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Three Gorges Reservoir with water level cyclical fluctuation, the alternate wetting and drying of the ecological environment, soil properties and seed bank species bound to large changes. In this paper, the Three Gorges Reservoir Drawdown special circumstances with flooding early on soil properties and seed bank dynamics of two consecutive years, explore the trend of its response to water level changes for the future Three Gorges Reservoir with vegetation restoration and reconstruction provides a theoretical basis. In similar geographical conditions, elect to cancel the fluctuating zone within the existing secondary shrub and abandoned farmland fixed sample 4 elevation gradient instead of flooding time, to an altitude of 145 m, 155 m, 165 m, 175 m and 175-185 m 185 m as a dividing line, Drawdown 145-155 m ,155-165 m ,165-175 m band is divided into three-segment elevation, native vegetation will be there as a control with ground vegetation, soil the physical nature of the surface water, soil chemical element, soil seed bank seasonal variation, interannual change the system, to explore the fluctuating zone soil physical and chemical properties of the seed bank of flooded early how to change, as well as the dominant species and environmental factors in seed bank , the results showed that: different months of surface soil water content rate, in addition to the maximum water holding capacity, capillary held water, minimum holding amount of water, non-capillary tube pore degree, degree of soil ventilation September highest outside, the soil quality of the water content, soil moisture, wool tube porosity, total porosity May highest in July, the lowest; soil bulk density in less in May and July, September minimum. Gradient increased with altitude, soil moisture content of the soil surface of each month did not show a consistent trend, but the longest section of the 145-155m soil physical properties flooded time worst. After two years of continuous flooding, reduce soil chemical element contents were 1.18% of the soil pH, total nitrogen, 20.16%, 30.80% of the total phosphorus, total potassium 6.87%, 103.75% available phosphorus, available potassium 16.90%, all copper 12.12% and 16.17% of the total manganese, total Zn 50.16%, while elevated levels were 7.22% organic matter, hydrolytic nitrogen 3.03% and 6.88% of the total iron, total Ca 31.89%, full magnesium 84.80%, full of sodium 98.44%; With the elevation gradient rise, flooding and human factors interfere with the various elements change the way quite different; With the deepening of the level of the soil, in addition to the available phosphorus, all copper, total iron, total manganese, total Zn, total Ca, full magnesium, sodium regularity trend did not show, the other elements of the performance in 2008 to gradually reduce the 2009 to gradually increase. 3 the flooded initial two vegetaion of type soil seed bank reserves existed significant differences in secondary shrub seed density of 6991 ± 954.33 grains / m2, abandoned farmland seed density of 22582 ± 6217.36 tablets / m2. Have flooded section of the lowest seed density, not flooded section of the highest. With the deepening of the soil layer, seed bank density decreased. Soil seed bank germination species belonging to 45 families, 97 genera and 118 species of annual and perennial herbaceous plants mainly individual total number of the total reserves of the soil seed bank, Gramineae, Compositae, Scrophulariaceae and cruciferous dominant families; lt; 0.01% of the 34 species, accounting for 28.82% of all the species. Two vegetation types within the soil seed bank closer to the number of species, species diversity index, evenness were higher, but the composition of the dominant species differences, lower ecological dominance. Non-flooded section of the highest biodiversity. Flooded section of the highest ecological dominance, have flooded the similarity index of the section and not flooded section. 4 flooded section of vegetation belonging to 47 families, 71 genera and 100 species, not flooded section of vegetation belonging to 84 families, 163 genera and 223 species of dominant families including Asteraceae, Leguminosae, Gramineae, Rosaceae, sedges Section. Species still with comparison, has flooded sections of vegetation species diversity index and richness index lower, not flooded section significantly increased; been flooded section, not flooded section of the soil seed bank has 79 species and 108 kinds, than still with an increase of 9 and 38; compared with the control with the total density of the soil seed bank, has been flooded section 32.32%, an increase of 103.12% not flooded section. Soil seed bank majority proportion, and 1-year-old herbal proportion greater than the proportion of perennial herbaceous plants herbaceous. The biodiversity of the soil seed bank index, richness index and evenness index and vegetation changes consistent. Section has been flooded, not flooded section, the number of species common control with vegetation and soil seed bank of 9,40 and 15, respectively, the similarity coefficient between soil seed bank and vegetation were 0.328,0.241 0.186 5 With month extension, the secondary shrub soil seed bank density gradually increase in abandoned farmland is gradually reduced. With increasing elevation gradient, 5,7,9, soil seed bank density performance increase gradually. The soil seed bank in May there were 79 species belonging to 36 families and 66 genera; July, the soil seed bank of 80 species belonging to 35 families and 69 genera; September soil seed bank of 73 species, belonging to 32 families and 64 genera, the each month main advantage Division Gramineae, Compositae, Scrophulariaceae, cruciferous. Soil seed bank of species biodiversity index gradually decreased, but the difference between the range is not great. Each month Fluctuating with the type of soil seed bank species live very close, mainly annuals, perennials, seeds, and the relative lack of tree seeds. With the extension of the flooding of years, secondary shrub and abandoned farmland soil seed bank density shown a reducing trend, and abandoned to reduce the proportion of cultivated land than secondary shrub. Soil seed bank in 2009 there were 85 species belonging to 35 families, 70 genera, 10 families, 27 genera and 33 species were reduced compared with the previous year. Secondary shrub ground vegetation to reduce the plant species to 105 species, 37 families and 78 genera, reduced abandoned farmland in 56 of 17 families and 44 genera advantage of bushes and trees belonging to Euphorbiaceae, Leguminosae, Rosaceae advantage herb belonging to the grass family, Asteraceae, Cyperaceae, Scrophulariaceae. Aboveground vegetation and soil seed bank species type similarity significantly improved. 7 Application canonical correspondence analysis (CCA) to study the physical properties of soil moisture, and chemical properties of the soil seed bank of each month the dominant species distribution relationship, elevation gradient, soil bulk density, the ventilation rate of the species seed bank storage distribution has a certain impact ; the pH value, total phosphorus, available phosphorus, sodium, calcium, total iron, total manganese and other chemical elements in the interpretation of the distribution of the dominant species in different months seed bank is strong.
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