Treeline migration and settlement recorded by Himalayan pencil cedar tree-rings in the highest alpine zone of western Himalaya, India

Abstract

Himalayan pencil cedar (Juniperus polycarpos) is an evergreen tree distributed from Afghanistan, Baluchistan, Kagan valley, Kashmir, Lahaul-Spiti to upper reaches of western Tibet1 . Naturally, the lower and upper limit of a tree species over a specific region varies due to the ecological settings of the area. Recently it has been noted that due to global/regional climatic changes there is marked change in distribution and composition of vegetation at its upper limit. Various studies from different parts of the globe indicate migration and shifting of treeline towards the higher altitudes2–15. Treeline migration/shifting have also been recorded from the Indian Himalaya by studying treeline dynamics over Uttarakhand-Himachal Pradesh16,17 and Sikkim18. Himalayan pencil cedar is known to grow generally at high altitudes with the highest treeline recorded from the forest of Juniperus tibetica at southeast Tibet (~4900 masl)19 and Juniperus sp. in Hunza-Karakorum (~3900 masl)20. Demarcation of the upper limit of treeline in complex mountainous terrains remains a challenging task.