Age dependent growth response of Cedrus deodara to climate change in temperate zone of Western Himalaya

The recent warming in the mountain regions affect forest productivity in terms of tree growth, especially in the Himalayan region. However, the effects of climate change on the response of radial growth of different age-class trees in the Himalayan region remains unclear. The sensitivity of different age-class trees can differ from younger to old age-class tree growth which create uncertainty in tree-ring calibration against the climatic parameters. In the present study, we assessed the effect of climate change on the radial growth of Cedrus deodara (cedar) from two different age classes; young (age < 100 years) and old (age > 100 years) in lower temperate zone of Indian Western Himalaya for the period 1950-2015 CE. We modelled basal area increment (BAI) using the Generalized additive model (GAM) which predicted the observed pattern of BAI as a function of year and random effect of tree. The trend of old age stand BAI increased significantly by 0.13 cm(2)/year whereas it significantly declined by-0.27 cm(2)/year for young deodar stand. However, from 1990 CE both age classes showed significant decline (p < 0.05) in BAI indicating reduction in tree productivity of cedar species which may be due to recent accelerated rise in temperature and decline in precipitation. Correlation analysis between BAI growth and climate revealed that the BAI from both age-class trees were mainly limited by spring season (March-May) climate, moreover, the signal was statistically strong for old age deodar stand. The tree age vs DBH relationship of old age stand forest showed significant positive relationship but no relationship was found for young age stand which indicated more environmental stress condition for young age deodar forest stand. Future efforts are required to identify the factors responsible for decline productivity of young deodar stand by using wide networks of tree-ring data.