Variations in the timing of different phenological stages of cambial activity in Abies pindrow (Royle) along an elevation gradient in the north-western Himalaya

High mountains around the globe are some of the most vulnerable ecosystems to climate change 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. There is a need to study the process of wood formation in Himalayan conifers to have a better understanding of their growth responses to predicted climate change. Variations in the climatic factors regulating cambial activity would result in changes in the timing of cambial phenology. In this study, the variations in the timing of different stages of cambial phenology (cell enlargement stage, wall-thickening stage and cell maturation stages) in pindrow fir (Abies pindrow) were investigated from anatomical observations of wood microcores collected during 2014-15 along an elevation range of c.2300?3000 m asl in the north-western Himalaya. The onset of all three cambial phenological stages was significantly correlated with elevation, with onset of cambial activity happening more than a week earlier at the lowest elevation than at the highest elevation site. Although the termination of wall-thickening and maturation stage appeared minimally related to elevation, the cell-enlargement stage showed significant correlation with elevation, with tracheid formation ceasing approximately three weeks earlier in trees at the highest elevation. The timing of these phenological stages did not show strong variations between the two study years. Our findings provide new data on the timings of cambial phenophases and help to understand tree growth response to ongoing changing climate in the Himalayan region.