RESPONSE OF SOIL MICROBIAL BIOMASS TO DROUGHT STRESS AND ATMOSPHERIC CO2 DOUBLING

Soil microbe plays an important role in terrestrial ecosystem, and it is the core of the biological geochemical cycle, which has a significant impact on the process of material circulation and transformation and energy flow in soil ecosystem. In this study, a short-term indoor culture experiment has been carried out with seedlings soybean (Yudou 19) as the test plant. Three kinds of soil water gradient(80%, 60%, 40% WHC) and two kinds of CO2 concentrations (350 ppm, 700 ppm) were set to study the changes of soil microbial biomass, soil microbial community structure and functional diversity under the control of environmental factors, and to discuss the response law of soil microbes to simulated climate change (drought and atmospheric CO2 doubling), so as to provide a new idea for the exploration of the possibility of soil microbial enhancing or weakening global climate change. Atmospheric CO2 doubling can significantly promote plant photosynthesis and can alleviate and compensate the inhibition of drought stress on plant photosynthesis in a certain range. Drought stress will result in a significant increase in the content of soluble organic carbon in soil, while CO2 doubling have no significant effect on the content of soluble organic carbon in soil. Therefore, it is possible for atmospheric CO2 doubling to accelerate the transformation of soil carbohydrates, increase the rate of degradation of soil organic carbon pool by increasing microbial biomass, and have a negative impact on climate change. While drought stress could release the circulation of soil carbon pool to some extent.