Effects of elevated root zone CO(2) on xerophytic shrubs in re-vegetated sandy dunes at smaller spatial and temporal scales

The below-ground CO(2) concentration in some crusted soils or flooded fields is usually ten or hundred times larger than the normal levels. Recently, a large number of studies have focused on elevated CO(2) in the atmosphere; however, only few have examined the influence of elevated root zone CO(2) on plant growth and vegetation succession. In the present study, a closed-air CO(2) enrichment (CACE) system was designed to simulate elevated CO(2) concentrations in the root zones. The physio-ecological characteristics of two typical xerophytic shrubs C. korshinskii and A. ordosica in re-vegetated desert areas were investigated at different soil CO(2) concentrations from March 2011 to October 2013. Results showed that plant growth, phenophase, photosynthetic rate, stomatal conductance, transpiration rate, and water use efficiency for the two xerophytic shrubs were all increased at first and then decreased with increasing soil CO(2) concentrations, and the optimal soil CO(2) concentration thresholds for C. korshinskii and A. ordosica were 0.554 and 0.317%, respectively. And A. ordosica was more tolerate to root zone CO(2) variation when compared with C. korshinskii, possible reasons and vegetation succession were also discussed. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s40064-015-1091-7) contains supplementary material, which is available to authorized users.