch (Betula utilis D Don) is a long live, broadleaf species native to the Himalayas.  However, this species has received limited attention for dendroclimatic studies world widely. In order to investigate the dendrochronolgical potential of this species in the central Himalayas, we analyzed 26 cores from 22 trees collected from Langtang National park, central Nepal, in May 2010. Based on these samples, we developed 371-year chronology extending back to 1639 AD. The chronological statistics, such as mean sensitivity and correlation between tree-ring series showed its high potentiality for the dendroclimatological study. In addition, the radial growth of Himalayan birch records clear climatic signals. Precipitation in May and early summer (March-May) plays a significant role (p<0.001) for the growth of this species. However, temperature of the month May have significant (p<0.05) inverse relations with the radial growth. The tree-growth climate relationship indicates the cool and moist condition in the early summer is a favorable condition for the growth of Himalayan birch in the central Himalayan region. In addition, tree ring of Himalayan birch clearly records the local and regional paleoclimatic drought events in 1999, 2000, 1960s, 1950s, 1790s and 1760s.