Abstract: In order to understand the effects of land-use patterns on soil organic carbon (SOC) pool, a study was conducted to examine the seasonal variation of soil dissolved organic carbon (DOC) and its correlation with soil moisture content, carbon (C) and nitrogen (N) concentrations in six adjacent land use types: (1) Lithocarpus glaber + Cyclobalanopsis glauca secondary forest, (2) Cunninghamia lanceolata plantation, (3) Phyllostachys edulis forest, (4) seedling nursery land, (5) slope cropland, and (6) paddy field in a hilly area of central Hunan, China. The results showed that DOC concentrations decreased with soil depth and with the minimum difference of DOC concentrations between soils layers occurring in autumn, while the proportion of DOC increased with increasing the soil depth. Soil DOC concentrations were significantly different among the land use types. Soil DOC concentrations decreased by 10%-12%, 11%-12%, 13%-19%, 18%-25% and 37%-42% in P. edulis forest, C. lanceolata plantation, paddy field, slope cropland and seedling nursery land, respectively, as compared with L. glaber + C. glauca secondary forest. The differences in DOC concentration among different land use types were maximum in summer. Seasonal variations in DOC concentration were considerable but a similar change pattern was found in the six land use types. Soil DOC concentrations were significantly higher in spring, summer and winter than in autumn. Positive correlations were found between DOC concentrations and soil moisture content, TOC, MBC, ROC, MOC, total N, and available N. These results demonstrated that landuse patterns significantly affected soil DOC concentration and its spatial distribution. Soil DOC concentrations were significantly reduced when secondary forests were converted to plantations or agricultural lands.

Key words: Electrona carlsbergi, morphological diversity, otolith, elliptical Fourier analysis