Carbon dynamics in degraded peatland and artificial soils of the Grosses Moos in the Berner Seeland the Grosses Moos in the Berner Seeland Effects of Effects of anthropogenic soil embankment on carbon stabilization anthropogenic soil embankment on carbon stabilization

Drained peatlands used for agriculture are significant sources of atmospheric CO₂ and are subject to severe degradation and land subsidence. The Grosses Moos in the Berner Seeland is a large, drained peatland area that is a key agricultural region in Switzerland. Intensive drainage combined with intensive agriculture over decades has led to peatland degradation in this region. Anthropogenic soil embankments, the application of a mineral cover, is a management strategy used to counteract this degradation. While recent flux-based studies have investigated emissions from these systems, a critical knowledge gap remains concerning the effect of this practice on the quantity, vertical distribution, and functional stability of the underlying SOC. This thesis provides the first analysis of how embankments alter SOC occurrence and investigates whether they can have a stabilizing effect. Adopting the conceptual framework that separates soil organic matter into POM and MAOM, this study compares original degraded peat profiles with adjacent backfilled profiles. Results show that most likely, embankment creates a geochemically inverted Anthrosol, burying the organic-rich peat horizon under a carbon-poor mineral cover and displacing the SOC maximum downwards from approximately 60 cm to below 100 cm. Paradoxically, this buried carbon is stored primarily in the coarse, POM-like fraction, which is considered biochemically labile. This suggests preservation is not due to chemical recalcitrance but to physical protection afforded by the embankment, which re-establishes anoxic conditions. Concurrently, the new mineral topsoil shows a relative increase in SOC within the fine, MAOM-like fraction, indicating that the added mineral matrix facilitates a new, more stable pathway for carbon stabilization through organo-mineral association. The study concludes that embankment establishes a dual system: the physical preservation of the old, labile peat stock at depth, coupled with the initiation of new, mineral-associated carbon stabilization in the surface layer. This thesis provides a unifying framework that reconciles the seemingly contradictory findings of flux-based studies. It helps to explain the continued CO₂ emissions observed by other researchers as originating from the new, active topsoil, while simultaneously accounting for the shift in carbon source away from old peat. It thereby offers a more holistic framework for evaluating this land management practice. The embankments could be a practical and efficient interim solution for agriculture to slow down the progressive degradation of peat, but not to stop it completely.