Carbon cycling in different fen paludicultures – Short and long-term stability of sequestered C under different future groundwater level scenarios. (CaCyPal)

• Applicants: Dr. Caroline Buchen-Tschiskale; Dr. Tim Eickenscheidt
• Subject Area: Ecology of Land Use ; Soil Sciences
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 559980277

In 2022, organic soils contributed 7.1% to the total national emissions in Germany. Paludiculture, the agricultural or forestry use of rewetted peatlands, is one promising mitigation measure for significant greenhouse gas (GHG) emission reduction of organic soils. Recent studies suggest high CO2-C sequestration rates with a mean uptake of approx. 13.0 t CO2-eq ha-1 yr-1 in well-managed paludicultures. The conversion of drained arable land to fen paludiculture could thus result in a mitigation potential of up to 53.4 t CO2-eq ha-1 yr-1, making paludicultures one of the most effective nature-based climate solutions. However, the long-term sustainability of the reported high CO2 uptake capacity remains uncertain, as all GHG paludiculture studies were conducted at sites where the plants had been established directly bevor the GHG measurements. Currently, the limited knowledge of the long-term effects of rewetting and paludiculture on GHG reduction complicates their inclusion in national inventories, hindering mitigation efforts and policy decisions. While emission reduction is crucial, the ability of paludicultures to mitigate GHG emissions must also be resilient to climate change, in particular to extended drought periods. Thus, there is an urgent need for long-term investigations and in depth understanding of the C cycle and mechanisms involved in C sequestration across a broad spectrum of paludicultures. The objective of the proposed project is to determine the fate of newly assimilated atmospheric CO2-C within the different C pools, and to assess the stability and potential risk of remobilization of recently sequestered C under constant wet vs. climate change-induced drought conditions across three different paludiculture species: Carex acutiformis, Phalaris arundinacea, Typha latifolia. We aim to quantify plant CO2 uptake, C transfer and metabolism within the plant-soil-atmosphere continuum at different time scales under field conditions. To achieve this, three different paludiculture species will be exposed one to nine times to 13C-enriched CO2 for a short time period during the vegetation period in 2026. Furthermore, the long-term GHG mitigation potential of the three different paludiculture species will be quantified and the impact of climate change-induced drought conditions will be evaluated. The work program comprises four main experiments to study the effects of short- to long-term stability of sequestered CO2-C in different paludiculture species. All field experiments will be conducted at a fully equipped, permanent research site of the HSWT-PSC. For high-frequency GHG and high-precision delta13C measurements in CO2 and CH4, we will use a novel robotic chamber GHG measurement system. In addition to the GHG and isotopic measurements, samples of plant biomass, DOC, dissolved CO2 and CH4, SOC, Cmic, and biochemical fractions of plant biomass and soil will be analyzed for delta13C isotopic signatures at the Thünen Institute.

• DFG Programme: Research Grants
• Major Instrumentation: Isotopic Analyzer for δ13C, CO2 and CH4