Assessing stabilisation and destabilisation processes - Tracing young and old carbon in subsoils

评估稳定和不稳定过程 - 追踪底土中年轻和古老的碳

• 批准号: 233438032
• 负责人: Privatdozent Dr. Axel Don
• 金额: --
• 依托单位: Institut für Agrarklimaschutz
• 依托单位国家: 德国
• 项目类别: Research Units
• 财政年份: 2013
• 资助国家: 德国
• 起止时间: 2012-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/233438032?language=en
• 关键词: Assessing; stabilisation; destabilisation; processes; Tracing

Subsoils store more than 50% of the global soil carbon, but little is known on stabilisation and destabilisation processes in subsoils. Subsoil organic carbon (OC) is derived from three major sources: OC leached into subsoils as dissolved organic carbon (DOC), OC derived from root litter and root exudates (together the two biogenic OC sources) and OC that was deposited with the formation of sedimentary bedrocks, so called geogenic OC or fossil OC. There are few studies on the contribution of these young and old OC sources to subsoil OC stocks. The aim of this subproject within SUBSOM is to trace the sources of subsoil OC, to differentiate between geogenic and biogenic OC and to assess the stability of young DOC derived subsoil OC and old geogenic OC in subsoils. In three workpackages (WPs) field experiments will be combined with laboratory analysis and incubation experiments on the vulnerability of different OC fractions in different soil types. Isotopic labelling (13C) will be used to trace the young DOC derived OC fraction and 14C will be used to trace the very old, geogenic OC fraction.At the SUBSOM observatories monitoring of soil CO2 fluxes will be continued (WP1) and the CO2 gradient based model will be validated using the Switch off joint experiment. Newly available data such as root turnover will be used to constrain the drivers of CO2 fluxes in subsoils based in a multifactorial analysis (machine learning algorithms) of this large observatory data set.The fate and stability of DOC in subsoil will be assessed in a joint experiment (DO13C inject, field campaigns led by our subproject) by applying a labelled DOC solution at three sites to two differed soil depths (WP2). Similarly, at the observatories the fate of the labeled litter applied onto the soil surface 20 months ago will be explored (Switch off experiment, sampling campaigns led by our subproject). Incubation experiments with addition of nutrients and easily available OC substrate will reveal the degree and mechanisms of stabilisation of such young DOC derived OC input. The role of geogenic OC in subsoils will be explored in a joint experiment (led by our subproject) at four sites with different sedimentary bedrock (loess, tertiary sand, sand stone, lime stone)(WP3). From deep cores (10 m) bedrock samples with almost 100% geogenic OC will be derived to quantify and characterised the geogenic OC fraction. Fractionation methods will be developed to separate geogenic from biogenic OC. The stability of geogenic OC entering subsoils (encounter with nutrients and easily available OC) will be assessed in incubation experiments.Data on the turnover and in-situ transport of DOC in different soil types and the contribution of geogenic OC to subsoil OC will be directly used as input variables in the numerical model developed within SUBSOM.

底土储存了全球50%以上的土壤碳，但对底土的稳定和不稳定过程知之甚少。底土有机碳（OC）的来源主要有三种：以溶解有机碳（DOC）的形式淋溶到底土中的OC、来自根凋落物和根分泌物的OC（两种生物源OC）和随沉积岩形成而沉积的OC，即地源OC或化石OC。关于这些年轻和年老的有机碳源对底土有机碳储量的贡献的研究很少。该子项目的目的是在SUBSOM中追踪底土有机碳的来源，区分地质和生物有机碳，并评估年轻DOC衍生底土有机碳和底土中古老的地质有机碳的稳定性。在三个工作包（WP）的现场实验将结合实验室分析和培养实验的脆弱性，不同的有机碳组分在不同的土壤类型。同位素标记（13 C）将用于追踪年轻DOC衍生的OC部分，14 C将用于追踪非常古老的地质OC部分。在SUBSOM观测站，将继续监测土壤CO2通量（WP 1），并将使用关闭联合实验验证基于CO2梯度的模型。新获得的数据，如根营业额将被用来限制在这个大型观测数据集的基础上，在多因素分析（机器学习算法）的底土中的CO2通量的驱动程序。DOC的命运和稳定性将在一个联合实验中进行评估（DO13 C注入，由我们的子项目领导的实地活动），通过在三个地点应用标记DOC解决方案，两个不同的土壤深度（WP 2）。同样，在观测站，将探索20个月前施加到土壤表面的标记垃圾的命运（关闭实验，由我们的子项目领导的采样活动）。培养实验中添加营养物质和容易获得的OC基板将揭示的程度和机制的稳定，这种年轻的DOC来源的OC输入。将在四个具有不同沉积基岩（黄土、第三纪砂、砂岩、石灰石）的地点进行联合实验（由我们的子项目牵头），探讨地气OC在底土中的作用（WP 3）。从深层岩心（10米）基岩样品与几乎100%的地质OC将得出量化和特点的地质OC部分。将开发分馏方法来分离地源OC和生物源OC。在培养实验中，将评估地质有机碳进入底土的稳定性（遇到养分和易获得的有机碳）。不同土壤类型中DOC的周转和原位迁移以及地质有机碳对底土有机碳的贡献的数据将直接用作SUBSOM中开发的数值模型的输入变量。