Background The study of the relationship between tree growth and environmental factors is important to improve the water use efficiency of forest trees and the rational management of forest trees. Previous studies have mostly focused on the relationship between tree whorl and climate, which lacks continuity and completeness of observation. A stem radial change recorder can continuously record stem diameter growth and reversible moisture-related shrinkage and swelling within the stem, providing information on the tree's moisture relationships and stem diameter growth.

Methods The Ailanthus altissima in Hebei was used as the experimental object, and the dynamic variations of stem diameter during the growing season (May 2021 to September 2021) of A. altissima was continuously monitored by means of a radial change recorder, and the sap flow and micrometeorological factors were simultaneously monitored, and the synergistic relationships between stem diameter and sap flow and micrometeorological factors were analyzed by correlation analysis method.

Results 1) The stem diameter of A.altissima increased by 3 246.856 μm from May to September, and the maximum diurnal variation range presented as June > May > July > August > September, the growth mainly concentrated from early May to mid-July. The diurnal variation of stem diameter showed the regular pattern of periodic contraction and expansion. 2) The variation of stem diameter and sap flow showed a negative correlation (P < 0.01), and the variation of stem diameter lagged behind the sap flow for 150, 120, 90, 30, and 30 min from May to September, respectively. 3) The variation of stem diameter also showed a negative correlation with solar radiation, air temperature and vapor pressure deficit, and a positive correlation with air humidity (P < 0.01), and there was also time lag. The change in stem diameter lagged behind the change in solar radiation and ahead of the change in vapor pressure deficit. The time lags between stem diameter and each meteorological factor tended to increase as the month progressed. 4) Under the stronger rainfall conditions, the stem diameter of A. altissima increased significantly, and the stem diameter did not shrink back to the original scale afterwards.

Conclusions The amount of stem diameter growth and variation characteristics varied among different months of the growing season. There is a time lag effect between stem diameter change and sap flow and meteorological factors, and this interrelationship varies in different growth periods. Rainfall is an important factor influencing stem diameter change, and adequate irrigation is beneficial to the radial growth of the stem during the growth stage of the A. altissima in this region.