沙地杨树人工林树干液流特征

 采用热扩散技术,对沙地杨树人工林107欧美杨树干液流密度动态特征进行研究,并对其周围环境因子中光合有效辐射、空气温度、空气相对湿度、风速、土壤温度和土壤含水量进行同步观测。结果表明:杨树树干南北方位测得的液流密度具有显著差异,并且具有显著相关关系;不同生长时期杨树液流速率差异显著,5—8月逐渐升高;不同个体间液流速率差异显著,冠幅是影响个体间差异的主要形态特征;杨树树干液流每天达到的峰值与光合有效辐射和水蒸气压亏缺达到的峰值存在一定的时滞,二者与液流的时滞分别提早30～60min和落后120～150min。5—7月影响树干液流密度日变化的主导因子是光合有效辐射,8月则是由光合有效辐射和水蒸气压亏缺共同决定。

Sapflow of P.× euramericanacv plantation trees in Sandy Soil

By the method of thermal dissipation,the characteristics of stem sap flow of P.×euramericanacv plantation was studied.Environmental factors including air temperature,air relative humidity,photosynthetically active radiation(PAR),soil temperature,wind speed and soil water content were also measured simultaneously with sap flow.The result showed that there were marked differences between sap flux density at south and at north on the trunk and sap flux density was found to be highly correlated between south and north.There existed marked differences in different months,sap flow rate was incresed from May to July.Difference can be seen at different trees,respectively,canopy size is the major influenced factor.There was a time lag between sap flux and PAR?vapor pressure deficit(VPD).The time lag for Par and VPD were ahead 30-60 min and after 120-150 min respectively.PAR was the dominant environmental variables affecting the diural variation of sap flow density in May,June and July,and in August were PAR and VPD.