[Radial growth dynamics of Chinese fir and its response to seasonal drought]

We explored the seasonal dynamics and climate responses of radial variation of Chinese fir, we continuously monitored intra-annual stem radial size changes with the automated dendrometers in central Jiangxi Province in 2016 and 2017. We analyzed daily and seasonal dynamics of radial variations, and their Spearman correlations with climatic factors. We found that the diurnal radial variations had a pattern of contraction during the day and expansion at night. The growth onset in 2017 was one month earlier than that in 2016, whereas the continuous tree water deficit in the dry season caused the cessation one month early. During the main growing season (from April to September), the radial increment was significantly positively correlated with precipitation and relative humidity but negatively correlated with photosynthetically active radiation and vapor pressure deficit in both wet and dry seasons. However, the correlation for tree water deficit was opposite to stem radial increment. Severe water deficit significantly enhanced the impacts of soil water content on stem radial variation in the dry season. Moisture condition was always the key factor affecting stem radial variation of Chinese fir. Appropriate measures such as increasing soil water content could promote stem radial growth during summer drought.