胡杨(Populus euphratica)树干液流特征及其与环境因子的关系

以2012年4—10月实测数据,对黑河下游胡杨树干液流特征及其与环境因子的关系进行了分析。结果表明:在整个生长季,胡杨(Populus euphratica)树干液流速率日变化具有明显的昼夜节律性,夜间存在明显的树干液流以补充白天蒸腾损失的大量水分,恢复植物体内的水分平衡;与其他天气条件下树干液流速率特征比较,阴雨天液流启动时间推迟,液流停止时间提前,液流历时缩短,且峰值显著缩小;树干液流的季节变化特征表现为液流速率在夏季的启动时间、到达峰值的时间、液流停止时间均早于春季和秋季;单株蒸腾耗水表现出明显的季节性格局,4月和10月中下旬耗水量较低,5—8月为主要耗水期,占整个生长季的75%;日间液流速率主要受到土壤含水量、水汽压差、光合有效辐射、相对湿度和气温的影响,夜间液流速率主要受到水汽压差、相对湿度的影响,整个生长季胡杨树干液流主要受光合有效辐射、土壤水分、气温和相对湿度的影响。

Xylem Sap Flow of Populus euphratica in Relation to Environmental Factors in the Lower Reaches of Heihe River

Sap flow of Populus euphratica and its relationship with environmental factors were analyzed based on the experimental data of sap flow and environmental factors in the lower reaches of Heihe River from April to October, 2012. The results showed that, the diurnal change of sap flow velocity showed minor fluctuations during the growing season. At night, the ascent of sap flow could be observed in the above main tree species owning to the existence of root pressure. In different weather condition, the sap flow velocity of P. euphratica presented that in overcast and rainy day the start time of sap flow was delayed, the stop time of sap flow was advanced, the time of sap flow was shortened and the peak significantly reduced. The seasonal variation of sap flow velocity of P. euphratica presented that the summer was sooner than spring and autumn in starting time, peak time and rapid-falling time.Transpiration of P. euphratica showed distinct seasonal patterns, April and October late water consumption is low, From May to August, and more than 70 percent occupied the average transpiration during the growing season, as the main water consumption.The sap flow velocity of P. euphratica is mainly affected by soil moisture, vapor pressure deficit, photosynthetically active radiation, relative humidity and temperature in daytime, vapor pressure deficit and relative humidity in nighttime, and photosynthetically active radiation, soil moisture, air temperature and relative humidity during the growing season. Multiple linear equation of sap flow velocity and environmental factors is established through stepwise regression.