Effects of competition and climate on tree radial growth of Pinus sibirica in Altai Mountains,Xinjiang, China

Aims As an important part of the ecosystems of Central Asia and the whole world, forest growth dynamics of the boreal forest in Altai Mountains can affect global thermal radiation, carbon balance and so on. Therefore, it is crucial to explore the main factors affecting tree radial growth of the boreal forest in Altai Mountains.Methods We selected Pinus sibirica in Kanas National Nature Reserve of Xinjiang as the target tree species, and established tree-ring chronology of P. sibirica. To explore the influence of competition and climate on radial growth of P. sibirica in the Altai Mountains, Xinjiang, we analyzed the relationships among the cumulated basal area increment (BAI), competition index and climate factors at different time intervals by applying various methods like linear mixed effect model and correlation analysis.Important findings The results of the linear mixed effect model showed that: (1) the BAI over the past 30 years can be best predicted by the sun of competitors’ diameter at breast height (SDBH). (2) Significant positive correlations were found between the standard chronology, and mean air temperature, mean maximum air temperature and mean minimum air temperature in March. (3) The highest value of the cumulated BAI was observed when air temperature was from 0 to 5 °C, and the competition index was below 100. The lowest value of the cumulative growth occurs when air temperature reaches -10 °C and the competition index exceeds 300. Tree radial growth of subject trees was influenced by both the diameter at breast height of the competing trees and the early growing season air temperature. Competition plays a more important role in affecting radial growth of P. sibirica than climate factors in this area. Therefore, our results would provide a scientific basis for forest management of P. sibirica in Kanas National Nature Reserve of Xinjiang.