Radial growth characteristics of dominant tree species in the southern greater khingan mountains of China

Abstract

Understanding radial growth responses of trees to climate change is essential for predicting forest dynamics under ongoing warming and aridification. This study analyzed the growth phenology and environmental sensitivity of Betula platyphylla and Populus davidiana in natural secondary forests of the southern Greater Khingan Mountains, northeastern China, during 2021–2023. B. platyphylla exhibited a 104±10.6-day growing season and a peak growth rate of 73.05 μm day⁻¹ in wet year 2021, which declined to 19.81 μm day⁻¹ in dry year 2023, with annual increments reduced by 66.9 %. These patterns indicate that B. platyphylla possesses a strong capacity for rapid environmental responsiveness. Its key environmental correlations shifted from air temperature (r = 0.60, P < 0.01) and soil temperatures (shallow soil: r = 0.43, middle soil: r = 0.34, deep soil: r = 0.29, all P < 0.01) in 2021 to relative humidity (r = 0.44, P < 0.01) and precipitation (r = 0.37, P < 0.01) in 2022, and predominantly negative correlations with soil temperatures (middle soil: r = -0.22, deep soil: r = -0.27, P < 0.01) in subsequent drought year 2023.

In contrast, P. davidiana maintained relatively stable phenology across years, with a consistent growth period of 58±6.6 to 56±3.3 days and peak growth rate varying from 28.53 to 15.13 μm day⁻¹. The species showed a pronounced lag in its environmental responsiveness: while showing moderate correlations with relative humidity (r = 0.35, P < 0.01) and vapor pressure deficit VPD (r = -0.32, P < 0.01) in 2021, it developed strong negative associations with air temperature (r = -0.31, P < 0.01) and VPD (r = -0.36, P < 0.01), alongside positive correlations with relative humidity (r = 0.32, P < 0.01) and precipitation (r = 0.37, P < 0.01) in 2022, with these patterns intensifying in 2023 (air temperature: r = -0.48, VPD: r = -0.51, relative humidity: r = 0.46, precipitation: r = 0.44, all P < 0.01). Both species experienced growth constraints under high temperatures (>25 °C) and vapor pressure deficit (>2.0 kPa) in 2022.

These divergent interannual strategies reflect fundamental physiological differences between the two species. B. platyphylla demonstrates dynamic environmental responsiveness characterized by shifting correlations from thermal to moisture factors under stress, which explains its substantial growth potential under favourable conditions and high sensitivity to environmental changes. In contrast, P. davidiana exhibits a lagged response mechanism with progressive strengthening of stress-avoidance correlations, as evidenced by its delayed but strengthening correlation with moisture variables. These contrasting physiological adaptations to climate stress—immediate versus lagged environmental responsiveness—provide critical insights for modelling temperate forest community dynamics and succession patterns under future climate scenarios.