Meta-analysis of climate effects on radial growth of Qinghai spruce in northwestern China

Radial growth of trees is highly sensitive to environmental changes, but the effect of climate on tree rings in Qinghai spruce (Picea crassifolia), a widely distributed endemic conifer in western China, is more complex than in many other conifers. A comprehensive understanding of the spatiotemporal climatic responses of its rings is needed to develop theoretical basis for designing strategies for its conservation and management. Here, our synthesis of the literature on responses of radial growth of Qinghai spruce to monthly climate variables in different environmental conditions by meta-analysis showed that precipitation and drought severity are the main limiting factors for Qinghai spruce radial growth in the semiarid region of northwestern China. In warmer and drier areas, radial growth of Qinghai spruce is mainly limited by drought. In the areas north of the 600-mm annual precipitation isoline, the tree-ring width (TRW) was significantly positively correlated with precipitation and significantly negatively correlated with temperature during the growing season (June-August). The limiting effect of drought on Qinghai spruce is also gradually increasing from southeast to northwest, to the west of 103 degrees E and within 37 degrees N-39 degrees N.