高浓度臭氧背景下城市森林物候对大气增温响应的敏感性及其机制

It is indisputable for climate warming and increasing of ground-level O3 concentration in recent years, which are two of research hotspots in the fields of global climate change in the world. Plant phenology is regarded as an important bio-indicator in detecting climate change, especially climate warming. Little information is known on the characteristics and physiological mechanisms of phenological change of plant induced by elevated O3 under climate warming. With the development of urbanization and the construction of urban forest，more attention is focused on the potential impact of elevated O3 on the urban forest ecosystem. Based on our long-term phenological observation of urban forest in Shenyang city of China under climate warming for many years, we will further carry out the study in the effects of increasing atmospheric temperature on phenology of urban forest under elevated O3 concentration by OTCs simulation with a comparison between urban and suburb. The phenolgy and the eco-physiological parameters of urban plants during phenological stages will be investigated and measured under increasing atmospheric temperature and/or elevated O3 in order to know the characteristics and mechanisms of phenological response of urban plant to climate warming under the background of elevated O3 concentration, which based on some statistic methods including stepwise regression analysis for lots of phenological and meteorological data collected by us from Shenyang city in recent decades. The main objectives of our studies in this project are to provide the scientific references for plant introduction, landscape planning, carbon balance evaluation, the sustainable development and management of urban forest as well as the development of phenological theory under climate change.

近年来，气候变暖和近地臭氧浓度增加已成不争事实，二者已成为气候变化领域中研究的热点。植物物候是感知气候变化尤其是气候变暖的重要生物指示器，但我们对气候变暖尤其在臭氧浓度升高背景下植物物候变化规律及其驱动的生理生态机制还知之甚少。本项目拟以我国沈阳典型城市森林主要植物为研究对象，基于我们多年来对沈阳城市森林及其物候的长期定位观测研究，利用OTC模拟系统，结合城郊对比试验，通过地面物候观测，开展大气增温、高浓度臭氧及二者复合对城市森林植物物候的影响研究，在测定植物物候期逆境生理指标基础上，根据沈阳城市森林多年物候及气象数据，采用逐步回归等多种统计分析法，阐明大气增温与高浓度臭氧及二者复合作用对城市森林物候影响的基本规律，揭示高浓度臭氧处理下城市森林物候对大气增温响应的敏感性及其生理生态机制，为气候变化背景下我国北方城市森林的植物引种、景观配置、碳量估算、可持续发展及丰富物候学理论提供科学依据。

气候变暖和大气臭氧（O3）污染已成为人类面临的重要环境问题。随着城市化发展，城市近地表气温升高和O3浓度增加日趋凸显。二者对城市森林生长代谢，包括物候变化会产生较大影响，但对二者复合情景下树木物候变化及其驱动的生理生态机制研究甚少。项目以我国东北典型“森林城市”沈阳市城市森林主要树种为研究对象，通过OTC控制实验，开展了大气增温（+ 2℃）和高浓度O3对城市森林树种物候及其相关生理代谢的影响研究，阐明了二者及其复合作用对城市树木物候变化的生理影响及互作机制。研究表明：.1）空气增温促进了城市树木生长及光合作用的增加，O3与之作用相反。增温下银中杨和银杏总生物量分别较对照显著增加34.2%和36.0%（P＜0.05），O3胁迫下二者分别较对照显著下降49.2%和26.4%（P＜0.05）；银杏对增温和O3的敏感性要高于银中杨，增温早期前者对二者光合作用具有显著促进作用；2）增温降低了城市树木叶片氧自由基积累和膜脂过氧化产物含量，提高了叶片多种抗氧化酶活性，而高浓度O3只在臭氧熏蒸早期有所升高，表现出积极的生理响应；3）增温显著减缓了O3对城市树木生长和光合作用的不利影响，前者能有效减缓O3对树木的氧化胁迫，延缓树木衰老。增温和O3对物候期生理影响存在显著交互作用；4）不同物候期城市树木对增温和O3的敏感性存在显著的种间差异。展叶盛期，增温处理下银中杨展叶速率增幅最大（46.3%，P＜0.05）。整个生长季，银杏对增温和O3敏感性最高，茶条槭和银中杨对O3具有一定耐受性；5）适宜增温导致城市树木春季物候期提前，秋季物候期推迟。增温处理使银杏展叶始期提前2天，生长季延长6天。高浓度O3导致树木展叶始期推迟，生长季缩短。增温和O3复合下城市树木春季物候期提前，秋季物候期推迟，生长季延长。研究结果为气候变暖和区域O3污染下城市森林树种选择及可持续发展提供重要科学依据和实践指导作用。