生长季内官厅库区小叶杨单株树干液流通量密度的研究

A Study on the Stem Sap Flow of Individual Trees of Populus simonii under Different Weather Conditions in Rainy Season in Guanting Reservoir

利用热脉冲液流仪和微型自动气象站，在北京市延庆县上辛庄水土保持站观测研究了雨季不同天气条件下官厅库区的小叶杨树干边材液流通量密度变化规律及其对环境因子（气象条件、土壤水分）的响应。结果表明，边材液流通量密度曲线在不同天气条件下均具有明显的昼夜变化规律：液流通量密度通常于清晨5：30“：30时开始上升；12：00-13：00时达到峰值；16：00时开始持续下降，20：00时下降速度变慢，至次日日出之前达到低谷。日液流通量密度（SFA）与日太阳辐射量（ESR）、日均空气温度（Ta）和日均空气相对湿度（RH）均存在极显著正相关关系，与日均0～40em土层蓄水量（Sw40）存在极显著负相关关系，经回归分析建立了日液流通量密度与各环境因子的线性关系：SFA=69．7＋5．63ESR＋3．12Ta＋0．239RH-1．13Su40（R=0．752）。

By using the method of heat pulse velocity recorder and watch dog weather station, the sap flux density of individual trees of Populus simonii under different weather conditions in rainy season was measured and its relation- ship with environmental factors was analysed in Shangxinzhuang Research Station for Soil and Water Conservation of Guanting Reservoir, which located in Yanqing County, Beijing. The results showed that the sap flow varied regular- ly with weather conditions in day time and in seasons. The sap flow started at 5：30 - 6： 30, and ascended to the peak during 12：O0 -13： 00, then began to decrease at 16：O0 and slowly decrease since 20： 00. It arrived at the lowest point at the time before the sun rises in next day. There were significant positive relationships between the daily accumulated sap flux（SFA） and some diurnal meteorological or soil environment factors, such as sun radiation （ ESR）, air temperature （Ta）, and relative air humidity （RH）. The relationship between SFA and soil moisture inthe layer of 0 - 40 cm （ Sw4o ） was a significant and negative one. Their regression equation was SFA = 69.7 ＋ 5.63ESR ＋ 3.12Ta ＋ 0. 239RH - 1.13Sw4o （ R = 0. 752）.