Abstract: Employing soil core method,an investigation in Maoershan Experiment Station was made on the root biomass,specific root length (SRL),and root length density (RLD) of Fraxinus mandshurica plantation (17 yr) within a growth season in stand level.The results showed that the total root biomass was 1 637 g·m^-2,in which,living biomass accounted for 85%,and necrotic biomass was 15%.In the living biomass,coarse roots (5～30 mm in diameter) had the highest percentage (69.95%),followed by fine roots (<1 mm in diameter) (13.53%),medium roots (2～5 mm in diameter) (7.21%),and small roots (1～2 mm in diameter) (9.31%).Among the four diameter classes,fine roots had a higher SRL (32.20 m·g^-1),while coarse roots had a lower one (0.08 m·g^-1).The total RLD in living biomass was 6 602.54 m·m^-2 in stand level,among which,fine root accounted for 92.43%,and the others was less than 8%.Fine root biomass and RLD had a positive correlation with soil available nitrogen,while no significant correlation was found between SRL and soil available nitrogen.

Key words: Lanthanum, Membrane permeability, Root exudate, Nutrient content