Growth, distribution and exudation of fine roots of Chinese fir trees grown in continuously cropped plantations
LIAO Li-Ping, Deng Shi-Jian, YU Xiao-Jun,HAN Shi-Jie (Institute of Applied Ecology, Academia Sinica, Shenyang 110015,China)
Fine root growth and distribution were investigated by the soil coring method respectively in Chinese fir plantations of first and second rotations. Biomass of live fine roots decreased markedly after Chinese fir plantation continuously cropping for one rotation, with biomass of live fine root of first rotation ranging from 646.4 to 799.7 g/m 2 , and second rotation falling into 284.4～536.9 g/m 2 . The farther the sampling point from the tree per se, the less the biomass of live fine root to certain extent. Analysis of the root exudates showed that contents of cations NH 4 +、Na + 、K + 、Ca 2+ 、 Mg 2+ did not change after replanted with Chinese fir for one rotation, but contents of the anions NO 3 -、Cl -、 SO 4 2- 、 HPO 4 2- decreased, and significant differences for Cl -、HPO 4 2- were detected (P0.05). The contents of Cl -、HPO 4 2- for the second rotation were only 1/4.7 and 1/65, respectively, of those in the first rotation. The decrease in growth of fine roots in 0～10 cm soil and change of root exudations could suggest the decline in productivity of the continuously cropped Chinese fir plantations.