| Jiangjin district is located in the upper reaches of the Yangtze River and at the end of the Three Gorges Reservoir area,playing an important protective role in building a solid ecological barrier.Due to the jacking effect caused by the flood discharge of the reservoir,the time and depth of natural flood inundation in Jiangjin District,located at the end of the Three Gorges reservoir,will increase.The high-frequency fluctuation of water level makes the bank slope of the natural drawdown zone in Jiangjin district seriously eroded,and the regional ecosystem is disturbed to a certain extent,resulting in serious degradation,specifically manifested in a series of problems such as riverbed erosion,water and soil loss,richness,biomass and vegetation coverage,and the distribution and fragmentation of the original vegetation,and endangering the living environment of residents around the Jiangjin revetment.In order to improve the erosion resistance of the riverbank zone in the urban area and maintain the safety of people’s lives and property in the urban area,the people’s Government of Jiangjin District successively launched and implemented four different flood control and bank protection projects in2016,namely,anchor rod frame beam slope protection,stone mesh slope protection,frame gravel slope protection and face brick slope protection(including anchor rod frame beam + stone mesh slope protection)and completed them in 2018.Due to the difference of restoration effect of different revetment projects and the influence of periodic hydrological gradient change in the region,the distribution pattern and species diversity of vegetation in the restored artificial revetment ebb Zone show obvious differences.Therefore,based on the theories of restoration ecology and community ecology,this paper sets up a total of 12 fixed transects(3 for each of the three types of artificial slope protection and 3 for the natural fluctuation area)and 75 quadrats(2m*2m)based on the natural fluctuation zone with less interference.Through periodic plant community investigation and sampling,this paper analyzes the differences in species composition,community type,species diversity and biomass after vegetation restoration of different slope protection types,Explore the environmental factors that affect the distribution pattern of plants,and build an evaluation index system according to the diversity,stability,ecological benefits and landscape effects of restored plant communities,so as to comprehensively evaluate the restoration effects of different slope protection vegetation.Through diversity analysis and restoration effect evaluation,it is expected to provide scientific decision-making and basis for reshaping the vegetation landscape of the ebb zone along the coast of Jiangjin district.At the same time,it is expected to provide scientific choices and suggestions for the vegetation restoration project of the ebb zone in the upper reaches of the Yangtze River and the reservoir area,and also provide systematic theoretical support and practical basis for stabilizing the ecological slope protection project in Jiangjin District,building the ecological barrier of the Yangtze River,and creating a high-quality ebb Zone landscape with regional cultural characteristics in Jiangjin district.The main results are as follows:There are 25 families,62 genera and 75 species of vascular plants recorded in the drawdown zone of Jiangjin section.The distribution of families and genera is mainly shown in the following three aspects: on the one hand,the proportion of families is mainly concentrated in Gramineae and Compositae,on the other hand,the phenomenon of single species and single genus is obvious in each family,and the composition of plant species is relatively simple.According to the distribution of plant life forms,there are 3 families,13 genera and 14 species of monocotyledons,19 families,46 genera and 57 species of dicotyledons,3 families,3 genera and 4 species of ferns.Dicotyledons account for more than half of the plant species in Jiangjin district.Among them,there are 27 species in the revetment vegetation restoration area and the natural fluctuation area,but the dominant plants have their own similarities and differences.Most of the dominant plants in the two areas are Poaceae,Apiaceae and Polygonaceae,but the top 10 dominant species in the two areas are only two species: Phalaris arundinacea and persicaria hydropiper.A total of9 species of alien invasive plants were found in the survey area,including 9 species in the slope protection area and 4 species in the natural drawdown zone.(1)Through the analysis of different slope protection methods α According to the comprehensive analysis of diversity,the diversity of bolt frame beam + stone mesh and frame gravel slope protection is the highest(Shannon Wiener diversity index and Simpson dominance index are the highest),and the diversity of face brick slope protection is the lowest;according to β According to the diversity analysis,the difference in plant composition between face brick slope protection and natural slope protection is the largest,and the difference in plant composition between bolt frame beam + stone mesh slope protection and natural slope protection is the smallest.In the slope protection area,the community composition of bolt frame beam + stone mesh slope protection is similar to that of frame gravel slope protection.At the same time,it can be seen from the correlation analysis between slope protection type and biomass,The plant community species diversity of the bolt frame beam + stone mesh slope protection is closest to that of the natural fluctuation area.The plant coverage is high and the growth is relatively lush.The frame gravel slope protection takes the second place,and the biomass of the face brick is the least.In conclusion,the plant diversity of different slope protection types is: bolt frame beam + stone mesh Slope Protection > Natural Slope Protection > frame gravel slope protection > face brick slope protection.(2)Under different water level gradients α The diversity comparison showed that there were significant differences in community composition between different water level gradients,mainly manifested in the obvious differences in plant composition as the distance along the environmental gradient increased.The plant community diversity in the middle of the riverbed and the ebb and flow zone is the highest(Shannon Wiener diversity index and Simpson dominance index are the highest).according to β According to the diversity analysis,the community composition difference between the riverbed and the upper part of the fluctuation zone is the largest,and the community composition between the riverbed and the lower part of the fluctuation zone is relatively close.Combined with the diversity analysis between the water level gradient and the biomass,the biomass of the riverbed is relatively high,followed by the middle,upper and lower parts of the fluctuation zone.The results show that the plant diversity under different water level gradients is as follows: middle part of the drawdown zone > riverbed > upper part of the drawdown zone > lower part of the drawdown zone.(3)The contact area of soil matrix is different between different slope protection.The soil matrix area of natural slope protection(100%)> frame beam of anchor rod(85%)+ soil matrix area of stone mesh slope protection(5%)> soil matrix area of frame gravel slope protection(5%)> soil matrix area of face brick slope protection(1%).However,there is no significant difference in soil fertility between different slope protection types and different water level gradients,indicating that soil fertility is not the main factor affecting the effect of plant restoration.(4)Through comprehensive analysis based on AHP and FCE fuzzy comprehensive evaluation method,it can be concluded that the restoration effects of four different slope protection types are as follows: anchor rod frame beam + stone mesh Slope Protection >Natural Slope Protection > frame gravel slope protection > face brick slope protection.Among them,the restoration effect of bolt frame beam + stone mesh slope protection is the best,the restoration effect of natural slope protection is good,and the restoration effect of frame gravel slope protection and face brick slope protection is medium. |
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