四川卧龙亚高山暗针叶林降水分配过程的氢稳定同位素特征

Hydrogen Stable Isotope Characteristics of the Precipitation Allocation Processes in Sub-Alpine Dark Coniferous Forest in Wolong, Sichuan Province

应用稳定氢同位素技术对四川卧龙巴郎山亚高山暗针叶林不同降水条件下3群落类型中降水、林冠穿透水和壤中流的变化动态进行跟踪研究。结果表明:降水δD与降雨量负相关显著(R2=0.456,p=0.043),降雨氢同位素存在显著的雨量效应。降水δD与林冠穿透水δD差异不显著(p=0.863)。壤中流δD与降水δD有明显差异(p=0.049),表明壤中流补给来源是降水,但不一定是当日当次降水直接补给。降水量的升高或降低引起壤中流δD升高或降低。当降水量0～10mm时,影响在降雨后第4天发生;当降水量在10～20mm时,影响在降雨第2～3天后发生;当降水量在20～30mm时,影响在降雨1～2天后发生。显示出亚高山暗针叶林对壤中流有显著的调控作用。降水δD与林冠穿透水δD的差值(用ΔδD表示)在3个不同群落中随着降雨量的增大呈现偏正态分布,当降水量在4.91～25.25mm时,ΔδD>0;当降水量<4.91mm及>25.25mm时,ΔδD<0;当降水量为12.65mm时,δD最大,这主要是林冠层蒸散过程和大气降水过程相互作用的结果。

The hydrogen stable isotope method was used to trace the change of precipitation, throughfall and interflow over time under different rainfall density in 3 types of sub-alpine dark conifer forests in Balang Mountain of Wolong Natural Reserve,Sichuan, China. The results showed： there was significantly negative correlation between rainfall △δD and precipitation amount;R^2 = 0.456, p = 0.043, which indicated there existed significant rainfall amount effect on δDin the precipitation. There was no significant difference between rainfall δD and throughfall δD, which showed throughfall was from the rainfall. The differences between rainfall δD and interflow δD was significant （p 〈 0.05）, which indicated that interflow derived from rainfalls in different time-lags. The result further illustrated that sub-alpine dark conifer played an important role in the regulation of interflow. The regulation happened in the fourth day after the 0 - 10 mm rainfall event; and the regulation happened in the second or third day after the 10 - 20 mm event, while regulation time was only 1 or 2 days after 20 - 30 mm event. The change of δD value difference （△δD） between rainfall and throughfall with precipitation was in the shape of shi-normal distribution.△δD 〉 0, when 4.91 mm≤ precipitation 〈 25.25 mm; △δD 〈 0, when precipitation 〈 4.91 mm or 〉 25.25 mm; and the maximum value happened when precipitation amount was 12.65 mm. The differences were the result in interaction between heavy isotope accumulation from evaporation of canopy and the precipitation processes.