辽河口芦苇湿地蒸散试验研究

Experimental study of evapotranspiration from Phragmites Australis wetland in Liaohe Estuary

在研究区用带有地下水补给的芦苇培养箱测量蒸散量,同时,采用PM-5型稳态气孔计测量了不同水深条件下芦苇的蒸腾速率,并与同一实验条件下的水面蒸发和裸地蒸发进行对照,分析了辽河口芦苇湿地区的蒸散耗水规律。研究结果表明:当控制水位在地表以上10 cm时,芦苇蒸腾速率曲线呈"单峰"型,而且芦苇的蒸腾作用在这种地表积水情况下随着栽培时间的延长受到抑制;当控制水位在-5 cm、-20 cm、-40 cm和-60 cm时,芦苇蒸腾速率变化曲线呈"双峰"型,并且出现明显的"午休"现象。芦苇群落的蒸散发比值有一个极小值埋深,在-20～-40 cm。地表积水时芦苇群落的蒸散量是自由水面蒸发量的2倍左右,水位在地表以下时芦苇群落蒸散量是裸地蒸发量的3.0～3.5倍。芦苇蒸散影响量与日均光合有效辐射、日均大气温度和日均相对湿度有很好的相关性。在以后的研究中,当无实测芦苇蒸散量数据时,可以通过建立芦苇蒸散影响量与气象因素的相关关系式,根据裸地蒸发量得到芦苇的蒸散量值。

To study the evapotranspiration regularity over the Phragmites Australis wetland,the field experiments were carried out in a test field of the Liaohe Estuary.The evaporation container with water supply was installed to measure the evapotranspiration from the Phragmites Australis wetland,and the transpiration was measured using A PM-5 porometer.Evaporations from water surface and bare soil are compared.The results shows that the water depth is 10 cm above the soil surface,the transpiration rate presents a single-peak curve pattern with the peak value occurring at around 14：00.While with the time progress,the transpiration rate decreases if Phragmites Australis is submerged in the water for a long time.When the water depth is below the soil surface,the transpiration rate will show a double peak pattern.The diurnal variation of transpiration exhibits a noon break phenomena at noon time（12：00） due to stoma closing.The water depth has a complicate influence on the ratio of evaporation and evapotranspiration.When the groundwater depth is about-20 to-40 cm,the ratio would be the smallest.The evapotranspiration is enhanced when the Phragmites Australis is planted in the wetland.The ratio of evapotranspiration from the open water surface with Phragmites Australis and evaporation of that without Phragmites Australis is about 2.When the water depth is below the soil surface,the ratio of evapotranspiration from the land with Phragmites Australis and from the bare soil will be in the range of 3 to 3.5.The daily evapotranspiration from the Phragmites Australis wetland varies significantly due to changing meteorological conditions.The Phragmites Australis evapotranspiration can be well correlated to climatic factors,such as the daily average of photosynthetic active radiation,the daily average air temperature and daily average relative humidity.The corresponding correlation equation can be established.The evapotranspiration from the Phragmites Australis wetland can be calculated using the equation when the observation is not available.