Legendary Old Conifer Trees in Western Himalaya: Environmental Chronicles

Abstract

The Himalayan mountain system is the abode of diverse tree species growing at different elevations from sub-tropical to sub-alpine regions. Many of the tree species growing in the Himalayan region are known to attain several centuries to millennial age. Trees growing in environments with seasonal climate produce annual growth rings, which represent yearly increment in radial growth. The physical and chemical properties of annual wood increments (ring-widths, wood density and isotopic composition) reflect the respective year’s environmental conditions that affected tree growth and physiology. Various parameters of the annual wood increments are used to glean the yearly environmental variations. This makes the trees a unique natural archive of past environmental changes the tree faced over its life time. Tree-ring studies, so far carried out in India have shown over two millennia old trees of Juniperus polycarpos in cold arid Lahaul in the western Himalaya. Other conifer trees spanning over millennium age are of Pinus gerardiana and Cedrus deodara growing in extreme dry environments in the western Himalaya. As in the era of changing global climate the mean temperature of the Earth is continuously increasing and disturbing the regular pattern of climate variables. In the recent decades, the observed changes of climate variables are becoming the cause of societal challenges and responsible for the loss of lives and natural resources. In view of this, the precisely dated growth ring sequences in such old trees have been used to develop climate records (temperature/precipitation) for regions of the origin of tree-ring chronologies. The tree-ring derived climate records from the high-altitude regions of the Himalaya, where instrumental records are limited, are of significant value to understand natural climate variability and associated socioeconomicchallenges in regional and global perspective.