Antarctica as a Model System for Responses of Terrestrial Carbon Balance to Warming

第一部分：非技术性说明：地球的陆地生态系统有可能减缓或加快气候变化的速度。方向部分取决于植物和微生物对变暖的反应。本研究以南极洲为模式生态系统，研究一个简化生态系统（与其他地方的陆地生态系统相比简化）对变暖处理的碳平衡。碳平衡由固碳（通过光合作用）和释放碳（植物和微生物呼吸）决定。因此，为了最好地评估植物和微生物对变暖的反应，这项研究使用了一种植物梯度，从冰川（没有植物，只有土壤微生物）开始，到一个完全被植物覆盖的旧场地。在野外进行的实验性升温是通过顶部敞开的温室来实现的，这些温室可以加热室内的空气和土壤。净生态系统碳交换，固存和释放碳的净结果，将在温暖和控制地块与最先进的气体交换机测量。实验室温度培养研究将补充实地工作，将碳通量的变化归因于个别植物物种和土壤微生物类群（即，“物种”）。这项研究的数据将输入地球系统气候变化模型。将通过由一家获奖的科学媒体制作公司制作的视频系列、南极博客以及通过与美国学校的互动（通过Skype进行现场访问和亲自访问），向更广泛的社区宣传这项研究的重要性。第二部分：技术说明：陆地生态系统碳平衡对变暖的反应将反馈到气候变化的速度，但这种反馈的大小和方向受到很大的限制。最不为人所知的是变暖对土壤碳损失的影响，阐明主要的微生物控制是一个重要的研究前沿。本研究采用一系列的实验和观察，调查微生物，包括自养类群，和植物控制的净生态系统生产力，以应对在完整的生态系统变暖。田间增温是通过使用顶部敞开的温室与对照地块配对来实现的，沿着生产力梯度沿着排列。沿着这一梯度，将在生态系统一级测量输入和输出的碳通量。目标是将变暖引起的净生态系统碳平衡变化与变暖对土壤微生物和植物的影响联系起来。田间研究将补充实验室温度孵育。由于土壤微生物在南极洲的地球化学循环中占主导地位，本研究的一个主要重点是确定细菌，真菌和古菌的变暖响应。这是使用尖端的稳定同位素技术，定量稳定同位素探测（qSIP）由提议的研究小组开发，可以识别活跃并参与处理新碳的分类群。该技术可以识别积极参与营养物质地球化学循环的单个微生物分类群（通过结合使用18 O-水和13 C-碳酸氢盐），因此可以与那些简单存在的（冷藏）区分开来。该研究进一步评估了植被的光合作用吸收碳及其对变暖的敏感性。研究结果将推动气候变化、植物和土壤微生物生态学以及生态系统建模方面的研究。科学交流将通过一个信息丰富的视频系列，每日南极博客，以及在线和亲自访问美国的学校来实现。这个奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估来支持。

Part I: Non-technical description:Earth’s terrestrial ecosystems have the potential to either slow down or hasten the pace of climate change. The direction depends in part on both plant and microbial responses to warming. This study uses Antarctica as a model ecosystem to study the carbon balance of a simplified ecosystem (simplified compared to terrestrial ecosystems elsewhere) in response to a warming treatment. Carbon balance is dictated by sequestered carbon (through photosynthesis) and released carbon (plant and microbial respiration). Hence, to best assess plant and microbial responses to warming, this study uses a plant gradient that starts at the glacier (no plants, only soil microbes) to an old site entirely covered by plants. Experimental warming in the field is achieved by open-top chambers that warm the air and soil inside. The net ecosystem carbon exchange, the net result of sequestered and released carbon, will be measured in warmed and control plots with a state-of-the art gas exchange machine. Laboratory temperature incubation studies will supplement field work to attribute changes in carbon fluxes to individual plant species and soil microbial taxa (i.e., “species”). Data from this study will feed into earth system climate change models. The importance of this study will be shared with the broader community through the production of a video series created by an award-winning science media production company, an Antarctic blog, and through interactions with schools in the United States (on-site through Skype and in-person visits). Part II: Technical description:Responses of the carbon balance of terrestrial ecosystems to warming will feed back to the pace of climate change, but the size and direction of this feedback are poorly constrained. Least known are the effects of warming on carbon losses from soil, and clarifying the major microbial controls is an important research frontier. This study uses a series of experiments and observations to investigate microbial, including autotrophic taxa, and plant controls of net ecosystem productivity in response to warming in intact ecosystems. Field warming is achieved using open-top chambers paired with control plots, arrayed along a productivity gradient. Along this gradient, incoming and outgoing carbon fluxes will be measured at the ecosystem-level. The goal is to tie warming-induced shifts in net ecosystem carbon balance to warming effects on soil microbes and plants. The field study will be supplemented with lab temperature incubations. Because soil microbes dominate biogeochemical cycles in Antarctica, a major focus of this study is to determine warming responses of bacteria, fungi and archaea. This is achieved using a cutting-edge stable isotope technique, quantitative stable isotope probing (qSIP) developed by the proposing research team, that can identify the taxa that are active and involved in processing new carbon. This technique can identify individual microbial taxa that are actively participating in biogeochemical cycling of nutrients (through combined use of 18O-water and 13C-bicarbonate) and thus can be distinguished from those that are simply present (cold-preserved). The study further assesses photosynthetic uptake of carbon by the vegetation and their sensitivity to warming. Results will advance research in climate change, plant and soil microbial ecology, and ecosystem modeling. Science communication will be achieved through an informative video series, a daily Antarctic blog, and online- and in-person visits to schools in the United States.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.