臭氧污染和氮沉降增加对杨树异戊二烯释放的复合影响研究

Isoprene (ISO) is the most representative biogenic volatile organic compounds emitted by plants. It plays an extremely important impact on atmospheric photochemical processes and global climate change. Tropospheric ozone (O3) pollution and the increase of atmospheric nitrogen (N) deposition are the main problems of global environmental change. They not only cause damage to growth and metabolism of plants but also have potential impacts on ISO emission. However, the combined effect of these two factors on ISO emission are still limited so far. The combined effect of elevated O3 and N deposition on ISO emission and canopy flux from poplar were investigated at Open Top Chambers and Free Air Ozone Concentration Enrichment system (O3-FACE). Poplar species were selected because they are widespread in China. The main aims are: to develop the linear or non-linear dose-response relationship between ISO emission and O3 doses or stomatal O3 uptake fluxes under different N deposition conditions; to uncover the mechanisms of the combined effect of elevated O3 concentration and N deposition on ISO emission by measuring ISO emission and relevant physiological and biochemical indexes at different leaf positions; to clarify the interaction of O3 pollution and N deposition on the seasonal and inter-annual variation of ISO exchange fluxes over the canopy. Canopy ISO emission flux of the poplar plantation was estimated by model algorithms combined with leaf biomass, leaf area and meteorological parameters. These results are relevant for the optimization of regional model of ISO emission and for predicting the response of terrestrial ecosystem to global environmental change.

异戊二烯（ISO）是植物释放的最具代表性的挥发性有机化合物单体，对大气光化学进程和全球气候具有重要的影响。近地层臭氧（O3）污染和大气氮（N）沉降增加是全球环境变化的主要问题，不仅危害植物生长和代谢，还影响植物源ISO释放。但目前O3和N沉降对植物源ISO释放的复合影响研究很少。本项目拟以我国广泛种植的杨树为研究对象，利用开顶气室和开放式O3熏蒸平台（O3-FACE），研究不同N水平下，ISO释放与O3剂量/吸收量的线性/非线性响应关系；通过测定杨树不同叶位ISO释放及相关生理生化指标，揭示复合作用对杨树ISO释放的影响机制；通过模式算法结合杨树人工林叶生物量、叶面积和气象参数估算杨树冠层ISO排放通量，阐明O3和N沉降共同增加对杨树人工林冠层ISO排放通量季节和年际变化规律的影响，为优化区域ISO评估模型和预测陆地生态系统应对全球变化的响应提供数据支撑。

异戊二烯(ISO)是植物释放的最具代表性的挥发性有机化合物单体。因其全球较高的排放总量及较高活性，其排放对大气环境质量和全球气候有非常重要的影响。臭氧污染和氮沉降不仅影响植物生长还影响植物ISO排放，但目前臭氧和氮沉降对植物源ISO复合影响研究还非常稀缺。本研究以杨树为研究对象，利用开顶气室(OTCs)和开放式臭氧熏蒸平台(O3-FACE)系统探究杨树ISO排放应对臭氧和氮沉降复合作用的响应。结果表明：1)臭氧和氮添加对杨树ISO排放的影响因冠层叶位的不同而具有明显差异。高浓度臭氧和氮添加不影响上部叶位排放，但臭氧处理显著降低中部和下部叶位ISO排放，氮添加则具有相反的作用；2)杨树ISO排放与AOT40和PODY相关性也因叶位及氮添加水平而异。上部叶位响应关系不显著，但中部叶位低氮处理以及下部叶位所有氮处理下杨树ISO排放与AOT40和PODY存在显著负相关性；3)长期处理比短期处理对臭氧和氮沉降对叶片和整株水平ISO排放的影响更显著，但由于臭氧和氮添加对整株叶面积的影响，叶片水平排放对复合作用的响应与整株水平ISO排放存在差异；4)长期臭氧暴露对排放的降低主要来自合成前体物的降低，但短期臭氧暴露对排放的影响可能来自酶活的改变。此外，不同基因型或倍性杨树ISO排放对臭氧污染的响应机制并不相同。敏感性杨树(二倍体)ISO排放的降低主要来自高浓度臭氧对ISO合成能力的影响如DMADP和ISPS酶活性和蛋白含量的降低，但臭氧对抗性杨树(三倍体)ISO排放能力的影响可能与叶片内部ISO排放的损失有关。研究为区域ISO排放总量的模拟优化提供理论参考和数据支持，对预测全球环境变化背景下陆地生态系统对大气环境及全球气候的反馈具有重要的意义。