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| DOI：10.13522/j.cnki.ggps.20180674 |
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| The Effect of water level fluctuation in yellow river on CO2 emission from an adjacent wetland is modulated by soil temperature |
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LYU Haibo
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1.College of Environment and life science, Weinan Normal University, Weinan 714000, China; 2. Weinan Normal University,Key Laboratory for Eco-Environment of Multi-river Wetlands in Shaanxi Province, Weinan 714000，China
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| Abstract: |
| 【Objective】 Change in groundwater and soil moisture alters soil redox thereby shifting microbial activity and affecting soil emission. The objective of this paper is to experimentally elucidate how water level fluctuation in river could affect CO2 emission from adjacent wetland.【Method】The study area was a wetland with reed (Phragmites australis Trin. ex Steud) adjacent the Longmen-Tongguan section of the Yellow River. We did field survey on CO2 emission from the wetland and conducted water-injecting monitoring experiments to measure CO2 emission at different water level fluctuation patterns. 【Results】 The impact of water level fluctuation in the river on CO2 emission was modulated by soil temperature. When soil temperature was in 13~23℃, with the water level in the river rising, CO2 emission from the soil increased first followed by a fall with the maximum reaching when the water level was 0 cm. In contrast, when soil temperature rose to 24~30 ℃ or higher than 30 ℃, CO2 emission from the soil decreased as the water level in the river was rising. Regression analysis found that R2 of the regression varied with soil temperature, and the results from both half water injection (Lh, injected to -30 cm water level) and full water injection (Lf, injected to 0 cm water level) suggested that CO2 emission decreased sharply, followed by a fluctuation which lagged behind the water level fluctuation, before oscillated under the same frequency as the water-level in the river. Calculation from all data revealed that the average emission in daytime and night was 3.05 and 2.74 μmol/(m2?s) respectively. In the seven days of experiment, the total CO2 emission rate were 2.47, 1.22, 1.39 mol ·m-2 for the control (undisturbed soil sample), Lh and Lf, respectively.【Conclusion】The influence of water level fluctuation in the Yellow River on CO2 emission from an adjacent wetland was impacted by soil temperature and diurnal temperature. In most cases, a rise in water level led to a decrease in CO2 emission, and CO2 emission in daytime was higher than that in night. The impact of one water level fluctuation in the river on CO2 emission could last for more than a week. |
| Key words: water level fluctuation; soil respiration; reed wetland; Yellow River |
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