Abstract: [Objective] Quantitative understanding of the radial growth dynamics of Eucalyptus urophylla×E. grandis in the dry season and the influencing factors can provide data support and theoretical guidance for improving the wood yield of eucalyptus forest and its scientific management.[Method]The radial growth of 5.5-year-old E. urophylla×E. grandis in dry season was studied using a DC₃ radial change recorder (Ecomatik, Germany), and the environmental factors inside and outside the forest were simultaneously observed. The relationship between the radial variation in dry season and various environmental factors was analyzed.[Result] The results showed that, the radial diurnalvariation of stems in dry season showed regular period icfluctuation under the influence of factors affecting stem water balance. The daily maximum value appeared in the morning (9:00-10:00) and the minimum value appeared in the afternoon (16:00-18:00). The stems in rainy days continued to expand and then remained unchanged. The maximum value was about 2 hours later than that on sunny days. The radial cumulative growth of E. urophylla×E. grandis stems in dry season was a volatility rising process, which could be divided into three periods:relative stable period, rapid growth period and dehydration contraction period. During the whole dry season, the dominant environmental factors affecting stem radial growth were different in different periods. The soil water content and temperature (soil temperature and atmospheric temperature) were the most important factors limiting the growth of stems in the dry season.[Conclusion]The main influencing factors affecting stem radial growth of E. urophylla×E. grandis in the dry season were water and temperature. If appropriate measures such as increasing soil temperature and soil water content (irrigation, etc.) can be applied in the dry season, the growth of E. urophylla×E. grandis stems will promoted.

Key words: stem radial variation, Eucalyptus urophylla×E. grandis, dry season, influencing factor