Abstract: Fraxinus mandshurica is a valuable timber species in Northeast China, with high ecological and economic value. We collected the F. mandshurica family materials for sowing and seedling cultivation in 2002 and afforested in 2004. Based on dendrochronology and wood anatomy methods, we analyzed the relationship between xylem anatomical characteristics and major climatic factors for Zhangguangcai Mountains (2007-2023) and Xiao Xing’an Mountains (2010-2022), and examined the effects of common low temperature years (2010 and 2012) on anatomical characteristics of xylem. The results showed that the xylem anatomical characteristics of F. mandshurica in the Zhangguangcai Mountains and Xiao Xing’an Mountains showed similar trends with the age of trees. Ring width and total vessel area exhibited a unimodal pattern of “first increasing and then decreasing” with tree age, with a rapid growth period of approximately 10 years in the young forest stage. The specific hydraulic conductivity, theoretical hydraulic conductivity, percentage of conductive area within xylem, and total vessel area of F. mandshurica in Zhangguangcai Mountains were significantly higher than those of Xiao Xing’an Mountains by 143.7%, 124.1%, 48.4%, and 43.3%, respectively. The annual ring width of F. mandshurica from both sites showed signifi-cant positive correlations with vessel number, total vessel area, and theoretical hydraulic conductivity. Conversely, it exhibited strong negative correlations with vessel density, percentage of conductive area within xylem, and specific hydraulic conductivity. Temperature and precipitation jointly influence the xylem anatomical characteristics, but the dominant climatic factors differed between the two sites. The growth of F. mandshurica in Zhangguangcai Mountains was primarily influenced by temperature. Growth during the growing season in the Xiao Xing’an Mountains was subject to the joint influence of temperature and precipitation, exhibiting sensitivity to high-temperature stress during summer. Low-temperature events led to a significant decrease in multiple anatomical indicators of F. mandshurica in both sites. In low-temperature years, ring width, mean vessel area, total vessel area, theoretical hydraulic conductivity and specific hydraulic conductivity of F. mandshurica in Zhangguangcai Mountains decreased significantly by 10.8%, 24.3%, 10.7%, 37.7% and 41.1%, respectively. In Xiao Xing’an Mountains, the decreases in these indicators were greater, with declines of 27.8%, 43.4%, 28.9%, 62.6%, and 55.8%, respectively. No.7 and No.12 F. mandshurica families exhibited strong resistance in both sites, which could be served as excellent cold-resistant F. mandshurica varieties for directional cultivation in Northeast China.

Key words: Fraxinus mandshurica, tree ring width, xylem anatomical characteristics, low-temperature event, ecological resilience