Abstract: Taking Tongjiang City of Sanjiang Plain as an example,spatial and temporal changes of cultivated land in typical wetland natural reserves were studied quantitatively,with driving forces analyzed and optimal regulation measures were put forward.The results indicated that the area of cultivated land has increased by 299,2258 hm² from 1954 to 2000,and the proportion increased from 1.37% to 49.58%.Landscape diversity increased from 0.4723 to 0.7436.Cultivated land has become the main land use type in this region.The decrease of wetland area led to the declination of ecological function,which has become the most important factor threatening the grain safety.Cultivated lands should be protected and optimally regulated.

Key words: Brachionus calyciflorus, Culture media filtrate, Colony formation, Growth, Microcystis aeruginosa, Scenedesmus obliquus, Chlorella vulgaris