Screening Of Plants Materials Of Hydro-fluctuation Belt In Three Gorges Reservoir Area

The soil water gradients varied from drought to water-logging, due to the periodical water level change of the hydro-fluctuation belt in Three Gorges Reservoir Area, which further influenced the living condition, and the physio-ecological characteristics of the existing species in hydro-fluctuation belt. The aim of this paper was to screen the existing plant materials suitable to hydro-fluctution belt, considering the peculiar conditions in hydro-fluctution belt, according to the ability of tolerance to low-oxygen in water-logging condition and water stress condition. The aim was also to provide the viable plant species and the theorical basis to the buffering vegetation belt of the river bank, and revegetation work in Three Gorges Reservoir Area.Four different kinds of treatment were applied to study the adaptability of Miscanthus floridulu, Polygonum chinense Linn., Pennisetum sinese Roxb, Alternanthera philoxeroides, Cyperus rotundus Linn. , including light drought stress (T1), normal water condition (CK), soil water saturation (T2) and soil submersion (T3), the parameters of the five herbareous plants were measured in different kinds of treatment, including photosynthesis, chlorophyll, growth and the response curve.Throughout a 100-day period, Cyperus rotundus Linn. had the best adaptability to water gradients change, which had no significant influence to height (P=0.5013>0.05), longth of leaf(P=0.7621>0.05), net photosynthethetic rate (Pn)(P=0.1146>0.05), conductance (Gs)(P=0.0586>0.05), transpiration rate (Tr)(P=0.7999>0.05), water use efficiency (WUE)(P=0.471>0.05), content of chls per weight(P=0.182>0.05). Light responding parameters including max photosynthetic rate (Pmax), light saturation point (LSP), light compensation point (LCP), showed the negative reaction to water-logging condition, which demonstrated that Cyperus rotundus Linn. had the great use efficiency of the low light, and transferred the emphasis of light-use to the low light in the soil water saturation and over saturation condition, and showed the better adaptation to adversity. Alternanthera philoxeroides had the second adaptation to the soil water content change, with the fine growth in water-logging, photosynthetic parameters, such as net photosynthesis rate, showed the positive reaction to water gradients. Compared to its tolerance to water-logging, the capacity of Alternanthera philoxeroides to tolerate drought was inferior. In contrast with the parameters in normal water condition, all the parameters in light water stress condition dropped by over 20%. Polygonum chinense Linn. had the adaptation to water gradients change in a definited period. Miscanthus floridulu and Pennisetum sinese Roxb had the ability to tolerate water stress and water-logging in a short time, which were not suitable to be planted for a long period in hydro-fluctuation belt. By combining the related literatures with the representation of all the plant species in the simulated experiments, the planting model in hydro-fluctuation belt was primarily concluded as following, from low elevation to high elevation, (1) Salix variegata Franch., Pterocarya stenoptera C. DC., Alternanthera philoxeroides. (2) Cleistocalyx operculatus, Taxodium distichum, Pennisetum sinese Roxb, Polygonum chinense Linn. (3) Taxodium ascendens Brongn , Quercus variabilis Blume ,Cyperus rotundus Linn.