Small-scale topography explains patterns and dynamics of dissolved organic carbon exports from the riparian zone of a temperate, forested catchment
<p>Export of dissolved organic carbon (DOC) from riparian zones (RZs) is an important component of temperate catchment carbon budgets, but export mechanisms are still poorly understood. Here we show that DOC export is predominantly controlled by the microtopography of the RZ (lateral variabili...
Guardado en:
| Autores principales: | , , , , , , , |
|---|---|
| Formato: | article |
| Lenguaje: | EN |
| Publicado: |
Copernicus Publications
2021
|
| Materias: | |
| Acceso en línea: | https://doaj.org/article/59cc6332c3c94f118f51616a86faf466 |
| Etiquetas: |
Agregar Etiqueta
Sin Etiquetas, Sea el primero en etiquetar este registro!
|
| Sumario: | <p>Export of dissolved organic carbon (DOC) from riparian zones (RZs) is
an important component of temperate catchment carbon budgets, but
export mechanisms are still poorly understood. Here we show that DOC
export is predominantly controlled by the microtopography of the RZ
(lateral variability) and by riparian groundwater level dynamics
(temporal variability). From February 2017 until July 2019 we studied
topography, DOC quality and water fluxes and pathways in the RZ
of a small forested catchment and the receiving stream in central
Germany. The chemical classification of the riparian groundwater and
surface water samples (<span class="inline-formula"><i>n</i>=66</span>) by Fourier transform ion cyclotron
resonance mass spectrometry revealed a cluster of plant-derived,
aromatic and oxygen-rich DOC with high concentrations
(DOC<span class="inline-formula"><sub>I</sub></span>) and a cluster of microbially processed, saturated
and heteroatom-enriched DOC with lower concentrations
(DOC<span class="inline-formula"><sub>II</sub></span>). The two DOC clusters were connected to locations
with distinctly different values of the high-resolution topographic
wetness index (TWI<span class="inline-formula"><sub>HR</sub></span>; at 1 m resolution) within the study
area. Numerical water flow modeling using the integrated surface–subsurface model HydroGeoSphere revealed that surface runoff from high-TWI<span class="inline-formula"><sub>HR</sub></span> zones associated with the DOC<span class="inline-formula"><sub>I</sub></span> cluster
(DOC<span class="inline-formula"><sub>I</sub></span> source zones) dominated overall discharge generation
and therefore DOC export. Although corresponding to only 15 % of the
area in the studied RZ, the DOC<span class="inline-formula"><sub>I</sub></span> source zones contributed
1.5 times the DOC export of the remaining 85 % of the area
associated with DOC<span class="inline-formula"><sub>II</sub></span> source zones. Accordingly, DOC quality
in stream water sampled under five event flow conditions (<span class="inline-formula"><i>n</i>=73</span>) was
closely reflecting the DOC<span class="inline-formula"><sub>I</sub></span> quality. Our results suggest
that DOC export by surface runoff along dynamically evolving surface
flow networks can play a dominant role for DOC exports from RZs with
overall low topographic relief and should consequently be considered
in catchment-scale DOC export models. We propose that proxies of
spatial heterogeneity such as the TWI<span class="inline-formula"><sub>HR</sub></span> can help to
delineate the most active source zones and provide a mechanistic basis
for improved model conceptualization of DOC exports.</p> |
|---|