LAUSR

Abstract Global climate models have indicated high probability of drought occurrences in the coming future decades due to the impacts of climate change caused by a mass release of CO 2 . Thus, climate change regarding elevated ambient CO 2 and drought may consequently affect the growth of crops. In this study, plant physiology, soil carbon, and soil enzyme activities were measured to investigate the impacts of elevated CO 2 and drought stress on a Stagnic Anthrosol planted with soybean (Glycine max). Treatments of two CO 2 levels, three soil moisture levels, and two soil cover types were established. The results indicated that elevated CO 2 and drought stress significantly affected plant physiology. The inhibition of plant physiology by drought stress was mediated via prompted photosynthesis and water use efficiency under elevated CO 2 conditions. Elevated CO 2 resulted in a longer retention time of dissolved organic carbon (DOC) in soil, probably by improving the soil water effectiveness for organic decomposition and mineralization. Drought stress significantly decreased C:N ratio and microbial biomass carbon (MBC), but the interactive effects of drought stress and CO 2 on them were not significant. Elevated CO 2 induced an increase in invertase and catalase activities through stimulated plant root exudation. These results suggested that drought stress had significant negative impacts on plant physiology, soil carbon, and soil enzyme activities, whereas elevated CO 2 and plant physiological feedbacks indirectly ameliorated these impacts.