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Response Of Soil Total Nitrogen Content To Environmental Factors And It's Effects On Plant Growth And Physiology At Chongming Dongtan

Posted on:2018-07-27Degree:MasterType:Thesis
Country:ChinaCandidate:Q ZhangFull Text:PDF
GTID:2310330512481185Subject:Ecology
Abstract/Summary:PDF Full Text Request
Water eutrophication caused by excessive nitrogen is one of the biggest environmental problems in coastal waters.Tidal wetlands are highly influenced by land and sea.Some environmental factors change quickly with high variations,haveing an important influence on nitrogen removal.Based on field survey and remotely sensed data,we investigated the effect of typical environmental factors on the nitrogen distribution in the tidal wetlands.An experiment was conducted at the tidal marsh to investigate the effects of nitrogen addition on the growth and physiology of salt marsh vegetation.The results include:1)The spatial distribution of surface 30 cm soil total nitrogen content was similar to that of salinity and surface elevation,which ishigh in the north and low in the south.Soil total nitrogen content in the surface 30 cm of Chongming Dongtan is highly heterogeneous.The soil total nitrogen content in the northern part is about 1.5 times that of the southern part,while the western part is about 1.2 to 1.5 times that of the eastern part.The types of vegetation and pattern of community successionwere significantly different in the north and south,with succession trend from low biomass to high biomass.The biomass of plant communities in the northern part is higher than that in the southern part.Most of the coastal wetlands in China areyoung marsh,with soil total nitrogen content lower than that in the inland wetlands.On account of overgrazing and reaping,the soil total nitrogen content at Chongming Dongtan is lower than that in the other coastal wetlands in China.Therefore,protection and restoration of coastal wetlands will increase nitrogen removal at the Yangtze Estuary.2)Plant tolerance of salinity and flooding has a major impact on soil total nitrogen content and plant nitrogen reserves.With the increase of salinity,soil total nitrogen content will increases in strong salt tolerance plants,and reduced in weak salt tolerance plants.Plant nitrogen reserves will decline with the increase of salinity.With the increase of flooding depth,plant nitrogen reserve has a significant reduction in Phragmites australis.Soil total nitrogen content in Scirpus mariqueter has a significant reduction in the deep flooding depth,but no significant change in Phragmites australis.Both plant nitrogen reserves and soil total nitrogen content have no obvious trend in Spartina alterniflora with the increase of flooding depth increases.The results from the field and controlled experiment are different.Salinity and flooding depth as the typical environment factors in tidal wetlandshave no obvious effects on the soil total nitrogen content in the controlled experiment.Vegetation types,microbial community,and development timemay have greater influence on soil total nitrogen content.3)High nitrogen content will restrain the growth of salt marsh plants,and reducethe ability of plant to absorb nitrogen.The current soil total nitrogen content in Yangtze Estuary is still lower than the level to inhibit plant growth.Levels of 100?200 mg·kg-1 nitrogen addition significantly improved the growth of Scripus mariqueter compared to the empty control group,indicated by the increases of plant height(up to 35%),plant density(up to 50%),total biomass(up to 40%)and leaf total chlorophyll concentration(up to 37%).The nitrogen content of Scripus mariqueter also reached the maximum of 5.9 gN·m-2 under addition of 200 mgN·kg-1.At present,the soil total nitrogen content value of Yangtze Estuary is still lower than the level to inhibit the growth of Scripus mariqueter.
Keywords/Search Tags:Chongming Dongtan, Salt marsh plant, Soil total nitrogen content, Nitrogen reserves
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