胡杨树干液流进程与太阳辐射的关系

Relationship between process of xylem sap flow of Populus euphratica and solar radiation

为了研究胡杨树干液流时间进程与太阳辐射间的关系,利用热比率液流测定系统和自动气象站对2012年4月至9月额济纳绿洲胡杨树干液流速率和太阳辐射进行了同步监测。结果表明：胡杨树干液流与太阳辐射的时间进程在不同的月份呈现出不同特点,树干液流的启动时间比太阳辐射晚1～4小时左右,随着太阳辐射的停止,液流速率开始迅速下降,但液流并没有停止,而是维持在一个较低的水平。太阳辐射与胡杨树干液流在各个月份均存在时滞效应,但不同的月份时滞时间不同,就4至9月而言,液流速率滞后于太阳辐射1小时到达峰值。胡杨在不同的生长发育阶段与太阳辐射的相关性不同,4月液流速率与太阳辐射呈负相关,5～9月液流与太阳辐射呈正相关,相关系数分别为-0.142、0.607、0.701、0.735、0.702、0.636。回归分析结果显示,在胡杨树干液流的数值模拟中,考虑液流相对于太阳辐射的滞后效应可以提高模型的拟合精度。

In order to investigate the relationship between time processes of solar radiation and sap flow systematically,sap flow velocity of P. euphratica and solar radiation were synchronously monitored from April to September in Ejina oasis by using heat ratio method and automatic weather station. The results showed that significant differences were found in changes of time characters of solar radiation and sap flow of P. euphratica in different months. The starting time of xylem sap flow of P. euphratica was generally 1 ～ 4 h later than that of solar radiation. When solar radiation came to zero,sap flow velocity were reduced rapidly but not stopped and remained at a low level. The time lag effect existed between xylem sap flow of P. euphratica and solar radiation. But the time lag was various in different months. In terms of April to September,sap flow peak was 1 hour later than the solar radiation peak. Sap flow velocity of P. euphratica was negatively with solar radiation on April and positively correlated with solar radiation from April to September,and the correlation coefficient was- 0. 142,0. 607,0.701,0. 735,0. 702 and 0. 636,respectively. The regression analysis showed that with time lag effect considered,model fitting precision would be improved in numerical simulation.