THE production of C0_2 in the soil results from the oxidation of soil organic matter by heterotrophic microorganisms and by the respiration of plant roots. The release of C0_2 from the soil is a major flux in theglobal carbon cycle, which is largely fuelled by plant production. In this note, we investigated the release of C0_2from soils of the karst region. We measured the amount of soil microbial biomass carbon,soluble organic carbon in the soil, and the flux of C0_2 from the soil surface over a 1-year period. Thisnote is to examine the factors affecting the flux of C0_2 from the soil surface in an ecosystem with nutrientpoor soils and limited amounts of soil microbial biomass. This study was conducted from June 1997 through May 1998 on a hill side, located in the suburbs ofGuiyang City in Guizhou Province of China (latitude 26°30’N, longitude 106°39’E). Situated 1 140m THE production of C0_2 in the soil results from the oxidation of soil organic matter by heterotrophic microorganisms and by the respiration of plant roots. The release of C0_2 from the soil is a major flux in the global carbon cycle, which is largely fuelled by plant production. In this note, we investigated the release of C0_2from soils of the karst region. We measured the amount of soil microbial biomass carbon, soluble organic carbon in the soil, and the flux of C0_2 from the soil surface over a 1-year period. is to examine the factors affecting the flux of C0_2 from the soil surface in an ecosystem with nutrientpoor soils and limited amounts of soil microbial biomass. This study was conducted from June 1997 through May 1998 on a hill side, located in the suburbs ofGuiyang City in Situated 1 140m. Guizhou Province of China (latitude 26 ° 30’N, longitude 106 ° 39’E). Situated 1 140m