水曲柳根系生物量、比根长和根长密度的分布格局

采用连续钻取土芯法在生长季内对东北林业大学帽儿山实验林场17年生水曲柳人工林根系取样，研究水曲柳不同直径根系现存生物量、比根长和根长密度及垂直分布状况.结果表明，水曲柳人工林根系总生物量为1 637.6 g·m^-2，其中活根生物量占85%，死根占15%.在活根生物量当中，粗根(直径5～30 mm)占的比例最高（69.95%），其次为活细根（直径<1 mm，13.53%），小根(1～2 mm)和中等直径的根(2～5 mm)比例较小（分别为7.21%和9.31%）.直径<1 mm活细根的比根长为32.20 m·g^-1，直径5～30 mm粗根的比根长为0.08 m·g^-1.单位面积上活根的总长度为6 602.54 m·m^-2，其中直径<1 mm的细根占92.43%，其它直径等级则不到活根总长度的8%.直径<1 mm的细根生物量与根长密度具显著线性关系（R²=0.923），但与比根长无显著相关关系（R²=0.134）.

Dynamic process of liquid phase sulfur and nitrogen in forest canopy under acid deposition

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.