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在中国科学院禹城综合试验站,采用涡度相关技术对夏玉米生长期间净辐射(Rn)、水汽通量(LE)、感热通量(Hs)和土壤热通量(G)进行了观测,并应用农田生态系统模型RZ-SHAW对水热过程和作物水分利用效率进行了模拟和分析.结果表明,夏玉米水汽通量具有明显的日变化与季节变化,Rn大部分用于玉米潜热的消耗,水汽通量与净辐射的比值(LE/Rn)随生长阶段呈上升趋势,在灌浆期达最大,约60%左右,但比用RZ-SHAW模型模拟的结果略低;RZ-SHAW模型模拟得到的夏玉米日蒸散量与实测值的变化比较符合;逐时水汽通量与相应时段内涡度相关实测值一致性指数(IA)均在0.75以上,均方差(RMSE)在1.0W·m?2以下.LE日变化呈倒“V”型,Hs呈倒“U”型并偏向午前,二者出现峰值的时间不同,Hs出现在11︰30左右,LE出现在13︰00左右,比Hs推迟一小时左右.CO2通量日变化呈不对称“V”型,峰值出现时间在11︰30左右.夏玉米4个生育期的群体水分利用效率(Fc+Rs)/LE在日出以后,随着光强的增强,水分利用效率迅速升高,至10时左右达到最大后开始下降,其最大水分利用效率为24.3g·kg?1,平均水分利用效率为10.3g·kg?1.
The net radiation (Rn), water vapor flux (LE), sensible heat flux (Hs) and soil heat flux (G) during the growth of summer maize were observed using the eddy covariance technique at Yucheng Integrated Experiment Station, Chinese Academy of Sciences , And the farmland ecosystem model RZ-SHAW was used to simulate and analyze the hydrothermal process and crop water use efficiency.The results showed that the moisture flux of summer maize had obvious diurnal and seasonal variations, and most of Rn was used for latent heat of corn The ratio of water consumption flux to net radiation (LE / Rn) increased with the growth stage and reached the maximum about 60% during the grain filling stage, but slightly lower than that obtained with the RZ-SHAW model. The RZ-SHAW model The simulated daily evapotranspiration of summer maize was in good agreement with the measured values. The coincidence index of the measured hourly water vapor flux and the eddy covariance within the corresponding time period was above 0.75, and the mean square error (RMSE) was 1.0W · m 2 or less, the change of daily diurnal variation was “V”, Hs was inverted “U” and tended to be noon, and the peak time was different between the two. Hs appeared at about 11︰30, LE appeared at about 13︰00, Hs delayed about an hour or so .CO2 flux changes were asymmetric “V” type, the peak appeared in the 11:30 Right After the sunrise, the water use efficiency (Fc + Rs) / LE of four maize growing stages increased rapidly with the increase of light intensity, and reached its peak at 10 o’clock and then began to decline. The maximum water use efficiency was 24.3 g · kg -1 and the average water use efficiency was 10.3 g · kg -1.