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（Populus×euramericana cv.‘74/76’）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。

Driving Influence of Environmental Factors on the Sap Flow of the Artificial Poplar Forest on Sandy Land

Stem sap flow is an important basis to characterize the transpiration of trees. Studying the dynamic characteristics of sap flow and the driving effects of environmental factors on it is of great significance to explore the physiological characteristics and water dynamic changes of trees. Populus×euramericana cv.‘74/76’ is one of the main fast-growing tree species widely cultivated and also a water-fertilizer-sensitive tree species. The amount of water directly affects its growth. Populus×euramericana cv.‘74/76’ in Luannan county forest farm in Tangshan city was taken as research object, the drip irrigation method was used to set the soil volumetric water content at 15%?20%, 10%?15% and 5%?10% respectively by controlling the irrigation time, the soil volumetric water content was respectively set as 15%?20%, 10%?15% and 5%?10% by drip irrigation, the sapwood flow rate of Populus×euramericana cv.‘74/76’ was measured by the thermal dissipation probe(TDP), and the solar radiation, air temperature, atmospheric humidity, atmospheric pressure, wind speed and other meteorological factors were simultaneously monitored by using the HOBO automatic weather monitoring station to explore the change rules of sap flow during day and night under different environmental conditions, establish a regression model between meteorological factors and the sap flow, analyze the water utilization of trees in different environments in order to provide guidance for the formulation of reasonable water irrigation strategies for fast-growing and high-yield plantation. Tharted earlier, peaked higher, lasted longer, and fluctuated more at night than cloudy and rainy de results showed that the sap flow was driven by different weather conditions, it on sunny days stays; The sap flow was also driven by soil moisture, under the condition of soil water shortage, the start time was late, the peak was low, the duration was short, and it changed steadily and increasingly at night. After time lag analysis, it is found that there is a "time lag effect" between the sap flow and meteorological factors, the sap flow lagged behind the solar radiation for 40 min, and was ahead of temperature, relative humidity and VPD (vapor pressure deficit) for 60min. There was a "hysteresis loop" relationship between sap flow and VPD, meteorological factors all had a significantly driving effect on the sap flow after the time lag dislocation, it had the greatest correlation with air temperature and stronger driving force during the day, while had the greatest correlation with VPD and stronger driving force at night. After time lag dislocation, the imitative effect of sap flow and meteorological factors was better than before. It can be seen that the environmental factors had an obvious driving effect on the sap flow, especially weather types, meteorological factors, and soil moisture, the regression model established between the weather factors and the sap flow after the time lag can better explain the relationship between the two mathematical relationship, meanwhile, sap flow can better reflect the water condition of sandy soil and the water consumption characteristics of trees, which provided a strong basis for the precise irrigation strategy of poplar fast-growing and high-yielding forests.