The competitive advantage of a constitutive CAM species over a C 4 grass species under drought and CO 2 enrichment

Kailiang Yu, Paolo D'Odorico, Scott L. Collins, David Carr, Amilcare Porporato, William R. L. Anderegg, William P. Gilhooly, Lixin Wang, Abinash Bhattachan, Mark Bartlett, Samantha Hartzell, Jun Yin (+4 others)
2019 Ecosphere  
2019. The competitive advantage of a constitutive CAM species over a C 4 grass species under drought and CO 2 enrichment. Abstract. Plants with crassulacean acid metabolism (CAM) are increasing in distribution and abundance in drylands worldwide, but the underlying drivers remain unknown. We investigate the impacts of extreme drought and CO 2 enrichment on the competitive relationships between seedlings of Cylindropuntia imbricata (CAM species) and Bouteloua eriopoda (C 4 grass), which coexist
more » ... n semiarid ecosystems across the Southwestern United States. Our experiments under altered water and CO 2 water conditions show that C. imbricata positively responded to CO 2 enrichment under extreme drought conditions, while B. eriopoda declined from drought stress and did not recover after the drought ended. Conversely, in well-watered conditions B. eriopoda had a strong competitive advantage on C. imbricata such that the photosynthetic rate and biomass (per individual) of C. imbricata grown with B. eriopoda were lower relative to when growing alone. A meta-analysis examining multiple plant families across global drylands shows a positive response of CAM photosynthesis and productivity to CO 2 enrichment. Collectively, our results suggest that under drought and elevated CO 2 concentrations, projected with climate change, the competitive advantage of plant functional groups may shift and the dominance of CAM plants may increase in semiarid ecosystems.
doi:10.1002/ecs2.2721 fatcat:4xzt34lwl5ce3dljuy3lstwwru