饱和供水条件下桂花树干液流特征及其影响因子
The Characteristics and Influencing Factors of Sap Flow in Osmanthus fragraus under Saturated Water Supply

目的：目前对桂花的研究主要集中在分类、香味、园林利用等方面，对其树干液流与环境因子之间关系却鲜有报道。研究桂花树干液流变化特征，分析其与温度、相对湿度、降雨、太阳辐射等环境要素间的响应，探索树干液流速率与环境要素间的线性与非线性关系，以阐明桂花蒸腾耗水规律并为其水分管理提供依据。方法：选取3棵具形态学特征一致的桂花作为标准样树，每棵样树在离地面1.3 m处的树干两侧各安置两个探针，对树干液流进行连续观测，以测定的平均值作为树干液流最终数值。同时建立便携式气象站，同步监测环境因子，绘制液流速率与气象要素同步变化过程曲线，对其进行相关分析与回归分析，并建立模型。结果：桂花日液流速率白天高夜晚低，日液流量：晴天 > 阴天 > 雨天。桂花液流日累计量夏季较大且变化幅度较大，冬季较小且平缓。液流速率(F)与相对湿度(RH)、温度(T)、饱和水汽压差(VPD)、太阳辐射(S)、风速(W)的Pearson相关系数分别为：？0.682、0.726、0.708、0.848、0.716。结论：桂花液流呈现明显的“日高夜低”现象，为“几”字型单峰曲线，降雨对树干液流速率影响明显，液流速率和液流量晴天远超阴雨天。液流速率与各环境因素均显著相关，其中饱和水汽压差、相对湿度与太阳辐射为主要影响因素，通过拟合得到多元线性回归模型为：F = 5.227RH + 122.875VPD + 48.094W + 28.397S ？ 520.732 (R2 = 0.886)。
Objective: At present, the research of Osmauthus fragraus mainly focuses on classification, fragrance, garden utilization, etc., but there are few reports on the relationship between SAP flow and environmental factors. The paper studies variation characteristics of the sap flow of Osmauthus fragraus, analyzes its response to temperature, relative humidity, rainfall, solar radiation and other environmental factors, and explores the linear and nonlinear relationship between sap flow rate and environmental factors, in order to clarify the law of transpiration and water consumption of Osmauthus fragraus and provides the basis for water management. Method: Three Osmauthus fragraus with the same morphological characteristics are selected as the standard sample trees. Two probes are placed on each side of the trunk of each sample tree 1.3 m above the ground to conduct continuous observation of sap flow, and the measured average value is taken as the final sap flow value. At the same time, a portable weather station is established to monitor environmental factors simultaneously, plot the synchronous curve of liquid flow rate and meteorological elements, carry out correlation and regression analyses, and establish a model. Result: The results show that the sap flow velocity of Osmauthus fragraus is high during the day and low at night. Diurnal cumulant of sap flow: Sunny day > cloudy sky > rainy day. Diurnal cumulant of sap flow was large and varied greatly in summer, but small and gentle in winter. The Pearson correlation coefficients between sap flow velocity (F), relative humidity (RH), temperature (T), vapor pressure deficit (VPD), solar radiation (S) and wind speed (W) respectively are: ？0.682, 0.726, 0.708, 0.848, 0.716. Conclusion: The diurnal curve of sap flow velocity is a single peak curve. Rainfall has significant effects on sap flow velocity, sap flow velocity and sap flow cumulant are much higher on sunny days than