Age structure of male and female F. mandshurica trees. The distributions between genders had no significant difference according to Kolmogorov-Smirnov test (P > 0.05), with a greater proportion in the mid-age classes. The figures indicated the sex ratios (male:female), and the significance deviated from expected 1:1 was examined by chi-square test. ** P < 0.01, * P < 0.05, † 0.05 < P < 0.1, ns P > 0.1.