Soil degradation induced by long-term agricultural managements is a great threat to future food security, biodiversity conservation and climate change through influencing soil quality and function. Microbial community mediated many soil processes including carbon (C), nitrogen (N) and phosphorus (P) cycling, thereby playing a key role in improving soil nutrient transformation and thus soil fertility and function. Change of soil microbial community abundance, composition and diversity was widely used as an indicator to reflect the soil quality. Therefore, investigating the response of the dynamics of soil microbial communities to long term agricultural practice is the key for evaluating the processes that influence soil quality (such as organic matter decomposition, nutrient cycling and ecosystem self-regulation) and indicating the reasonability and validity of agricultural practice. In addition, most studies indicated that the environmental changes could modify the microbial communities while the driving mechanism and timescale of microbial community succession or genetic evolution remain elusive. Unlike previous studies on soil microbial community, focusing on their changes under a series of environmental treatments, we pay more attention on how long the stage of microbial community composition in native soils could be consistent with that in mature soils under directional domestication, e.g. simulating fertile soil by adding water and organic materials into the arid and barren soil.
Biochar is the pyrolysis product of biomass under high temperature and hypoxia, which is more stable than most forms of carbon in soil organic matter. It is conducive to the soil carbon sequestration and improve soil fertility, alleviate climate change and improve soil nutrient balance under long-term conditions. Biochar plays an important role in biogeochemistry. "Priming effect" is a process of increasing the mineralization rate of soil organic matter after the input of exogenous organic matter. The enhancement of degradation of soil organic matter caused by the increase of exogenous organic matter is called "positive priming effect ", and the slowing down of degradation of soil organic matter caused by the input of exogenous organic matter is called "negative priming effect". There is interaction between biochar and mineralization of soil organic matter. Therefore, it is of great practical significance to explore the interaction mechanism between biochar and soil organic matter, understand the mineralization rate of pyrolytic organic matter and its potential impact on the stability of soil organic matter (SOM), provide theoretical basis for the study of global carbon cycle and global climate change. Although there are many previous studies on the mechanism of biochar on the priming effect of soil organic matter, most of them explore the influence of biochar and soil properties on the priming effect of soil organic carbon under the homogenouse of biochar and soil. Few studies consider the spatial hetrogenouse of soil-biochar interface micro domain, that is, not all the biochar is in direct contact with the soil. Therefore, we need to pay more attention to the mineralization of soil organic carbon in soil-biochar micro domain. The concept of "charosphere" is similar to the concept of rhizosphere, which refers to the special area around the biochar. In charosphere, the pH, porosity and other characteristics of the soil are different from those of biochar and soil. In this study, soil and biochar were separated to evaluate the effects of biochar and different distance intervals on soil organic carbon component structure and soil microbial diversity. At the same time, the real-time dynamic changes of soil O2 and pH in the charosphere will be observed by using the planar optode. It is of great significance to understand more deeply impact of biochar on soil organic carbon in the charosphere to reveal the interaction mechanism between biochar and soil organic matter.