Abstract: In this paper, the aboveground and belowground biomasses and rootshoot ratio of vegetation in the Stipa klemenzii steppe in Sonid Right Banner, Inner Mongolia were analyzed based on the data of aboveground and underground biomasses of vegetation in the steppe in growing season, and seasonal dynamic variation models of rootshoot ratio of vegetation were developed. The results are as follows: (1) The curve of aboveground biomass of vegetation in the S. klemenzii steppe in 2011 was remarkably unimodal, the peak value was 46.14 g•m^-2 and occurred in late June. The curve of seasonal dynamic change of underground biomass was N-shaped, the peak and lowest values occurred in late July and late August, and their values were 1 275.46 g•m^-2 and 365.1 g•m^-2, respectively. The peak value of underground biomass occurred one month later than that of aboveground biomass; (2) The rootshoot ratio of vegetation in the S. klemenzii steppe in 2011 was fluctuated seasonally, the lowest value (16.8) and the highest value (51.05) occurred in late August and late July respectively; (3) There was a significant correlation between the aboveground biomass and the rootshoot ratio in 2011, in which the correlation in August was the highest, and the correlation coefficient was as high as 0.626, so the aboveground biomass in August could be used to simulate the variation of root-shoot ratio of vegetation in the S. klemenzii steppe.

Key words: Stipa klemenzii steppe, biomass, root-shoot ratio, seasonal dynamic change, Sonid Right Banner, Inner Mongolia