Abstract:

The Tianshan Mountains is one of the most important tree ring research area in China. In order to understand the response mechanism of the radial growth of the trees in upper forest to environment, this paper conducted a simulation to reveal the relationship between the process of radial growth and the environmental factors based on the VS-oscilloscope model using the observed daily temperature and precipitation data of Balikun Weather Station of Hami City, Xinjiang, China from 1960 to 2015 and 52 tree cores from 26 trees collected at upper forest of the Balikun Mountain, east of Tianshan Mountains. According to the method of dendrochronology, all samples were surfaced, cross-dated and measured according to standard dendrochronology techniques. Finally, we established a tree ring width chronologies by core samples of Picea schrenkiana. The results shows as follows: (1) The correlation coefficient between the simulated tree ring width index and the actual tree ring width index is 0.645 (P<0.01), the consistency between the two trends indicating that the model has achieved good simulation results. (2) The main limiting factors for tree radial growth are soil moisture from April to May and from July to August. Temperature is the main factor determining the beginning of tree growing season, but the growth rate determined by temperature is not obvious in the formation of wide and narrow rings. (3) The correlation coefficient between simulated tree-ring width index and the end date of the growing season was -0.413 (P<0.01).It shows that the end date of growing season has some influence on the growth of tree ring width. (4) In addition, the simulation results also show that with the gradual increase of temperature in the region since 1984,the length of the tree growing season has an increase tendency, but overall the growth rate of trees has been declined. The increase in temperature since 1984 may be the main reason for the decline of tree growth. This study from a physiological point of view reveals the main limiting factors and time periods in the process of radial growth of the upper forest trees in the eastern Tianshan Mountains, which could provide some reference for tree ring study at this area in the future.

Key words: tree rings, Picea schrenkiana, radial growth, VS-oscilloscope model