There is a lack of information regarding carbon (C) storage in the Austrian grassland ecosystems. Therefore, C pools in six representative vegetation types on three different permanent grassland sites in Styria were quantified. C storage in grasslands mainly depends on the vegetation type, soil properties (particularly temperature, moisture and nutrient content, amorphous iron and aluminum oxides) and management intensity. The total C stock in montane and subalpine grassland ecosystems varies from 6 to 10 kg Cm−2. Manuring increases and mowing without manuring or overgrazing decreases the C stocks. Total C storage is highest at moderate management intensity. Soil C stocks are considerably higher than biomass C stocks. Montane grassland soils store 5-10 kg Cm−2 (0-50 cm). Subalpine grassland soils, rich in rock fragments, contain 5-7 kg C m−2 (0-30 cm). In montane grassland soils, large amounts of C (> 40 %) are stored in subsoil (10-50 cm). In subalpine grassland soils, C storage is more concentrated in the topsoil. Amorphous Fe- and Al-oxides contribute substantially to C storage in the subsoil. C concentration in topsoil is strongly affected by the root biomass. Root and stubble biomass are important sources of soil organic matter, especially in unmanured meadows and mountain pastures.