C:N:P stoichiometry regulates soil organic carbon mineralization and concomitant shift of microbial community in paddy soil

Prof. Tida Ge1, Dr.  Zhenke  Zhu1, Prof.  Jinshui  Wu1

1Institute Of Subtropical Agriculture, Chinese Academy Of Sciences, Changsha , China

Soil carbon (C) and nutrient status, e.g., of nitrogen (N), and phosphorous (P), and their stoichiometric ratios play crucial roles in modifying the microbial metabolism of C in terrestrial ecosystems. However, the mechanisms by which microorganisms regulate soil C mineralization in response to resource C:N:P stoichiometry in paddy soils are not well understood. In this study, stoichiometric control on added substrate-C (glucose) and soil organic carbon (SOC) mineralization was assessed by a manipulation experiment based on N only, P only and N plus P fertilization in a 100-days incubation experiment using flooded paddy soil.  Glucose-C mineralization was stimulated by nutrient addition, and increased by up to 11.6% with combined N and P application compared with that upon exclusive glucose addition. During the incubation period, about 4.5% of SOC was mineralized in all five treatments, being enhanced by glucose application and reduced by P fertilization. Glucose-C and SOC mineralization increased exponentially with the dissolved organic carbon (DOC):NH4+-N, DOC:Olsen P, and microbial biomass (MB)C:MBN ratios, whereas glucose-C mineralization was negatively associated with the MBC:MBP ratio. This suggests that the P addition relieved the microbial P limitation and increased microbial activities of metabolizing labile C. The bacterial community structure shifted in response to treatments and time, and was significantly affected by the soil and microbial biomass C:N:P stoichiometries. The decrease of negative associations between bacterial taxa in the P-added treatments indicates that microbial competition for nutrients was alleviated. Through 16S rRNA amplicon sequencing, we found that labile C and available nutrients stimulated copiotrophs (Clostridia and β-Proteobacteria) and increased the activities of β-glucosidase and β-acetylglucosaminidase. In contrast, at later stages of the incubation, when the available substrate was exhausted, Syntrophus was found as the keystone species. Hence, soil microbial communities shifted their keystone species to utilize available C or metabolize recalcitrant soil C to acquire necessary elements to maintain the microbial C:N:P stoichiometric balance in response to the change of resource C:N:P stoichiometry.

Biography: Prof. Dr. Tida Ge, from Institute of Subtropical Agriculture, Chinese Academy of Science. He was the awardee of Newton Advanced fellowship and National Excellent Youth Science Funding of NSFC, and the Member of CAS Youth Innovation Promotion Association. Tida Ge’s main area of research has focused on understanding below-ground processes with specific focus on nutrients behaviour in soil-plant-microbial systems. Ge’s current work also included carbon sequestration in paddy agricultural systems, the mechanistic understanding of carbon fluxes and pools in plant-soil systems by isotopic tracing techniques, particulate organic carbon in farm systems. Another aspect of research currently undertaken by Professor Ge is the mitigation of methane and nitrous oxide with rice straw incorporation in paddy soils. He has attained important achievements in carbon sequestration in paddy soils. Up to now, he has published more than 40 SCI-indexed papers in international top journals, such as Geochimica et Cosmochimica Acta, Soil Biology and Biochemistry, , Plant and Soil, Applied and Environmental Microbiology, etc.

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