Abstract:

Abstract:  Soil carbon storage is an important parameter for the study of carbon cycling and global change. Accurate calculation of this parameter is limited by data sources for a long time. Multipurpose geochemical survey, using a scheme of grid sampling and analyses from double layers (surface and deep layer), provides large quantities of precise soil geochemical data for soil carbon storage of China. This paper aims at developing a soil carbon storage calculation method to be used as the criterion for China Geological Survey. A concept of “Unit Soil Carbon Amount  (USCA)”, defined as the amount (weight) of carbon storage in the unit area (4 km2) of multipurpose geochemical survey, was put forward as the basic unit to be cumulated for the calculation of soil carbon storage of a region or the whole China. On the basis of 414 soil profiles from 14 provinces, it was found that soil organic carbon (TOC), differing from soil inorganic carbon and other elements, has a trend of exponentially decreasing with depth. Integral analysis of exponential curve contrasting with the linear model affords the uncertainties of linear model and exponential model for carbon storage calculation. It was found that the integration of TOC with the linear model has errors between +20% to +100%, much higher than that of the exponential model (-10% to +20%). So, it was suggested that the “Unit Soil Organic Carbon Amount (USCATOC)” should be calculated by exponentially integrating TOC between the surface and deep soil layer. However, the “Unit Soil Inorganic Carbon Amount (USCATIC)” may be calculated by linear model. The “Unit Soil Total Carbon Amount (USCATC)” is the sum of the “Unit Soil Organic Carbon Amount” and the “Unit Soil Inorganic Carbon Amount”. It was also suggested that the soil nitrogen storage should be calculated by the scheme of exponential model similar to the organic carbon and that the “Unit Soil Element Amount (USEA)” for all the other elements may be calculated by linear model like the inorganic carbon.

Key words:

Key words: multipurpose geochemical survey; soil profile; exponential model; Unit Soil Carbon Amount