Abstract: According to the mowing grassland of the Leymus chinensis meadow steppe in Hulun buir, researching the mechanism of community species diversity variation from the plant functional group species richness and the important value based on fertilization. Analyzing relevant indices in different methods including one-factor/two-factor variance analysis, linear regression and the curve regression. The results showed that: (1) Adding the concentration fertilizer reduced community species richness gradually, which was also affected by the fertilization year. Functional group species richness of Leguminosae and Cyperaceae was sensitive to the variation of fertilization concentration (P<0.05); Ranunculaceae and Cyperaceae were influenced significantly by fertilization year (P<0.05); Cyperaceae and weeds were affected by the interactive effects both fertilization concentration and fertilization year (P<0.05). (2) In addition to the Cyperaceae and weeds functional group, there has significant impact on important value of Gramineae, Leguminosae, Ranunculaceae and Compositae in definite fertilization concentration(P<0.05).The functional group important value of Gramineae and Compositae increased with the aggrandized fertilization concentration while the Leguminosae, Ranunculaceae and Weeds decreased accordingly. (3) The response of functional groups important value was sensitive to annual rainfall and the Gramineae, Leguminosae function group important value were reduced in arid environment while the other functional group important value was increased accordingly. Because of the different response to the fertilization on functional group richness and important value, we should also give full consideration to the interannual precipitation conditions and fertilization year before fertilization in order to achieve the sustainable utilization of grassland resources.

Key words: mowing land, fertilization, functional group, richness, importance value, precipitation