城市园林银杏液流变化特征及其主要影响因子

园林植被的蒸腾作用对城市生态系统的水量平衡至关重要，并且能够调节小气候环境。本研究通过热扩散探针法(TDP)，对校园绿地中29 a和24 a的银杏树干液流速率进行动态监测，量化不同时间尺度城市园林绿地中银杏的蒸腾变化规律，并分析其与环境因子的关系。结果表明，同一时期，29 a银杏的树干液流速率和液流通量均大于24 a银杏，且在生长季旺盛期差异显著(P＜0.05)。29 a和24 a银杏蒸腾耗水季节性变动趋势相同，均为夏季＞春季＞秋季＞冬季。除自身生理调节以外，银杏树干液流速率变化受多种因子影响，土壤因子中，树干液流速率对表层土壤温度的变化最为敏感；气象因子中，对太阳辐射的变化最为敏感。不同季节影响银杏树干液流速率的主要环境因子不同，从不同季节出发建立回归模型，能够更好地解释对环境因子的响应。树龄与环境因子的改变，都会影响城市园林植被的蒸腾耗水量，是园林绿化配置与管理应考虑的重要因素。

Characteristics of the Sap Flow and Its Impacting Factors of Ginkgo biloba in Urban Green Spaces

The transpiration of garden vegetation is very crucial to the water balance of urban ecosystem and can regulate the environmental microclimate.In this study,the sap flow of Ginkgo biloba trees with the ages of 24- and 29-year-old in a campus was monitored by thermal dissipation probes (TDP).The characteristics of sap flow and its relationship with environmental factors were analyzed on different time scales.It was found that the sap flow velocity and flux of 29-year-old G.biloba tree were higher than that of 24-year-old one,and the differences were significant in the vigorous growth season (P<0.05).The seasonal variation trend of transpiration water consumption of 24- and 29-year-old G.biloba on seasonal scale was the same.Transpiration water consumption was the highest in summer,followed by spring and autumn,and the lowest in winter.In addition to the regulation of plant physiological functions,the change of sap flow velocity of G.biloba was affected by various influential factors.Among soil factors,sap flow velocity was the most sensitive to the change of surface soil temperature.Among meteorological factors,it was the most sensitive to the change of solar radiation.The impacting factors affecting the sap flow velocity of G.biloba in different seasons were different.The regression model based on season can better explain its response to environmental factors.Tree age and environmental factors had certain effects on transpiration water consumption of urban garden vegetation,which should be considered in the allocation and management of landscaping vegetation.