中文摘要：

利用SF-300树干液流仪对祁连山中段青海云杉（Picea crassifolia）2011年生长季树干液流进行监测,研究了在典型天气条件下青海云杉的夜间树干液流特征,以及气象因子和树形特征对其夜间液流变化的影响.结果表明：典型晴天、阴天,夜间树干液流速率分别在（2.78±0.64）～（5.02±1.06）g·cm^-2·h^-1、（2.31±0.62）～（3.94±1.22）g·cm^-2·h^-1之间波动,其平均值分别为（3.55±0.28）g·cm^-2·h^-1、（3.06±0.24）g·cm^-2·h^-1;夜间树干液流量分别占当日总液流量的（34.51±6.20）%、（46.06±11.20）%.夜间树干液流速率与饱和水汽压差、气温呈显著相关关系,与风速相关性不显著;夜间树干液流与胸径、树高、边材面积、胸径平方与树高之积呈显著线性相关,与冠幅相关性不显著.青海云杉夜间树干液流的变化是其生理特征与环境因素综合作用的结果,夜间树干液流可能用于夜间蒸腾和植物体内部的水分补充.

英文摘要：

Nocturnal sap flowhas ecological and physiological significant for plants,and it is part of plant water that cannot be ignored. The variations of Picea crassifolia nocturnal sap flows in different weather conditions and their responses to meteorological factors and tree size in the Qilian Mountains are analyzed,in order to have a better understanding of the transpiration of Picea crassifolia. During June 12 to October 16,2011,sap flowvelocities of seven Picea crassifolia trees were measured continuously by SF-300 heat pulse meters. Microclimate data were collected synchronously by two automatic weather stations in Pailugou watershed. The nocturnal sap flowvelocity was measured from（ 2. 78 ± 0. 64） g ·cm^-2·h^-1 to（ 5. 02 ± 1. 06） g ·cm^-2·h^-1 in typical sunny days and from（ 2. 31 ± 0. 62） to（ 3. 94 ± 1. 22） g ·cm^-2·h^-1 in typical cloudy days,with the average values of（ 3. 55 ± 0. 28） g ·cm^-2·h^-1 and（ 3. 06 ± 0. 24） g ·cm^-2·h^-1,respectively. Nocturnal sap flowis（ 34. 51 ± 6. 20） % of the total daily flowin typical sunny days and（ 46. 06 ± 11. 20） % of that in typical cloudy days. Nocturnal sap velocity is significantly correlated with vapor pressure deficit and temperature,and insignificantly correlated with wind speed. Nocturnal sap flowhas linear relationships with diameter at the breast height,tree height,sapwood area,product of tree height and the square of diameter at the breast height,respectively.But nocturnal sap flowis insignificantly related with crown size. In conclusion,the variation of nocturnal sap flowof Picea crassifolia is controlled by its physiological characteristics and the environmental factors. Nocturnal sap flowof Picea crassifolia is used for transpiration and water recharge.