亚热带红壤区青冈栎液流特征及其与气象因子的相关性

Sap Flow Characteristics of Cyclobalanopsis glauca and Its Correlation with Meteorological Factors in Substropical Red Soil Area

采用Granier热扩散式探针和自动气象站同步观测青冈栎(Cyclobalanopsis glauca)树干液流与气象因子,探讨树干液流特征及其对气象因子变化的响应。结果表明:①生长季晴天液流为典型的宽峰型变化,呈明显的季节变化规律,表现在开始启动、到达峰值和保持较大速率的时间不同。不同月份平均液流速率大小顺序依次为:7月(0.001 847 cm·s-1)、6月(0.001 734 cm·s-1)、8月(0.001 517 cm·s-1)、9月(0.001 361 cm·s-1)、5月(0.001 350 cm·s-1)、10月(0.001 171 cm·s-1)、4月(0.001 108 cm·s-1);②雨天液流日变化规律因降雨时段不同表现出一定的差异。全天降雨状态下,液流无明显的启动,呈无规律的小幅波动。降雨发生在液流活动结束之后,液流呈单峰型变化。降雨发生在液流活动结束之前,降雨结束后液流仍会呈现典型的单峰型变化;③液流速率与平均净辐射、空气温度呈显著正相关,与空气相对湿度呈显著负相关,相关程度大小顺序为平均净辐射(0.636**)、空气温度(0.424**)、相对湿度(-0.118**)。液流速率与平均净辐射、相对湿度的多元线性回归方程的拟合效果良好,回归方程和回归系数的相关性检验均达到极显著水平。

We studied the sap flow characteristics of Cyclobalanopsis glauca and its correlation with meteorological factors by u- sing stem sap flow determining system and auto weather station, simultaneously. In sunny days, the diurnal variations of sap flow display wide-peaked curves. There is obvious seasonal dynamics mainly because of different time points in the time of starting, peak and the lasting time at the relatively high level of sap flow velocity. The order of average monthly sap flow velocity is July （0. 001 847 cm ·s-1） 〉June （0. 001 734 cm ·s-1 ） 〉August （0. 001 517 cm·s-1 ） 〉 September （0. 001 361 cm·s-1）〉 May （0.001 35 cm ·s-1）〉 October （0. 001 171 cm·s-1）〉 April （0. 001 108 cm ·s-1）. In rainy days, the sap flow velocity is much lower than that in sunny days based on the same time point. The diurnal changes of sap flow show remarkable differences due to the time and intensity of precipitation. The variance analysis results showed significantly positive correlations between Js and air temperature （Ta） as well as average net radiation （ANR）, but signifi- cantly negative correlation between Js and relative humidity （Rh）. The correlation strength between meteorological factors and Js is ANR （0.636） 〉Ta （0.424 ） 〉 Rh（ -0. 118 ）. We obtained the good fitting results of regression equation be- tween two meteorological factors （ANR and Rh） and sap flow velocity with R2 of 0.93. The regression models and all the parameters were significant at P〈0.01.