Preliminary Research Of Soil Physical And Chemical Properties Of Different Vegetation Communities Of Cove-typed Beach At Typical Tributaries Of The Three Gorges Reservoir Area

The ecological environment construction of the bay-edge beach in the Three Gorges Reservoir Area is directly related to the ecological landscape,biological habitat,propagation and growth,water quality in the reservoir area,sedimentation,stability of the river bank,and biodiversity of the beach.This paper studies the environmental status and physicochemical characteristics of the vegetation communities in typical riverside beach banks of the Three Gorges Reservoir,and the effect of physicochemical properties on vegetation and soil,which helps to better understand vegetation,soil and environment.The influence of the beach side will provide scientific reference for vegetation restoration and reconstruction of the Hewan-type beach in the Three Gorges reservoir area.In this paper,18 sampling points of six transects were set up on the Hewan-type edge beach?Yellow River Section of Pengxi River?in the Three Gorges Reservoir area.The vegetation community and soil were investigated and sampled.Field surveys include vegetation composition,height,frequency,and coverage.Laboratory analysis of various soil samples includes soil moisture content,organic carbon content,pH value,ammonium nitrogen,available nitrogen,available phosphorus,available potassium,soil CO₂concentration,soil CH₄ concentration,and soil heavy metal content.The main results are as follows:?1?The vegetation of the bay-type beach at Huangshi section of the Pengxi River is rich in vegetation,including Bermudagrass,leeches,corn,wax gourd,cheekbones,rhodamine,vitex,leeks,bark moss,plantain,and grass.A total of 12 families,15genera,16 species,including 4 species of shrubs,a total of 12 kinds of herbaceous plants,herbaceous plants are mainly annual herbs.The specific distribution of families,genus and species is as follows:1 genus and 1 genera of Verbenaceae,Rhus,and Hollyaceae,which are species of shrubs or arbors;1 species and 1 genus of Compositae,semi-shrubs;leguminosae,cruciferous Each family is 1 species of 1genera and is an annual herb;1 species and 2 genera of Anatidae are annual herbaceous plants;3 species of 3 genera of Gramineae are annual herb or perennial herb;1 genera of Cyperaceae and Amaranthaceae One species is a perennial herb;Psychnaceae is a species of one species and is an annual herb.There are 2 species and2 species of cucurbitae,which are annual creeping plants.According to the analysis of vegetation height,frequency,coverage,and important values,the shore beach vegetation is divided into 5 communities:rapeseed-maize community,phyllostachys edulis-mint community,leeches-Community of small forage weeds,leech-koutrel root communities,and Bermudagrass root communities.?2?From the species composition of communities in communities within the transect,herbaceous plants have obvious advantages in the riverside beach,and there are few in the non-submerged area over 175 meters.Inundation area dominates,indicating that the vegetation is water-resistant.Strong,fertile,and adaptable to the environment.On the contrary,the absence or quantity of shrub vegetation and arbor vegetation in submerged areas below 175 meters indicates that it is difficult for native shrubs and trees to survive after the natural environment changes at the riverbanks.It can be seen that the succession of the vegetation communities of the riverside beach in the Three Gorges Reservoir area shows a trend of development from a complex shrub-herb community to a multi-herb group and a single herb community.Therefore,by artificially implanting water-resistant and alkali-resistant herbs and shrubs,the diversity of river bay-type beach species can be increased to realize the transformation of river bay-type edge beach vegetation and promote the alternation of river bay-type beach beach communities.And the diversity of vegetation communities.?3?The pH,organic carbon,ammonium nitrogen,available potassium,and available phosphorus of the vegetation in the same area of the beach have changed to varying degrees.The pH value of the herb community was higher than that of other communities,and the pH value of the herbaceous community increased closer to the river.The change of soil organic carbon in the vegetation community was similar to the pH value,but the changes of organic carbon,available phosphorus,and available potassium were greatly affected by farmland irrigation in non-submerged areas,resulting in different organic carbon,available phosphorus,and available potassium contents in different vegetation communities.There was a large fluctuation,and the soil nutrients of the side beach vegetation were high and the soil was fertile.The ranks of the grass communities in the herb community gradually increased,indicating that the risk of eutrophication in the soil and water bodies increased.?4?The contents of CO₂ and CH₄ in the vegetation communities in the same zone were not consistent with climate and water level.The contents of CO₂ and CH₄ in the soil of Bermudagrass community were higher than those in other vegetation communities.The content of CO₂ and CH₄ in the soil decreased with increasing altitude,indicating that the decomposition of organic carbon,decomposition of withered vegetation,and the respiration of vegetation roots will increase the content of soil CO₂ and CH₄.There was a significant correlation between soil CO₂ content and soil organic carbon,pH,and available potassium.?5?There was no significant change in soil heavy metal content in the vegetation communities in the same area along the edge of the beach.There was a trend of migration of heavy metals towards the riverside herbaceous vegetation community,but the trend was not obvious.Different vegetation communities in the growth stage,a certain absorption of heavy metals in the soil,therefore,artificially increasing the diversity and type of vegetation in the riverside beach will help reduce the heavy metal pollution of the Three Gorges reservoir water body.There is no obvious significant relationship between the height,coverage and plant species of the vegetation community and various physical and chemical properties of the soil.This shows that the edge beach ecosystem of the Three Gorges reservoir area is relatively fragile and a relatively stable ecological system cannot be formed.Strengthening the ecological restoration and construction of the reservoir in the reservoir area will help enhance the diversity and stability of the beach ecosystem.