Climatic response of Picea crassifolia tree-ring parameters and precipitation reconstruction in the western Qilian Mountains, China

Cores of thick leaf spruce from the western Qilian Mountains were subjected to densitometric analysis to obtain data for seven tree-ring parameters (tree-ring width, earlywood width, latewood width, maximum density, minimum density, mean earlywood density and mean latewood density). The chronologies were analyzed individually and then compared with each other. Most of these variables show moderately high values of common variance and mean interseries correlation except latewood and maximum densities. The relationships between the different tree-ring parameters and climate data are also presented. The growth/climate response analyses reveal that the radial growth of thick leaf spruce is the mainly controlled by total annual precipitation (July-June). Herein the residual ring width chronology was used to reconstruct annual (July-June) precipitation of Jiuquan for the period 1768-2009 A.D., and it accounted for 45.0% of the precipitation variance. Multi-taper spectral analysis reveals the existence of significant 11.1-year, 4.9-year, and 2.0- to 3.4-year periods of variability. Spatial analysis shows that the precipitation of Jiuquan has strong common signals for the northern margin of the Tibetan Plateau and Hexi Corridor. Drought events in our reconstruction are compared to the historical archives and other moisture-sensitive tree ring width series in the Hexi Corridor. The results reveal common climatic extremes over much of the Hexi Corridor. Many of these events have had profound impacts on the peoples of the Hexi Corridor over the past several centuries.