Biogeochemical indicators of peatland degradation – a case study 1 of a temperate bog in Northern Germany

15 Organic soils in peatlands store a great proportion of the global soil carbon pool and can lose 16 carbon via the atmosphere due to degradation. In Germany, most of the greenhouse gas 17 (GHG) emissions from organic soils are attributed to sites managed as grassland. Here we 18 investigated a land use gradient from near-natural wetland (NW) to an extensively managed 19 (GE) to an intensively managed grassland site (GI), all formed in the same bog complex in 20 northern Germany. Vertical depth profiles of δ 13 C, δ 15 N, ash content, C/N ratio, bulk density, 21 as well as radiocarbon ages were studied to identify peat degradation and to calculate carbon 22 loss. At all sites, including the near-natural site, δ 13 C depth profiles indicate aerobic 23 decomposition in the upper horizons. In the topsoil, δ 15 N increased in the order NW<GE<GI 24 owing to differences in peat decomposition and fertilizer application. Depth profiles of δ 15 N 25 differed significantly between sites with increasing δ 15 N values in the top soil layers parallel 26 to an increase in land use intensity. At both grassland sites, the ash content peaked within the 27 first centimeters. In the near-natural site, ash contents were highest in 10-60 cm depth. The 28 ash profiles, not only at the managed grassland sites, but also at the near-natural site indicate 29