Effects of stream ecosystem metabolisms on CO2 emissions in two headwater catchments, Southeastern China

Headwater streams, as critical zones due to their proximity to terrestrial sources, emit large quantities of CO2 owing to their higher drainage density of catchments, substantial total areas, and stream lengths. Stream ecosystem metabolism (EM, i.e. photosynthesis and respiration) can significantly...

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Autores principales:	Chen Gong, Weijin Yan, Peipei Zhang, Qibiao Yu, Yanqian Li, Xinyan Li, Dongsheng Wang, Ruyuan Jiao
Formato:	article
Lenguaje:	EN
Publicado:	Elsevier 2021
Materias:	CO2 Ecosystem respiration Gross primary production Headwater streams In-stream DOC removal efficiency Uptake velocity Ecology QH540-549.5
Acceso en línea:	https://doaj.org/article/48bd6f94487941638306585629292a57
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spelling	oai:doaj.org-article:48bd6f94487941638306585629292a572021-12-01T04:59:36ZEffects of stream ecosystem metabolisms on CO2 emissions in two headwater catchments, Southeastern China1470-160X10.1016/j.ecolind.2021.108136https://doaj.org/article/48bd6f94487941638306585629292a572021-11-01T00:00:00Zhttp://www.sciencedirect.com/science/article/pii/S1470160X21008013https://doaj.org/toc/1470-160XHeadwater streams, as critical zones due to their proximity to terrestrial sources, emit large quantities of CO2 owing to their higher drainage density of catchments, substantial total areas, and stream lengths. Stream ecosystem metabolism (EM, i.e. photosynthesis and respiration) can significantly affect the in-stream carbon cycle. However, how stream CO2 emissions respond to ecosystem respiration (ER) is still not well known. Here we report in-situ daily observations of headwater stream gross primary production (GPP), ecosystem respiration (ER), isotopic composition of dissolved inorganic carbon (δ13CDIC) and CO2 emissions conducted in five streams in two headwater catchments of the Changjiang River in Southeastern China. The results show that δ13CDIC, pCO2, and CO2 emission rates have significant diel variations. Both the day and night δ13CDIC values were more depleted than the theoretical values in the two catchments, but the nocturnal depletion was greater. The headwater streams have high EM, with an average ER of −1.99 ± 0.82 g C m−2 d−1and GPP of 1.52 ± 0.84 g C m−2 d−1 in the two catchments. ER increases with DOC concentration but decreases with water discharge.The nocturnal pCO2 (3885 ± 2959 μatm) was significantly higher than in daytime (2525 ± 2221 μatm). The higher nocturnal CO2 emission rate (225 ± 165 mg C m−2h−1) was about 42 % higher than in daytime. DOC uptake velocity (Vf) was 0.46 ± 0.14 m d−1, and increased with lower water discharge and lower catchment-scale DOC yield. DOC loss rate (ζ) was 0.96 ± 1.25 d−1 and declined exponentially with higher water discharge and catchment-scale DOC yield. Moreover, the removal fraction of DOC via ER was about 0.32 ± 0.14, contributing to 31 ± 16 % of the CO2 flux in streams. The re-estimated annual CO2 flux was about 14.62 ± 4.99 Tg C yr−1 from the Changjiang headwater streams network. This study emphasizes the necessity of incorporating the effects of EM into the river network's CO2 emissions and the importance of the headwater streams to river carbon cycling.Chen GongWeijin YanPeipei ZhangQibiao YuYanqian LiXinyan LiDongsheng WangRuyuan JiaoElsevierarticleCO2Ecosystem respirationGross primary productionHeadwater streamsIn-stream DOC removal efficiencyUptake velocityEcologyQH540-549.5ENEcological Indicators, Vol 130, Iss , Pp 108136- (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	CO2 Ecosystem respiration Gross primary production Headwater streams In-stream DOC removal efficiency Uptake velocity Ecology QH540-549.5
spellingShingle	CO2 Ecosystem respiration Gross primary production Headwater streams In-stream DOC removal efficiency Uptake velocity Ecology QH540-549.5 Chen Gong Weijin Yan Peipei Zhang Qibiao Yu Yanqian Li Xinyan Li Dongsheng Wang Ruyuan Jiao Effects of stream ecosystem metabolisms on CO2 emissions in two headwater catchments, Southeastern China
description	Headwater streams, as critical zones due to their proximity to terrestrial sources, emit large quantities of CO2 owing to their higher drainage density of catchments, substantial total areas, and stream lengths. Stream ecosystem metabolism (EM, i.e. photosynthesis and respiration) can significantly affect the in-stream carbon cycle. However, how stream CO2 emissions respond to ecosystem respiration (ER) is still not well known. Here we report in-situ daily observations of headwater stream gross primary production (GPP), ecosystem respiration (ER), isotopic composition of dissolved inorganic carbon (δ13CDIC) and CO2 emissions conducted in five streams in two headwater catchments of the Changjiang River in Southeastern China. The results show that δ13CDIC, pCO2, and CO2 emission rates have significant diel variations. Both the day and night δ13CDIC values were more depleted than the theoretical values in the two catchments, but the nocturnal depletion was greater. The headwater streams have high EM, with an average ER of −1.99 ± 0.82 g C m−2 d−1and GPP of 1.52 ± 0.84 g C m−2 d−1 in the two catchments. ER increases with DOC concentration but decreases with water discharge.The nocturnal pCO2 (3885 ± 2959 μatm) was significantly higher than in daytime (2525 ± 2221 μatm). The higher nocturnal CO2 emission rate (225 ± 165 mg C m−2h−1) was about 42 % higher than in daytime. DOC uptake velocity (Vf) was 0.46 ± 0.14 m d−1, and increased with lower water discharge and lower catchment-scale DOC yield. DOC loss rate (ζ) was 0.96 ± 1.25 d−1 and declined exponentially with higher water discharge and catchment-scale DOC yield. Moreover, the removal fraction of DOC via ER was about 0.32 ± 0.14, contributing to 31 ± 16 % of the CO2 flux in streams. The re-estimated annual CO2 flux was about 14.62 ± 4.99 Tg C yr−1 from the Changjiang headwater streams network. This study emphasizes the necessity of incorporating the effects of EM into the river network's CO2 emissions and the importance of the headwater streams to river carbon cycling.
format	article
author	Chen Gong Weijin Yan Peipei Zhang Qibiao Yu Yanqian Li Xinyan Li Dongsheng Wang Ruyuan Jiao
author_facet	Chen Gong Weijin Yan Peipei Zhang Qibiao Yu Yanqian Li Xinyan Li Dongsheng Wang Ruyuan Jiao
author_sort	Chen Gong
title	Effects of stream ecosystem metabolisms on CO2 emissions in two headwater catchments, Southeastern China
title_short	Effects of stream ecosystem metabolisms on CO2 emissions in two headwater catchments, Southeastern China
title_full	Effects of stream ecosystem metabolisms on CO2 emissions in two headwater catchments, Southeastern China
title_fullStr	Effects of stream ecosystem metabolisms on CO2 emissions in two headwater catchments, Southeastern China
title_full_unstemmed	Effects of stream ecosystem metabolisms on CO2 emissions in two headwater catchments, Southeastern China
title_sort	effects of stream ecosystem metabolisms on co2 emissions in two headwater catchments, southeastern china
publisher	Elsevier
publishDate	2021
url	https://doaj.org/article/48bd6f94487941638306585629292a57
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Effects of stream ecosystem metabolisms on CO2 emissions in two headwater catchments, Southeastern China

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