环境因子对沙地人工杨树林树干液流的驱动影响

以唐山市滦南县林场 107 速生杨为研究对象，使用滴灌法将土壤体积含水量分别设置为 15%～20%、10%～15%和 5%～10%，利用热扩散式探针法（TDP）测定杨树边材液流速率，同时监测太阳辐射、气温、大气湿度、大气压、风速等气象因子，探寻不同环境条件下 107 杨树树干日间和夜间的液流变化规律，分析不同环境下林木对水分的利用，为速生丰产林制定合理的水分灌溉策略提供指导。结果表明，晴天树干液流较阴雨天启动时间早、峰值高、持续时间长、夜间波动大；土壤缺水条件下，树干液流启动时间晚、峰值低、持续时间短，夜间液流变化平缓且增高；树干液流与气象因子存在“时滞效应”，树干液流滞后于太阳辐射 40min，而提前于气温、相对湿度、VPD（水汽压亏缺）60min；树干液流与 VPD 呈现“迟滞回环”关系，时滞错位后气象因子对树干液流均具有显著驱动作用，日间树干液流与气温相关性最大，驱动力较强，而夜间与 VPD 相关性最大，驱动力较强；经过时滞错位后树干液流与气象因子拟合效果优于时滞错位前。可见，环境因子对树干液流具有明显的驱动作用，树干液流可以较好地反映沙地土壤的水分情况和林木的水分消耗特征。

Taking the 107 fast-growing poplar in Luannan County Forest Farm, Tangshan City as the research object, this study set the soil volumetric water content to three levels: 15%–20%, 10%–15%, and 5%–10% via drip irrigation. The sap flow velocity of poplar stems was measured using the thermal dissipation probe (TDP) method, while meteorological factors including solar radiation, air temperature, atmospheric humidity, atmospheric pressure and wind speed were monitored. This study aimed to explore the diurnal and nocturnal sap flow variation patterns of 107 fast-growing poplar stems under different environmental conditions, analyze tree water use under varying environments, and provide guidance for formulating reasonable water irrigation strategies for fast-growing and high-yield forests. The results showed that sap flow on sunny days started earlier, had higher peak values, lasted longer and exhibited greater nocturnal fluctuations compared to rainy and overcast days. Under soil water deficit conditions, sap flow started later, had lower peak values and shorter duration, with gentle and increased nocturnal sap flow changes. There was a "time-lag effect" between sap flow and meteorological factors: sap flow lagged behind solar radiation by 40 minutes, but preceded air temperature, relative humidity and VPD (vapor pressure deficit) by 60 minutes. The sap flow exhibited a "hysteresis loop" relationship with VPD. After time-lag correction, all meteorological factors had significant driving effects on sap flow: during the daytime, sap flow had the strongest correlation with air temperature, showing a strong driving force, while at night, it had the strongest correlation with VPD, also exhibiting a strong driving force. The fitting effect between sap flow and meteorological factors after time-lag correction was better than that before correction. It can be seen that environmental factors have obvious driving effects on sap flow, and sap flow can well reflect the soil water status of sandy land and the water consumption characteristics of trees.