Elevated CO(2) shifts the functional structure and metabolic potentials of soil microbial communities in a C(4) agroecosystem

Atmospheric CO(2) concentration is continuously increasing, and previous studies have shown that elevated CO(2) (eCO(2)) significantly impacts C(3) plants and their soil microbial communities. However, little is known about effects of eCO(2) on the compositional and functional structure, and metabolic potential of soil microbial communities under C(4) plants. Here we showed that a C(4) maize agroecosystem exposed to eCO(2) for eight years shifted the functional and phylogenetic structure of soil microbial communities at both soil depths (0–5 cm and 5–15 cm) using EcoPlate and functional gene array (GeoChip 3.0) analyses. The abundances of key genes involved in carbon (C), nitrogen (N) and phosphorus (P) cycling were significantly stimulated under eCO(2) at both soil depths, although some differences in carbon utilization patterns were observed between the two soil depths. Consistently, CO(2) was found to be the dominant factor explaining 11.9% of the structural variation of functional genes, while depth and the interaction of depth and CO(2) explained 5.2% and 3.8%, respectively. This study implies that eCO(2) has profound effects on the functional structure and metabolic potential/activity of soil microbial communities associated with C(4) plants, possibly leading to changes in ecosystem functioning and feedbacks to global change in C(4) agroecosystems.