Assessing the stability of radial growth responses to climate change by two dominant conifer trees species in the Tianshan Mountains, northwest China

Abstract

As global climate warming intensified in the latter half of the 20th century, the radial growth of trees exhibited unstable climate responses and growth trends, thereby reducing the accuracy of growth-climate ecological relationship and the scientificity of forest management based on tree rings. We assessed the temporal stability of radial growth responses and determined the growth patterns of two dominant co-occurring conifer tree species, Siberian larch (Larix sibirica) and Schrenk spruce (Picea schrenkiana), in the Tianshan Mountains of northwest China under a climate that shifted from warm-dry to warm-wet. The primary conclusions were as follows: (1) drought in the growing season was the main limiting factor of radial growth of the two tree species in recent decades through the analysis of the dynamic relationships between tree radial growth and climate factors; (2) Siberian larch had divergent responses to mean temperature in summer of the previous year, while Schrenk spruce had relatively stable responses to the mean temperature, total precipitation and monthly standardized precipitation-evapotranspiration index (SPEI) in spring of the current year by comparing the response variations before and after the abrupt increases in temperature and the moving correlation function; and (3) Siberian larch showed first increasing and then decreasing trends, while Schrenk spruce showed continuously decreasing trends based on calculating the basal area increment (BAI). The study results confirmed that forests in arid and semiarid environments would be subjected to more serious drought impacts, resulting in radial growth decline, tree mortality and community degradation with climate warming in the future. Therefore, it is important to adopt effective management measures for different species according to their response characteristics to climate change.