Soil organic carbon storage and soil CO2 flux in the alpine meadow ecosystem

High-resolution sampling, measurements of organic carbon contents and ^sup 14^C signatures of selected four soil profiles in the Haibei Station situated on the northeast Tibetan Plateau, and application of ^sup 14^C tracing technology were conducted in an attempt to investigate the turnover times of soil organic carbon and the soil-CO^sub 2^ flux in the alpine meadow ecosystem. The results show that the organic carbon stored in the soils varies from 22.12×10^sup 4^ kg C hm^sup -2^ to 30.75×10^sup 4^ kg C hm^sup -2^ in the alpine meadow ecosystems, with an average of 26.86×10^sup 4^ kg C hm^sup -2^. Turnover times of organic carbon pools increase with depth from 45 a to 73 a in the surface soil horizon to hundreds of years or millennia or even longer at the deep soil horizons in the alpine meadow ecosystems. The soil-CO^sub 2^ flux ranges from 103.24 g C m^sup -2^ a^sup -1^ to 254.93 gC m^sup -2^ a^sup -1^, with an average of 191.23 g C m^sup -2^ a^sup -1^. The CO^sub 2^ efflux produced from microbial decomposition of organic matter varies from 73.3 g C m^sup -2^ a^sup -1^ to 181 g C m^sup -2^ a^sup -1^. More than 30% of total soil organic carbon resides in the active carbon pool and 72.8%281.23% of total CO^sub 2^ emitted from organic matter decomposition results from the topsoil horizon (from 0 cm to 10 cm) for the Kobresia meadow. Responding to global warming, the storage, volume of flow and fate of the soil organic carbon in the alpine meadow ecosystem of the Tibetan Plateau will be changed, which needs further research.[PUBLICATION ABSTRACT]