Are interactions of labile substrates with biochars the key process explaining C stabilization by biochars? A proof of concept by isotopic approaches.

难降解物质在土壤有机质动态变化中起着重要作用，具有重要的生态功能。然而，关于不稳定的底物和生物炭之间的相互作用的信息很少，这一缺乏阻碍了对土壤过程的任何预测和对生物炭应用于改善土壤质量的关键评估。这项建议旨在确定在培养过程中与生物炭接触的低分子有机物、粘液、细根和粗根中日益复杂的底物的转化途径。通过对生物炭(C-13)和底物(C-14)采用双重同位素标记，并遵循利用生物分析和土壤划分为密度和团聚体部分的途径，将从机理上理解由此产生的生物、生物物理和生化相互作用和反应。析因实验设计结合土壤生物、生物物理和生化分析，将有助于阐明基质、基质施用量、生物炭年龄和土壤水分对相互作用和途径的影响。将使用不同测量模式的近红外和中红外光谱来表征基质，即纯(新鲜产生的)生物炭、土壤和生物炭混合物中的轻组分在生物炭老化过程中的特征，以及土壤、粘液和新鲜或老化的生物炭的混合物。此外，通过优化化学计量学方法，将实现改进的使用全光谱的定量测定，重点是纯物质、涂层物质和老化物质的估计精度。双同位素标记方法的结果与光谱方法相结合，将从机理上理解解释生物炭稳定碳的关键过程。该项目提供了区分纯生物炭和陈化生物炭对土壤过程的影响的工具，将改进对生物炭在农业中的使用情况的量化和评估。

Refractory and labile substances play a significant role in the dynamics of soil organic matter and have key ecological functions. Only little information, however, is available on the interactions between labile substrates and biochar – a lack which hampers any prognoses of soil processes and critical appraisals of biochar applications for improving soil quality. This proposal aims at identifying transformation pathways for substrates of increasing complexity in the order low molecular weight organic substances, mucilage, fine roots and coarse roots in contact with biochar in incubations. A mechanistic understanding of the resulting biological, biophysical and biochemical interactions and reactions will be achieved by employing dual isotopic labelling for biochar (C-13) and substrates (C-14) and following the pathways using biological analyses and soil partitioning into density and aggregate fractions. The factorial experimental designs in combination with soil biological, biophysical and biochemical analyses will allow elucidation of the effects of substrates, substrate application rate, biochar age and soil moisture on the interactions and pathways.Near and mid-infrared spectroscopy in different measurement modes will be employed to characterize the substrates, i.e. pure (freshly produced) biochar, light fractions of the mixtures of soils and biochar during biochar ageing and mixtures of soils, mucilage and fresh or aged biochar using band assignments. Additionally, improved quantitative determinations using the full spectra with foci on estimation accuracies for pure, coated and aged substances will be achieved using an optimization of chemometric approaches.The results of the dual isotopic labelling approaches in combination with the spectroscopic approaches will give a mechanistic understanding of the key processes explaining C stabilization by biochars. Providing the tools to differentiate the impact of pure and aged biochars on soil processes, this project will allow an improved quantification and evaluation of the use of biochars in agriculture.