Biogeochemical Effects Of Salt-marshes On Nutrients Cycling At Coastal Tidal Flat, Yangtze Estuary

Estuanne and coastal tidal flat are important environmental interfaces of sea-terrestrial interaction. Sediments exported from land by rivers settled down in the estuaries, so do the chemicals transported here hydrologically. Estuaries are the pools of sediments, the barriers of contaminations, and they are the mirror of the effects of natural factors and strong human activities on environment. Biogeochemical cycling of carbon, nitrogen and phosphorus are the key components of global nutrient cycling. They play the important parts in the element geochemical behavior and contamination cycle. Their concentration and distribution can effect the growth of estuarine biology, and the decomposition, release and deposition of nutrients are controlled on contrary. The reactions between them make the ecological balance of the whole estuaries. Therefore, studies on the sources, distributions, transfer and the environmental effect of nutrient in estuarial ecosystem have been one of the headline scientific problems in the fields of matter cycling researches in the complex environment condition of estuaries.In this dissertation, we selected Chongming east tidal flat (CM) as the typical Yangtze estuarine intertidal flat research site, focused on investigating the distribution, accumulation, transportation of nutrients such as carbon, nitrogen and phosphorus and their ecological effects in the system of plant-sediment, and tried to expand the study of nutrient cycling in the Yangtze estuary and other estuarine and coastal tidal flats. The main conclusions can be summed up as follows.(1) In the salt marshes of the Chongming east tidal flat, carbon, nitrogen and phosphorus content of Scirpus mariqueter had different seasonal variations. The organic carbon (OC) content turns a small variation. The variation of total nitrogen (TN) turns a "U" shape curve, and so does the variation of total phosphorus (TP). The nutrient distribution differs a bit between aboveground segments and underground ones. The peak values of nutrient contents per square meter turn on in late summer or autumn. The stable cabon and nitrogen isotopes dynamically fractionated due to nutrients transportation among atmosphere, plants and sediments system. In summer,...