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| Titel |
Quantifying the effects of clear-cutting and strip-cutting on nitrate dynamics in a forested watershed using triple oxygen isotopes as tracers |
| VerfasserIn |
U. Tsunogai, D. D. Komatsu, T. Ohyama, A. Suzuki, F. Nakagawa, I. Noguchi, K. Takagi, M. Nomura, K. Fukuzawa, H. Shibata |
| 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 ; 11, no. 19 ; Nr. 11, no. 19 (2014-10-07), S.5411-5424 |
| Datensatznummer |
250117626
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| Publikation (Nr.) |
 copernicus.org/bg-11-5411-2014.pdf |
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| Zusammenfassung |
| Temporal variations in the stable isotopic compositions of nitrate dissolved
in stream water eluted from a cool–temperate forested watershed (8 ha) were
measured to quantify the biogeochemical effects of clear-cutting of trees
and subsequent strip-cutting of the understory vegetation, dwarf bamboo
(Sasa senanensis), with special emphasis on changes in the fate of atmospheric nitrate that
had been deposited onto the watershed based on Δ17O values of
nitrate. A significant increase in stream nitrate concentration to 15 μmol L−1 in spring of 2004 was correlated with a significant
increase in the Δ17O values of nitrate. Additionally, the high
Δ17O values of +14.3‰ suggest that the
direct drainage of atmospheric nitrate accounted for more than 50% of
total nitrate exported from the forested watershed peaking in spring.
Similar increases in both concentrations and Δ17O values were
also found in spring of 2005. Conversely, low Δ17O values less
than +1.5‰ were observed in other seasons, regardless
of increases in stream nitrate concentration, indicating that the majority
of nitrate exported from the forested watershed during seasons other than
spring was remineralized nitrate: those retained in the forested ecosystem
as either organic N or ammonium and then been converted to nitrate via
microbial nitrification. When compared with the values prior to
strip-cutting, the annual export of atmospheric nitrate and remineralized
nitrate increased more than 16-fold and fourfold, respectively, in 2004, and
more than 13-fold and fivefold, respectively, in 2005. The understory
vegetation (Sasa) was particularly important to enhancing biological consumption
of atmospheric nitrate. |
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