Restoring peat bogs in Central Europe (ReVersal)

The project ReVersal (Restoring peatlands of the nemoral zone under conditions of varying water supply) aims at identifying appropriate methods for the restoration of peat bogs in Central Europe under conditions of climate change. At present, the restoration of bogs often leaves the sites to natural succession, although this may result in high methane emissions and no medium-term perspective of reestablishing bog hydrology. This is due to a patchy understanding of physicochemical and biological processes controlling the development and restoration of bogs and on the lack of data and models on indicators of ecosystem conditions, such as on the spatio -temporal dynamics and budgets of gas fluxes, biodiversity, or hydrology. Peat degradation alters the water holding capacity and reduces the potential to buffer variations in water availability, constraining rewetting and restoration of ecosystem functioning. Therefore, interdisciplinary approaches are needed to restore and preserve degraded peat bogs in the long term and to re-establish bog vegetation as a key to initiate peat formation and to avoid high methane emissions after rewetting. The ReVersal project aims to develop a spatio-temporally explicit indicator framework for peatland restoration success across peat bog sites affected by drainage and/or extraction. This will be achieved by the synergistic consideration of biological and biogeochemical conditions, greenhouse gas fluxes, and biodiversity along degradation and restoration trajectories under past, current and future climatic and socio -economic conditions. Based on this consideration, uncertainties of conservation and restoration approaches will be evaluated and adaptive management strategies considering trade-offs between restoration goals will be developed. These strategies can be transferred across landscapes via remote-sensing based models. These questions are being dealt with by a consortium of scientists from Germany, Austria, the Netherlands and Poland. The Austrian sub-project focuses on determining lipid biomarkers from peat from all sites as well as elaborating trade-offs the adaptive Management Strategy for the entire project by establishing a decision support system that can be calibrated locally.

We established radiocarbon chronologies for all study sites, revealing restoration trajectories from highly degraded to successfully restored peatlands. Our multi-proxy approach identified clear indicators of restoration success: e.g., Sphagnum cover (>95% of pre-disturbance level), shrub and vascular plant cover (<105 % of pre-disturbance level), a water table depth of 10 cm 5 cm, a C/N >42, bulk P content < 370 ppm, and a bulk density < 0.08 g cm-3. Palaeoecological data confirmed that successful peat regrowth depends on three key factors: peat quality, vegetation type (linked to previous land use), and water availability. Greenhouse gas measurements also revealed critical thresholds for restoration. Sites with water tables near the surface showed highest CH emissions, particularly those dominated by Sphagnum and sedges. However, our long-term restored sites in Poland and Austria achieved near-pristine CH flux levels of ~350 kg ha-1 yr-1, demonstrating that successful restoration can restore natural carbon cycling. Rewetting consistently reduced enzymatic activities and peat mineralization, though CH and CO dynamics depended on peat quality and nutrient status. Our remote sensing approach successfully detected contrasting hydrological trends - wetting in Northern/Western Europe versus drying in Central Europe. The developed web-based monitoring tool now covers all European peatlands, providing end-user friendly operation with quality-checked data and trend analysis for individual pixels. This tool has been validated at all restoration sites in ReVersal and specific test sites in Germany and can be easily used by practitioners using the Google Earth Engine App platform. Advanced vegetation classification, combined with surface topography and wetness data, may in the future be used for robust upscaling of greenhouse gas budgets from local to regional scales. This methodology will significantly contribute to reducing monitoring costs compared to traditional field surveys.