Abstract: Under plastic film unmulching,soil microorganism activity was obviously increased and the amount of bacteria,actinomyces and fungi were increased by 1.5,0.3 and 0.8 times,respectively,in comparison with unmulched treatrnents.There were variations among groups of soil microorganisms.The intensity of respiration and nitrogen fixation was distinctly inhanced;The conversion rate of available nutrients was accelerated and contents of soil available N and P were significantly higher than control plots during seedling stage.It was observed that the development of corn was rapid and total growing period was short.Corn yield per hactare reached 11.4t,which was 18.6% higher than unmulched treatments.

Key words: coastal wetland, vegetation type, soil nematode, community structure.