Ecosystem Responses to Stratospheric Ozone Reduction

9524144平流层臭氧损失主要是由人类活动产生的化学物质造成的，它导致到达地球的太阳紫外线b辐射量增加。紫外线b辐射能够破坏生物系统，包括DNA。然而，针对平流层臭氧耗竭的潜在生物学后果的研究只有很少的一部分，而在陆地生态系统的层面上几乎没有任何研究。本研究是对阿根廷乌斯怀亚附近太阳紫外线b升高的生态系统水平的研究。该遗址位于南美洲南端，与南极半岛隔着德雷克海峡。这个地方的臭氧减少比世界上任何其他有可观植物覆盖的陆地生态系统的地方都要明显。造成这种现象的有三种现象：所谓的“臭氧空洞”可以直接从头顶经过，消耗臭氧的空气团可以从臭氧空洞向北飘去，臭氧层的普遍侵蚀在高纬度地区和南半球最为突出。在研究地点，当天空晴朗时，紫外线b的通量非常高，而当多云时，相对于太阳总辐射，紫外线b的通量非常高。因此，这将是一个极端的案例研究，以确定臭氧减少对生态系统的影响。将对一个灌草群落进行为期三年的现场实地研究。将对急性暴露（如臭氧空洞从头顶经过时）和慢性暴露（生长季节和多季节暴露）对紫外线b升高的影响进行评估。对于急性暴露于高紫外线b和高紫外线b /（太阳总辐射）比下的反应，将确定对DNA和光合作用的损害。急性暴露将作为自然事件（通过下载卫星图像和预测头顶通道来跟踪臭氧空洞的进动）和用特殊的紫外线灯系统模拟这种事件来研究。大部分工作将针对长期暴露在种群一级（例如，植物种群的繁殖和扩大或缩小）和生态系统一级的影响。研究人员将确定物种间竞争平衡的变化、年度生物事件的时间、昆虫对植物的消耗以及植物凋落物的分解。如果太阳紫外线b影响这些生态系统水平的过程，对这些系统的功能和完整性有许多影响。最近在阿根廷收集的初步证据表明，阳光紫外线b对DNA损伤、植物生长和昆虫食草性有很大影响。凋落物分解的变化可能影响生态系统碳平衡和大气二氧化碳浓度。如果我们要预测大气化学变化的生物学后果并制定合理的管理策略，了解这种变化的方向和幅度是必不可少的。

9524144 Stratospheric ozone loss, resulting primarily from chemicals generated by human activities, results in an increased amount of solar ultraviolet-B radiation reaching the earth. Ultraviolet-B radiation is capable of damaging biological systems, including DNA. Only a modest amount of research, however, has been directed toward the potential biological consequences of stratospheric ozone depletion, and virtually nothing has been done at the level of terrestrial ecosystems. This research is an ecosystem-level study of the responses to elevated solar ultraviolet-B resulting near Ushuaia, Argentina. The site is on the southern tip of South America across the Drake Passage from the Antarctic Peninsula. This location experiences more pronounced ozone reduction than at anywhere else in the world where terrestrial ecosystems with appreciable plant cover occur. Three phenomena contribute to this: The so-called "ozone hole" can pass directly overhead, parcels of ozone-depleted air can float northward from the ozone hole, and a general erosion of the ozone layer is most prominent at high latitudes and in the Southern Hemisphere. At the study site, extremely high fluxes of ultraviolet-B can occur when skies are clear and, when cloudy, there can be very high ultraviolet-B relative to total solar radiation. Thus, this will be an extreme case study to determine ecosystem-level effects of ozone reduction. A three-year, on-site field study of a shrub-grass community will be conducted. Effects of elevated ultraviolet-B will assessed for both acute exposures, such as when the ozone hole passes overhead and as chronic, growing-season and multi-season exposures to elevated ultraviolet-B. For responses to acute exposures to high ultraviolet-B and high ultraviolet-B/(total solar radiation) ratios, damage to DNA and photosynthesis will be determined. Acute exposures will be studied both as natural events (tracking the precession of the ozone hole by downloading satellite-based images and anticipating overhead passage) and by simulating such occurrences with special UV lamp systems. Most of the effort will be directed to effects of chronic exposures at the population level (e.g., reproduction and expansion or contraction of plant populations) and at the ecosystem level. Researchers will determine changes in competitive balance among species, timing of annual biological events, plant consumption by insects, and decomposition of plant litter. If solar ultraviolet-B affects such ecosystem-level processes, there are many implications for the function and integrity of these systems. Preliminary evidence collected recently in Argentina shows large effects of sunlight ultraviolet-B on DNA damage, plant growth and insect herbivory. Changes in litter decomposition may affect ecosystem carbon balance and atmospheric carbon dioxide concentrations. Knowledge of the direction and magnitude of such changes is essential if we are to predict the biological consequences of changing atmospheric chemistry and develop rational management strategies.