 |
| Titel |
Riparian and in-stream controls on nutrient concentrations and fluxes in a headwater forested stream |
| VerfasserIn |
S. Bernal, A. Lupon, M. Ribot, F. Sabater, E. Martí |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1726-4170
|
| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 6 ; Nr. 12, no. 6 (2015-03-24), S.1941-1954 |
| Datensatznummer |
250117879
|
| Publikation (Nr.) |
 copernicus.org/bg-12-1941-2015.pdf |
|
|
|
|
|
| Zusammenfassung |
| Headwater streams are recipients of water sources draining through
terrestrial ecosystems. At the same time, stream biota can transform and
retain nutrients dissolved in stream water. Yet studies considering
simultaneously these two sources of variation in stream nutrient chemistry
are rare. To fill this gap of knowledge, we analyzed stream water and
riparian groundwater concentrations and fluxes as well as in-stream net
uptake rates for nitrate (NO3−), ammonium (NH4+), and soluble
reactive phosphorus (SRP) along a 3.7 km reach on an annual basis. Chloride
concentrations (used as conservative tracer) indicated a strong hydrological
connection at the riparian–stream interface. However, stream and riparian
groundwater nutrient concentrations showed a moderate to null correlation,
suggesting high in-stream biogeochemical processing. In-stream net nutrient
uptake (Fsw) was highly variable across contiguous segments and
over time, but its temporal variation was not related to the vegetative
period of the riparian forest. For NH4+, the occurrence of
Fsw > 0 μg N m−1 s−1 (gross uptake >
release) was high along the reach, while for NO3−, the occurrence of
Fsw < 0 μg N m−1 s−1 (gross uptake
< release) increased along the reach. Within segments and dates,
Fsw, whether negative or positive, accounted for a median of 6,
18, and 20% of the inputs of NO3−, NH4+, and SRP,
respectively. Whole-reach mass balance calculations indicated that in-stream
net uptake reduced stream NH4+ flux up to 90%, while the stream
acted mostly as a source of NO3− and SRP. During the dormant period,
concentrations decreased along the reach for NO3−, but increased for
NH4+ and SRP. During the vegetative period, NH4+ decreased,
SRP increased, and NO3− showed a U-shaped pattern along the reach.
These longitudinal trends resulted from the combination of hydrological
mixing with terrestrial inputs and in-stream nutrient processing. Therefore,
the assessment of these two sources of variation in stream water chemistry is
crucial to understand the contribution of in-stream processes to stream
nutrient dynamics at relevant ecological scales. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|