Abstract: Twelve main typical steppe populations in Inner Mongolia were selected to investigate the effects of different cutting system on their aboveground standing biomass.The results showed that the test populations could be categorized into 3 groups,i.e.,1) group with decreasing biomass,which included Leymus chinensis,Agropyron michnoi,Caragana microphylla and Carex korshinskyi,with L.chinensis and C.microphylla as the representatives.The average aboveground standing biomass of L.chinensis was decreased by 63.37%,64.96%,45.64% and 34.18% after 2 cuttings a year,1 cutting a year,1 year cutting and 1 year resting,and 2 years cutting and 1 year resting,while that of C.microphylla decreased by 81.79%,63.33%,40.29% and 26.30%,respectively,compared with the control; 2) group with increasing biomass,which included Koeleria cristata,Artemisia scoparia,A.frigida,and Salsola collina,and K.cristata and A.frigida were the representatives.The biomass of K.cristata was increased by 94.84%,287.79%,132.86% and 211.74%,while that of A.frigida was increased by 193.02%,210.47%,154.65% and 160.47%,respectively.The biomass increase of K.cristata and A.frigida was derived from their population changes,while that of A.scoparia and S.collina was come from the decrease of community densities and the more suitable conditions for seed germination; 3) group with fluctuated biomass,which included Stipa grandis,Achnatherum sibiricum,Artemisia commutata and Serratula centauroides,and the change patterns of their biomass were between those of the former 2 groups.

Key words: Cutting system, Population biomass, Leymus chinensis, Koeleria cristata, Artemisia commutata