Classification And Functional Evaluation Of Riparian Zone Of Rivers Entering Baiyangdian

Baiyangdian is an important ecological function zone in the Xiongan New District.River which enters the Baiyangdian carries the important tasks of flood control and water delivery to the Baiyangdian,and ecological protection of the river corridor.In recent years,there have been problems such as unreasonable or even lack of structure and poor vegetation growth in the vegetation zone along the banks of the river.This has led to poor ecological functions such as water purification,water conservation capacity,and habitat for water and land organisms.In this paper,6 rivers entering Baiyangdian are the research objects.Based on remote sensing analysis,field surveys,indoor experiments and other methods,classify the types of riparian zones and evaluate the functional level of various riparian zones;Use the In VEST model to simulate the riparian zone,and propose the most suitable vegetation zone width and the best vegetation type to provide a theoretical basis for vegetation restoration in the riparian zone,so as to enhance Baiyangdian’s environmental regulation and control ability in Xiongan New District.The main research results are as follows:(1)According to the topography and land use types around the riparian zone,the dominant functions of the riparian zone in different sections of the river are determined,the riparian zones of the six rivers are divided into five types: water conservation riparian zone,sediment and nutrient retention type,nutrient filtration and landscape type,the riparian zone with habitat providing function and low water consumption,and the nutrient filtering type riparian zone.Analyzing the vegetation characteristics of the riparian zone,it is found that 6 riparian zones that enter the Baiyangdian are the most abundant in herb species,with 68 species in total,accounting for 81.93% of the investigated plant species.The vegetation zone width of the water conservation riparian zone is the largest(up to 50m),and the four diversity indexes are all large,the nutrient filtration and landscape type are the narrowest(less than 20m),and the diversity index is the smallest.(2)Based on the principal component analysis method,the functional evaluation of 79 sample points in 5 types of riparian zones was carried out.The riparian zone with a higher level of function usually can reach a vegetation zone width of 50 m,with a combination of arbor-shrub-grass,arbor-grass and other vegetation patterns inside,and the growth of arbor and understory plants is in good condition.The main reasons for the low functional level of the riparian zone are: sparse vegetation zone,less litter under forest,low vegetation diversity index,bare slopes without vegetation,and negative effects on nitrogen and phosphorus and sediment retention efficiency is low,and leisure and entertainment facilities are scarce.(3)The In VEST model is used to calculate the water production,the purification rate of nitrogen and phosphorus nutrients and the interception of sediment in the riparian zone of different scenarios.A shrub-grass zone with a width of 20-100 m can play a better role in water production,and shrub-grass zone with width of 50 m has the best effect,which can increase the water production by 31.31% compared with the actual scenario.The vegetation zone with a range of 20～100m and dominated by trees and shrubs can better purify nitrogen and phosphorus nutrients.20 m wide arbor-grass zone can increase the nitrogen purification rate of the riparian zone by 64.02%.The effect is the best;20m wide arbor forest zone can increase the phosphorus purification rate by 10.09%.Vegetation zone with a width of 10-20 m and 30-100 m can play a better role in intercepting sediment.The arbor-shrub-grass belt with a width of 20 m has the best effect,which can be increased by 57.13% compared with the actual scenario.Integrating the above-mentioned functions of the riparian zone,the 20 m width shrub-grass configuration can achieve the greatest improvement effect,and can increase the total value of the function by33.76% on the basis of actual scenarios.