Decomposition of soil organic matter (SOM) plays an essential role in terrestrial carbon (C) cycling. So far, there is un-sufficient knowledge about how soil organic carbon (SOC) decomposition rates vary at a large spatial scale and which factors control SOM decomposition.

Empirical studies have undoubtedly improved scientists' understanding of decomposition of SOC and also allowed for development and validation of models used to stimulate SOM dynamics. In simulating decomposition of SOC, SOM models have played an important role. With the increased use of models for regional and global applications, understanding the roles of these control variables play on SOC decomposition becomes crucial.

Through laboratory incubation of soil samples exclude plant roots and develop a three-pool SOM decomposition model with C transfers between pools (active, slow, and passive) and applied the techniques of data assimilation (also known as deconvolution analysis) , a team of researchers from Nanjing Forestry University, University of Oklahoma, Institute of Subtropical Agriculture, Chinese Academy of Sciences(ISA), National Natural Science Museum, and Kansas State University have estimated decomposition rates of the active, the slow, and the passive SOC pools with laboratory soil incubation data sets, to examine the roles of different factors that play in decomposition of SOC and identify the most important controlling factors at a large spatial scale.

The researchers found that hypotheses of soil property-C decomposition relationships have not been explicitly tested at large spatial scales. "A data-assimilation approach to evaluate the roles of soil properties and environmental factors in regulating decomposition of SOC was used in our study," said leader researchers XU Xia, SHI Zheng and LI Dejun (from ISA). "Soil physical and chemical properties regulated decomposition rates of the active and the slow C pools. Decomposition rates were lower for soils with high clay content, high field water holding capacity (WHC), and high C:N ratio."

The researchers also found that clay content is the most important variable in regulating decomposition of SOC. In contrast to the active and slow C pools, soil properties or environmental factors have little effect on the decomposition of the passive C pool. Inverse soil property-C decomposition relationships and quantitatively evaluate the essential roles of soil texture (clay content) in controlling decomposition of SOC at a large spatial scale.

The research was supported by the National Science Foundation (NSF) under grant DEB 0743778, the Office of Science (BER), Department of Energy under grant DE-SC0004601, the Jiangsu Specially-Appointed Professors Program, and the Priority Academic Program Development of Jiangsu Higher Education Institutions.

The study entitled "Soil properties control decomposition of soil organic carbon: Results from data-assimilation analysis" has been published in Volume 262, Issue 2016 of Geoderma, details could be found at http://www.sciencedirect.com/science/article/pii/S0016706115300677.