Variations of forest soil organic carbon and its influencing factors in east China

Forest and soil types are the main factors that influence the distribution pattern of soil organic carbon (SOC) in forests across east China. In general, SOC density was largest in north-eastern China, followed by south-eastern China, and lowest in middle-eastern China, due to regional climate and the dominant forest type (young plantations in middle-eastern China). Forest SOC plays an important role in the carbon cycle in China, but large spatial heterogeneity and insufficient field observations lead to large uncertainties in the estimation of SOC. The objectives of this study were to evaluate forest SOC density in different geographic regions, forest types, and soil types and to investigate the spatial variation of SOC in forests across east China. The estimation of forest SOC was based on 348 soil profiles, which were collected from 116 forest sites in east China during 2008-2011. The average SOC content was 17.5 g C kg(-1), which leads to an average SOC density of 12.4 kg C m(-2). The average SOC density in the organic horizon and mineral horizon was 5.47 and 6.91 kg C m(-2), respectively, with 44.2 % SOC density dominating in the organic horizon. The average forest SOC density in north-eastern, middle-eastern, and south-eastern China was 13.5, 9.95, and 13.3 kg C m(-2), respectively. SOC distribution varied among regions, forest types, and soil types in east China. The importance of influencing factors switched with depth, precipitation, and temperature dominating in the organic horizon and soil texture dominating in the mineral horizon.