Scientists Find Rate of Global Soil Organic Carbon Turnover
The estimation of turnover rate of soil organic carbon has been a key and difficult problem. Especially, the problem how to select a simple and efficient parameter to indicate soil organic carbon turnover on the global scale has not been resolved.
Isotope 13C indicates the source and turnover path. Research showed that the isotope value increases but the carbon content decreases with the depth on soil profile.
On account that the burning of fossil fuel leads to the increase in the content of 13C-depleted carbon, resulting in the accumulation of 13 C depleted carbon on the soil surface, and the carbon isotope ratio is 1-2 unit higher in plant root system than that in whole plan. This also resulted in the higher isotope ratio in subsoil.
In addition, the fractional distillation of carbon by microbes in the process of soil organic matter decomposition.
This resulted in 12C leaves the system but 13C accumulated in soil, forming the trend that the 13C signal strengthened with soil depth.
Vast research indicate the organic matter decomposition by microbes is the major reason for the increase of 13C with soil depth and this trend can be used efficiently to indicate the turnover rate of soil carbon.
Based on the mentioned principal, Research Assistant WANG Chao and co-workers in the research group of Bio-geo Chemistry at Institute of Applied Ecology (IAE), Chinese Academy of Sciences, analyzed the variation of carbon isotope and carbon content on 27 soil profiles collected from North China grassland and compiled the published data from 149 soil profiles all over the world with depth more than one meter.
Their work indicated that all profiles showed isotope value increase and carbon content decrease along with increase in depth, showing significant negative correlation and evidenced that the negative correlation well indicates the soil carbon turnover rate; on global scale, the turnover rate of soil organic carbon is significantly positively correlated to the turnover rate of litters.
Moreover, the turnover rate of soil organic carbon is well explained by climate factors and the physic and chemical properties of soil.
The results provide an idea for soil carbon turnover research and new parameters for bio-geochemistry modeling.
The results were published entitled as Stable isotopic constraints on global soil organic carbon turnover in Biogeosciences.
The work was supported by Youth 973 project, NNSFC, CAS Front Key Project and Youth Innovation Promotion Association of the Chinese Academy of Sciences.
