Elevated CO2 concentrations affect the growth patterns of dominant C3 and C4 shrub species differently in the Mu Us Sandy Land of Inner Mongolia

Abstract

Elevated CO2 levels can improve growth and water use efficiency (WUE). However, the influence of atmospheric CO2 concentrations higher than 800 ppm has been less of a concern and has received little attention. In this study, experiments were conducted to explore the responses of four species to elevated CO2 levels. Seedlings of the four species were grown in growth chambers under four different CO2 concentrations. The results showed that elevated CO2 levels resulted in increased net assimilation rates (NARs) (12%–90%) and WUEs (1%–258%) as well as decreased leaf area ratios (LARs) (11%–72%) for the four species. For the two Artemisia species (Artemisia sphaerocephala Krasch. and Artemisia ordosica Krasch.), elevated CO2 significantly increased the relative growth rate (RGRs) (4%–8%) and total biomass increment (19%–44%), while elevated CO2 concentrations resulted in decreased RGRs (2%–20%) and transpiration rates (49%–61%) for Hedysarum laeve Maxim., and increased the height increment (7%–96%) of Caragana korshinskii Kom. The differences among the two Artemisia species (C4 species), and C. korshinskii and H. laeve (C3 species) might be associated with their different photosynthetic pathways. These findings suggest that the two Artemisia species had a stronger ability to adapt to CO2 concentration elevation. Considering its high WUE, C. korshinskii should be applied for vegetation restoration in water-limited areas affected by a warming climate.