Climate-Growth Relationships of West Himalayan Fir (Abies pindrow) along an Altitudinal Gradient in Northwestern Himalaya

Abstract

Climate change which includes an increase in temperature, changes in precipitation, retreating of glaciers, has a significant impact on ecosystem dynamics and the social communities. High mountains around the globe are some of the most vulnerable systems and of great concern for conservation. The Himalayan mountains are experiencing a higher warming than average global warming, which can significantly impact their biodiversity, vegetation distribution and ecosystem structure. The plants growing in the Himalaya will have to adapt accordingly to survive the changing climate. Variations in climate impact tree growth and significantly influence cambial phenology and wood formation. There is no study as of now that has investigated the dynamics of cambial phenology in Himalayan conifers. There is a need to precisely document cambial phenology and wood formation in Himalayan trees to better understand climate-growth relationships and their response to future climate change. Studies have shown that climate-growth relationships vary along the distribution range of a species. In mountain species, growth is generally sensitive to precipitation at the lower altitudinal limit and to temperature at the higher altitudinal limit of a species. In the Himalaya, such information regarding the varied response of tree growth to climate along its altitudinal distribution range is limited to very few studies. Generally, it is assumed that climate-growth relationships are stable over time. However, a number of recent studies have shown that these relationships have been changing especially in the higher northern latitudes. This phenomenon has been termed as “divergence problem” in northern forests. Furthermore, the instrumental records of temperature and precipitation data are limited in most parts of the globe. In the Himalayan region, the instrumental records are relatively short. Long-term records of climate are crucial to understand the recent climate change. Tree rings offer an excellent proxy to extend the instrumental climate data. The advantage of climate reconstructed using tree ring parameters as proxy is that it is annually resolved and can be well calibrated and verified. Therefore, the broad objectives of this thesis were to understand the cambial phenology and annual growth ring formation along an altitudinal range of the west Synopsis 12 Himalayan fir, Abies pindrow. The tree rings of this species were studied to understand the response of radial growth to regional temperature and precipitation over the species altitudinal range. The temporal stability of these climate-growth relationships was studied to understand the impact of climate change on the growth response of species to climate. Finally, the tree-ring sensitivity of site chronologies to climatic factors was used to reconstruct the past climate of Srinagar for hundreds of years. The findings from this thesis will give new insights into the dynamics of cambial phenology and climate-growth relationships and help in better understanding of potential impacts of climate change on tree growth and forest productivity in Himalaya