Abstract:

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 (r² 0.608), total nitrogen (r² 0.369) and free iron (r² 0.598) concentrations while the amounts of DOC were closely related to the amounts of organic carbon (r² 0.829), N (r² 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.

Key words: Chinese Fir, forest soil, percolating water, DOC, soil nutrients