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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2019-494
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-494
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 02 Jan 2020

Submitted as: research article | 02 Jan 2020

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This discussion paper is a preprint. It is a manuscript under review for the journal Biogeosciences (BG).

Decadal variation of CO2 flux and its budget in a wheat and maize rotation cropland over the North China Plain

Quan Zhang1,2, Huimin Lei2, Dawen Yang2, Lihua Xiong1, and Pan Liu1 Quan Zhang et al.
  • 1State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan, China
  • 2State Key Laboratory of Hydroscience and Engineering, Department of Hydraulic Engineering, Tsinghua University, Beijing, China

Abstract. Carbon sequestration in agro-ecosystems has great potentials to mitigate global greenhouse gas emissions. To assess the CO2 sequestration and the decadal trend of an irrigated wheat-maize rotation cropland, the net ecosystem exchange (NEE) with the atmosphere was measured by using an eddy covariance system from 2005 through 2016 over the North China Plain. To evaluate the detailed CO2 budget components of this typical cropland, a comprehensive experiment was conducted in the full 2010–2011 wheat-maize rotation cycle by combining the eddy covariance NEE measurements, a soil respiration experiment that differentiated between heterotrophic and below-ground autotrophic respirations, plant carbon storage samplings and soil organic carbon measurements. Over the past decade from 2005 through 2016, the average of total NEE, Gross Primary Productivity (GPP), Ecosystem Respiration (ER) for wheat were −363.6 (± SD 97.8) gC m−2, 1173.9 (± 189.1) gC m−2 and 810.0 (± 161.0) gC m−2, and were −135.8 (± 168.2) gC m−2, 1007.6 (± 296.5) gC m−2, and 871.8 (± 283.5) gC m−2 for maize. The multiple regression revealed that, air temperature was the dominant factor of CO2 fluxes for wheat; but in the maize season, incoming short-wave radiation and groundwater table were the dominant factors. For the full 2010–2011 cultural cycle, the CO2 fluxes for wheat and maize were as follows: NEE −437.9 and −238.8 gC m−2, GPP 1078.2 and 779.7 gC m−2, ER 640.4 and 540.8 gC m−2, soil heterotrophic respiration 376.8 and 292.2 gC m−2, below-ground autotrophic respiration 135.5 and 115.4 gC m−2, above-ground autotrophic respiration 128.0 and 133.2 gC m−2. The net biome productivity was 58.8 (± SD 45.8) gC m−2 for wheat and 3.9 (± 42.9) gC m−2 for maize, indicating that wheat was a weak CO2 sink and maize was close to CO2 neutral to the atmosphere for this cultural cycle. However, when considering the total CO2 loss in the fallow period, the net biome productivity was −41.2 (± 3.1) gC m−2 yr−1 for the full 2010–2011 cycle, implying that the cropland was a weak CO2 source in this period. The detailed investigation of the CO2 budget components of this study provides valuable knowledge for sustainable cropland management in the context of climate change.

Quan Zhang et al.
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Quan Zhang et al.
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Short summary
Research on climate change has been popular over the past decades. The greenhouse gas emission is found to be responsible for climate change. Among all the ecosystems, cropland is the main food source of the mankind, its carbon cycle and contribution to the global carbon balance interest us. Our evaluation of the typical wheat/maize rotation cropland over the North China Plain shows it is a net CO2 emission to the atmosphere, and the emission will continue to rise in the future.
Research on climate change has been popular over the past decades. The greenhouse gas emission...
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