A preliminary evaluation of the cold resistance of four tree species was conducted by studying the dynamic changes in cold resistance physiological indicators of branches of Fraxinus mandshurica, Phellodendron amurense, Juglans mandshurica and Tilia amurensis during the natural overwintering process with the aim of selecting the tree species with the strongest cold resistance among them and further providing some reference for cross-regional introduction of broad-leaved tree species in the southern part of Daxing’an mountains.

Four samples were collected during natural low temperature stress to determine theirs REC, enzyme activity of POD, SOD and CAT, content of MDA, SS, SP, Pro and water by using 2-year-old branches of 4 tree species from September 2023 to March 2024, and the cold tolerance of them was preliminarily evaluated by combining correlation analysis and fuzzy membership function methods.

1) The REC of 4 tree species showed a trend of first increasing and then decreasing with temperature changes; The MDA content of F. mandshurica seedlings showed a trend of first increasing and then decreasing, while the other 3 tree species showed a trend of “up-down-up”; 2) Except for J. mandshurica, the SP content of other tree species showed a single peak trend of first increasing and then decreasing; Except for P. amurense seedlings, which showed a trend of first decreasing and then increasing SS content, all other tree species showed a gradually increasing trend; In 4 sampling months, the Pro content of P. amurense was the highest among the tree species, followed by J. mandshurica, and the Pro content of F. mandshurica and T. amurensis was lower than that of P. amurense and J. mandshurica; 3) The protective enzyme activity of 4 tree species did not show a consistent pattern. The SOD enzyme activity of J. mandshurica changed the most, while the POD enzyme activity of P. amurense changed the most. The CAT enzyme activity of P. amurense and J. mandshurica was higher than that of F. mandshurica and T. amurensis in all 4 sampling months; 4) Except for the trend of “up-down-up” in the moisture content of the branches of T. amurensis, the other 3 tree species showed the opposite trend to that of T. amurensis; 5) The membership function values of F. mandshurica, P. amurense, J. mandshurica, T. amurensis were 0.489, 0.488, 0.484, and 0.480, respectively.

The relative physiological indexes of cold resistance of 2-year-old branches of different tree species are significantly different in the process of natural low temperature stress. Combined with the comprehensive evaluation value of membership function, it can be preliminarily determined that P. amurense has the strongest cold resistance and shows adaptability to low temperature, and T. amurensis has the weakest cold resistance.