Redox induced mobilisation of DOC from riparian wetlands (ReDOCs)

DFG KN 929/28-1

Riparian wetlands are major sources of dissolved organic carbon (DOC) to streams. Increasing DOC concentrations were observed for many northern streams during the last decades, with potential implications for carbon (C) storages of wetland soils and streamwater quality. In soils, organic C is often associated with or bound to iron (oxy) hydroxides. These associations of iron (Fe) and organic C may immobilise and protect soil organic matter from mineralisation under oxic conditions. However, organic C can be remobilised if ferric Fe is reduced under anoxic conditions or if redox mediated changes in pH increase its solubility. Redox processes are therefore presumably important drivers of DOC dynamics in both wetland soils and the adjacent streams. 

To address this knowledge gap, experimental catchment studies are needed that trace these processes from the source areas of DOC to the stream network; and modelling techniques able to extract causal links from observational data need to be applied. The objective of this project is thus to mechanistically understand the interplay between DOC, Fe, and pH for boreal and temperate catchments featuring riparian wetlands. We combine (A) the investigation of water along wetland-to-stream transects, looking at DOC molecular signatures that indicate specific mobilisation processes and (B) novel causal discovery methods to trace mobilisation and transport processes of DOC across scales. The proposed study site is the Krycklan catchment in northern Sweden, providing long data records and excellent field infrastructure for the proposed experimental and modelling work. Process understanding obtained at Krycklan is planned to be transferred to German catchments using Bayesian networks.