Long-term effect of atmospheric CO₂ concentration and temperature co-elevation on maize biomass and the phosphorus fraction in the rhizosphere of maize

In agrosystems, crop plants normally increase phosphorus acquisition to achieve yield gain by increasing root growth and changing biochemical characteristics in the rhizosphere, which likely affects soil phosphorus transformation.However, few studies have investigated the long-term effect of elevated CO₂ concentration and temperature on crop growth, soil phosphorus fraction and relevant microbial mechanisms.The study used open-top growth chambers to mainly investigate the effect of elevated CO₂ and warming on soil phosphorus fractions and relevant functional genes in Mollisols.The results showed that the elevated CO₂ concentration and temperature for 4 consecutive years increased the maize biomass by 10%~40% and phosphorus uptake by 20%~80%.Long-term CO₂ and temperature co-elevation decreased NaHCO₃-extractable inorganic phosphorus (NaHCO₃-Pi) concentration in the rhizosphere by 24% while increased NaHCO₃-extractable organic phosphorus (NaHCO₃-Po) by 22% compared with the control.However, elevated CO₂ concentration, warming, and CO₂ plus warming reduced NaOH-Po by 27%, 74%, and 20%, respectively.In addition, CO₂ and temperature co-elevation increased the activity of acid phosphatase, which was negatively correlated with NaOH-Po.The CO₂ and temperature co-elevation increased the copy numbers of phoC(acidic phosphatases producing gene), phoD(alkaline phosphatases producing gene) and pstS(phosphate-specific transporter gene) genes in the rhizosphere.These results suggest that long-term CO₂ and temperature co-elevation promotes crop growth and alters soil phosphorus fractions through changing the abundance of functional genes and phosphatase activity.Climate change may impact the microbial eco-function on phosphorus transformation and consequent phosphorus cycling in Mollisols.