Low hydrological connectivity after summer drought inhibits DOC export in a forested headwater catchment
<p>Understanding the controls on event-driven dissolved organic carbon (DOC) export is crucial as DOC is an important link between the terrestrial and the aquatic carbon cycles. We hypothesized that topography is a key driver of DOC export in headwater catchments because it influences hydrolog...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2021-09-01
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| Series: | Hydrology and Earth System Sciences |
| Online Access: | https://hess.copernicus.org/articles/25/5133/2021/hess-25-5133-2021.pdf |
| _version_ | 1819239748877680640 |
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| author | K. Blaurock B. Beudert B. S. Gilfedder J. H. Fleckenstein J. H. Fleckenstein S. Peiffer L. Hopp |
| author_facet | K. Blaurock B. Beudert B. S. Gilfedder J. H. Fleckenstein J. H. Fleckenstein S. Peiffer L. Hopp |
| author_sort | K. Blaurock |
| collection | DOAJ |
| description | <p>Understanding the controls on event-driven dissolved organic carbon (DOC) export is crucial as DOC is an important link between the terrestrial and the aquatic carbon cycles. We hypothesized that topography is a key driver of DOC export in headwater catchments because it influences hydrological connectivity, which can inhibit or facilitate DOC mobilization. To test this hypothesis, we studied the mechanisms controlling DOC mobilization and export in the Große Ohe catchment, a forested headwater in a mid-elevation mountainous region in southeastern Germany. Discharge and stream DOC concentrations were measured at an interval of 15 min using in situ UV-Vis (ultraviolet–visible) spectrometry from June 2018 until October 2020 at two topographically contrasting subcatchments of the same stream. At the upper location (888 m above sea level, a.s.l.), the stream drains steep hillslopes, whereas, at the lower location (771 m a.s.l.), it drains a larger area, including a flat and wide riparian zone. We focus on four events with contrasting antecedent wetness conditions and event size. During the events, in-stream DOC concentrations increased up to 19 mg L<span class="inline-formula"><sup>−1</sup></span> in comparison to 2–3 mg L<span class="inline-formula"><sup>−1</sup></span> during baseflow. The concentration–discharge relationships exhibited pronounced but almost exclusively counterclockwise hysteresis loops which were generally wider in the lower catchment than in the upper catchment due to a delayed DOC mobilization in the flat riparian zone. The riparian zone released considerable amounts of DOC, which led to a DOC load up to 7.4 kg h<span class="inline-formula"><sup>−1</sup></span>. The DOC load increased with the total catchment
wetness. We found a disproportionally high contribution to the total DOC
export of the upper catchment during events following a long dry period. We
attribute this to the low hydrological connectivity in the lower catchment
during drought, which inhibited DOC mobilization, especially at the
beginning of the events. Our data show that not only event size but also
antecedent wetness conditions strongly influence the hydrological
connectivity during events, leading to a varying contribution to DOC export
of subcatchments, depending on topography. As the frequency of prolonged
drought periods is predicted to increase, the relative contribution of
different subcatchments to DOC export may change in the future when
hydrological connectivity will be reduced more often.</p> |
| first_indexed | 2024-12-23T13:57:03Z |
| format | Article |
| id | doaj.art-b1c546fbe1e24103a4e7c1d6a0d32888 |
| institution | Directory Open Access Journal |
| issn | 1027-5606 1607-7938 |
| language | English |
| last_indexed | 2024-12-23T13:57:03Z |
| publishDate | 2021-09-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Hydrology and Earth System Sciences |
| spelling | doaj.art-b1c546fbe1e24103a4e7c1d6a0d328882022-12-21T17:44:25ZengCopernicus PublicationsHydrology and Earth System Sciences1027-56061607-79382021-09-01255133515110.5194/hess-25-5133-2021Low hydrological connectivity after summer drought inhibits DOC export in a forested headwater catchmentK. Blaurock0B. Beudert1B. S. Gilfedder2J. H. Fleckenstein3J. H. Fleckenstein4S. Peiffer5L. Hopp6Department of Hydrology, Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth, Bayreuth 95447, GermanyDepartment of Nature Conservation and Research, Bavarian Forest National Park, Grafenau 94481, GermanyDepartment of Hydrology, Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth, Bayreuth 95447, GermanyDepartment of Hydrogeology, Helmholtz Centre for Environmental Research, Leipzig 04318, GermanyHydrological Modeling Unit, Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth, Bayreuth 95447, GermanyDepartment of Hydrology, Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth, Bayreuth 95447, GermanyDepartment of Hydrology, Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth, Bayreuth 95447, Germany<p>Understanding the controls on event-driven dissolved organic carbon (DOC) export is crucial as DOC is an important link between the terrestrial and the aquatic carbon cycles. We hypothesized that topography is a key driver of DOC export in headwater catchments because it influences hydrological connectivity, which can inhibit or facilitate DOC mobilization. To test this hypothesis, we studied the mechanisms controlling DOC mobilization and export in the Große Ohe catchment, a forested headwater in a mid-elevation mountainous region in southeastern Germany. Discharge and stream DOC concentrations were measured at an interval of 15 min using in situ UV-Vis (ultraviolet–visible) spectrometry from June 2018 until October 2020 at two topographically contrasting subcatchments of the same stream. At the upper location (888 m above sea level, a.s.l.), the stream drains steep hillslopes, whereas, at the lower location (771 m a.s.l.), it drains a larger area, including a flat and wide riparian zone. We focus on four events with contrasting antecedent wetness conditions and event size. During the events, in-stream DOC concentrations increased up to 19 mg L<span class="inline-formula"><sup>−1</sup></span> in comparison to 2–3 mg L<span class="inline-formula"><sup>−1</sup></span> during baseflow. The concentration–discharge relationships exhibited pronounced but almost exclusively counterclockwise hysteresis loops which were generally wider in the lower catchment than in the upper catchment due to a delayed DOC mobilization in the flat riparian zone. The riparian zone released considerable amounts of DOC, which led to a DOC load up to 7.4 kg h<span class="inline-formula"><sup>−1</sup></span>. The DOC load increased with the total catchment wetness. We found a disproportionally high contribution to the total DOC export of the upper catchment during events following a long dry period. We attribute this to the low hydrological connectivity in the lower catchment during drought, which inhibited DOC mobilization, especially at the beginning of the events. Our data show that not only event size but also antecedent wetness conditions strongly influence the hydrological connectivity during events, leading to a varying contribution to DOC export of subcatchments, depending on topography. As the frequency of prolonged drought periods is predicted to increase, the relative contribution of different subcatchments to DOC export may change in the future when hydrological connectivity will be reduced more often.</p>https://hess.copernicus.org/articles/25/5133/2021/hess-25-5133-2021.pdf |
| spellingShingle | K. Blaurock B. Beudert B. S. Gilfedder J. H. Fleckenstein J. H. Fleckenstein S. Peiffer L. Hopp Low hydrological connectivity after summer drought inhibits DOC export in a forested headwater catchment Hydrology and Earth System Sciences |
| title | Low hydrological connectivity after summer drought inhibits DOC export in a forested headwater catchment |
| title_full | Low hydrological connectivity after summer drought inhibits DOC export in a forested headwater catchment |
| title_fullStr | Low hydrological connectivity after summer drought inhibits DOC export in a forested headwater catchment |
| title_full_unstemmed | Low hydrological connectivity after summer drought inhibits DOC export in a forested headwater catchment |
| title_short | Low hydrological connectivity after summer drought inhibits DOC export in a forested headwater catchment |
| title_sort | low hydrological connectivity after summer drought inhibits doc export in a forested headwater catchment |
| url | https://hess.copernicus.org/articles/25/5133/2021/hess-25-5133-2021.pdf |
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