不同冻融阶段灌水对土壤蒸发影响的模拟研究

Change in Evaporation from Soil as Affected by Irrigation at Different Freeze-thaw Stages

【目的】研究不同冻融阶段灌水对土壤蒸发的影响。【方法】冻融期进行了未灌水裸地L0和7个不同时间灌水处理(即L1(20041130)、L2(20041214)、L3(20041227)、L4(20050106)、L5(20050216)、L6(20050225)和L7(20050315),灌水1次,灌水量225 m3/hm2)的田间土壤水热监测,运用水热耦合模型(SHAW)模拟计算了土壤蒸发。【结果】冻融期灌水处理的土壤累积蒸发量比未灌水处理增加24.0%~150.0%,不稳定冻结阶段灌水促进土壤蒸发,与未灌水处理相比土壤累积蒸发量增加22.4%~27.0%;稳定冻结阶段灌水对土壤蒸发的影响较弱,L3处理和L4处理土壤累积蒸发量最少,较其他灌水处理低3.8%~67.1%;消融解冻阶段灌水处理L6处理的土壤蒸发量最高,较其他处理高55.3%~97.1%。【结论】不稳定冻结阶段和消融解冻阶段灌水后土壤蒸发能力较强,不利于水分在土壤中蓄存;稳定冻结阶段灌水后对3 d内的土壤蒸发影响较弱;冻融期灌水后土壤累积蒸发量约为灌水量的8.6%~9.3%。

【Background and Objective】Seasonal permafrost is widely distributed in north China and water evaporation from such soils depends on both soil water content and freeze-thawing process.In this paper,we experimentally studied the change in evaporation with irrigation at different stages of the freeze-thawing process.【Method】The experiment was conducted in a field;a bare plot without irrigation was taken as the control(CK).The treatments were to irrigate the 225 m 3 per hm 2 of water at different freeze-thaw stage s,which were represented by L1-L7.Evaporation from the soil in all treatments was simulated using t he heat-water model(SHAW).【Result】Irrigation during the freeze-thaw period increased the cumulative soil evaporation by 24.0%~150.0%,compared with the CK.Irrigation during the unstable freezing stage enhanced evaporation,and compared with CK,it increased the cumulative evaporation by 22.4%~27.0%.Irrigation during the stable freezing stage affected evaporation the least,especially L3 and L4 treatments,where the evaporation was 3.8%~67.1%lower than that in other treatments.Irrigation during the thawing period led to the highest cumulative evaporation,increasing by 55.3%~97.1%,compared with other treatments.【Conclusion】I rrigation during the unstable freezing and thawing stages increased evaporation greatly and should be avoided.In contrast,irrigation during the stable freezing stage affected evaporation the least in the first 3 days after the irrigation.Irrigation during the freeze-thaw period could result in 8.6%~9.3%of the irrigating water lost via evaporation.