Abstract: Soil water-soluble organic carbon (WSOC) is the most active component in soil carbon cycling. The change of land use pattern can greatly affect the composition and structure of soil organic carbon, and further, affect the exchange features between atmospheric and soil carbon. Taking the soils under four different land use patterns (cropland, poplar land, compound crop-poplar management, and meadow) in coastal area of northern Jiangsu as test objects, the variations of their WSOC were determined, and the correlations of the WSOC with soil total organic carbon (TOC), readily oxidation carbon (ROC), and some other soil physical and chemical properties were analyzed. There existed significant positive correlations between the soil WSOC and the soil TOC, total nitrogen, and ROC, and significant negative correlations between the soil WSOC and the soil C/N, pH, and bulk density. The soil WSOC content decreased with increasing depth, which had the same variation trend as soil TOC. In different soil layers, the WSOC content had little difference among the land use patterns. In cropland and meadow, the WSOC content had significant difference between 0-10 cm and 10-25 cm soil layers; under compound poplar-crop agroforestry system, the WSOC content had significant difference between 10-25 cm and 25-40 cm soil layers.  

Key words: Larix spp., biomass, nutrient distribution, organ.