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Ma H.,Tsinghua University | Yang D.,Tsinghua University | Lei H.,Tsinghua University | Cai J.,Management Office of the Weishan Irrigation District | Tetsuya K.,University of Kitakyushu
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2011

Water cycle during 2006-2009 in a typical agricultural field of the Weishan irrigation district, which is located along the downstream of Yellow River in the North China Plain, was analyzed using the Hydrus-1D model. The equation for calculating the bulk surface resistance was modified according to the observed data. The simulated ET was compared with the observed ET by the eddy covariance system, and the result showed that simulation using modified resistance equation provided much better results than that of the original model. ET analysis showed that, for areas covered with seasonal vegetation, LAI determined the seasonal variation of ET, while weather condition determined ET variation at a much smaller time scale (e.g., one week). Comparing the simulated soil water content with the observed data by TDR, showed that the model could simulate soil water appropriately. Water balance analysis showed that about 80% of the rainfall and irrigation were consumed by ET, and drainage from the field mainly occurred during rainy season.

Lei H.M.,Tsinghua University | Yang D.W.,Tsinghua University | Cai J.F.,Management Office of the Weishan Irrigation District | Wang F.J.,Binzhou Bureau of Meteorology
Science China Earth Sciences | Year: 2013

The irrigated areas in the northern region of China are important food production areas. Therefore, studies on the variability of the carbon balance in these agro-ecosystems are fundamental for the management of carbon sequestration. This paper simulated the long-term variability of the carbon balance in a typical irrigated area along the lower Yellow River from 1984 to 2006, using a process-based ecosystem model called the Simple Biosphere Model, version 2. The mean annual gross primary production (GPP), mean annual net assimilation rate (NAR), mean annual soil respiration (Rs), and mean annual net ecosystem exchange (NEE) were 1733, 1642, 1304, and -338 g C m-2 a-1, respectively. A significant increasing trend in the seasonal total NAR during the wheat growing season, and a significant decreasing trend in the seasonal total NAR during the maize growing season were detected. However, no significant trend was found in the annual NAR, Rs, and NEE. The average carbon sequestration was 1. 93 Tg C a-1 when the grain harvest was not taken into account, and the carbon sequestration amount during the maize season was higher than that during the wheat season. However, the agro-ecosystem was a weak carbon source with a value of 0. 23 Tg C a-1, when the carbon in the grain was assumed emitted into the atmosphere. © 2012 Science China Press and Springer-Verlag Berlin Heidelberg.

Zhang Q.,Tsinghua University | Yang D.,Tsinghua University | Lei H.,Tsinghua University | Bo H.,Management Office of the Weishan Irrigation District | Cai J.,Management Office of the Weishan Irrigation District
Qinghua Daxue Xuebao/Journal of Tsinghua University | Year: 2015

Soil respiration in a typical wheat cropland was measured from April to June, 2011 to understand the diel variations of the total soil respiration, heterotrophic respiration, autotrophic respiration, and their corresponding controlling factors in wheat croplands in the North China Plain. The root exclusion method was used to measure total soil respiration, heterotrophic respiration and autotrophic respiration. The results showed that the total soil respiration and the heterotrophic respiration both had single peaks at around 14:00, while the autotrophic respiration did not have apparent diel characteristics. The ratio of autotrophic respiration to the total soil respiration varied little throughout the day but varied some during different growth stages. The heterotrophic respiration was more closely related to the air temperature than to the soil temperature. In addition, the heterotrophic respiration was negatively correlated to the relative humidity. The autotrophic respiration was dependent on the gross primary production with a time lag. In summary, the diel variations of soil respiration in a field were mainly dependent on the air temperature, relative humidity and photosynthesis rate. ©, 2015, Press of Tsinghua University. All right reserved.

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