中国北方城市草坪蒸散特征及影响因素研究——以河北张家口市某早熟禾草坪为例

Characteristics and Drivers of Turf Evapotranspiration in Northern China:A Case Study of Turf(Poa pratensis)in Zhangjiakou City,Hebei Province

中国北方城市不合理的草坪灌溉以及草坪扩张导致的地表水分大量蒸散,不仅加剧了北方干旱区水资源短缺,也严重制约了水资源可持续发展以及节水城市的建设。以中国北方干旱区河北省张家口市典型早熟禾草坪为研究对象,通过蒸渗仪实测和基于气象和土壤水分要素构建的主成分回归模型,明确了月、日、时不同时间尺度上的草坪蒸散规律及关键影响因子。结果表明:(1)草坪蒸散呈现"夏季高、冬季低"的季节性特征,最高/最低出现在6/2月份,平均值为5.27/0.29 mm/d;(2)典型日逐小时草坪蒸散呈现"早晚低、中午高"的单峰型变化,蒸散变化受日照时长和气温影响最大;(3)10 cm和20 cm深度的土壤水分消耗动态与草坪蒸散变化高度同步;(4)蒸散与影响因子建立主成分回归模型拟合程度较好,R^(2)=0.70(p<0.01),与蒸散相关性大的影响因素依次为:光合有效辐射>气温>10 cm土壤含水率>空气湿度>风速>20 cm土壤含水率>30 cm土壤含水率。研究结果解析了城市草坪蒸散耗水规律,对城市节水灌溉提供了科学依据。

Turf evapotranspiration,resulting from turf expansion and excessive irrigation,is the primary aspect with respect to the consumption of urban water resources in northern China.Moreover,water shortage has become a threat to local economic development and ecological security.Understanding the mechanism of turf evapotranspiration contributes to sustainable utilization of urban water resources and establishment of water-saving society.Taking the typical turf(Poa Pratensis)in Zhangjiakou City of Hebei Province as the study object,the dynamic variations of turf evapotranspiration and impacting factors were analyzed at month-,day-and hour-scale based on the data from weighing lysimeter and principal component analysis.The results indicated that:(1)Turf evapotranspiration showed the highest(lowest)value in summer(winter)during the year,with the average peak value 5.27(0.29)mm/d in June(February).(2)The hourly evapotranspiration changes in a typical day exhibited a single-peak state,where low evapotranspiration occurred in the morning and evening but high evapotranspiration occurred in the noon at a day-scale.Specifically,turf evapotranspiration was significantly affected by solar radiation and air temperature.(3)At the depths of 10 cm and 20 cm,the dynamics of turf evapotranspiration were highly consistent with that of soil moisture.(4)Established principal component regression model greatly simulated(R^(2)=0.70,p<0.01)the relationship between turf evapotranspiration and affecting factors,and the degrees of correlation were as follows:photosynthetic effective radiation>air temperature>soil water content at 10 cm>air humidity>wind speed>soil water content at 20 cm>soil water content 30 cm.This study revealed the change in turf evapotranspiration,and provided a scientific basis for the establishment of urban water-saving society in Zhangjiakou City.