尾巨桉液流密度动态及其影响因子分析

采用热扩散树干液流仪监测树干液流，自动气象站同步监测环境因子，研究尾巨桉不同季节液流密度日变化、液流密度日均值和月均值的季节变化及其主导环境影响因子。结果表明，尾巨桉单木液流密度日变化呈现昼高夜低的典型单峰变化规律；不同季节液流密度日变化差异较大，主要表现在液流密度启动并迅速增加时刻、液流密度峰值及到达时刻、白天液流持续时间和液流密度降低并保持微弱时刻；液流密度的季节动态总体表现为春季和夏季最大，秋季其次，冬季最小。光合有效辐射和水汽压亏缺是影响尾巨桉液流密度的主导因子，但研究地区土壤含水率不是限制液流密度的主要因子。以光合有效辐射和水汽压亏缺为自变量拟合的线性回归方程可用于估算尾巨桉液流密度瞬时值，为估算液流通量奠定基础。

Dynamics of sap flow density of Eucalyptus urophylal ×Eucalyptus grandis and relationship with environmental factors

To study daily change, seasonal change of sap flow density of Eucalyptus urophylla×Eucalyptus grandis and also to find dominant factors impacting on sap flow density, the method of Grainier thermal dissipation probe was adopted to measure the sap flow density, and weather station was utilized to monitor air environmental factors.The results showed that daily change of sap flow density of Eucalyptus urophylal ×Eucalyptus grandis presented an obvious change rule with high density during the day but low in the night.There were some large differences of daily change of sap flow density among seasons, which were the start and rapid increasing time of sap flow density, the top and arrival time of sap flow density, the last time of sap flow density in the day and the time of tiny sap flow density at dusk.In seasonal change rule, sap flow density in spring and summer showed higher than others, followed by that in autumn, and the lowest in winter.Photosynthetically active radiation ( PAR) and atmospheric pressure deficit ( VPD) were the dominant factors influencing sap flow density, soil volume water content ( VWC) was not a main factor to restrict sap flow density in the area.The linear regression equation could be used to estimate the instantaneous sap flow density, and it is going to lay a foundation for estimating sap flow flux of Eucalyptus urophylla×Eucalyptus grandis in the future.