Dendroclimatic Response of Picea crassifolia along an Altitudinal Gradient in the Eastern Qilian Mountains, Northwest China

Using tree-ring data collected from five stands of Qinghai spruce (Picea crassifolia) along an altitudinal gradient in the eastern Qilian Mountains, northwest China, we investigate the differences of the chronologies' statistical parameters and climatic-growth relationships along the gradient. Our results indicate that the radial growth-climate patterns are similar at all studied elevations, and tree growth in this region is strongly related to drought conditions. Growth-temperature and precipitation correlations reveal very coherent patterns for the four lowest sites, showing significant (p < 0.05) correlation with July-August temperatures and August precipitation in the previous year and March temperatures in the current year. For the upper treeline site, the chronology is negatively and significantly (p < 0.05) correlated with August temperature and December precipitation in the previous year. In addition, individual chronologies are significantly (p < 0.05) correlated with the Self-calibrated Palmer Drought Severity Index for many months. The cross-correlation matrix of the individual chronologies indicates all the correlation coefficients are significant (p < 0.01), confirmation that tree growth is predominantly influenced by common climate factors. The outstanding drought periods recorded by the five chronologies took place during A.D. 1860-1875, the 1880s, and 1905-1935. Pluvial periods took place during A.D. 1800-1810 and 1975-1990.