Characteristics of soil microbial communities in particulate organic matter and mineral-associated organic matter along calcareous succession process

Abstract:

After undergoing weathering and being influenced by topography, vegetation, climate, time and biology, the carbonate rocks gradually evolved into black calcareous soil, brown calcareous soil, yellow calcareous soil and red calcareous soil. [Objective] This study aims to investigate the microbial community characteristics of particulate organic matter (POM) and mineral-associated organic matter (MAOM) in calcareous soil at different succession stages, providing a theoretical basis for the study of organic matter stability mechanism in karst soil. [Methods] Black calcareous soil, brown calcareous soil, yellow calcareous soil, and red calcareous soil from the Nonggang Nature Reserve in Guangxi were chosen as the research objects, and soil organic matter (SOM) was divided into POM and MAOM by using wet screening method. The soil physicochemical properties and soil microbial community characteristics were analyzed. [Results] During the succession process of calcareous soil, the soil organic carbon, total nitrogen, and exchangeable calcium contents of POM and MAOM showed a decreasing trend, and the C/N of MAOM was greater than that of POM, whereas the C/P of POM was greater than that of MAOM. The bacterial diversity was higher in black calcareous soil of POM and MAOM, and the diversity of bacteria and fungi in the four type calcareous soil of MAOM was higher than that in POM. Acidobacteria, Proteobacteria, and Ascomycota were the dominant phyla in POM and MAOM along the succession process of calcareous soil. Total phosphorus was a key factor affecting the changes of bacterial communities in POM and MAOM during calcareous soil succession, while dissolved organic carbon and soil organic carbon were key factors affecting the changes of fungal communities in POM and MAOM during calcareous soil succession, respectively. The microorganisms from black calcareous soil in POM and MAOM may have undergone ecological niche differentiation, and bacteria and fungi tend to cooperate more closely along calcareous soil succession. [Conclusion] During the succession process of calcareous soil, the nutrients and microbial diversity of POM and MAOM decrease. POM may be the main source for microbial nutrients, and MAOM is more conducive to be the long-term stable accumulation of carbon. This study can provide a theoretical basis for the role of microorganisms in the formation of organic matter during the succession process of karst soil.