Effects of elevated CO2 and drought on chemical composition and decomposition of spring wheat (Triticum aestivum)

The effects of elevated CO2 concentration and drought on the chemical composition and decomposition of spring wheat (Triticum aestivum L.) leaf litter were investigated. The results obtained were as follows: (i) decomposition of leaf litter material grown under elevated CO2 and drought (ED) was significantly reduced (P=0.007), but no significant changes occurred under elevated CO2 (EW) (P=0.203) or drought (AD) (P=0.599). The loss of mass of leaf litter material decomposing under ambient CO2 (AW) was higher than that under AD and ED, but the difference between AW and EW was insignificant (P=0.318); (ii) compared with leaf litter material from plants grown under AW, ED litter had higher total C content, despite decreased soluble carbohydrates, and lower total N content, and hence increased C/N ratio; (iii) tannins and lignin were not significantly correlated with the loss of mass, but increased concentrations of lignin and tannins in the decomposing wheat material might reduce the rate of litter turnover in later stages of decomposition; (iv) the decreased decomposition rate at ED was the result of an increase in the C/N ratio, a decrease in total N content, and inhibition of soil microbial activity by drought. So there will be the need to increase external N inputs and decrease stalks to the spring wheat field to increase decomposition rates if CO2 concentration increases and semi-arid regions become drier in the future.