Impacts of Climate Change on Antarctic Vascular Plants: Warming and UV-B Radiation

9615268日有强有力的证据表明，南极半岛的气候在本世纪发生了明显的变化。 天气记录表明，在过去的45年里，半岛的一些地方夏季平均气温上升了1摄氏度。 除了这一变暖趋势外，春季臭氧消耗事件已导致有充分证据证明的紫外线-B辐射水平的增加。 这些区域气候的快速变化为评估气候变化对维管植物的影响提供了独特的机会。 虽然在南极洲只有两种原生维管植物物种（Deschampsia anastritica和Colobanthus quitensis），而且分布稀少，这证明植物生存的条件十分严峻，但已有迹象表明，气候变化正在对这些物种产生重大影响。 根据沿着半岛的人口普查，区域变暖似乎导致这些物种的数量迅速增加。 增强的紫外线-B水平对这些物种的影响不太清楚。 一项实验已经开始，其中温度和紫外线辐射水平操纵周围自然生长的Deschampsia和Colobanthus植物在南极半岛，以评估他们对这些因素的反应。 评估包括检查这些植物在变暖或排除不同紫外线成分后光合作用、生长和繁殖的变化。 在第一场赛季的增长显着改善下变暖的治疗。 排除紫外线没有任何重大影响，尽管从这一短期评估中得出结论还为时过早。 将继续进行实地操作，并在四个关键领域的植物反应评估中扩大：（1）光合作用，（2）一般热适应，（3）繁殖，（4）土壤。 这些地区对于了解南极洲植物对气候变化的反应至关重要。 (1)光合作用-南极植物具有独特的光合作用特征，包括在接近冰点的温度下进行光合作用的能力和对中等温度的高度敏感性。 利用体外和体内技术，包括气体交换，叶绿素荧光和酶测定，负责这些独特的光合特性的机制将被检查。还将确定这些物种是否可以改变这些特征以应对气候变化。 (2)一般的热适应性-这些植物还必须具有良好的热适应性，使它们能够在南极生存。这些植物的细胞膜稳定性，渗透势和过冷特性将被注意到，以确定这些特性如何改变响应我们的现场操作。(3)繁殖-变暖似乎大大提高了这些植物的有性繁殖。 然而，高水平的UV-B可能会破坏花粉，从而降低繁殖成功率。 这些相反的因素的影响将通过检查生产和生活力的花粉和种子在现场操作。 (4)土壤-养分循环在控制植物对气候变化的反应方面起着重要作用。基线信息将收集在我们的实地操作下的土壤和植物中的营养物质（C，N，P）库，这将与土壤呼吸的测量相补充。

9615268 Day There is strong evidence that the climate of the Antarctic Peninsula has changed appreciably in this century. Weather records indicate that mean summer air temperatures have risen 1oC over the past 45 yr at some Peninsula locations. In addition to this warming trend, springtime ozone depletion events have resulted in well-documented increases in UV-B radiation levels. These rapid changes in regional climate provide a unique opportunity to assess the impacts of climate change on vascular plants. While the presence of only two native vascular plant species (Deschampsia antarctica and Colobanthus quitensis) and their sparse distribution in Antarctica attest to the severe conditions for plant survival, there are already indications that climate changes are exerting a strong influence on these species. Regional warming appears to be leading to rapid increases in populations of these species, based on censuses along the Peninsula. The influence of enhanced UV-B levels on these species is less clear. An experiment has been initiated in which temperature and UV radiation levels are manipulated around naturally growing Deschampsia and Colobanthus plants on the Antarctic Peninsula to assess their response to these factors. Assessment involves examining changes in photosynthesis, growth and reproduction of these plants following warming or exclusion of different UV components. During the first field season growth significantly improved under warming treatments. Exclusion of UV did not have any significant effects, although conclusions from this short-term assessment would be premature. Field manipulations will be continued, and expanded in the current assessment of plant responses in four key areas: (1) photosynthesis, (2) general thermal adaptations, (3) reproduction, and (4) soils. These areas are critical to understanding plant responses to climate change in Antarctica. (1) Photosynthesis - Antarctic plants have unique photosynthetic charact eristics including the ability to photosynthesize at near freezing temperatures and a high sensitivity to moderate temperatures. Using in vitro and in vivo techniques including gas exchange, chlorophyll fluorescence and enzyme assays, the mechanisms responsible for these unique photosynthetic traits will be examined. It will also be determined whether these species can alter these traits in response to changes in climate. (2) General thermal adaptations - These plants must also possess well-developed thermal adaptations that allow them to survive in the Antarctic. Cell membrane stability, osmotic potentials and supercooling characteristics of these plants will be noted to determine how these characteristics change in response to our field manipulations. (3) Reproduction - Warming appears to substantially improve sexual reproduction in these plants. However, high levels of UV-B may reduce reproductive success by damaging pollen. The influence of these opposing factors will be observed by examining the production and viability of pollen and seeds under field manipulations. (4) Soils - Nutrient cycling plays an important role in controlling plant responses to changes in climate. Baseline information will be collected on pools of nutrients (C, N, P) in soils and plants under our field manipulations, which will be complimented with measurements of soil respiration.