荒漠河岸胡杨(Populus euphratica)树干液流的时滞效应

以2012年4—9月树干液流速率与环境因子的实测数据,分析了荒漠河岸胡杨(Populus euphratica)树干液流的时滞效应。结果表明:不同月份胡杨树干液流速率对不同环境因子的时滞不同;4—9月,胡杨树干液流速率峰值时间比太阳辐射峰值时间晚约1h,比空气温度峰值时间早约1h,比水汽压差峰值时间早约2h,比空气相对湿度谷值时间早约2h;对影响胡杨树干液流速率的环境因子进行了主成分分析,发现胡杨树干液流速率与1h以前的第1主成分、第2主成分相关性最高,相关系数分别为0.864、0.875;对错位前后胡杨树干液流速率与环境因子进行多元线性回归分析发现,在胡杨树干液流的数值模拟中,考虑液流相对于环境因子的时滞效应可以提高模型的拟合精度。

Time Lag Characteristics of Stem Sap Flow of Populus euphratica in Desert Riparian Forest

The time lag between the stem sap flow of Populus euphratica and environmental factors were analyzed based on the experimental data of sap flow and environmental factors from April to September, 2012. The results showed that, in different seasons and for different environmental factors,the time lag effect varied obviously.The sap flow velocity of P. euphratica from April to September was lagged behind 1 hours to Photosynthetic radiation, but advanced of 1 hour to air temperature, of 2 hours to relative humidity, of 2 hours to vapor pressure deficit. The correlation coefficient were 0.709、0.766、-0.804 and 0.81. Principal component analysis could be used to simplify the complexity. The time lags of both the first and the second principal components were 1 hour in advance of the sap flow of P. euphratica. The regression analysis showed that with time lag effect considered, model fitting precision would be improved.