Abstract: Different accumulations of Ce due to a longterm application of rare earth elements were simulated in yellow cinnamon soil to study the ecological effect of rare earth on soil microflora. The sensitivity of different groups of soil microbes to Ce is decreased in the order of bacteria>actinomycetes>fungi. The amount of bacteria is inhibited when the concentration of Ce is larger than 10% of adsorption capacity (AD), and the growth of actinomycetes was stimulated at its concentration of <10% AD. Ce concentration ranged in 5～50% AD had a strong stimulation on the amount of soil fungi, and that of >5% AD inhibited aerobic cellulolytic bacteria and ammonifying bacteria. Ce accumulations of 5～10% AD and 5～50% AD stimulated the amounts of cellulolytic and proteolytic fungi, respectively. Under the stress of high accumulation of Ce, the population structures of actinomycetes, fungi, cellulolytic fungi and ammonifying microbes were changed in different degrees.

Key words: Cerium, Accumulation, Soil microflora, assessment methodology., formation mechanism, VOSCs, Geosmin, black and odorous water body