极端干旱条件下柽柳种群蒸散量的日变化研究

Diurnal Variation of Evapotranspiration of Vegetation under Extreme Dry Condition —Taking Tamarix ramosissima in Ejina as an example

利用波文比能量平衡法对额济纳绿洲柽柳种群蒸散进行测定。结果表明,在晴朗无云的条件下,蒸散速率日变化呈单峰型。蒸散从早晨630以后出现,上午蒸散率上升过程缓慢,到中午达到峰值,随后蒸散速率迅速下降,到1600蒸散速率降到最小,夜间无蒸散,常出现负值,呈大气凝结过程。净辐射对蒸散起决定作用,蒸散速率的变化趋势与净辐射变化基本一致,其日变化具有相同的峰型。柽柳种群蒸散量随风速的增加而增加。土壤温度对柽柳种群蒸散速率的影响不大,但土壤温度的增加值的变化与蒸散速率的变化基本一致。土壤含水量的变化对蒸散速率产生影响,土壤含水量降低,蒸散速率减弱,土壤含水量增加,蒸散速率加快。相关分析表明,环境因子对蒸散速率影响的贡献依次为土壤温度的升高值>净辐射>风速>土壤含水量>空气温湿度。

This article makes use of the Bowen Ratio-equilibrium Energy Method to measure evapotranspiration of Tamarix ramosissima in Ejina oasis. The results showed that the diurnal variation of evapotranspiration rate were obvious and single-peak curve under the clear and cloudless term. Evapotranspiration begins at 6:30 in the morning and the rising rate of evapotranspiration is smooth in the morning, attains the peak by noon, later evapotranspiration rate quick decreases and to the least at 16:00. No evapotranspiration happens in evening, while the evapotranspiration rate often appears negative and has a coagulation process. The net radiation plays critical role in plant evapotranspiration. The trend of net radiation change is similar to evapotranspiration rate; the diurnal variation has the same peak type. Evapotranspiration of Tamarix ramosissima increases with the wind velocity. Soil temperature has minor influence on the evapotranspiration of Tamarix ramosissima, but variety of soil temperature has basic consistence with change of evapotranspiration rate. Evident relation existed between the variations and the soil moisture, the evapotranspiration went down while the soil moisture decreased, the evapotranspiration went up quickly when the soil moisture increased. The correlation analysis showed that the order of fitness degree between evapotranspiration rate and single environment factor was: variety of soil temperature>net radiation>wind speed>soil moisture>air temperature and humidity.