Abstract: Concentrations of ozone (O₃) near ground level in the northern hemisphere have increased substantially in the past few decades. Currently, the effects of elevated O₃ concentration on the litter of woody plants were poorly investigated, particularly in China. In order to reveal the effects of elevated O₃ concentration on the chemical composition of leaf litter of G. biloba and forecast subsequent decomposition, an experiment was conducted to study the variations of the chemical composition in leaf litter of G. biloba exposed to elevated O₃ concentrations (80 and 120 nmol·mol^-1) during two successive growing seasons (2012-2013) in open top chambers (OTCs). The results showed that elevated O₃ significantly increased N and K contents, while significantly reduced the content of total phenolics and the ratios of C/N and lignin/N. The contents of C, P, and lignin and the ratio of C/P of leaf litter from the elevated O₃ treatments were not significantly different from those of the control. Elevated O₃  (120 nmol·mol^-1) significantly decreased the content of soluble sugar by 38%. The content of condensed tannins significantly increased by 343% under 80 nmol·mol^-1 O₃, while no significant change was found under 120 nmol·mol^-1 O₃ compared to the control. Different O₃ concentrations caused different changes in chemical composition of leaf litter of G. biloba. We inferred that such variations of litter chemical composition might affect the decomposition of leaf litter and material cycling (especially C) in forest ecosystems in O₃polluted areas.

Key words: Robinia pseudoacacia community, functional structure., hilly-gully region of Loess Plateau, native plant community