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A Microbial-explicit Soil Organic Carbon Decomposition Model (MESDM) Coupled with Noah-MP: Development and Test in Semiarid Grassland
张霞
中国科学院大气物理研究所LASG
Explicit representation of soil microbial processes in soil organic carbon decomposition model (microbial-explicit model) has received increasing attention, since soil heterotrophic respiration in earth system models (ESMs) remains one of the greatest uncertainties for predicting climate-carbon feedbacks. Microbial-explicit models have made advancements in site- and global-scale studies. However, it is still a challenge to improve parameterization of soil heterotrophic respiration response to drying-rewetting cycle in these models. Moreover, few microbial-explicit models have been incorporated into land surface model to further validate soil respiration simulation rigorously using field observations. In this study, we develop a microbial-explicit decomposition model (MESDM), based on two main assumptions: 1) extracellular enzymes remain active in dry zone, and 2) microbes in wet zone might be in metabolically active or potentially active states while microbes in dry zone are in dormancy, by dividing soil volume into wet and dry zones. The vertically-layered MESDM is incorporated into Noah-MP land surface model, and tested against half-hourly field observation at Santa Rita site in semiarid grassland characterized by the pulsed precipitation. The results show that the Noah-MP coupled with MESDM can successfully reproduce observed soil respiration pulses of various sizes in response to precipitations (Birch effect), thereby improving the simulation of net ecosystem exchange. In addition, the MESDM model could simulate real priming effect caused by grass root exudate inputs. Finally, the mechanisms responsible for Birch effect and priming effect, respectively, were investigated through analyzing the evolution of modeled carbon pools.