Stability evaluation of radial growth of Picea schrenkiana in different age groups in response to climate change in the eastern Tianshan Mountains

Abstract

Global warming causes an unstable response in tree radial growth at high latitudes in the Northern Hemisphere. Additionally, different climatic responses of different age groups of trees have been found due to their different physiological mechanisms. In this study, the response stability and growth trend of three age groups (young < 100a, middle 100–200a, old ≥ 200a) of Picea schrenkiana (Schrenk spruce) to climate change and the causes of the different responses in different age groups were analyzed in the relatively dry climate of the eastern Tianshan Mountains. The results showed that: (1) With the abrupt increase in temperature in 1989, the annual mean minimum temperature became the dominant radial growth-limiting factor of the three age groups of Schrenk spruce. (2) The radial growth of the middle and young groups was more sensitive than that of the old group based on growth-climate correlation analysis. (3) The radial growth of the different age groups had different responses to climate factors, and all age groups were unstable on time scales. (4) The trend of the linear regression simulation of the basal area increment (BAI) indicated that the Schrenk spruce had the same growth trends in different age groups with growth first increased and then decreased; however, the decreased growth rate was higher in the middle and young age groups than in the old age group after the abrupt increase in temperature. Therefore, we should pay active attention to the impact of drought on Schrenk spruce in the eastern Tianshan Mountains and should particularly strengthen the conservation and management of the middle and young age groups.