Abstract: Dynamics of shrub populations are important factors affecting the carbon budget of natural grassland ecosystems. Shrub biomass and the soil carbon stock beneath shrubs are among the most uncertain components in grassland ecosystem carbon accounting. Warm shrub tussock is widely distributed in hilly areas in northwestern Henan and comprises a ‘typical' (i.e. reference) regional vegetation type. To elucidate the carbon sequestration characteristics of a warm shrub tussock grassland ecosystem, the carbon density of above ground shrub and herb biomass, and the associated soil carbon density were measured in seven plots of different areas in northwestern Henan, and ecosystem carbon density was calculated. The mean vegetation and mean soil organic carbon densities were 2360.07 and 4610.47 g C·m^-2, respectively. The vegetation carbon density for shrub vegetation was 981.63 g C·m^-2, while that of the herb layer was 1387.44 g C·m^-2. The carbon density was mainly contributed by the roots, which accounted for 93.04% of the total vegetation biomass. For shrubs, the root biomass was 41.51%, of total biomass; for herbs it was slightly more. The soil carbon density accounted for 62.80% of the total ecosystem carbon density. Across the seven plots measured, there were differences in the characteristics of ecosystem carbon sequestration. For vegetation carbon density, the plots ranked: P₁>P₅>P₂>P₄>P₆>P₇>P₃, but the difference was not significant (P>0.05). For soil carbon density the ranking was P₁>P₂>P₆>P₅>P₄>P₃>P₇, with significant differences between P₁ and P₄, P₃, and P₇ (P<0.05). The ranking for ecosystem carbon density was P₁>P₂>P₆>P₅>P₄>P₇>P₃, with P₁ being significantly different from P₄, P₃ and P₇ (P<0.05).

Key words: shrub tussock grassland, biomass distribution, carbon density, northwest Henan