Determination of atmospheric nitrogen deposition to a semi-natural peat bog site in an intensively managed agricultural landscape
Hurkuck, Miriam | Brümmer, Christian | Mohr, Karsten | Grünhage, Ludger | Flessa, Heinz | Kutsch, Werner L.
Rising levels of atmospheric nitrogen (N) deposition have been found to affect the primary productivity and species composition of most terrestrial ecosystems. Highly vulnerable ecosystems such as nutrient-poor bogs are expected to respond to increasing N input rates with a decrease in plant species diversity. Our study site – a moderately drained raised bog and one of only very few remaining protected peatland areas in Northwestern Germany – is surrounded by highly fertilised agricultural land and intensive livestock production. We quantified the annual deposition of atmospheric N over a period of two years. Dry deposition rates of different N species and their reactants were calculated from day and night-time concentrations measured by a KAPS denuder filter system. Dry N deposition amounted to 10.9 ± 1.0 kg N ha−1 yr−1 (year 1) and 10.5 ± 1.0 kg N ha−1 yr−1 (year 2). More than 80% of total deposited N was attributed to ammonia (NH3). A strong seasonality in NH3 concentrations and depositions could be observed. Day and night-time concentrations and depositions, however, did not differ significantly. Total N deposition including bulk N deposition resulted in about 25 kg N ha−1 yr−1. Our results suggest that the intensive agricultural land management of surrounding areas and strongly emitting animal husbandry lead to N inputs into the protected peatland area that exceed the ecosystem's specific critical load up to fivefold. This gives rise to the assumption that a further shift in plant species composition with a subsequent alteration of the local hydrological regime can be expected.
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