Abstract. Accurate estimation of soil organic carbon (SOC) storage and determination of its pattern controlling factors is critical to understanding the ecosystem carbon cycle and ensuring ecological security. The Sanjiang Plain of China, an important grain production base, is typical of ecosystems, yet the SOC storage and pattern of this region has not been fully investigated because of the deficient soil investigations. In this study, 419 soil samples and a geostatistical method were used to estimate the total SOC storage and density (SOCD) of this region with the former being 2.324 Pg C, and the latter value being higher than the mean value for the whole country. The SOCD was found to have notable changes in spatial and vertical distribution. In addition, the vegetation, climate, and soil texture, as well as the agricultural activities, were demonstrated to have remarkable impacts on the variation of SOCD. Soil texture had stronger impacts on the distribution of SOCD than climate in the Sanjiang Plain. Specifically, the clay content explained the largest proportion of the SOC variation and was thus the most dominant environmental controlling factor. As far as climatic factors are concerned, precipitation exhibited more significant effects on SOCD than temperature. In addition, the effects of both climate and soil texture on SOCD were reduced with increasing soil layer depth. The results from this study provide the most updated knowledge on the storage and pattern of SOC in the Sanjiang Plain, and the analysis conducted here could contribute to the determination of ecosystem carbon budgets and understanding of ecosystem services.
Plant biomass and soil organic carbon are main factors influencing dry-season ecosystem carbon rates in the coastal zone of the Yellow River Delta
