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Kalbitz, Karsten ; Geyer, Stefan:
Different effects of peat degradation on dissolved organic carbon and nitrogen.
In: Organic Geochemistry.
Bd. 33
(2002)
Heft 3
.
- S. 319-326.
ISSN 1873-5290
DOI: https://doi.org/10.1016/S0146-6380(01)00163-2
Abstract
The dynamics of dissolved organic matter (DOM) are closely related to organic matter processes such as decomposition, humification, and stabilization of organicmatter in soils. Nevertheless, it is unknown whether dissolved organic carbon (DOC) and nitrogen (DON) have an equal response to these processes. We analyzedDOC 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 stagesof humification. The results show that intact peatlands had higher DOC concentrations than degraded peatlands. Clearly, DOC concentration depends on soilorganic carbon content and therefore on the degree of peat degradation. However, intact and degraded peatlands showed similar DON and inorganic Nconcentrations suggesting that DON release is dependent on soil inorganic N rather than the organic N pool. Moreover, a high degree of peat degradation resulted inlower 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 theradiocarbon age of DOM increase with peat degradation and humification indicating a high C turnover, an increased microbial modification and age of DOC. On theother 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 DOMat sites treated with inorganic N fertilizers suggest that N fertilization promotes a release of amino acids depleted in N-15 and subsequent condensation withcarbohydrates to humic substances.