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| Kalbitz, K; Geyer, S: Different effects of peat degradation on dissolved organic carbon and nitrogen, Organic Geochemistry, 33, 319-326 (2002) | |
Abstract:
The dynamics of dissolved organic matter (DOM) are closely related to organic matter processes such as decomposition, humification, and stabilization of organic
matter in soils. Nevertheless, it is unknown whether dissolved organic carbon (DOC) and nitrogen (DON) have an equal response to these processes. We analyzed
DOC and DON concentrations of topsoil, groundwater, and surface water of six differently used sites characterized by differences in peat degradation. Carbon
(C-13, C-14) and nitrogen (N-15) isotopes of DOM were related to a humification index in order to detect differences between DOC and DON at different stages
of humification. The results show that intact peatlands had higher DOC concentrations than degraded peatlands. Clearly, DOC concentration depends on soil
organic carbon content and therefore on the degree of peat degradation. However, intact and degraded peatlands showed similar DON and inorganic N
concentrations suggesting that DON release is dependent on soil inorganic N rather than the organic N pool. Moreover, a high degree of peat degradation resulted in
lower DOC/DON ratios than the C/N ratio of the solid phase indicating a preferential release of DON from soil organic matter. Further, delta(13)C ratios and the
radiocarbon age of DOM increase with peat degradation and humification indicating a high C turnover, an increased microbial modification and age of DOC. On the
other hand delta(15)N ratios decrease, probably as a result of N fertilization. The promoting effect of inorganic N on DON release and a high humification of DOM
at sites treated with inorganic N fertilizers suggest that N fertilization promotes a release of amino acids depleted in N-15 and subsequent condensation with
carbohydrates to humic substances. |
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