Abstract: In Libo County of Guizhou Province, a karst plot (K) and a non-karst plot (NK) with similar forest covers located in a peak-cluster region, representative of a widely spreading landform in Southwest China, were chosen to study comparatively the soil water movement characteristics in the non-main root zone of the Earth flatland, which is the most important micro-habitat with soil cover in the study plots. From May 2008 to July 2009, rainfall samples as well as two kinds of soil water samples were collected. These water samples were measured for δ18O and δD. Based on the comparison of isotopic compositions between rainfall and soil water as well as the relationships between δ18O and δD for these water samples, several conclusions could be drawn . The mixing effect of soil water base flow (SWBF) for K is weak, whereas for NK it is relatively strong except for the uppermost 20-centimeter soil layer. Piston flow (PF) is probably an important percolation mechanism for SWBF in K, while in NK SWBF might percolate downward partly as PF. In K, there are some evidence for the existence of preferential flow with a high degree of heterogeneity. In general, the evaporation effect on soil water is relatively weak except for the uppermost 10-centimeter soil pore water in NK. These conclusions have implications not only for water management and utilization strategies, but also for further study of water and nutrients used by plants in karst areas.

Key words: soil water; δ18O; δD; piston flow; preferential flow

EARTH AND ENVIRONMENT Vol. 39, No.2, Tot No.283, 2011, Page 271-279