Ecological Management Model Of The Middle And Steep Slopes Of The Three Gorges Reservoir And The Physiological Response Of The Legume Crops To Cr(VI) Stress In The Ecological Barrier Zone

"The ecological environment construction and protection in the reservoir region" was listed as one of the six goais in Three Gorges follow-up planning in 2011.Whereas,what has gained multi-concern is how to develop ecological slope protection technology to deal with ecological environment security problem in water-level fluctuation zone,which has also become an important,difficult and hot point with the advancement of the study.The Three Gorges Reservoir ecological environmental problems which were most concentrated,most severe,most difficult to solve and urgent governance was on the middle and steep soil slope.It is rarely reported on ecological management mode.Meanwhile,heavy metal pollution of soil in the ecological barrier area of the Three Gorges Reservoir area was very serious.It has great practical significance to improve the soil ecologlical security in the reservoir area,so as to improve the ecological security of the reservoir area.Therefore,on the basis of full investigation,this paper carries out the research from the following two aspects.On the one hand,the paper from the aspects of engineering design,vegetation restoration and landscape effect,discusses the ecological management mode of the high and middle planting in the middle and steep slopes of the Three Gorges reservoir.On the other hand,selection of main crops of soybean and mung bean in ecological protection area of Three Gorges Reservoir,analysis the physiological response to Cr6+ stress.The main results were as follows:(1)In the down to the three gorges reservoir area ecological environment problems,on the basis of full investigation,we put forward the concept of "The Ecological Management Model of the Contour Plantation on the Middle and Steep Soil Slope in Water-level Fluctuation Zone of the Three Gorges Reservoir",focused on the design structure and working performance.To improve foundation stability in the middle and steep soil slope of ecosystem through the open circulation of the reinforced concrete frame.To strengthen vegetation coverage and soil fertility in the water-level fluctuation zone through the plane surface greening by contour plantation and vertical greening by geocell plantation.To increase biodiversity and landscape levels in the water-level fluctuation zone through the suitable plant arrangements of different altitude levels in the water-level fluctuation zone,such as:"Tree-Shrub-Grass-Vine"(177-170m),"Shrub-Grass-Vine"(170-160m)and "Grass-Vine"(160-145m).On that basis of which,we further proposed the Optimizing Design Scheme of this model in practical application.On one hand,model materials can be alternative.For instance,concrete materials can be replaced by the new type of ecological environmental protection material and soil matrix can be taken paced of by implant bags.On the other hand,model structure can be flexible.For instance,canceling the junction-plate to reduce the construction cost and eliminating the transverse connection between different monomers can lower the maintainence cost.(2)Physiological responses of soybean to chromium stress shows that:the accumulation capacity of Cr6+ in plant was proportional to the treatment concentration.Cr6+ accumulated in leaves was mainly distributed in the cell wall(37.14%-63.52%),and was least distributed in the mitochondria and chloroplasts(<12%).The absorbance of the dominating bands nearl 064?1 404?1 635?2 924?3 417cm-1 which corresponded to organic substances(e.g.carbohydrates and amino acids)elevated initially and then decreased in root tissues,but no obvious changes in stems was noted.The absorbance of the dominating bands near 1 110,1 396,1 651,2 924,3 433cm-1.which corresponded to the small organic substances contain O-H(carbohydrate)in cotyledons were transported to the roots firstly and then reacted with Cr6+ formated chelates to reduce the toxicity of Cr6+.These results demonstrate that soybean is suitable for phytoremediation of Cr6+contaminated soils and aids in improvement of soil quality from the aspect of food safety.(3)In addition,the results show that:the peak shape of all components of mung bean seedlings remained largely unchanged before and after adsorption of heavy metals,and only the absorption peaks of some functional groups such as hydroxy(3 328-3 361 cm-1),carboxy(1 402-1 440cm-1)and acylamino(1 620-1 645cm-1)that participated in heavy metal adsorption shifted to some extent.The majority of characteristic peaks of chemical components associated with plant physiology in the plant roots decreased with the increase of the concentration of heavy metals.The characteristic peaks of chemical components associated with plant physiology in the stems and leaves of mung bean seedlings treated at different concentrations of heavy metals were mostly higher than or close to the control.The Cr6+ accumulation in the aerial parts(stems and leaves)of mung bean seedlings was obviously lower than that in roots,and the chromium content of the aerial parts of plants increased with the increase of Cr6+ treatment concentration.Comprehensive analysis shows that mung bean seedlings have some remediation effect and endurance ability against heavy metal contaminated soil.Mung bean seedlings had potential utilization value in the technical field of phytoremediation of Cr6+ contaminated soil.