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.

地下土壤储存了全球土壤碳的 50% 以上，但人们对地下土壤的稳定和不稳定过程知之甚少。底土有机碳 (OC) 来源于三个主要来源：以溶解有机碳 (DOC) 形式浸入底土的 OC、来自根凋落物和根系分泌物的 OC（这两个生物源 OC 来源）以及随着形成而沉积的 OC。沉积基岩，所谓地成OC或化石OC。关于这些年轻和古老的有机碳来源对地下有机碳储量的贡献的研究很少。 SUBSOM 内该子项目的目的是追踪底土 OC 的来源，区分地源 OC 和生物 OC，并评估底土中年轻 DOC 衍生的底土 OC 和旧地源 OC 的稳定性。在三个工作包 (WP) 中，现场实验将与实验室分析和孵化实验相结合，研究不同土壤类型中不同 OC 组分的脆弱性。同位素标记 (13C) 将用于追踪年轻的 DOC 衍生的 OC 部分，而 14C 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 (WP1) 和 CO2 梯度基于模型将使用关闭联合实验进行验证。新获得的数据（例如根周转率）将用于基于对这个大型观测站数据集的多因素分析（机器学习算法）来限制底土中二氧化碳通量的驱动因素。底土中 DOC 的命运和稳定性将联合评估通过在三个地点将标记的 DOC 溶液应用到两个不同的土壤深度 (WP2) 进行实验（DO13C 注入，由我们的子项目领导的田间活动）。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）。添加营养物质和容易获得的 OC 底物的孵化实验将揭示这种年轻的 DOC 衍生的 OC 输入的稳定程度和机制。将通过联合实验（由我们的子项目领导）在四个具有不同沉积基岩（黄土、次生砂、砂岩、石灰岩）的地点进行联合实验来探索地成OC在底土中的作用（WP3）。从深部岩心 (10 m) 中，将获得几乎 100% 地源 OC 的基岩样品，以量化和表征地源 OC 部分。将开发分馏方法以将地源 OC 与生物源 OC 分开。地源OC进入下层土的稳定性（与养分和容易获得的OC相遇）将在孵化实验中进行评估。不同土壤类型中DOC的周转和原位传输的数据以及地源OC对下层土OC的贡献将直接得到用作 SUBSOM 内开发的数值模型中的输入变量。