Die auswirkungen erhöhter stickstoffeinträge auf den löslichen organischen kohlenstoff und stickstoff im boden: ein vergleich von zwei unterschiedlich stark stickstoffbelasteten sandböden unter kiefernnutzung (pinus sylvestris l.): Impacts of increased nitrogen inputs on the dynamics of soluble organic carbon and nitrogen in the soil: a comparison between two scots pine forests with different atmospheric n inputs

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The impact of atmospheric N deposition on the dynamics of dissolved organic carbon and nitrogen were investigated in a microcosm study of two Scots pine forest soils (cambisol, podzol) from northern Germany receiving different atmospheric nitrogen inputs. The soils were fertilized with two different nitrogen doses (45 kg N ha−1 a−1, 90 kg N ha−1 a−1) in order to simulate the impacts of further increasing nitrogen inputs. On both sites, the nitrogen treatment showed no response to the DOC and DON leachate concentrations in all soil layers. In contrast, water-soluble organic carbon (WSOC) and water-soluble organic nitrogen (WSON) contents decreased in most of the investigated top soil layers of the podzol, while these parameters remained almost unchanged in the cambisol. The nitrogen induced changes of the WSOC and WSON contents were well correlated to other hot- and cold-water-extractable carbon and nitrogen fractions in the mineral soil, while correlations in the organic layers were mostly nitrogen independent. The results show, that the impacts of increasing nitrogen inputs on the WSOC and WSON dynamics are much more pronounced on the N stressed podzol than on the cambisol, while no differences were detected for the DOC and DON dynamics on both sites. The reasons for this might be differences in the composition of the microorganism populations and differences in the carbon and nitrogen sources for the WSOC and the WSON as well as the DOC and DON.