Effects of soil texture and land use interactions on organic carbon in soils in North China cities' urban fringe

Limited information exists on the linkages between soil texture and land use on C storage efficiency. Organic C concentration in soils at the rural–urban interface was measured in 1982, 2000, and 2006 to determine controlling factors and optimal land use type to enhance soil organic C (SOC) storage in benchmark soil textural classes in the North China Plain's Daxing district. Soil texture was the key to attaining elevated SOC concentrations in different land use types under different management intensities. From 1982 to 2006, the order of increasing SOC concentrations across land use types was fine sand (FS) < sand loam (SL) < light loam (LL) < middle loam (ML), indicating that soil with larger proportions of fine particles has larger storage capacities and rates of SOC accumulation. Since 1982, increased use of inorganic fertilizers, intensive cropping and increased crop yields, and the practice of returning crop residues to the soil have been beneficial to C storage in agricultural soils across the district. Diversification of land uses was extensive since 2000, but only the continuous wheat–maize (WM1982–WM2000–WM2006) system has maintained elevated SOC concentrations across the range of soil texture classes ranging from FS to ML. Differential declines in SOC concentrations were observed in most other land uses that included vegetables, watermelon, fruits, and other cash crops. Conversion of a WM land use type to horticultural land use types was more detrimental to FS soils than to finer-textured SL or LL soils, particularly with the continuous use of low-biomass producing land use types in urban fringe areas in the North China Plain.