Response of radial growth of Abies nephrolepis to environmental factors in Changbai mountain

Studying the radial growth of trees is crucial for reconstructing past climatic conditions and predicting the future adaptability of forests to climate change, and for developing sustainable forest management strategies.

The Gompertz model was used to fit the growth curve of Abies nephrolepis to determine the time of growing season. The periodic cycle method, daily value method and zero growth model were used to extract the daily radial variation, and the correlation between the radial variation in the growing season and environmental factors such as air temperature and humidity, soil temperature and humidity was processed and analyzed.

1) The growth season of Abies nephrolepis began in early May and ended from late July to August. The maximum growth rate appeared before the summer solstice; 2) The annual radial variation sequence of Abies nephrolepis has obvious seasonal characteristics. The rapid water replenishment expansion in early spring and the freeze-thaw cycle of stem in winter leads to higher radial variation, while the long period caused by continuous cooling in summer and continuous contraction of low temperature in winter makes the daily radial variation of periodic cycle method significantly different from other methods; 3) During the growing season, sufficient rainfall and low saturated vapor pressure deficit were the key factors to promote the daily radial growth of Abies nephrolepis, while the minimum temperature at night significantly affected the expansion growth process of radial variation. The daily value method and the zero growth model emphasize the synergistic effect of multiple hydrothermal conditions such as average air temperature, soil temperature and humidity, while the periodic cycle method emphasizes the role of water factors (saturated vapor pressure difference, rainfall), and the periodic cycle method has a higher interpretation of growth variables about 60%.

Rainfall and saturated vapor pressure difference were the dominant environmental factors in the growing season of Abies nephrolepis in the study area, followed by the highest air temperature and soil moisture. The periodic cycle method is more suitable for the study of short-term tree radial growth in this area than other methods.