用土钻法研究了不同连栽代数杉木细根生长与分布, 结果表明, 杉木连栽1代后, 细根生物量明显减少, 第1代杉木活细根生物量的范围为646.4～799.7 g*m-2, 而第2代则为284.4～536.9 g*m-2. 在一定距离范围内, 离树体的距离越远, 细根分布越少. 杉木连栽后, 主要减少了表层土壤(0～10cm)细根的生长. 根系分泌物的分析表明, 杉木连栽1代后, 根系阳离子NH4+、Na+ 、K+ 、Ca2+、 Mg2+的分泌量没有变化, 而阴离子NO3-、Cl-、 SO42-、 HPO42-的量都减少, 但只有Cl- 和HPO42-差异显著(P＜0.05). 第2代杉木根系分泌物中的HPO42-量仅为第1代的1/65. 根-土界面磷交换过程的阐明有利于说明第2代杉木根系HPO42-分泌量减少的原因. 杉木连栽后, 表层土壤细根生长的减少和根系分泌行为的改变可能是生产力下降的重要原因.%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/m2, and second rotation falling into 284.4～536.9 g/m2. 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 NH4+、Na+ 、K+ 、Ca2+、 Mg2+ did not change after replanted with Chinese fir for one rotation, but contents of the anions NO3-、Cl-、 SO42-、 HPO42- decreased, and significant differences for Cl-、HPO42- were detected (P＜0.05). The contents of Cl-、HPO42- 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.
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