Research progress on the responses of soil respiration components to climatic warming.

Global carbon cycle is being profoundly altered by climate change. As an important component of the global carbon cycle, soil respiration is tightly linked to the carbon transfer among plants-soil-microbes. Soil respiration can be divided into the heterotrophic respiration and root-derived respiration (i.e., actual root respiration and rhizomicrobial respiration). Responses of soil respiration to climate warming may be different, since its components differ in occurrence sites and sources of soil organic carbon. However, the current literatures can not fully clarify the precise partition and quantification of soil respiration components. The influences of climate warming on soil respiration and related mechanisms are still unclear, which greatly limits our understanding of the accurate assessments of soil carbon cycle as well as the changes in the carbon balance of terrestrial ecosystems under climate change. We systematically summarized the progress of partitioning techniques of soil respiration components, and compared the results of partitioning of soil respiration components using different techniques. We further discussed the progress on the responses of soil respiration components to climate warming. To exactly distinguish and quantify soil respiration components, we proposed that the present techniques should be modified. Furthermore, future studies should focus on how to accurately partitioning root-derived respiration in the field for comprehensively understand soil carbon cycle and the changes of carbon budget in terrestrial ecosystems under global change. Moreover, more attention should be paid on the responses of soil respiration components to various environmental factors.