Abstract:

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 ΔδD and precipitation amount; R²=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 (ΔδD) between rainfall and throughfall with precipitation was in the shape of shi-normal distribution. ΔδD >0, when 4.91 mm≤precipitation<25.25 mm; ΔδD<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.

Key words: hydrogen stable isotope, sub-alpine dark coniferous forest, precipitation allocation, Wolong