基于双作物系数的旱作玉米田蒸散估算与验证

摘要

农田蒸散(ET)准确估算与区分对理解土壤-植物-大气连续系统水分传输动力学过程和调控机制具有重要意义.本研究基于FAO-56 Penman-Monteith(PM)模型计算参考作物蒸散量(ET0),运用双作物系数法计算黄土高原东部地区旱作玉米田2011-2012年蒸散(ETFAO),以同期涡度相关系统实测值(ETEC)作为标准值对双作物系数法计算结果进行评价,并将玉米田ET区分为土壤蒸发和作物蒸腾.结果表明:2011年春玉米生长季ET0、ETEC和ETFAO分别为628、400.3和492.7mm,双作物系数法RMSE、AAE和R2分别为0.864mm·d-1、0.678mm·d-1和0.755,且R2达极显著水平(P<0.01);2012年三者分别为553、372.6和441.4mm,RMSE、AAE和R2分别为0.676mm·d-1、0.693mm·d-1和0.781,R2亦达极显著水平(P<0.01),说明双作物系数法在该地区模拟旱作春玉米ET有较高的精度.基于双作物系数法对ET进行区分表明,2011年全生育期土壤蒸发和作物蒸腾分别占ET的36.4%和63.6%;2012年分别占ET的31.7%和68.3%,说明旱作春玉米田ET主要来自春玉米蒸腾.%Evapotranspiration (ET) is the only term which appears in both land surface energy balance equation and water balance equation, accurate estimation of ET is challenging but of impotance for assessing biomass production, allocation of water resources, and improving crop water ues efficiency in rainfed agricultural ecosystem. This paper invested the applicability of FAO dual crop coefficient approach in estimating ET and its components (plant transpiration and soil evaporation) of rainfed maize in semi-arid region of the Loess Plateau. Continuous measurements of ET with eddy covariance system in 2011 and 2012 were used to validate the performances of FAO dual crop coefficient approach. The results indicated that reference evapotranspiration were 628mm in 2011 and 553mm in 2012. The FAO dual crop coefficient approach was acceptable in estimating ET compared to eddy covariance measurements, with RMSE, AAE and R2 of 0.864mm·d-1, 0.678mm·d-1 and 0.755 (P<0.01) in 2011, 0.676mm·d-1, 0.693mm·d-1and 0.781 (P<0.01) in 2012, and the measured and estimated ET values were 400.3 and 492.7mm in 2011, 372.6 and 441.4mm in 2012, which confirmed the good performances of FAO dual crop coefficient for estimating ET. Soil evaporation and maize transpiration accounted for 36.4% and 63.6% of total ET in 2011, 31.7% and 68.3% in 2012, respectively, indicating that maize transpiration was the main component of ET.