Composition, Age-Structure and Dendroecology of High Altitude Treeline Forest in the Western Himalaya, India

•At the ecotone, A. spectabilis shows poor regeneration while R. campanulatum shows good regeneration.•Tree-ring investigation shows treeline migration upward at the rate of 10 m/decade for the past 200 years.•Tree growth climate relationship shows precipitation of current year April month is conducive for A. spectabilis.•Temperature of the previous year’s September and current year’s April, May shows negative relation with radial growth.•Temperature of winter month shows positive correlation with radial growth indicating the sensitivity of A. spectabilis to warming scenario.