Abstract:

The objective of this paper was to determine the relationship s between the behaviors of stable isotope contents (δD) and the patte rns of water transportation in precipitation, spring water and soil water. Water samples were taken from 3 community types of sub-alpine dark coniferous forest in the Wolong Nature Reserve of Sichuan Province, China, during the summer of 20 03. The results showed: 1) The δD in surface soil (litter layer) water was d irectly affected by δD of precipitation because they displayed similar dynamics; 2) The distri bution pattern of δD for the soil profiles of the 3 communities reflected the change of δD for the precipitation. The δD values were low in the upper soil layer (0～5 cm), increased rapidly in the middle soil layer (30～40 cm ), and became stab le in the lower soil layer (50～60 cm); 3) Soil water δD in the surface layer seemed to be also influenced by the δD values in shallow underground water; 4) The δD value of soil water ranged between the δD v alue of precipitation and that of underground water, which indicated that both p recipitation and underground water were the sources of soil water in these sub-alpine dark coniferous forests. Within 5 days of a 14.8 mm rain event, the contr I bution of precipitation to soil water decreased with increase of soil depth: 75 .49%～99.97% in the litter layer, 66.68%～83.01% in 0～5 cm, 24.50%～8 0.57% in 30～40 cm, and 21.22%～29.17% in 50～60 cm, respectively. 5) The δD value of shallow underground water changed little and was not signif icantly affected by the δD of precipitation. The constant val ue of δD may suggest that shallow underground water represent the average conditions of precipitation over the years.

Key words: hydrogen stable isotope, soil water, sub-alpine dark con iferous forest, Wolong, Sichuan