中文摘要：

北半球近地大气O3浓度在最近几十年里持续升高，对陆地生态系统产生深远的影响。本文选取5年生银杏（Ginkgobiloba）为研究对象，利用开顶式气室（OTCs）开展了3个不同浓度的O3（自然对照浓度约40nmol·mol-1、处理浓度80和120nmol·mol-1）熏蒸试验，持续熏蒸2个生长季（2012-2013年）后，于2013年11年月初收集其凋落叶，测定并分析不同处理下银杏凋落叶化学成分的变化。结果表明：与对照相比，高浓度O3处理组银杏凋落叶的N、K含量均显著升高，总酚含量以及C／N、木质素／N降低；而C、P、木质素含量以及C／P并未呈现出显著差异。可溶性糖、缩合单宁含量在两高浓度O3处理下变化趋势并不一致：与对照相比，可溶性糖含量仅在120nmol·mol-1处理下表现出显著差异，降低38％；缩合单宁含量在80nmol·mol。处理下显著升高（343％），而在120nmol·mol-1处理下无显著变化。木本植物凋落物的化学组成在O3熏蒸下会发生一定变化，这种变化可能会对树木凋落物在O3污染地区的分解及区域气候变化下森林生态系统的物质循环，特别是碳循环产生重要影响。

英文摘要：

Concentrations of ozone （03 ） near ground level in the northern hemisphere have increased substantially in the past few decades. Currently, the effects of elevated 03 concentration on the litter of woody plants were poorly investigated, particularly in China. In order to reveal the effects of elevatedO3 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 sig- nificantly 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 03（ 120 nmol . mol-1） significantly de- creased the content of soluble sugar by 38%. The content of condensed tannins significantly in- creased 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.