Labor für Isotopen-Biogeochemie

Excessive nutrient supply may threaten the carbon storage function of nutrient limited peatlands. We conducted a detailed study in a bog ecosystem (Wylde Lake peatland, Canada), which was once ombrotrophic and since AD 1954 borders a water reservoir, which is enriched with nutrients. Our objective was to elucidate whether the inner peatland parts maintain typical characteristics of a pristine bog. To achieve this goal, along a transect of study sites, we dated peat cores, determined nutrient concentrations and N input and mapped the vegetation. The peatland's central part showed large N input rates of ~4.3 g N m^-2 y^-1, but even greater rates of 5.90 ± 0.10 g N m^-2 y^-1, were found in the pe-riphery. Elements essential for plant growth, such as N, P, S, Ca, Mg, Mn, Fe, Cu and Zn were increased in concentration upwards in the profile of all peat cores, especially near the reservoir, presumably due to supply by the reservoir water. Also, a more graminoid dominated vegetation near the reservoir indicated a transformation of the once ombrotrophic bog into a poor fen. To our surprise and in contrast to pre-vious studies the peatland did not seem to decay after long-term excessive nutrient load, instead it accelerated peat accumulation, leading to maximum growth rates of up to 500 g C m^-2 y^-1 immediately after flooding of the reservoir. Peatland functioning in terms of carbon storage appeared maintained.