Abstract: A field plant functional groups (PFGs) removal experiment was conducted in 2005 〖KG-*2〗-〖KG-*7〗2007 to study the effects of plant diversity in a Le ymus chinensis community of typical steppe in Inner Mongolia on the topsoil (0〖KG-*2〗-〖KG-*7〗10 cm) carbon (C) and nitrogen (N) pools. In the three succ essive years, the topsoil total C and N contents had a slight change (<15%). They changed little in 2005, but were significantly higher in 2006 than i n 2007 (P<005). The topsoil NH4+-N content had a greater inter-annu al change, being 80% higher in 2006 than in 2007, while the NO3--N content had less significant change (P>005). There was a positive linear relation ship (P<005) between the number of removed PFGs and the content of soil NO3--N, which meant that the decrease of plant diversity increased so il NO3--N content, and consequently, led to a possible soil nitrogen loss through leaching.

Key words: CO₂ storage flux, effective storage flux, molar mixing ratio, air temperature, water vapor, atmospheric pressure.