| Wetlands are important natural ecosystems with high value for biodiversity conservation,climate regulation and human welfare.Currently wetlands are being degraded in Yangtze River estuary,an ecologically important region,as a result of reclamation,over-exploitation and climate change.Current study concludes that the primary process for restoration of coastal wetlands is the reconstruction of wetland vegetation.Therefore,the research object of this research is the restoration of the ecosystem of Nanhui Dongtan wetland in Shanghai,and based on a large number of field investigation and control experiments,combined with laboratory analysis,the following main conclusions are drawn:(1)The survey shows that Nanhai Dongtan wetland Scirpus mariqueter space distribution is very limited,mainly concentrated in the Nanhui Dongtan wetland from south of the fourth phase of siltation project areato the east of East China Sea Bridge.The paper studied Scirpus mariqueter ecosystem at the Nanhui coastal reclamation region from September to October in 2015.We analyzed 12 environmental factors by canonical correspondence analysis(CCA),which contains soil organic carbon,total phosphorus,total nitrogen,nitrate,nitrite,ammonia,orthophosphate,pH,moisture content,particle size,salinity,tidal elevation of 101 soil sampling sites.The results showed that there was a positive correlation(P<0.01)between the vegetation distribution and tidal elevation,meanwhile the vegetation communities are mainly distributed in the range of tidal elevation about 2.5m-3.4m.The results about community coverage,density,height are as follow: 1)Scirpus mariqueter density was positive correlated(P<0.01)with SOC and salinity,and vegetation density and pH was negatively correlated(P<0.01);2)There was a significant correlation(P<0.01)between Scirpus mariqueter height and soil water content,organic carbon,and salinity.And particle size was negatively correlated to the vegetation height;3).Aboveground biomass of Scirpus mariqueter was comprehensive affected by all environmental factors,and it was also increased with the increase of soil organic carbon and conductivity.In conclusion,tidal elevation,soil organic carbon and salinity are the main environmental factors affecting Scirpus mariqueter distribution.This study has some significance for future coastal wetlands ecological restoration or remediation.(2)Different temperatures and salinity affect the germination rate of Scirpus mariqueter seeds and bulbs.In this paper,the optimum germination temperature and salinity of Scirpus mariqueter seeds and bulbs were investigated by laboratory experiment.The results showed that the optimum germination temperature of Scirpus mariqueter was about 30 ?,and the optimum salinity was broad,and the germination rate was higher at 0-5 ‰.The optimal temperature of sprouting of Scirpus mariqueter was 25 ?,which was lower than that of seed germination.The optimum germination rate was similar to that of seed,and the germination rate was higher at low salinity.(P <0.05).The results showed that the germination rate of the bulb was higher than that of the seed germination(P <0.05).(3)Based on the investigation distribution dynamics and ecosystem of Scirpus Mariqueter,the vegetation community that we reconstructed density was a cluster(20 plants,about 0.04m2)per 10m2 in Nanhui East mudflats,where the total restored area was 10hm2.Through comparing the diversity of TOC,TN,TP and macro benthos in restoration and contrast area,we could explore the ecological restoration effects of the project finally.Results shows that:(1)in the area of restoration,the Scirpus Mariqueter was in good condition and its coverage rate was up to 83.4% in Oct.from the initial 0.4%.That was to say the vegetation coverage expanded to 208.5 times than before;(2)As to Dec,2016,through of comparison and analysis,the TOC increased 44.9% than the check plot,that was significantly(P<0.05).Inversely,the TN and TP declined 17.19% and 19.80% respectively,and the nutrient removal also affected significantly(P<0.05).(3)Judging from the study results,the abundance of macro benthos in soil in restoration area(53ind./m2)increased 61.11% than the abundance in contrast area(87ind./m2).As suggested above,the study succeeded to rebuild the Scirpus Mariqueter community and accelerate the process of ecological restoration in Nanhui East mudflat.Simultaneously,the results provided scientific basis for the rehabilitation of degraded wetlands in the Yangtze estuary and the conservation of Scirpus mariqueter.In this study,the distribution mechanism of Scirpus mariqueter in the area was analyzed by the investigation of Scirpus mariqueter in Nanhui Wetland.The effects of temperature and salinity on the reproduction of Scirpus mariqueter were studied by the germination experiments of seeds and bulbs.Finally,the community reconstruction of Scirpus mariqueter was carried out on the degraded beach of Nanhui Beach,and the ecological restoration effect evaluation. |
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