Coupling Relationship Between Plant Community And Ecological Factors And Plant Allocation Pattern In Dagu River Basin

Watershed is one of the important components of terrestrial ecosystem,and also an important place for the survival of surrounding organisms.With the increasingly prominent ecological problems such as the weakening of ecosystem services and the loss of biodiversity in the watershed,more and more attention has been paid to the ecological problems in and around the watershed.Dagu River basin,known as the mother river of Qingdao,is the largest and most abundant watershed of Qingdao.The protection and ecological restoration of Dagu River basin has become a hot issue at present.In this paper,Dagu River basin within Qingdao city area is taken as the research object.GIS software is used to rasterize the research area,and grids with spacing of0.1°×0.1°(11000m×11000m)are drawn,and the intersection of grid longitude and latitude lines is set as the sampling points.Systematic investigation of plant community data,soil factors(organic matter,p H,etc.),and other ecological factors(slope,slope position).TWINSPAN analysis software was used to classify the plant communities around dagu River basin,and Simpson index,Shannon-Wiener index and Pielou evenness index were calculated respectively.Canonical correspondence analysis(CCA)was used to rank and analyze ecological factors and plant communities.Finally,according to the results of the study,the most effective plant community configuration pattern was selected in Dagu River basin.The research conclusions are as follows:(1)According to the survey results of Dagu River basin,there are 176 plant species in total,among which 113 are herbaceous plants,27 tree plants and 36 shrub plants,accounting for 64.21%,15.34% and 20.45% respectively.The herbaceous layers accounted for 11.73%,22.40% and 36.75% in chenopodiaceae,compositae and gramineae,respectively.The largest proportion of shrub layer were lonicera,Rhinoceros and Rosaceae,accounting for 8.33%,11.11% and 31.45%,respectively.The largest proportion of tree layers were Luteaceae,Salicaceae and Pinaceae Spreng,accounting for 11.11%,14.81 and 22.22% of tree layers.(2)In Dagu River basin,the community diversity index was herb layer(14.81)>shrub layer(4.33)>tree layer(3.27).The shannon-winner diversity index was herbaceous layer(1.37)> shrub layer(1.22)> tree layer(0.75).Simpson diversity index was herb layer(0.80)> shrub layer(0.72)> tree layer(0.45).The Pielou diversity index was shrub layer(0.964)> tree layer(0.931)> herb layer(0.74),which was due to the large difference of plant species in different layers.The herb layer had the most species,while the tree layer had the lowest.The plant communities in Dagu River basin were divided into 10 plant community types according to the binary indicator species division method.The results of the analysis were consistent with the field survey and showed obvious spatial aggregation.(3)The ecological factors in Dagu River basin showed obvious spatial variation trend,that is,the closer to the estuary,the total soil k content showed a weak increase trend,and the contents of total N,total P,available N and available P of other ecological factors showed a decreasing trend.Among them,p H is between 7.5 and 9.5,with an average of 8.6.Organic matter content ranged from 0.2% to 3.5%,with an average of1.66%.The total N content ranged from 0.74g/kg to 7.35g/kg,with an average of3.166g/kg.The total P content ranged from 0.181g/kg to 1.335g/kg,with an average of0.820g/kg.The total K content ranged from 10.407g/kg to 27.456g/kg,with an average of 18.428g/kg.The available N content ranged from 0.42mg/kg to 3.75mg/kg,with an average of 2.746g/kg,and the available P content ranged from 0.28mg/kg to 2.84mg/kg,with an average of 1.509g/kg.Heavy metal,two interval was bigger,from the study area as a whole,the first part of shenyang,located in pingdu,jiaozhou junction,the surrounding industrial park is more,the second part is located at the river mouth sample,this is due to the alluvial sediment of heavy metals and artificial breeding factors such as heavy metal content is higher,as a whole by outside interference factors.The manganese content ranged from 100.92mg/kg to 524.66mg/kg,with an average of248.600mg/kg.The chromium content ranged from 14.99mg/kg to 125.15mg/kg,with an average of 70.671mg/kg.The copper content ranged from 13.18mg/kg to82.20mg/kg,with an average of 41.140mg/kg.The lead content ranged from 16.77mg/kg to 97.55mg/kg,with an average of 41.939mg/kg.(4)The order of ecological factors affecting the distribution and composition of plant communities in Dagu River basin was total P> organic matter > total K>p H>available P> slope aspect > total N > copper > manganese > lead > chromium.For trees,the order was total P > available N > organic matter > slope aspect > p H > available P >total K > total N > lead > manganese > chromium > copper.The shrub layer was total P > organic matter > available P > slope aspect > available N > total K > total N > p H >copper > chromium > lead > manganese.The herbaceous layer was organic matter >total P > slope aspect > total K > available N > available P > p H > total N > manganese >lead > copper > chromium.The synthesis of ecological factors plays a comprehensive ecological role on plants and has important reference value and guiding significance for the selection of plant species and the pattern of landscape plant allocation.(5)Based on the investigation,research and analysis of plant communities in Dagu River basin,and the principles of adaptation to local conditions,diversity and stress resistance,the plant communities for ecological restoration in Dagu River basin were selected:Community: Tamarix ramosissima-Boxwood-Poetland community,suitable for planting in the site of heavy metal pollution area;This kind of plant community is suitable for planting in the transitional section of the site,which has certain soil remediation ability and can also reflect the landscape of plants.Populus tomentosa-Forsythia-reed community,this kind of plant community has a relatively developed root system,which has a prominent effect on protecting soil erosion and enriching soil organic matter,and is suitable for planting in water protection areas.Herbaceous layer: mainly native landscape plants of the site,such as reed,zephyrrhiza,setaria setaria,pokeweed,etc.,with appropriate introduction of bulbar grass,Oriental cattail,etc.The shrub layer.The original shrub layer of the design site is a small amount of boxwood and euonymus,which should be used as the basis for the later design to create the plant community pattern of the shrub layer,such as boxwood,euonymus,photinia,phnom penh,etc.Tree layer: the original tree vegetation of the site is only part of populus tomentosa planted in row and a small amount of tamarix ramosissima growing naturally,which should be taken as the main tree species in the later design,and accompanied by companion species such as ginkgo biloba and Plum.