Crop-assimilative carbon in the farmland ecosystem - an important source for carbon turnover in soil.

摘要

Crop-assimilated carbon (C), an important source of soil organic carbon (SOC), represents a key linked component of the C cycle in the soil-plant-atmosphere continuum. In the farmland ecosystem, however, the quantitative characterization and mechanism involved in the distribution and transformation of the assimilated C in soil over the plant's life cycle are problems relatively easily ignored. Research in this area is therefore indispensable for a thorough understanding of the process and characteristics of the organic C cycle in farmland soil. This paper provides an overview on: (1) the distribution, transformation rules, and structural features of crop-assimilated C in soil and its contribution to SOC and the function of microorganisms in the transformation of assimilated C. (2) The chemical compositions and structural features of the assimilated C after its entry into soil organic matter. (3) The relationship between assimilated C, rhizosphere deposition, and C isotope technology. Based on the findings, we consider that further research on the distribution of crop-assimilated C in the soil-crop system and the quantitative relations of several C-transformation steps such as crop input, transformation, protection, and stabilization in different ecosystems should be conducted. Moreover, the component and structure of 'new C' input into the soil by rhizosphere deposition in C assimilation and its relationship with oxidation and mineralized stability should also be accounted for.