臭氧污染与氮胁迫对油松生理生态及地下根际的交互影响机制

Global tropospheric ozone (O3) concentration has increased in recent decades due to the urbanization development. The harmful effects of high O3 on plants are catching the attention of most researchers around the world. Under O3 stress, plants usually appear damage spot in leaves. And high O3 also accelerates leaf senescence, impairs the photosynthesis ability and other physiological and biochemical processes. Therefore the carbon assimilation is limited, especially the carbon allocation to root is reduced. As a result, the root growth and structure, even the symbionts composition in rhizosphere were greatly affected. Global climate change and extreme weather condition increase the interaction of O3 and other environmental factors. Significantly, nitrogen (N) deposition has sharply increased via industrialization and human activities. Trying to completely understand the responses of forest ecosystem under changing environment, particularly the responses of the urban ecosystem under interaction effects of O3 and N deposition, Chinese pine seedling is selected as advanced garden plant. Through the measurement of above-ground (Photosynthesis ability, physiological and biochemical trails) and below-ground (Root growth, root structure and ectomycorrhiza diversity etc.) under different O3 and N concentrations, we assess the plant resistance against O3 with N deposition comprehensively. This research serves the theoretical and practical basis for anti-air pollution and ecology improvement in the polluted city area.

随着城市化进程加剧，近几十年来全球对流层臭氧的浓度持续增加，高浓度臭氧对植物的影响备受关注。在臭氧胁迫下，植物叶片会出现伤害斑，加速老化，进而导致植物光合能力下降等一系列生理指标发生变化。同时导致碳固定下降，特别是根部碳分配比例减少，进而间接影响地下根系的生长以及根际微生物的组成。全球气候变化和极端气候常态化使得臭氧和环境因子的交互作用大大增加。受人类活动和全球工业的影响，氮沉降也不断加剧，为了进一步了解森林生态系统应对全球气候变化的响应，尤其是城市生态系统对臭氧污染以及氮沉降交互作用的响应机制，本研究选用优秀园林植物油松幼苗进行研究，通过不同臭氧浓度和氮施加浓度的梯度处理，对松树光合能力以及其他生理生化指标进行测定。此外对根系生物量、根系形态变化、外生菌根的多样性进行分析研究。全面分析在氮沉降条件下植物抵御臭氧的能力，为全球气候变化下我国治理城市空气污染，提高城市生态环境提供理论依据。

随着城市化进程加剧，近几十年来全球对流层臭氧浓度及氮沉降持续增加，高浓度臭氧同氮沉降及其交互作用对植物生长影响备受关注。本项目模拟不同浓度臭氧及氮施加，研究发现臭氧和氮沉降对油松生长影响显著。120ppb O3处理下，高氮沉使油松株高增加，在臭氧浓度为60ppb时，中浓度的氮水平油松生长最快。随着氮沉降增加，油松针叶、茎的生物量显著升高。新老叶片的光合速率在生长季不同时期对臭氧及氮胁迫响应不同。氮在生长季初期对光合速率影响显著，臭氧对新叶光合速率的影响主要在生长季末。对于去年生老叶，臭氧及氮沉降未对其光合速率产生影响。油松针叶MDA的含量、SOD活性及游离脯氨酸的含量受臭氧及氮沉降影响显著，可溶性蛋白含量不受影响。此外，0-10cm和10-20cm土层中根表面积在120ppb臭氧处理下随着氮沉降加剧而增加；60ppb臭氧处理下，中浓度的氮使得根系表面积最大。上层土壤中根系总根长受臭氧影响显著，下层土壤中受氮影响显著。臭氧及氮的交互作用影响表层土壤细根总长，粗根总长度主要受氮影响。油松外生菌根在臭氧浓度60ppb时侵染率降低。臭氧影响土壤表层外生菌根侵染率，下层土壤中外生菌根侵染率分别受氮和臭氧两个因素的影响。油松外生菌根群落构成主要是子囊菌门Ascomycota和担子菌门Basidiomycota。在属水平上发现丝盖伞属Inocybe、Fusarium属为耐臭氧菌种，Pustularias属和Wilcoxina属为耐高氮菌种。乳牛肝菌属Suillus、Neonectria属、Dactylonectria属的菌种随着氮沉降加剧减少。项目结果表明，臭氧及氮沉降影响油松生长，可通过改变根系结构，外生菌根侵染率及群落构成导致地上部分，生理指标及光合能力的改变。更科学的验证了臭氧同氮沉降对油松生长的影响机制，为适地适树及合理的绿化造林提供了科学理论依据。