关 键 字(英文)：Subtropics Nitrogen deposition Tree seedlings Biomass production Allocation
摘 要(英文)：To better understand the effects of elevated nitrogen deposition on biomass production and allocation in seedlings of Schima superba and Cryptocarya concinna , the dominant species in subtropical monsoon evergreen broadleaved forests in China , a simulated nitrogen deposition field experiment was conducted. S. superba and C. concinna seedlings were exposed to five nitrogen treatments using NH4NO3 solutions of 0 , 0. 12 ,0. 24 , 0. 36 and 0. 72 mol N·L - 1 . Solutions were applied twice a month from January through November ,2003 , equivalent to nitrogen deposition rates of 0 , 5 , 10 , 15 and 30 g N·m- 2·a - 1 . Each treatment was divided into three subplots and 40 seedlings of each of the two species were transplanted into each subplot . The two species responded differently to the different rates of nitrogen deposition. The stem base diameter , height ,whole-plant biomass and relative growth rate of C. concinna seedlings grown in 5 , 10 , 15 g N·m- 2·a - 1
treatments were all higher than those in the control plot ; however , the stem base diameter , height , whole-plant
biomass and relative growth rate of treated S . superba seedlings were lower than those in the control plot with the exception of the 10. 0 treatment . The leaf-weight ratio of seedlings of the two species was the lowest in the highest treatment , implying that the high N deposition was harmful to the foliage. The branch-and- stem weight ratio of seedlings of both species was the highest in the highest treatment indicating that the biomass allocated to branches and stems increased under high N deposition. The rootweight ratio and the root to shoot ratio of seedlings in the control plots were the highest , demonstrating that the ratio of biomass allocated to roots decreased under the conditions of elevated nitrogen deposition. Overall , except for the highest N treatment , nitrogen additions enhanced the growth of C. concinna but had the opposite effect on S . superba individuals ,indicating that C. concinna seedlings were more resistant to high nitrogen loads.
模拟氮沉降对南亚热带两种乔木幼苗生物量及其分配的影响 