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| Seasonal variation in carbon exchange and its modulating factors of a double cropping rice ecosystem in Southern China |
| Received:August 29, 2017 |
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| KeyWord:eddy covariance;carbon exchange;double cropping rice ecosystem |
| Author Name | Affiliation | E-mail | | WEI Jia-bin | College of Agriculture, Hunan Agricultural University, Changsha 410128, China | | | XU Hua-qin | College of Agriculture, Hunan Agricultural University, Changsha 410128, China | xu7541@163.com | | ZHOU Ling-hong | College of Agriculture, Hunan Agricultural University, Changsha 410128, China | | | CHENG Xiao-lin | College of Agriculture, Hunan Agricultural University, Changsha 410128, China | | | TANG Xian-liang | College of Agriculture, Hunan Agricultural University, Changsha 410128, China | | | FU Zhi-qiang | College of Agriculture, Hunan Agricultural University, Changsha 410128, China | | | TANG Qi-yuan | College of Agriculture, Hunan Agricultural University, Changsha 410128, China | | | TANG Jian-wu | College of Agriculture, Hunan Agricultural University, Changsha 410128, China | |
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| Abstract: |
| In this study, the CO2 flux of a typical double cropping rice ecosystem was continuously monitored by the eddy covariance technique. The carbon exchange[Net ecosystem exchange(NEE), Gross primary productivity(GPP) and Ecosystem respiration(Reco)] in the double cropping rice ecosystem and its regulatory factors were analyzed. The results showed that the NEE of the double cropping rice ecosystem had clear diurnal and seasonal variations. The daily diurnal variation in NEE showed a significant U-shaped curve during the growing season, and the peak values were different for each month. The seasonal variation in NEE showed two uptake periods(when NEE was negative) and three emission periods(when NEE was positive). The NEE results showed two significant carbon uptake periods in the growing season of the early rice stage and the late rice stage. The average daily value for NEE in early rice was -0.58 g C·m-2, and the maximum appeared on June 20(-1.77 g C·m-2). The average value for NEE in late rice was -1.28 g C·m-2 and the maximum appeared on September 19(-2.23 g C·m-2). There were two carbon emission periods during the non-crop growing period in winter, where the mean value was 2.68 g C·m-2. The daytime NEE during rice cultivation was significantly affected by photosynthetically active radiation. The nighttime NEE was significantly affected by the soil temperature at 5 cm depth, and the temperature sensitivity at the winter fallow stage was higher than in the double cropping season when the temperature was higher. The total NEE for the whole year indicated that the double cropping rice ecosystem created carbon emissions that reached 778.4 g C·m-2, while GPP was 1 643.7 g C·m-2, and Reco was 2 425.8 g C·m-2. Therefore, the southern double-cropping rice ecosystem has a very significant potential for carbon sequestration and emission mitigation. |
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