| Shanghai is a city built on wetland.50%of total land area of Shanghai is wetlanduntil2004. Nanhui east-beach wetland was included in the list of national importantwetland. Nanhui east-beach wetland is in the intersection of estuary of the Yangtze riverand Hangzhou bay.This is the largest coastal wetland in the estuary of the Yangtze river.The north area of Nanhui east-beach is connected with Pudong east-beach, and facesChongming east-beach and Jiuduan island, and the west area of which is connected withFengxian beach, the total area of which is33100hm2. Nanhui east-beach is importanttransfer station, overwinter habitat and breeding sites of birds migration ofinland-Pacific ocean of north-east Asia, because vegetation is luxuriant, invertebratesand fish are rich, Food of birds is abundant. So far, investigation and researches of thespecies, floral composition, community characteristics and relationship betweencommunity structure and environment factors of Nanhui east-beach haven’t beenreported. I carried out this research in order to fill the blank, provide the firsthandsurvey data for the work of wetland-protecting in the future. I expect that this isvaluable for ecological restoring and protection of wetland in China. The results of thisresearch is that as shown below:(1) Plants at Nanhui east-beach include46families,102genus,126species. Thefamilies in which species is most are Gramineae, Compositae and Cyperaceae. Theorder of coast wetlands in Shanghai by which the number of plants’ species is fromlarge to small is Nanhui east-beach, Chongming east-beach, fengxian gulf and Jiuduanisland. The composition of plant species is influenced strongly by invasive species in three main beach of Shanghai. Transparency and salinity of water at Nanhui east-beachare higher than that of Dianshan lake.(2) The order of floral composition at Nanhui east-beach by which the size of floralcomposition is from big to small is cosmopolitan distribution, temperate distribution,tropical distribution and subtropical distribution. The difference of Nanhui east-beach isthe smallest with Chongming east-beach, and is the largest with Dianshan lake.(3) Salinity, conductivity, NH4+-N and TP at st10, st8, st16, st9and st17are higher thanthat of other station. This five stations belong to high-salinity stations. Chlorophyll a,nutrient of Nitrogen and Phosphorus, organic material are rich at st2, st3, st4, st13, st15,st23and st25. This seven stations belong to eutrophic stations. Illumination in watersurface is high at other stations, this means transparency is high. Strong positivecorrelation is present between st9, st19and illumination in water surface, this indicatesthe water at this two stations is clear. Strong positive correlation is present between st6and attenuation rate of illumination, this means the water of st6is turbid. Strong positivecorrelation is present between st23at Dishui lake and chlorophyll a, this implies Dishuilake is algae-type lake. Strong positive correlation is present between st10and TP inwater, this suggests st10is influenced greatly by pollutants from land, and wave andturbulence are fierce at st10.(4) On the basis of similarity of environmental factors, st12&st13, st10&st20andst8&st17that each pair is in the same area are the most similar stations-pair, andst1&st2, st3&st16, st15&st24and st19&st21are the second most similar stations-pair.(5) Extremely significant positive correlation is present among NH4+-N, TP and salinity.The existing of a large amount of NH4+-N and TP of sea water at intertidal zone atNanhui east-beach is due to stirring by fierce wave, and not because of salinitysuperficially.(6) There are5families,8genus and8species submerging and floating plants. They areVallisneria natans, Hydrilla verticillata, Ceratophyllum demersum, Cabombacaroliniana, Myriophyllum spicatum, Lemna minor, Spirodela polyrrhiza, Hydrocharisdubia. By means of TWINSPAN communities of submerge and floating plants atwetland of Nanhui east beach are divided into3main communities: Vallisneria natans+Hydrilla verticillata+Ceratophyllum demersum in the rich-nutrient water andsubstrate; Cabomba caroliniana+Lemna minor+Spirodela polyrrhiza+Hydrocharisdubia in the low-organics high-transparency water; Myriophyllum spicatum in the high-salinity water. Occurrence frequency of Ceratophyllum demersum, Cabombacaroliniana is the highest. Biomass of Myriophyllum spicatum and Ceratophyllumdemersum is the largest, the significant difference is present with that of other submergeand floating plants.(7) Vallisneria natans and Ceratophyllum demersum occur in water that salinity andNH4+-N are low, N and P in substrate are high, and water depth is deep. Myriophyllumspicatum occur in water that salinity, NH4+-N, N and P in substrate are high, and waterdepth is deep. Cabomba caroliniana, Lemna minor, Spirodela polyrrhiza andHydrocharis dubia occur in water that salinity, NH4+-N, N and P in substrate are low,and water depth is shallow.(8) Strong positive relevance is present between Vallisneria natans and total phosphorusin water and substrate, positive relevance is present between Vallisneria natans andnitrogen element in substrate and water depth at certain degree, strong positiverelevance is present between Ceratophyllum demersum and C/N in substrate, positiverelevance is present between Ceratophyllum demersum and total nitrogen in water atcertain degree, strong negative relevance is present between Vallisneria natans,Ceratophyllum demersum and ORP in substrate, very strong positive relevance ispresent between Myriophyllum spicatum and salinity and NH4+-N in water, positiverelevance is present between Myriophyllum spicatum and COD and chlorophyll a atcertain degree, and the content of organic material in area that Myriophyllum spicatumgrows is high, negative relevance is present between Cabomba caroliniana, Lemnaminor, Spirodela polyrrhiza, Hydrocharis dubia and COD, total organic carbon,chlorophyll a, turbidity in water and carbon element in substrate at some extent.(9) The aquatic plants at Nanhui east-beach wetlands are divided into13maincommunities, they are Scirpus mariqueter community and Spartina alternifloracommunity which are always in the high-salinity water area, Myriophyllum spicatumcommunity which is in the high salinity and organics water area, Typha anqustifoliacommunity which grow in swamp, Aster subulatus community and Solidago canadensiscommunity which grow dominantly on the drought or wet soil, xerophytic weedscommunity in which Sesbania cannabina is often dominant, Ranunculusjaponicus+Sonchus arvensis+Scirpus triqueter community and Triarrhena sp.community which are always in wet high-organics stations, Echinochloa crusgalicommunity and Tripolium vulgare+Cyperus glomeratus community which grow often in the high-organics flooded area, Alternanthera philoxeroides community andPhragmites australis community, which grow always on the high-N soil.(10) The environment factors which influence reed community most greatly are salinity,reducing material in soil, C/N in soil, N and P in soil, moisture content of soil. Largerbiomass, density and height of reed are present in low-salinity and organicshigh-nutrient and moisture content area in Nanhui east-beach. Most strongest positivecorrelation is present between reed biomass and N in soil.(11) Fierce competition of reed with Alternanthera philoxeroides and Solidagocanadensis for ecological niche is present, because they are often in the most similarhabitat in Nanhui east-beach.(12) Reed can adapt to human disturbance to some extent, Reed can constitutesingle-species community in the low-salinity, rich-nutrient and high-moisture contentspacious area after human disturbance. |
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