Rhizodeposition is the main source of carbon and energy for nutrient mobilization in subsoil (RhizoCNP)

根际沉积是微生物在土壤中调动养分的重要碳源和能量来源，但关于根际沉积在底土中的重要性还没有数据。本项目旨在估算土壤C输入量，追踪土壤中由蚯蚓和根系形成的生物孔隙中的根源C，计算根源C的收支及其对土壤养分迁移的贡献。具有不同根系的植物（菊苣和苜蓿）将在田间用13 CO2标记，并在受控条件下用13 C和14 C标记。随后，碳预算将遵循两种同位素，包括掺入微生物分子标记物（13 C-PLFA）和生物孔涂层。将通过分析根源C（14 C）的分布概况以及N（15 N）、P（33 P）和K的消耗（取决于到根的距离和沿沿着的距离）（通过14 C磷光体成像）来估计底土中的放射性球扩展。将在分批实验中测试底土和生物孔隙中养分（N，P）的可用性以及根系分泌物对养分的动员作用。基于脂质生物标志物的组成，将开发一种评价单个生物孔起源的方法。该子项目将提供参数，用于模拟C流内和进入底土，根际扩展，营养物质和根分泌物的扩散概况，以及取决于根距离的营养物质可用性。

Rhizodeposition is a very important source of carbon (C) and energy for microorganisms mobilizing nutrients in soil, but no data is available regarding the importance of rhizodeposition in subsoil. This project aims on the estimation of C input into subsoil, tracing the root-derived C in biopores formed by roots and earthworms, calculation of the budget of root-derived C and its contribution to nutrient mobilization in subsoil. Plants with different root systems (chicory and alfalfa) will be labeled in field by 13CO2 and under controlled conditions by 13C and 14C. Subsequently, the C budget will be followed by both isotopes including incorporation into microbial molecular markers (13C-PLFA) and biopore coatings. Rhizosphere extension in the subsoil will be estimated by analyzing distribution profiles of root-derived C (14C) and depletion of N (15N), P (33P), and K, depending on distance to root and along individual roots (by 14C phosphor-imaging). Availability of nutrients (N, P) in subsoil and biopores and nutrient mobilization by root exudates will be tested in batch experiments. An approach to evaluate the origin of individual biopores will be developed based on composition of lipid biomarkers. The subproject will deliver parameters for modeling of C flow within and into the subsoil, rhizosphere extension, diffusion profiles of nutrients and root exudates, and nutrient availability depending on distance to roots.