Hydro-ecological controls on dissolved carbon dynamics in groundwater and export to streams in a temperate pine forest
We studied the export of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) from forested shallow groundwater to first-order streams, based on groundwater and surface water sampling and hydrological data. The selected watershed was particularly convenient for such study, with a...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2018-02-01
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| Series: | Biogeosciences |
| Online Access: | https://www.biogeosciences.net/15/669/2018/bg-15-669-2018.pdf |
| _version_ | 1819025364199931904 |
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| author | L. Deirmendjian D. Loustau L. Augusto S. Lafont C. Chipeaux D. Poirier G. Abril G. Abril G. Abril |
| author_facet | L. Deirmendjian D. Loustau L. Augusto S. Lafont C. Chipeaux D. Poirier G. Abril G. Abril G. Abril |
| author_sort | L. Deirmendjian |
| collection | DOAJ |
| description | We studied the export of dissolved inorganic carbon (DIC) and dissolved
organic carbon (DOC) from forested shallow groundwater to first-order
streams, based on groundwater and surface water sampling and hydrological
data. The selected watershed was particularly convenient for such study, with
a very low slope, with pine forest growing on sandy permeable podzol and with
hydrology occurring exclusively through drainage of shallow groundwater (no
surface runoff). A forest plot was instrumented for continuous eddy
covariance measurements of precipitation, evapotranspiration, and net
ecosystem exchanges of sensible and latent heat fluxes as well as CO<sub>2</sub>
fluxes. Shallow groundwater was sampled with three piezometers located in
different plots, and surface waters were sampled in six first-order streams;
river discharge and drainage were modeled based on four gauging stations. On
a monthly basis and on the plot scale, we found a good consistency between
precipitation on the one hand and the sum of evapotranspiration, shallow
groundwater storage and drainage on the other hand. DOC and DIC stocks in
groundwater and exports to first-order streams varied drastically during the
hydrological cycle, in relation with water table depth and amplitude. In the
groundwater, DOC concentrations were maximal in winter when the water table
reached the superficial organic-rich layer of the soil. In contrast, DIC (in
majority excess CO<sub>2</sub>) in groundwater showed maximum concentrations at low
water table during late summer, concomitant with heterotrophic conditions of
the forest plot. Our data also suggest that a large part of the DOC mobilized
at high water table was mineralized to DIC during the following months within
the groundwater itself. In first-order streams, DOC and DIC followed an
opposed seasonal trend similar to groundwater but with lower concentrations.
On an annual basis, leaching of carbon to streams occurred as DIC and DOC in
similar proportion, but DOC export occurred in majority during short periods
of the highest water table, whereas DIC export was more constant throughout
the year. Leaching of forest carbon to first-order streams represented a
small portion (approximately 2 %) of the net land CO<sub>2</sub> sink at the
plot. In addition, approximately 75 % of the DIC exported from
groundwater was not found in streams, as it returned very fast to the
atmosphere through CO<sub>2</sub> degassing. |
| first_indexed | 2024-12-21T05:09:30Z |
| format | Article |
| id | doaj.art-12e2edaf5d0147089aa8dbd4b4704fbb |
| institution | Directory Open Access Journal |
| issn | 1726-4170 1726-4189 |
| language | English |
| last_indexed | 2024-12-21T05:09:30Z |
| publishDate | 2018-02-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Biogeosciences |
| spelling | doaj.art-12e2edaf5d0147089aa8dbd4b4704fbb2022-12-21T19:15:05ZengCopernicus PublicationsBiogeosciences1726-41701726-41892018-02-011566969110.5194/bg-15-669-2018Hydro-ecological controls on dissolved carbon dynamics in groundwater and export to streams in a temperate pine forestL. Deirmendjian0D. Loustau1L. Augusto2S. Lafont3C. Chipeaux4D. Poirier5G. Abril6G. Abril7G. Abril8Laboratoire Environnements et Paléoenvironnements Océaniques et Continentaux (EPOC), CNRS, Université de Bordeaux, Allée Geoffroy Saint-Hilaire, 33615 Pessac CEDEX, FranceINRA, UMR 1391 Interactions Sol-Plante-Atmosphère (ISPA), 33140 Villenave-d'Ornon, FranceINRA, UMR 1391 Interactions Sol-Plante-Atmosphère (ISPA), 33140 Villenave-d'Ornon, FranceINRA, UMR 1391 Interactions Sol-Plante-Atmosphère (ISPA), 33140 Villenave-d'Ornon, FranceINRA, UMR 1391 Interactions Sol-Plante-Atmosphère (ISPA), 33140 Villenave-d'Ornon, FranceLaboratoire Environnements et Paléoenvironnements Océaniques et Continentaux (EPOC), CNRS, Université de Bordeaux, Allée Geoffroy Saint-Hilaire, 33615 Pessac CEDEX, FranceLaboratoire Environnements et Paléoenvironnements Océaniques et Continentaux (EPOC), CNRS, Université de Bordeaux, Allée Geoffroy Saint-Hilaire, 33615 Pessac CEDEX, FranceDepartamento de Geoquímica, Universidade Federal Fluminense, Outeiro São João Batista s/n, 24020015, Niterói, RJ, Brazilalso at: Laboratoire d'Océanographie et du Climat, Expérimentations et Approches Numériques (LOCEAN), Centre IRD France-Nord, 32, Avenue Henri Varagnat, 93143 Bondy, FranceWe studied the export of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) from forested shallow groundwater to first-order streams, based on groundwater and surface water sampling and hydrological data. The selected watershed was particularly convenient for such study, with a very low slope, with pine forest growing on sandy permeable podzol and with hydrology occurring exclusively through drainage of shallow groundwater (no surface runoff). A forest plot was instrumented for continuous eddy covariance measurements of precipitation, evapotranspiration, and net ecosystem exchanges of sensible and latent heat fluxes as well as CO<sub>2</sub> fluxes. Shallow groundwater was sampled with three piezometers located in different plots, and surface waters were sampled in six first-order streams; river discharge and drainage were modeled based on four gauging stations. On a monthly basis and on the plot scale, we found a good consistency between precipitation on the one hand and the sum of evapotranspiration, shallow groundwater storage and drainage on the other hand. DOC and DIC stocks in groundwater and exports to first-order streams varied drastically during the hydrological cycle, in relation with water table depth and amplitude. In the groundwater, DOC concentrations were maximal in winter when the water table reached the superficial organic-rich layer of the soil. In contrast, DIC (in majority excess CO<sub>2</sub>) in groundwater showed maximum concentrations at low water table during late summer, concomitant with heterotrophic conditions of the forest plot. Our data also suggest that a large part of the DOC mobilized at high water table was mineralized to DIC during the following months within the groundwater itself. In first-order streams, DOC and DIC followed an opposed seasonal trend similar to groundwater but with lower concentrations. On an annual basis, leaching of carbon to streams occurred as DIC and DOC in similar proportion, but DOC export occurred in majority during short periods of the highest water table, whereas DIC export was more constant throughout the year. Leaching of forest carbon to first-order streams represented a small portion (approximately 2 %) of the net land CO<sub>2</sub> sink at the plot. In addition, approximately 75 % of the DIC exported from groundwater was not found in streams, as it returned very fast to the atmosphere through CO<sub>2</sub> degassing.https://www.biogeosciences.net/15/669/2018/bg-15-669-2018.pdf |
| spellingShingle | L. Deirmendjian D. Loustau L. Augusto S. Lafont C. Chipeaux D. Poirier G. Abril G. Abril G. Abril Hydro-ecological controls on dissolved carbon dynamics in groundwater and export to streams in a temperate pine forest Biogeosciences |
| title | Hydro-ecological controls on dissolved carbon dynamics in groundwater and export to streams in a temperate pine forest |
| title_full | Hydro-ecological controls on dissolved carbon dynamics in groundwater and export to streams in a temperate pine forest |
| title_fullStr | Hydro-ecological controls on dissolved carbon dynamics in groundwater and export to streams in a temperate pine forest |
| title_full_unstemmed | Hydro-ecological controls on dissolved carbon dynamics in groundwater and export to streams in a temperate pine forest |
| title_short | Hydro-ecological controls on dissolved carbon dynamics in groundwater and export to streams in a temperate pine forest |
| title_sort | hydro ecological controls on dissolved carbon dynamics in groundwater and export to streams in a temperate pine forest |
| url | https://www.biogeosciences.net/15/669/2018/bg-15-669-2018.pdf |
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