Abstract: Based on the measurement of the CO2-release rate of soil respiration and litter decomposition in Stipa grandis Smim steppe in Xilin River Basin, Inner Mongolia, the authors analyzed the seasonal dynamic pattern of soil respiration and litter decomposition and their relation to the aboveground biomass, belowground biomass and environmental factors. The results were as follows: (1) The seasonal dynamic pattern fit nearly a trapezoidal curve and the highest CO2-release rate appearing in the late August was 2.51 gC·m-2·d-l; (2) The seasonal dynamic pattern of CO2-release rate was generally consistent with that of the aboveground biomass, especially with the green aboveground biomass, but was not consistent with or even contrary to that of the belowground biomass; (3) The litter layer on the soil surface could slow down the emission of CO2 from soil to atmosphere; (4) The soil moisture (x) was highly correlated with the CO2-release rate (y), which could be described by a logarithmic regression model: y = 3.4691og10x-2.053 (r = 0.92, P < 0.01).

Key words: Stipa grandis steppe, Soil respiration, Litter decomposition, Aboveground biomass, Belowground biomass