Short-term effects of an exceptionally hot and dry summer on decomposition of surface peat in a restored temperate bog

The restoration of drained peat bogs in Northwest (NW) Europe is an important task of soil protection, but needs to cope with warmer and drier summers. Our examination took place in the Pietzmoor bog (Schneverdingen, NW Germany) that had been drained for fuel peat extraction until the 1970s and rewetted since then. We determined carbon dioxide (CO2) efflux in situ and in laboratory incubations. Also, we analyzed pore water for dissolved organic carbon (DOC), total and dissolved organic N (DON), nitrate (NO3–) and ammonium (NH4+) concentration. In Schneverdingen, the summer 2003 was record-breaking hot (mean temperature June to August elevated > 3 K compared to long-term average) and dry (precipitation during the same period < 59% of long-term average). In July 2003, the water table in the Pietzmoor subsided to > 42 cm below the surface in July 2003, when in situ soil CO2 efflux was up to 23.4 g m–2 d–1 compared to 15.7 g m–2 d–1 in September. Prior to March 2003, DOC concentrations in pore water were < 180 mg l–1 and NH4+ was the dominant fraction of mineral N. In July 2003, DOC concentration rose to 249 g l–1, DON concentrations more than doubled, and NO3– became the dominant fraction of mineral N. Due to the increased future likelihood of hot and dry summers in NW Germany, peat bog restoration efforts need take care that a water table close to the surface is maintained.