Study On The Construction And Optimal Allocation Of Aquatic Plant Communities In Beijing River Restoration

With the rapid development of society,river health problems are becoming increasingly serious,and the social service functions of river ecosystems are lacking.As a kind of ecological restoration technology,aquatic plant restoration technology has become one of the hot spots in river ecological restoration research at home and abroad.This paper focuses on two key aspects of aquatic plant restoration technology: species selection and optimal allocation.Using modern information methods,a platform for aquatic plant community species selection is established,and a community species combination and space-time optimal allocation method are proposed.Based on discussing the construction and allocation model of aquatic plant communities at the ecological division scale of river systems in Beijing,expand the design and practice of the aquatic plant community construction and optimal allocation scheme for the river in the Guishui River Shiyuan section.The effects of engineering applications were monitored and evaluated,with a view to providing evidence and recommendations for the application of aquatic plant restoration technology and river ecological restoration practices.The findings are as follows:(1)The aquatic plant database platform based on python provides species selection functions for specific damaged river sections,and supports the addition,deletion,modification,improvement and search of aquatic plant species in the database,in order to expand the aquatic plant restoration Filter scope.Based on environmental factors,the preliminary selection function of species,six types of environmental factors,such as soil,water temperature,light intensity,water depth,velocity,and water quality,that affect plant growth are selected as preliminary screening conditions for the initial species of aquatic plant communities;based on the preferred functions of restoration goals and a completely independent analytic hierarchy process model,three criteria layer indicators were selected : water quality restoration indicators,water ecosystem dynamic balance indicators,social service function indicators,heavy metal restoration,nitrogen and phosphorus removal rate,algae inhibition capacity,and organic matter restoration Capacity,soil slope protection function,biodiversity,hydrophilic entertainment,water supply,economic productivity,landscape function 9 indicators layer indicators to complete the species optimization screening of specific restoration goals.(2)Based on the structural composition,structural characteristics,and community development trends of natural aquatic plant communities,the principles and methods for optimizing the community structure and space-time configuration of artificially constructed aquatic plant communities are proposed.The dominant species of dominant community function were determined based on the niche concept,and the internal structural composition of the community was optimized according to the common combinations of dominant species and associated species.When the space is optimally configured,the water level of the community in the direction of the vertical river is arranged from shallow to deep in order to the emergent plants,floating plants,and submerged plants,and the aquatic plants of the same life form are arranged in stripes or patches along the horizontal direction of the river.The optimized time configuration takes into account the growth conditions and restoration effects of aquatic plants under different seasonal conditions and time scales.It summarizes the optimal planting time,planting density and propagation the method of 16 common aquatic plants.The growing season is taken as an example to introduce the seasonal matching method of plants in the cold season in northern China.At the same time,it is proposed that the composition of the community needs to be artificially adjusted to optimize the function of the community at different stages of the application of aquatic plant restoration engineering.(3)Study the ecological restoration goals of different ecological areas in Beijing's river system,and refer to the aquatic plant database platform to screen suitable species at the ecological division scale,and propose a model for the construction and allocation of aquatic plant communities suitable for Beijing's river system.Based on the results of Beijing's tertiary ecological zoning,the regional characteristics of 24 tertiary ecological zones were analyzed to identify the most important ecological restoration targets in the region.A total of 25 families,36 genera,and 48 species of common aquatic plants in Beijing were summarized.As a preliminary plant bank,combined with the ecological restoration goals of 24 ecological zones,the aquatic plant database platform was used to optimize the selection of 13 suitable aquatic plants.With reference to the survey results of aquatic plant communities in Beijing's rivers,a total of 39 groups of suitable aquatic plant community combinations were proposed,including a single dominant species community,an emergent plant community,a floating plant community,a submerged plant community,and a multi-dominant layer compound plant community.(4)Study the method of river segmentation in the Guishui River Shiyuan section,analyze the design methods and principles of aquatic plant community construction and optimal allocation at a smaller scale,and take the Yaheyuan River section as an example to carry out the design and practice of aquatic plant communities.After the implementation,effect monitoring and evaluation will be performed.After conducting on-site investigation and evaluation of 9 sampling points in the Guishui River World Park section,the study area was divided into 5 river sections in combination with Beijing's three-level ecological zoning.The water quality and plant monitoring results of the river section show that the end of the World Park section The water quality of ?-2-1-3 and Yaheyuan River section ?-2-3-5 is better,and the restoration target is mainly water ecological restoration.The lower part of Sanlihe River ?-1-5-6 and the first section of Shiyuan section ?-1-8-9 Poor water quality,mainly for water quality restoration,III-1-6-8 in the lower part of Xiadu Park is near the urban area,mainly for socio-economic service function restoration.Taking the aquatic ecological restoration project of the Yaheyuan River section as an example,the design scheme of the aquatic plant community is introduced,and the corresponding aquatic plant restoration project is implemented in the entire section of the Guishui River Shiyuan section.One year later,the water quality monitoring results show that the pollution reduction of the main stream of the Guishui River before and after the inflow reaches 58.81% and 14.92% of total nitrogen and 3.8% and 41.23% of total phosphorus;In the section of the river near the Yaheyuan River,the average value of the Shannon-Wiener Index SW of biodiversity increased from 0.915 to 2.05,with the highest value reaching 2.3,and the biodiversity was greatly improved.