In the world's carbon budget more carbon dioxide is being released than is taken up by plants, oceans, and the atmosphere. Semiarid rangeland soils can contain sizeable amounts of carbonates and limestone particles. These soils under present climatic conditions could still be a sink for some of the unaccounted for carbon dioxide or naturally releasing the carbon as part of the geologic carbon cycle. Bowen ratio systems are being used to measure carbon dioxide fluxes at desert shrub and grass plant community types. Soil and aboveground biomass samples are collected to evaluate carbon storage. Carbon is sequestered during the growing season and released during dormancy. Variability in soil carbon samples makes it difficult to evaluate soil carbon storage changes. Aboveground biomass fluctuates with annual precipitation. Calculation of annual carbon dioxide fluxes indicates that the two sites are releasing carbon to the atmosphere with greater releases at the location with higher soil carbonates.