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| Titel |
Geomorphic control on the δ¹⁵N of mountain forests |
| VerfasserIn |
R. G. Hilton, A. Galy, A. J. West, N. Hovius, G. G. Roberts |
| 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 (2013-03-13), S.1693-1705 |
| Datensatznummer |
250018149
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| Publikation (Nr.) |
 copernicus.org/bg-10-1693-2013.pdf |
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| Zusammenfassung |
| Mountain forests are subject to high rates of physical erosion which can
export particulate nitrogen from ecosystems. However, the impact of
geomorphic processes on nitrogen budgets remains poorly constrained. We have
used the elemental and isotopic composition of soil and plant organic matter
to investigate nitrogen cycling in the mountain forest of Taiwan, from 24
sites with distinct geomorphic (topographic slope) and climatic
(precipitation, temperature) characteristics. The organic carbon to nitrogen
ratio of soil organic matter decreased with soil 14C age, providing
constraint on average rates of nitrogen loss using a mass balance model.
Model predictions suggest that present day estimates of nitrogen deposition
exceed contemporary and historic nitrogen losses. We found ∼6‰ variability in the stable isotopic composition
(δ15N) of soil and plants which was not related to soil
14C age or climatic conditions. Instead, δ15N was
significantly, negatively correlated with topographic slope. Using the mass
balance model, we demonstrate that the correlation can be explained by an
increase in nitrogen loss by non-fractioning pathways on steeper slopes,
where physical erosion most effectively removes particulate nitrogen.
Published data from forests on steep slopes are consistent with the
correlation. Based on our dataset and these observations, we hypothesise
that variable physical erosion rates can significantly influence soil
δ15N, and suggest particulate nitrogen export is a major, yet
underappreciated, loss term in the nitrogen budget of mountain forests. |
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