Comparison Of Ecological Functioning Of Main Natural Plant Communities And Restored Plant Communities In Chongming Dongtan

In recent years,global warming,environmental pollution,large area reclamation and biological invasion have caused changes of the structure and functioning of wetland ecosystems,decline of biodiversity,stability,stress-tolerance and productivity of wetland ecosystems.Large area loss of wetland and fragmentation of habitats occurred and led to wetland degradation these years due to human activities and climate change.Based on global researches,wetland ecological restoration projects can effectively reduce wetland fragmentation,and alleviate the current situation of wetland reduction.Hence,wetland ecological restoration and reconstruction has become a hot spot in wetland ecology.The Yangtze River Estuary is one of the 50 ecologically sensitive areas of the world.Chongming Dongtan in this area is the important stopover of the East Asia-Australasia Flyway,and was listed as wetlands of international importance in 2002.In recent years,wetland degradation and fragmentation become more and more severe due to large scale of reclamation of intertidal zones and the invasion of Spartina alternifora.Native Scirpus mariqueter has important ecosystem service values to Chongming Dongtan,but is now under severe threaten.The distribution area of Scirpus mariqueter has declined from 135km2 to less than 40km2 in Dongtan.Large area of Scirpus mariqueter monoculture has disappeared and only a few small patches remained.In order to control and eliminate the invasive Spartina alterniflora,to improve the habitat quality of birds in Chongming Dongtan,and to maintain bird diversity and restore local ecosystem functioning,the Shanghai municipal people's government started the project "Ecological control of Spartina alterniflora and improvement of bird habitats in Chongming Dongtan Wetland" in 2013.The restoration of native Scirpus mariqueter community was one of the important components of this project.This paper studies the differences of ecosystem functioning among natural plant communities(Scirpus mariqueter community,Scirpus mariqueter-spartina alterniflora community,Phragmites australis community)and artificial restoration communities(artificial Scirpus mariqueter community,artificial Oryza satliva L.community)in Chongming Dongtan using plant growth performance(ramet density,canopy height,aboveground biomass,belowground biomass,total biomass and root:shoot ratio),benthic animal community structure(diversity,density and biomass)and bird community structure(diversity and density).This study is to evaluate the effects of scirpus mariqueter restoration project.The main results are as follows:1)Ramet density,canopy height and root:shoot ratio of plant communities in Chongming Dongtan were all significantly affected by site and season.Spartina alterniflora had little effects on Scirpus mariqueter communities in spring,but significantly inhibited the growth of Scirpus mariqueter in summer.Ramet density and root:shoot ratio of Scirpus mariqueter community were significantly higher than those of other community typies.Canopy height and biomass of Phragmites australis were significantly higher than other communities.Within artificial communities,ramet density and root:shoot ratio of Scirpus mariqueter community were higher than those of Oryza saliva L.community,but only the difference of ramet density in spring was significant.Artificial Scirpus mariqueter community and natural Scirpus mariqueter community had little difference in general,which reflected a satisfactory restoration effect.2)Seed bank size of Scirpus mariqueter was significantly affected by site and season.Scirpus mariqueter seed bank reached the peak in autumn,while no seed was found in summer.Seed bank size of the natural Scirpus mariqueter community in the intertidal zone was higher than that of the artificial Scirpus mariqueter community in the reclaimed area due to the differences in population age and density.Through the reduction of seed number from autumn to winter,it can be inferred that artifical Scirpus mariqueter community can provide some food for the winter birds.3)In Chongming Dongtan,the major macrozoobenthos were Crustacean species,while Mollusca species were less abundant and Annelida species were rare.Macrozoobenthos diversity,density and biomass of natural communities were higher than those of the artificial restoration communities.Biomass and density of macrozoobenthos were the highest in spring,relatively lower in summer and autumn,and rose a little in winter.There was little change in diversity among different seasons.Within natural communities,macrozoobenthos diversity,biomass and density of Scirpus mariqueter community and Scirpus mariqueter-Spartina alterniflora community were higher than those of Phragmites australis community.Within artificial communities,macrozoobenthos diversity,biomass and density of Scirpus mariqueter community were higher than that of Oryza sativa L.community,but only the difference of diversity index in summer was significant.From winter and spring to summer and autumn,Stenothyra Stenothyra glabra increased in abundance in natural Scirpus mariqueter community and Scirpus mariqueter-Spartina alterniflora community at the cost of Corbicula fluminea and Sinonovacula constricta.In artifical Scirpus mariqueter community and Oryza sativa L.community,Assiminea sp.reduced with the incresase of Assiminea violacea from winter and spring to summer and autumn.4)Dominant bird species in the study area were wading,birds,while Passeriformes species were less abundant.Due to the differences in food,human disturbance and open water area,bird diversity and density in natural Scirpus mariqueter community,Scirpus mariqueter-Spartina alterniflora community and artifical Scirpus mariqueter community were higher than those in Phragmites australis and Oryza sativa L.communities.The rank of bird density in nautral communities was as follows:Scirpus mariqueter community>Scirpus mariqueter-Spartina alterniflora community>Phragmites australis community.Diversity index difference among different plant communities was little.Within artificial communities,bird density and diversity of artifical Scirpus mariqueter community were higher than those in Oryza sativa L.community.Among all the community types,bird density of artificial Scirpus mariqueter community ranged between natural Scirpus mariqueter community and Scirpus mariqueter-Spartina alterniflora community.Diversity index was higher in natural and artificial Scirpus mariqueter communities than in other plant communities.In general,bird communities in artificial Scirpus mariqueter community were similar to those in natural Scirpus mariqueter community,which indicated that the restoration of Scirpus mariqueter community could have positive effects on the restoration of migratory bird habitats.