中文摘要：

森林是陆地生态系统中最重要的碳库，森林土壤中的碳占全球土壤有机碳的73％，在全球碳循环中起着重要作用（David et a1．，1988）。溶解有机碳（dissolved organic carbon，简称DOC）虽然仅占有机碳的很小部分，但对调节阳离子淋洗、金属溶解、矿物风化、土壤微生物活动以及其他土壤化学、物理和生物学过程具有重要意义。DOC是土壤活性物质，容易被土壤微生物分解，在提供森林土壤养分方面发挥着重要作用（Dosskey et al．，1997）；DOC在水中可溶，对森林土壤生态系统中元素的迁移及铝毒性有深刻影响。

英文摘要：

Leaching of dissolved organic carbon （DOC） and the associated nutrient elements can be a significant form of loss from Chinese Fir plantations due to intensive cultural treatments. We studied the concentrations and fluxes of DOC in soil percolating water in recently planted, young and mature Chinese Fir stands in southeastern China. Soil samples were collected from 0 - 20, 20 - 40 and 40 - 60 cm in each stand. Soil percolating water was collected with non-suction lysimeters installed at the mid-slope in a line perpendicular to the slope at the depth of 20, 40 and 60 cm. DOC concentrations in soil percolating water ranged from 6.08 to 21.05 mg·L^-1 （mean：12.76 mg·L^-1）, decreasing with increasing soil depth. The DOC concentration of the young stand remained the lowest regardless of measuring time. However, the DOC concentration of the recently planted stand was the greatest in May while the DOC concentration of the mature stand was greatest in July when compared to other plantations. DOC concentrations were highly correlated with soil organic carbon （ r^2= 0.608） , total nitrogen （ r^2= 0.369） and free iron （ r^2 = 0.598） concentrations while the amounts of DOC were closely related to the amounts of organic carbon （ r^2 = 0. 829）, N （ r^2 = 0.721） and P （ r^2= 0.377）, suggesting the important influence of DOC on the transportation of other elements, especially nutrient elements, in the soil.