Abstract: To clarify the effects of elevated ozone (O₃) concentration on leaf litter decomposition, we carried out a litterbag experiment and examined the decomposition rate and nutrient release of leaf litter of G. biloba L. exposed to ambient air (about 40 nmol·mol^-1) and elevated O₃ concentration (160 nmol·mol^-1) using open-top chambers (OTCs). Leaf litter from 10-year-old G. biloba incubated under ambient air (about 40 nmol·mol^-1) and elevated O₃ concentration (160 nmol·mol^-1) for one growing season was collected. There were four treatments: decomposing under ambient air for those incubated under ambient air (AA, control); decomposing under elevated O₃ concentration for those incubated under ambient air (AE); decomposing under ambient air for those incubated under elevated O₃ concentration (EA); decomposing under elevated O₃ concentration for those incubated under elevated O₃ concentration (EE). Compared with leaf litter incubated under ambient air, the contents of K, Mg, P, Ca, Mn, condensed tannins, lignin, and total phenols of litter incubated under elevated O₃ concentration significantly decreased (P<0.05), while N content increased by 15.87% (P<0.01). After 195 days decomposition, compared with AA group, the decomposition of lignin was lower in AE group (P<0.05), while the release of C and N was higher, especially for those incubated under elevated O₃ concentration (P<0.05). The remaining rates of lignin, C, and N in group AA were 25.22%, 41.29% and 75.68%, while those in group AE were 29.89%, 36.61% and 70.17%, respectively. Our results suggest that increasing atmospheric O₃ concentration can indirectly affect carbon and nitrogen cycling of urban forest ecosystems by altering litter decomposition of main tree species.

Key words: Ginkgo biloba L., leaf litter, elevated ozone concentration, decomposition rate, nutrient release.