Climate response in cell characteristics of Picea crassifolia along elevation gradient in Qilian Mountains, northwestern China

In order to investigate the climate response of wood cell characteristics of Picea crossifolia at three elevations in the Qilian Mountains, northwestern China, we measured radial diameter, number and wall thickness of tracheids of P. crossifolia using Silviscan-3. Residual chronologies of radial diameter, number and wall thickness of tracheids were established by dendrochronological methods based on variation of cell characteristics with elevation and calendar year. Relationships between cell characteristics and monthly mean temperature and monthly total precipitation were analyzed. The results indicated that radial diameter of tracheids increased but the number of tracheids decreased with the rise of elevation; there was no obvious change in wall thickness at three elevations. Radial diameter of tracheids was negatively correlated with temperature, but positively associated with precipitation. The number of tracheids was positively correlated with temperature, but negatively with precipitation. Temperature in June and July, and precipitation in May and June had a significant influence on radial diameter and number of tracheids. Tracheid wall thickness was positively correlated with temperature, but negatively with precipitation. Temperature had a stronger effect on tracheid wall thickness than precipitation. Effect of temperature on cell characteristics was consistent at three elevations, while the impact of precipitation decreased with the rise of elevation. Our findings suggest that precipitation, instead of temperature, is the main factor restricting the distribution of P. crossifolia along elevation gradient.