| This paper took Yichang and Chongqing City in the reservoir area of the Three Gorges Project as the research areas,and selected seven typical artificial restoration hydro-fluctuation-belts,by reading a lot of literature and field investigation,the ecological recovery pattern of the hydro-fluctuation-belt in the study area was classified into different types.The multidisciplinary theories such as soil science,botany,restoration ecology and soil and water conservation were applied,the combination of field investigation and laboratory experiment analysis was used to study the plant communities diversity of hydro-fluctuation-belt ecological recovery pattern in different water level,the spatial distribution characteristics and diversity change rules of hydro-fluctuation-belt vegetation in different water level gradient were analyzed,the carbon fixation and oxygen release capacity of plants in different ecological recovery patterns of the hydro-fluctuation-belt were studied,the effect of soil and water conservation of different ecological recovery patterns in the hydro-fluctuation-belt was analyzed through the shear strength experiment of root biomass and three soil complexes.The main findings are as follows:(1)According to a large number of literatures and field investigation,the author divided the seven typical artificial restoration hydro-fluctuation-belts in the reservoir area of the Three Gorges Project into four different ecological recovery patterns according to the previous classification of the hydro-fluctuation-belt by referring to the water level,slope and plant,and type of engineering measures,they were:plant cultivation model,terrace model,vicissitudes model and vetiver grass reinforcement model.(2)When the water level was between 145m and 155m,the ecological restoration pattern was the plant cultivation model and terrace model,respectively in Xiangxi estuary and Shibao Town of Zhongxian County had the highest biodiversity;When the water level was between 155m and 165m,there were three recovery modes:plant cultivation model,terrace model and vetiver grace reinforcement model,the plant cultivation model and vetiver grace reinforcement model of Qukou Town and Shibao Town had the highest biodiversity;the terrace model the biodiversity took the second place,Wangu Temple and Puxi Village of Kaixian County had the lowest biodiversity.When the water level was between 165m and 175m,there were four recovery modes:plant cultivation model,vetiver grace reinforcement model,terrace model and vicissitudes model,the plant cultivation model in Hanfeng Lake had the highest biodiversity,the terrace model and vicissitudes model,the biodiversity took the second place,the vetiver grace reinforcement model had the lowest biodiversity.Generally speaking,in the case of vegetation biodiversity,when the water level is between 145m and 155m,the plant cultivation model of in Xiangxi estuary or Shibao Town should be selected,when the water level is between 155m and 165m,in the gentle slope hydro-fluctuation-belt,the plant cultivation model in Qukou Town and Shibao Town should be selected,vetiver grace reinforcement model should be chosen for steep slope hydro-fluctuation-belt.When the water level is between 165m and 175m,the plant cultivation model of Hanfeng River in Kaixian County should be selected.(3)With the increase of height,the species in hydro-fluctuation-belt increased,the number of individuals among the species was more and more uniform,and the biological diversity was gradually increased.When the water level was between 145m and 175m,the bermuda grass in the terracing model was the dominant species,and the plant advantage in the middle and low water level in other hydro-fluctuation-belt was the bermuda grass.Most plants were more suitable for survival at high water level,and plants represented by bermuda grass are suitable for distribution at low and middle water level in the hydro-fluctuation-belt.Water level is the dominant factor determining plant distribution.(4)When the water level of the hydro-fluctuation-belt was between 145m and155m,the plant cultivation model of Qukou Town and Puxi Village had higher carbon fixation and oxygen release values,which were 7213.86g/m~2,5343.6g/m~2,5832g/m~2and 4320g/m~2 respectively.The carbon fixation and oxygen release values of Shuibatian terrace model were relatively lower,which were 2418.7g/m~2 and 1791.6g/m~2respectively.When the water level was between 155m and 165m,the plant cultivation model of Qukou Town and Puxi Village had higher carbon fixation and oxygen release values,which were significantly higher than other models,namely 7134.48g/m~2,5284.8g/m~2,5572.8g/m~2 and 4128g/m~2,respectively.The carbon fixation and oxygen release values of terrace model were relatively lower,which were 2031.44g/m~2 and1504.8g/m~2 relatively,the carbon fixation and oxygen release values of vetiver grace reinforcement model were lowest,which were 653.34g/m~2 and 499.6g/m~2.When the water level was between 165m and 175m,the carbon fixation and oxygen release values of vicissitudes model and terrace model were highest,which were 2198.34g/m~2,1628.4g/m~2 and 2003.94g/m~2 and 1484.4g/m~2,the carbon fixation and oxygen release values of plant cultivation model were the second,the carbon fixation and oxygen release values of vetiver grace reinforcement model were 742g/m~2 and 549g/m~2respectively,the carbon fixation and oxygen release values were the lowest.In general,in the case of plant carbon fixation and oxygen release,plant cultivation model in Kaixian Town should be selected when the water level is between 145m and 165m.When the water level was between 165m and 175m,vicissitudes model or terrace model should be selected,at this water level,tree and shrub,ascendens mucronatum and bamboo-willow can survive,through the measurement of the photosynthetic rate of these three species,it was found that the carbon fixation and oxygen release capacity per unit field area of bamboo-willows was the strongest,when selecting the trees and shrubs in hydro-fluctuation-belt of 165-175m in Three Gorges Reservoir Region,the ecological benefits of carbon fixation and oxygen release could be taken into account,and the bamboo-willows should be selected preferentially.(5)Compared with plain soil,the cohesion of root soil complexes of different ecological recovery modes in hydro-fluctuation-belt increased at different degrees,when the water level was between 145m and 155m,the soil cohesive force growth rate reached 32.0%~101.1%;When the water level was between 155m and 165m,the adhesion growth rate of the ecological recovery models of the hydro-fluctuation-belt was 32.2%~100.4%;When the water level was between 165m and 175m,the adhesion growth rate of the ecological recovery models of various hydro-fluctuation-belt was12.7%~91.7%.The total root length and biomass aggregate degree of plant root system were different under different ecological recovery modes in different hydro-fluctuation-belts,at the same water level,the larger the total root length and biomass set of the root,the greater the cohesive force of the corresponding pattern hydro-fluctuation-belt and the greater the shear strength of the root soil complex,the total root length of plant root system and the biomass aggregate of root reflect the content of root in soil,indicating that the content of root in soil is in positive proportion to the shear strength of root soil complex,with the rise of water level,the cohesive force of the corresponding root soil complex of each pattern of settlement zone decreased,which means that the root soil complex of low-water vegetation has the best shear capacity,this might be due to the abundant water at low water level and the extremely tolerant nature of herbaceous plants such as the bermuda grass,which were suitable for living under flooded conditions and had a good growing environment to live well. |
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