北京是世界上最缺水的城市之一,为了改善北京的生态环境,北京已建立起庞大的城市绿地系统,至2010年底,绿地总面积已达62 672 hm2.园林植物在发挥生态、景观等多种有益效能的同时,自身生长需要大量水资源.北京2005年绿地灌溉用水量约为1.9亿m3,占当年北京城市总用水量的5.5％(程维新等,2002).在北京的园林绿地中,草坪占相当大的比例,据北京市园林绿化局提供的资料,截止2010年底,北京建成区草坪总面积达9 694.9hm2,其中以草地早熟禾(Poa pratensis)和高羊茅(Festuca arundinacea)为主,占草坪总面积的73％.%The evapotranspiration characteristics of the common lawn species of Poa pratensis and Festuca arundinacea in Beijing was investigated by the weighing method of Microlysimeter. The result revealed that the daily evapotranspiration of the lawn was high at noon and low in morning and evening, and the change pattern had appropriate ecology synchronism with solar radiation and other environmental factors. Daily mean evapotranspiration of P. Pratensis, under full sunlight and half shade was 5.78 kg · m-2 and 3.86 kg · m-2 respectively. While the daily average of F. Arundinacea, under full sunlight, half shade and all shade, was 4.41 kg · m-2, 3.03 kg · m-2 and 2.63 kg · m-2 respectively. According to physical and physiological characteristics of the grass after withdrawing water, soil moisture content of the lawn could be divided into three grades, sufficient water supply (water potential -0. 18 ~ -0.06 Mpa) , slight water deficit ( water potential - 0. 44 ~ - 0. 18 Mpa) and medium water deficit( water potential - 1. 06 ~ - 0. 44 Mpa) . Reduction of sunlight and soil moisture content could reduce evapotranspiration consumption of the lawn. Compared with full sunlight and sufficient water supply, and slight water deficit could reduce evapotranspiration of P. Pratensis and F. Arundinacea by 62. 0% and 47. 0% respectively. Evapotranspiration of F. Arundinacea in half shade and medium water deficit could reduce 76. 0% . Control of water supply and sunlight for the lawn could reduce consumption of water and save irrigation water.
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