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运用Granier热扩散探针法对半干旱黄土丘陵区不同胸径辽东栎进行树干液流测定,并对太阳辐射、空气温湿度、降水量、土壤水分等环境因子进行同步观测,分析不同胸径辽东栎在不同土壤水分条件下树干液流变化特征及其对环境因子的响应.结果表明:辽东栎液流日变化特征总体上与太阳辐射和空气水汽压亏缺呈相同趋势,但液流峰值出现时间早于两个气象环境因子的峰值时间.同一树木个体在土壤水分条件较高时期的树干液流通量高于土壤水分较低时期.在相同土壤水分条件下,大径级样本液流通量显著高于小径级样本.采用指数饱和曲线函数对液流通量与太阳辐射和空气水汽压亏缺以及两因子的综合指标进行拟合,效果良好,可以反映液流通量对气象环境因子的响应规律.不同胸径辽东栎在不同土壤水分条件下的拟合曲线特征和拟合参数差异表明,在土壤水分较高时段,液流通量可快速上升至饱和值,而在土壤水分较低时段,液流通量上升缓慢.小径级样本对土壤水分变化的反应更加剧烈.单位空气水汽压亏缺的日液流通量值(日液流通量与空气水汽压亏缺的比值)在两种土壤水分条件下的比值与边材面积呈线性相关,且小径级样本的斜率高于大径级样本,进一步表明小径级样本对土壤水分的变化较为敏感,说明在土壤含水量较低时段,大径级样本较厚的导水组织对土壤水分供应不足起到了缓冲作用.
Using the Granier thermal diffusion probe method, the sap flow of Quercus liaotungensis with different DBH in the semi-arid loess hilly region was measured and the environmental factors such as solar radiation, air temperature and humidity, precipitation and soil moisture were observed synchronously. The results showed that the diurnal variation of the flow of Quercus liaotungensis had the same trend with the solar radiation and air-water vapor pressure deficit, but the peak of the flow peak appeared early At the peak time of two climatic and environmental factors, the sap flow flux of the same tree species in the period of higher soil moisture was higher than that in the lower soil moisture level. Under the same soil moisture conditions, the large-diameter sample fluid flux was significantly higher Small diameter sample.The fitting of the liquid flux with solar radiation and air vapor pressure deficit and the comprehensive index of two factors by using the function of exponential saturation curve with good effect can reflect the response law of the liquid flux to the meteorological environment factor.Different diameter Quercus liaotungensis curve fitting characteristics and fitting parameters under different soil moisture conditions showed that the differences in soil moisture During the high period, the liquid flux can rapidly rise to saturation value, while the liquid flux rises slowly in the period of low soil moisture, and the response of the small diameter class sample to soil moisture change becomes more acute. The daily liquid flux of air vapor pressure deficit The value of ratio (daily fluid flux to air vapor pressure deficit) was linearly correlated with sapwood area under both soil moisture conditions, and the slope of the smaller diameter sample was higher than that of the larger diameter sample, further indicating that the smaller diameter sample It is more sensitive to the change of soil water content, indicating that the water-bearing tissues with larger diameter samples have a buffer effect on the supply of soil moisture in the period of low soil moisture content.