无水分胁迫下行作物蒸发散与双涌源能量分配和交换关系

以内蒙古浑善达克沙地人工草地种植的行作物——青贮玉米为研究对象，将FAO-56的双作物系数法与双涌源能量平衡模型相结合，计算了太阳入射能量按叶面积指数（LAI）分配到两个涌源（冠层、土壤表面）的有效能量A_c和A_s、潜热通量λE_c和λE_s以及显热通量H_c和H_s.分析两个涌源在有效能量驱使下的潜热和显热通量相互作用.结果表明，1）在无水分胁迫条件下，冠层H_c与λE_c相互作用使冠层吸收微热平流，强化蒸腾作用，加大蒸腾量.蒸腾（以潜热通量表示）超过冠层有效能量的增量(λE_cⁱ-A_cⁱ).最大值出现在生长发育阶段LAI为0.6的7月15日到LAI为2.4 的8月9日之间，其平均值为4.32 MJ·m^-2·d^-1.2）无水分胁迫情况下，λE_s和H_s相互作用，除强湿润过程后的1~2 d外，其他各天土壤均以低于土壤表面有效能量的速率蒸发.蒸发强度取决于土壤表面有效能量消散为土壤潜热通量的百分比，这个百分比最小值出现在生长中期阶段，其平均值为11.5%；最大值出现在生长初始阶段，其平均值为51.9%.3）两个涌源潜热通量是蒸散过程中能量交换的主要成分，在生长发育、中期、后期阶段转换为两个涌源潜热通量的有效能量均占总能量的83%以上.

Relationships between row crop evapotranspiration and two sources-energy partition and exchange under non-water stress condition

With the maize harvested for green fodder and grown at the Hunshandake sand area as test row crop,and by combining two sources- energy balance model with dual crop coefficient approach presented in FAO-56,this paper estimated the available energy partitioned into two sources, canopy and soil surface (Ac and As), and the latent and sensible heat fluxes, lambdaEc, lambdaEs, Hc and Hs. The results showed that under non-water stress condition, the interaction between Hc and lambdaEc made canopy absorbed a micro-advection to enhance transpiration expressed by latent heat flux,with the value of (lambdaE(i)c-A(i)c). The greatest enhancement of transpiration occurred at the crop development stage with leaf area index between 0.6 and 2.4, and the average of the enhancement was 4.32 MJ x m(-2) x d(-1). Soil evaporation was in progress with a rate below the available energy of soil, due to the interaction between Hc and lambdaEc under non-water stress condition, except a few days immediately after heavy rain. The evaporation rate depended on the percentage of soil available energy dissipated as latent heat flux. The average value of minimum percentage, 11.5%, occurred at mid-season stage,while that of maximum percentages,51.9%, occurred at initial stage. Latent heat fluxes were the important components of energy exchange during the process of evapotranspiration. The available energy dissipated as latent heat fluxes of the two sources during crop development, mid-season, and late season stages accounted for over 83% of the total energy.