RESEARCH ARTICLE Warming-Induced Decline of Picea crassifolia Growth in the Qilian Mountains in Recent Decades

Warming-induced drought has widely affected forest dynamics in most places of the north-ern hemisphere. In this study, we assessed how climate warming has affected Picea crassi-folia (Qinghai spruce) forests using tree growth-climate relationships and the normalized difference vegetation index (NDVI) along the Qilian Mountains, northeastern Tibet Plateau (the main range of Picea crassifolia). Based on the analysis on trees radial growth data from the upper tree line and the regional NDVI data, we identified a pervasive growth decline in recent decades, most likely caused by warming-induced droughts. The drought stress on Picea crassifolia radial growth were expanding from northeast to southwest and the favor-able moisture conditions for tree growth were retreating along the identical direction in the study area over the last half century. Compared to the historical drought stress on tree radial growth in the 1920s, recent warming-induced droughts display a longer-lasting stress with a broader spatial distribution on regional forest growth. If the recent warming continues with-out the effective moisture increasing, then a notable challenge is developed for Picea cras-sifolia in the Qilian Mountains. Elaborate forest management is necessary to counteract the future risk of climate change effects in this region