Dissertation Research: Linking microbial ecophysiology to soil organic matter abundance and stabilization

陆地生态系统依赖土壤有机质(SOM)来维持农业生产力和其他重要的生态系统服务，但全球SOM储量受到环境变化的威胁。目前，减轻SOM损失的能力受到我们对SOM形成和长期持久性调节过程的理解的限制。近年来，关于土壤有机质形成和持久性的新概念不断涌现，表明土壤有机质主要来源于土壤微生物。与强调复杂植物衍生化合物在土壤有机质形成中的重要性的旧概念形成鲜明对比的是，如果更好地了解机制，对微生物过程的新强调可能会极大地改善土壤有机质管理。具体地说，人们对调节微生物生产的微生物生理特性和微生物产品在不同土壤类型中的命运知之甚少。为了解决这一知识差距，这项研究的广泛目标是将微生物生理特性与SOM的形成和持久性联系起来。这一目标将通过长期的实验室研究来实现，以跟踪不同土壤类型中微生物过程产生的新形成的有机质。土壤的粘土矿物学和来自植物的碳输入不同，因此，将根据不同的微生物群落和生理特征进行选择，这可能会导致新形成的SOM的长期稳定性不同。在整个实验过程中，将对与生物量合成、SOM形成速率、SOM化学、微生物生物多样性和SOM持久性有关的微生物生理特性进行测量。这项工作的结果将有助于改进现有的SOM形成和稳定模型，并将表征微生物生理、碳输入质量和土壤环境之间的重要关系。这项研究将对微生物生态学、土壤和生态系统科学做出基础性贡献，并可能改变我们减轻土地利用转换和气候变化对土壤有机质损失的不利影响的方式。具体地说，这项研究可以鼓励土地利用保护、恢复和农业管理的新方法，强调通过管理微生物生物量生产间接建立土壤有机质。

Terrestrial ecosystems depend on soil organic matter (SOM) for sustaining agricultural productivity and other vital ecosystem services, yet global SOM stocks are threatened by environmental change. Currently, the ability to mitigate SOM losses is limited by our understanding of the processes regulating SOM formation and long-term persistence. In recent years, new concepts of SOM formation and persistence have emerged suggesting that SOM is largely derived from soil microbes. Contrasting sharply with older concepts that emphasize the importance of complex plant-derived compounds in SOM formation, the new emphasis on microbial processes might dramatically improve SOM management if only the mechanisms were better understood. Specifically, there is relatively little known about the microbial physiological traits that regulate microbial production and the fate of microbial products in different soil types. To address this knowledge gap, the broad objective of this research is to link microbial physiological traits to SOM formation and persistence. This objective will be met using a long-term laboratory study to track newly formed SOM derived from microbial processes in different soil types. The soils vary in their clay mineralogy and carbon inputs from plants and, as a result, will select for different microbial communities and physiological traits, which together will presumably lead to differences in the long-term stability of the newly formed SOM. Throughout the experiment, measurements will be made of microbial physiological traits that can be linked to biomass synthesis, rates of SOM formation, SOM chemistry, microbial biodiversity, and SOM persistence.Results from this work will lead to improvements in current models of SOM formation and stabilization and will characterize the important relationships among microbial physiology, carbon input quality, and the soil environment. This study will make fundamental contributions to microbial ecology and soil and ecosystem science and could change how we mitigate the adverse effects of land-use conversion and climate change on SOM losses. Specifically, this research could encourage new approaches for land-use conservation, restoration, and agricultural management that emphasize the indirect building of SOM by managing microbial biomass production.