Minerals and their interactions with dissolved organic matter as regulators of microbial necromass stabilization in soil

据推测，微生物的死物质对稳定土壤有机质有重要贡献。然而，所谓的“埋葬效应”，即坏死物质的积累和随后的稳定化，仍然没有在机械水平上得到很好的理解。溶解有机质在活性矿物表面的吸附是土壤碳稳定的主要过程。在此，我们因此计划（i）研究生产和反应性（生物降解性和吸附性）溶解的有机物沿着分解连续体从植物凋落物到微生物necromass，和（ii）同时检查如何吸附稳定的有机化合物形状的结构的微生物群落，其碳和能量的使用。该项目将首次在对物质和能量通量进行定量评估的基础上，描述坏死物质形成与溶解有机物吸附之间的相互作用。因此，它将有助于SPP 2322的中心假设C（边界条件）和B（生物复杂性）。拟议的研究链接直接在原地分解的植物凋落物和微生物necromass与深入分析的基本过程，以确定necromass稳定的所有步骤。这包括：（一）关于分解植物凋落物和微生物坏死物（细菌和真菌）产生溶解有机物的培养实验，（二）使用不同原始矿物的吸附实验，（三）吸附前后溶解有机物的生物降解性试验，（四）矿物结合有机物的稳定性试验，以及（五）在自然土壤中培养碳标记的植物凋落物和微生物坏死物。这种逐步的实验方法能够量化和解释碳和能量从可变有机源到矿物表面的转移效率的差异。溶解和吸附的有机物的分子组成和能量含量的测定，以及微生物群落的分析，使用最先进的方法，如FT-ICR-MS和XPS等，允许获得新的洞察土壤中的坏死物稳定的机制。该项目将增加我们对矿物质如何调节微生物能量利用的了解，从而有助于开发能够明确表示微生物周转的新一代土壤碳模型。

Microbial necromass is presumed to significantly contribute to stable soil organic matter. Yet, the so-called ‘entombing effect’, i.e. the built-up and subsequent stabilization of necromass-derived matter, is still not well understood on a mechanistic level. The sorption of dissolved organic matter to reactive mineral surfaces is widely known as a major process of soil carbon stabilization. Herein, we thus plan (i) to study production and reactivity (biodegradability and sorptivity) of dissolved organic matter along the decomposition continuum from plant litter to microbial necromass, and (ii) to concurrently examine how sorptive stabilization of organic compounds shapes the structure of the microbial community, and its carbon and energy use. The project will, for the first time, describe interactions between necromass formation and dissolved organic matter sorption on basis of a quantitative assessment of matter and energy fluxes. It will, therefore, contribute to Central Hypotheses C (Boundary conditions) and also B (Biological complexity) of the SPP 2322. The proposed research links direct in situ decomposition of plant litter and microbial necromass with in-depth analyses of underlying processes to identify all steps of necromass stabilization. This includes: (i) incubation experiments on the production of dissolved organic matter from decomposing plant litter and microbial necromass (bacteria and fungi), (ii) sorption experiments using different pristine minerals, (iii) biodegradability tests for dissolved organic matter before/after sorption, (iv) tests of the stability of mineral-bound organic matter, and (v) incubations of carbon-labelled plant litter and microbial necromass in natural soil. This step-wise experimental approach enables to quantify and explain differences in the transfer efficiency of carbon and energy from variable organic sources to mineral surfaces. The determination of the molecular composition and energy content of dissolved and sorbed organic matter as well as the analysis of the microbial community using state-of-the-art methods, such as FT-ICR-MS and XPS among others, allow for gaining novel insight into the mechanisms of necromass stabilization in soil. The project will add to our understanding how minerals regulate microbial energy use, and thus, contribute to the development of new-generation soil carbon models with explicit representation of microbial turnover.