Elevation-influenced variation in canopy and stem phenology of Qinghai spruce, central Qilian Mountains, northeastern Tibetan Plateau

摘要

Key messageCanopy and stem phenology of Qinghai spruce, central Qilian Mountains, respond to different environmental factors depending on season and elevation.AbstractTo understand vegetation species response to climate change, much research has been devoted to changes in forest phenology. Results of such studies are not only of scientific interest; they are potentially of great use in forest management. This study focuses on variations in canopy and stem phenology as affected by climate and elevation. We collected data on canopy phenology (as recorded in the Normalized Differential Vegetation Index) and stem phenology [using the Vaganov-Shashkin (V-S) model] in Qinghai spruce (Picea crassifolia) growing at two sites in the central Qilian Mountains, Northeast Tibetan Plateau. One site was at a higher elevation, near the local alpine tree-line, and the other was near the local lower tree-line. At both sites, a significant correlation was found between canopy and stem spring phenology. This would seem to be mainly due to spring temperatures. No such correlation was found between canopy and stem autumn phenology. The study suggests that the main factors affecting stem growth after the beginning of growing season would be temperature and soil moisture, and that these have different effects depending on elevation. At the lower elevation, soil moisture seems to be the main factor limiting growth. At the higher elevation, temperature was the determining factor. Climate change will have different effects depending on elevation.