Study On The Suitable Plant Configuration Model In The Drawdown Zone Of The Three Gorges Reservoir

In order to restore the damaged ecosystem of the Three Gorge Reservoir and improve the stability of the ecosystem in the reservoir area.This paper takes the analysis of above-ground vegetation biodiversity,dominant species,similarity and important values of the Three Gorges Reservoir as the entry point,to build appropriate plant configuration mode in the falling zone of the dry and tributary towns.The study founded that:(1)Compared with natural restoration,the diversity index under artificial restoration is more obvious by years of different elevations in main tributary and tributary,and did not reach a relatively stable stage.(2)Different life-type dominant species in same year,showing seasonal differences;Important values for the same dominant species generally reach a maximum in the fall.(3)The perennial vegetation is the main dominant species in the 175-185 m control elevation section,165-175 m and 145-155 m elevation section of the fluctuation zone,annual dominant plants are the main dominant species in the 155-165 m elevation zone.(4)In different years in main stream,Digitaria violascens,Digitaria sanguinalis,Torilis scabra,Arthraxon hispidus,Artemisia carvifolia,Conyza japonica,Kalimeris indica,Phragmites australis are dominant species with more than 20% in the upper reaches of the 175-185 m control section;Xanthium sibiricum,Bidens pilosa,Artemisia carvifolia,Alternanthera philoxeroides,Hemarthria altissima and Artemisia argyi are main dominant species of aboveground vegetation in the 165-175 m elevation section;Aeschynomene indica,Setaria viridis,Echinochloa crusgalli and Cynodon dactylon are main dominant species of aboveground vegetation in the 155-165 m elevation section;Echinochloa crusgalli,Eleusine indica,Polygonum hydropiper,Xanthium sibiricum,Cynodon dactylon and Cyperus rotundus are main dominant species of aboveground vegetation in the 145-155 m elevation section.(5)In the tributary of aboveground vegetation,Arthraxon hispidus,Digitaria violascens,Imperata cylindrica,Artemisia argyi,Oxalis corniculata,Hemarthria altissima and Cyperus rotundus are main dominant species in the 175-185 m elevation section;Polygonum hydropiper,Setaria viridis,Echinochloa crusgalli,Conyza japonica,Aeschynomene indica,Cynodon dactylon,Hemarthria altissima,Alternanthera philoxeroides,Daucus carota and Humulus scandens are main dominant species in the 165-175 m elevation section;Echinochloa crusgalli,Polygonum hydropiper,Aeschynomene indica,Bidens pilosa,Xanthium sibiricum,Setaria viridis and Cynodon dactylon are main dominant species in the 155-165 m elevation section;Echinochloa crusgalli,Xanthium sibiricum,Polygonum hydropiper,Bidens pilosa,Pharbitis purpurea and Aeschynomene indica are main dominant species in the 145-155 m elevation section.(6)Annual dominant species account for the major components of dominant species in soil seed banks in different elevation main tributary and tributary;Compared with the dominant species of aboveground vegetation,its have relatively high frequency and important value in soil seed bank are generally non-dominant species in aboveground vegetation.(7)In different years of the main stream,the dominant species of soil seed bank: Youngia japonica,Torilis scabra,Acalypha australis,Oxalis corniculata,Artemisia argyi,Oxalis corymbosa and Ranunculus japonicus are with a frequency of more than 50% in the upper reaches of the 175-185 m control stream;Setaria viridis,Alopecurus aequalis Sobol,Gnaphalium affine,Stellaria media,Youngia japonica,Youngia japonica,Digitaria sanguinalis,Mazus japonicus,Oxalis corniculata and Cynodon dactylon are with a frequency of more than 75% in the 165-175 m elevation section;Setaria viridis,Youngia japonica,Mazus japonicus,Digitaria sanguinalis,Gnaphalium affine,Digitaria violascens,Kummerowia striata,Hydrocotyle sibthorpioides,Hydrocotyle sibthorpioides,Cyperus rotundus,Artemisia argyi,Oxalis corniculata,Equisetum hyemale and Cynodon dactylon are with a frequency of more than 75% in the 155-165 m elevation section;Setaria viridis,Kummerowia striata,Eclipta prostrata,Mazus japonicus and Conyza japonica are main dominant species in the 145-155 m elevation section.(8)Different years of the stream,the dominant species of soil seed bank: Youngia japonica,Setaria viridis,Oxalis corymbosa,Oxalis corniculata and Alternanthera philoxeroides,are dominant species with a frequency of 100% in 175-185 m control elevation;Youngia japonica,Alopecurus aequalis Sobol,Gnaphalium affine,Cardamine hirsuta,Mazus japonicus,Ranunculus sceleratus,Digitaria sanguinalis,Digitaria violascens and Cynodon dactylon are with a frequency of 100% in the 165-175 m elevation section;Youngia japonica,Digitaria violascens,Aeschynomene indica,Cynodon dactylon and Cyperus rotundus are with a frequency between 75%-100%,in the 155-165 m elevation section;Echinochloa crusgalli,Setaria viridis,Youngia japonica,Stellaria media,Cynodon dactylon,Ranunculus japonicus,Rumex acetosa and Nepeta fordii Hemsl are with a frequency between 75% and 100% in the 145-155 m elevation section.(9)Fluctuations zone of different elevations in dry and tributary,the similarity between aboveground vegetation and soil seed bank in different years and seasons is relatively low,generally between 0.03-0.40,does not reach a relatively stable state between different years,all of which fluctuate.(10)�Joe + Irrigation + Grass + Vine��Joe + Grass��Grass + Grass�and�Irrigation + Grass + Vine� are common combination growth pattern on the ground of the 175-185 m control elevation in the dry and tributary;�Grass + Grass��Grass + Vine� are common combination growth pattern on the ground in the 165-175 m elevation zone of the main tributary and tributary;�Grass + Grass� is common combination growth pattern on the ground in the 145-155 m and 155-165 m elevation sections of the main tributary and tributary.(11)Under different years,different seasons and different restoration conditions,the inter-species correlation intensity between the different elevation sections and the control elevation sections of the main tributary and tributary fluctuation zone is generally greater than 0.30,but the correlation between species is not significant(P?0.05).