摘要
本文应用Microlysimeter现场原位测定土面蒸发,以此为上边界条件,运用土壤动力学原理,提出了一种新的模拟根系吸水速率S(z,t)的方法,该方法与所选取的平均时段δt密切相关,研究表明:在冬小麦蒸腾速率较弱的前期及较强的后期,分别选取δt=10d,5d模拟S(z,t)可以获得较好的结果,分析冬小麦根系吸水速率的模拟结果可知:冬小麦根系吸水在灌浆-乳熟期达最高峰;若近地表水分充足,则吸水高峰出现在土壤上部,否则根系下扎,吸水高峰随之下移.
Based on the theory of soil water dynamics and more practical and rational upper boundary condition of one dimensional vertical unsaturated flow,a new approach to modeling water uptake rates by roots S(z,t) is put forward in this paper by using the evaporation data from the soil surface measured in situ by Microlysimeter.The accuracy of the modeling result depends on the value of averaging time step δt,in the earlier growth stages of plants,δt can be set bigger than that in the later stages due to the fact of weaker transpiration.As for the winter wheat,the simulated soil moisture content profiles are in reasonable agreement with the measured if δt is selected as 10d in the earlier stages and 5d in the later growth periods respectively.The winter wheat's S(z,t)in the stages between jointing and harvest has been simulated with the application of the new proposed numerical model about water uptake by roots.The results have shown that:1,the maximum water uptake rate of the winter wheat appears in the stages between milking and milky maturity,2,the roots of the winter wheat grow towards the soil layer with abundant and easier to be absorbed water,namely,if water is sufficient near the soil surface,the water absorbing peak of roots will appear in the upper soil profile,otherwise,the roots will stretch deeper,and the peak move to the lower layer accordingly.
出处
《水利学报》
EI
CSCD
北大核心
1998年第6期69-76,共8页
Journal of Hydraulic Engineering
基金
国家自然科学基金"八五"重大项目
河北省科委"九五"重点科技攻关项目资助