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| Titel |
The impact of four decades of annual nitrogen addition on dissolved organic matter in a boreal forest soil |
| VerfasserIn |
M. O. Rappe-George, A. I. Gärdenas, D. B. Kleja |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 10, no. 3 ; Nr. 10, no. 3 (2013-03-01), S.1365-1377 |
| Datensatznummer |
250018129
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| Publikation (Nr.) |
 copernicus.org/bg-10-1365-2013.pdf |
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| Zusammenfassung |
| Addition of mineral nitrogen (N) can alter the concentration and quality of
dissolved organic matter (DOM) in forest soils. The aim of this study was to
assess the effect of long-term mineral N addition on soil solution
concentration of dissolved organic carbon (DOC) and dissolved organic
nitrogen (DON) in Stråsan experimental forest (Norway spruce) in central
Sweden. N was added yearly at two levels of intensity and duration: the N1
treatment represented a lower intensity but a longer duration (43 yr) of N
addition than the shorter N2 treatment (24 yr). N additions were terminated
in the N2 treatment in 1991. The N treatments began in 1967 when the spruce
stands were 9 yr old. Soil solution in the forest floor O, and soil mineral
B, horizons were sampled during the growing seasons of 1995 and 2009. Tension
and non-tension lysimeters were installed in the O horizon (n = 6), and
tension lysimeters were installed in the underlying B horizon (n = 4): soil
solution was sampled at two-week intervals. Although tree growth and O
horizon carbon (C) and N stock increased in treatments N1 and N2, the
concentration of DOC in O horizon leachates was similar in both N treatments
and control. This suggests an inhibitory direct effect of N addition on O
horizon DOC. Elevated DON and nitrate in O horizon leachates in the ongoing
N1 treatment indicated a move towards N saturation. In B horizon leachates,
the N1 treatment approximately doubled leachate concentrations of DOC and
DON. DON returned to control levels, but DOC remained elevated in B horizon
leachates in N2 plots nineteen years after termination of N addition. We
propose three possible explanations for the increased DOC in mineral soil:
(i) the result of decomposition of a larger amount of root litter, either
directly producing DOC or (ii) indirectly via priming of old SOM, and/or
(iii) a suppression of extracellular oxidative enzymes. |
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