Water Use Of Plants Along The Bank Of The Three Gorges Reservoir

The water table in the Three Gorges Reservoir has been raised significantly since the construction of the Three Gorges Dam across the Yangtze River. Little is known about how such a change in local hydrological condition will affect the ecophysiology of plants along the bank of the river. In this dissertation research, we conducted a series of investigations on characteristics of water relations for plants along the bank of the Three_Gorges Reservoir and their possible responses ot wate level increase.In a Pinus-Quercus forest along the Bank of Three Gorges Reservoir, differences in water relations between newly formed riparian plants and their non-riparian counterparts were investigated over an entire year period by comparing stable isotope compositions of xylem water, leaf water potentials and foliar carbon isotope ratios between the dominant plants at a newly-formed riparian site and those at two non-riparian sites at higher elevations. Surprisingly, the isotopic compositions of xylem water indicated that the plants in newly-formed riparian zone acquired water mainly from the soil previously infiltrated by local rain rather than the Yangtze River water. Predawn water potentials (ψpd) of the riparian trees were also similar to those at the non-riparian sites, indicating no difference in water availability between them. Similarly, no significant differences in midday water potentials (ψmd) were found between them. Leafδ13C values of plants across the three sites also showed no difference, even though there was a significant difference among species. Leaf photosynthesis, stomatal conductance and water use efficiency of plants between riparian site and non-riparian site were similar, too. Our results indicate that plants at the newly-formed riparian area along the bank of the Three Gorges Reservoir do not depend on the Yangtze River water for their water sources and that rise in the water...