Contrary results of Nitrogen, carbon and ...

Over the last 30 years, rewetting has occurred on several million hectares of peatland in Europe, Asia and other parts of the world. Rewetting was proposed as a valid strategy to restore the unique biodiversity of peatlands. In recent years, the focus has increasingly been on the re-creation of carbon and nutrient sink functions, in order to decrease the climate impact and mitigate the eutrophication of water bodies respectively. However, as a result of historical landuse and soil subsidence, there is a tendency for eutrophic shallow lakes to form after rewetting (water depth mostly < 1m), potentially elevating nutrient mobilization and greenhouse gas emissions, plus hindering the development of target vegetation. Overthe last decades, comprehensive laboratory and field research has improved the understanding of the processes controlling the formation of these “novel ecosystems” and the development and change of these physico-chemical processes over time can effect restoration targets and goals. For example, nitrogen removal can be very successful in the short-term, however this paper suggests that extended rewetting periods up to several decades may be necessary in severely degraded fens before other ecological functions and ecosystem services are fully restored. It is expected that observed phosphorus, dissolved organic matter and greenhouse gas pulses to the external environment could still continue for decades after initial rewetting. In this light, soil analysis andother investigations prior to rewetting can afford insight into matter fluxes, vegetation development or microbial changes that may occur throughout restoration. An improved knowledge and understanding of the process of matter turnover, both under differing environmental settings and temporally, allows for a better assessment of different ecological and societalconsequences of rewetting severely degraded peatlands.