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| Titel |
Temporal variation of nitrate and phosphate transport in headwater catchments: the hydrological controls and land use alteration |
| VerfasserIn |
T.-Y. Lee, J.-C. Huang, S.-J. Kao, C.-P. Tung |
| 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. 4 ; Nr. 10, no. 4 (2013-04-18), S.2617-2632 |
| Datensatznummer |
250018207
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| Publikation (Nr.) |
 copernicus.org/bg-10-2617-2013.pdf |
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| Zusammenfassung |
| Oceania rivers are hotspots of DIN (dissolved inorganic nitrogen) and DIP
(dissolved inorganic phosphorus) transport due to humid/warm climate,
typhoon-induced episodic rainfall and high tectonic activity that create an
environment favorable for high/rapid runoff and soil erosion. In spite of
its uniqueness, effects of hydrologic controls and land use on the transport
behaviors of DIN and DIP are rarely documented. A 2 yr monitoring study
for DIN and DIP from three headwater catchments with different cultivation
gradient (0 To 8.9%) was implemented during a ~ 3 day
interval with an additional monitoring campaign at a 3 h interval during
typhoon periods. Results showed the DIN yields in the pristine, moderately
cultivated (2.7%), and intensively cultivated (8.9%) watersheds were
8.3, 26, and 37 kg N ha−1 yr−1, respectively. For the DIP yields, they were
0.36, 0.35, and 0.56 kg P ha−1 yr−1, respectively. Higher year-round DIN
concentrations and five times larger in DIN yields in intensively cultivated
watersheds indicate DIN is more sensitive to land use changes. The high
background DIN yield from the relatively pristine watershed was likely due
to high atmospheric nitrogen deposition and large subterranean N pool. The
correlations between runoff and concentration reveals that typhoon floods
purge out more DIN from the subterranean reservoir, i.e., soil, by contrast,
runoff washes off surface soil resulting in higher suspended sediment
with higher DIP. Collectively, typhoon runoff contributes 20–70% and
47–80%, respectively, to the annual DIN and DIP exports. The DIN yield to
DIP yield ratio varied from 97 to 410, which is higher than the global mean
of ~ 18. Such a high ratio indicates a P-limiting condition in
stream and the downstream aquatic environment. Based on our field observation,
we constructed a conceptual model illustrating different remobilization
mechanisms for DIN and DIP from headwaters in a mountainous river, which is
analogous to typical Oceania rivers and the headwater of large rivers in
similar climate zones. Our study advanced our understanding about the role of
cyclones, which exert hydrological control, and land use on nutrient export
in the Oceania region, benefiting watershed management under the context of
climate change. |
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