干热河谷主要造林树种生长季树干液流的时滞特征

Time Lag Characteristics of Stem Sap Flow of Main Afforestation Tree Species during Their Growth Season in Yuanmou Dry-hot Valley of Southwest China

应用热扩散式探针法测定了元谋干热河谷生长季主要造林树种山合欢、印楝、大叶相思、新银合欢、赤桉、柠檬桉的树干液流,并将液流与太阳辐射和水汽压亏缺数据进行逐行错位分析,探讨树干液流与蒸腾驱动因子之间的时滞效应,结果表明:(1)树干液流速率与太阳辐射、水汽压亏缺存在明显的时滞,均呈现树干液流均滞后于太阳辐射,提前于水汽压亏缺;(2)所选干热河谷6个研究树种的种间时滞效应的差异较小,在日尺度上,树干液流很大程度都依赖于太阳辐射的变化;(3)干热河谷主要造林树种生长季树干液流与PAR和VPD之间的时滞长短与树木的地径、高度、冠幅、边材面积以及夜间水分补充量等的相关关系均不显著,可知树形因子和夜间水分补充量对该区所测树木树干液流与PAR和VPD之间时滞的影响较小甚至没有。

The method of thermal dissipation probes（TDP） was applied to measure the sap flow of the main afforestation tree species,such as Albizzia kalkora,Azadirachta indica,Acacia auriculaeformis,Leucaena leucocephala,Eucalyptus camaldulensis and Acacia confusa,during their growth season in Yunmou dry-hot valley.Meteorological factors such as photosynthetic active radiation（PAR）,air temperature（T）,relative humidity（RH）,water vapor pressure deficit（VPD） and wind speed（WS）were measured at the same time.Cross-correlation analysis was used to estimate the time lag between the stem sap flow and the driving factors of canopy transpiration among the tree species.The results indicated：（1） The stem sap flow of the six tree species was significantly correlated with the radiation（PAR） and vapor pressure deficit（D）,and the stem sap flow lagged behind PAR but ahead of D.（2） There was a small difference among the time lags of the six tree species.And the diurnal sap flow was more dependent on PAR than on D.（3） The time lag between the stem sap flow and PAR/D was not correlated with the tree features,such as DBH,tree heigh,canopy area,sapwood area and the nocturnal water recharge.