Abstract: To elucidate the effects of exogenous organic substrate and calcium carbonate on the organic carbon mineralization in lime soils and to deepen the understanding of the characteristics of soil organic carbon turnover, the terra fusca, rendzina, and zonal red soil were collected from the Karst region in Huanjiang of Guangxi, and a 100-day incubation experiment was conducted, with the fluxes of CO₂ and ¹⁴C-CO₂ from the soils determined. Three treatments were installed, i.e., no exogenous addition (CK), addition of ¹⁴Clabeled rice straw (S), and addition of ¹⁴Clabeled calcium carbonate (C). In treatments S and C, the mineralization of soil organic carbon was promoted obviously, and the priming effect of ¹⁴Clabeled rice straw and ¹⁴Clabeled calcium carbonate on the organic carbon mineralization in the terra fusca, rendzina, and zonal red soil after 100-day incubation was 28.7%, 46.2%, and 15.5%, and 127.0%, 175.3%, and 100.1%, respectively. In the apparent cumulative mineralization, the contribution rate of ¹⁴Clabeled calcium carbonate in the terra fusca, rendzina, and zonal red soil was 40.4%, 48.4%, and 19.6%, respectively. Soil type, exogenous additives, and their interaction had significant effects on the priming effect of the soil organic carbon mineralization, the contribution of the additives to the apparent cumulative mineralization, and the cumulative mineralization volume (or rate) (P<0.01). This study indicated that the addition of exogenous organic substrate and calcium carbonate altered the characteristics of soil organic carbon mineralization, and, as for the lime soils, the contribution of inorganic carbonate should be taken into consideration in the study of the mineralization and turnover of soil organic carbon and the assessment of their effects on atmosphere CO₂.  

Key words: maximum light use efficiency, VPM, FLUXNET, parameter optimization.