Project coordination: Field site management, data synthesis and modeling of subsoil C-turnover

底土有机质的高~(14)C年龄表明周转速率非常慢。然而，对存档土壤样品的分析以及14CO2和DO14C通量的测量表明，底土C库的一部分具有年到十年的周转时间，因此对全球C循环有贡献。优势流和非优势流在14C含量和微生物活性上的明显差异表明，土壤有机质(SOM)的长期稳定性也可能是由于其与微生物活动热点的空间分离所致。其他底土特有的因素，如低O2分压、低温和低水分动态，可能还会控制SOM周转。为了对底土中的碳素动态进行建模，需要尽可能地了解和量化这些因素及其潜在的周转机制的影响。此外，碳通量必须量化，其来源必须确定。这一协调次级项目的中心目标是确保各次级项目之间的密切合作，以便汇编和综合所有相关成果，以便制定模型。为此，将详细规划和协调底土观测站的建立和安装以及所有实地活动，如采样活动、通量测量和额外的实地试验。将建立一个基于网络的共同数据库和交流平台，并定期更新所有参与者可查阅的所有活动的表格，以支持这一工作。地基观测站将由一名技术人员管理。协调科学家将定期召集与其他小组或小组的会议，讨论结果和协调实验。此外，他/她还将为参加活动的博士生举办暑期班，并举办讲习班，向国际观众介绍成果。碳通量和14C分析的数据将被综合起来，以便通过概念模型更好地了解土壤中的碳动态，并将其作为输入参数，用于改进和适应土壤中碳周转的数值模型。数值模型的开发和验证是博士生的任务。

The high 14C age of subsoil organic matter suggests very slow turnover rates. However, analyses of archived soil samples and 14CO2 and DO14C flux measurements indicate that a sub-stantial part of the subsoil C-pool has annual to decadal turnover times and thus contributes to the global Ccycle. Distinct differences in 14C content and microbial activity between preferential flow paths and bulk soil indicate that the long-term stability of soil organic matter (SOM) may also result from its spatial segregation from hot spots of microbial activity. Other subsoil specific factors such as low O2 partial pressure, low temperatures and low moisture dynamics may additionally control SOM turnover. In order to model C-dynamics in subsoils, the influence of these factors with the underlying mechanisms on turnover needs to be understood and quantified wherever possible. In addition, C-fluxes have to be quantified and their sources have to be identified. The central objective of this coordination subproject is to ensure the close collaboration between the subprojects in order to compile and synthesize all relevant results for model development. To this end, the set-up and installation of the subsoil observatories and all field activities like sampling campaigns, flux measurements and additional field experiments will be planned in detail and coordinated by this project. This will be supported by the creation of a web-based common database and communication platform together with a regularly updated table of all activities accessible to all participants. The subsoil observatory will be managed by a technician. The coordinating scientist will regularly call in meetings with the other groups or with subgroups for discussion of results and coordination of experiments. Furthermore he/she will organize a summer school for the participating PhD students and workshops for the communication of results to an international audience. The compiled data on C-fluxes and 14C analyses will be synthesized to gain an improved understanding of C dynamics in subsoils with a conceptual model and it will be used as input parameters for the improvement and adaptation of a numerical model of C-turnover in soils. The development and validation of the numerical model is the task of a PhD-student.