Effect of vegetation reestablishment on greenhouse gas emissions from a small headwater stream, Eifel/Lower Rhine Valley (TERENO Network, Germany)

Headwater streams are increasingly recognized as hotspots of greenhouse gas (GHG) emissions within river networks, driven by strong land–water interactions, high biological activity, turbulence, and groundwater inputs. Despite their disproportionate contribution to atmospheric fluxes of CO₂, CH₄, and N₂O, the processes linking GHG emissions to dissolved organic matter (DOM) dynamics along the soil–water continuum remain insufficiently understood, particularly under varying hydrological conditions and land-use change.This study investigates the interactions between stream GHG emissions and DOM quantity and quality in a forested headwater catchment. The research is conducted in the Wüstebach catchment, located in the Eifel National Park (Germany) and part of the TERENO long-term environmental observation network. Here, we present preliminary results focusing on how hydrology and land cover influence the coupling between GHG dynamics and DOM characteristics.Water chemistry and GHG samples are collected bi-weekly over one year along about 500 m stream reach, from the source to the gauging station, at ten locations along the main stem and three locations along a nearby control stream. Sampling points are spaced approximately every 100 m and positioned upstream and downstream of tributaries, allowing assessment of spatial variability, tributary inputs, and land-use effects on GHG concentrations and fluxes.Preliminary results reveal pronounced seasonal and hydrological controls on GHG emissions. Mean CO₂ and N₂O fluxes are higher during winter and autumn, whereas CH₄ fluxes peak during summer. Increasing discharge is associated with enhanced CO₂ and N₂O fluxes in both streams, while CH₄ fluxes show no consistent relationship with discharge. Both dissolved concentrations and atmospheric fluxes of CO₂, CH₄, and N₂O are consistently higher in the clearcut stream compared to the reference stream. In the clearcut area, elevated dissolved organic carbon (DOC) concentrations correlate positively with increased CO₂ concentrations in stream water. In contrast, CO₂ emissions show the expected negative relationship with DOM aromaticity (SUVA₂₅₄) in the reference stream, but this relationship is absent in the clearcut stream, indicating altered DOM processing and carbon turnover following land-use change.