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

第一部分：非技术描述：地球陆地生态系统具有减缓或加速气候变化步伐的潜力。这个方向部分取决于植物和微生物对变暖的反应。本研究以南极洲为生态系统模型，研究简化生态系统（与其他地方的陆地生态系统相比简化了）对变暖处理的碳平衡。碳平衡是由封存的碳（通过光合作用）和释放的碳（植物和微生物呼吸）决定的。因此，为了最好地评估植物和微生物对变暖的反应，本研究使用了从冰川开始（没有植物，只有土壤微生物）到完全被植物覆盖的旧地点的植物梯度。野外的试验性升温是通过对室内空气和土壤进行加热的开顶室来实现的。生态系统的净碳交换，即固碳和释放碳的净结果，将用最先进的气体交换机在暖地和对照地进行测量。实验室温度孵化研究将补充实地工作，将碳通量的变化归因于单个植物物种和土壤微生物分类群（即“物种”）。这项研究的数据将用于地球系统气候变化模型。这项研究的重要性将通过制作由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现场和亲自访问）与更广泛的社区分享。第二部分：技术描述：陆地生态系统对变暖的碳平衡的响应将反馈给气候变化的速度，但这种反馈的大小和方向很少受到限制。最不为人所知的是变暖对土壤碳损失的影响，澄清主要的微生物控制是一个重要的研究前沿。本研究通过一系列的实验和观察，探讨了在完整生态系统中，微生物（包括自养类群）和植物对生态系统净生产力的控制对变暖的响应。现场升温是使用开顶室与对照区配对，沿生产力梯度排列。沿着这个梯度，将在生态系统水平上测量流入和流出的碳通量。目标是将气候变暖引起的生态系统净碳平衡变化与气候变暖对土壤微生物和植物的影响联系起来。实地研究将辅以实验室温度培养。由于土壤微生物主导着南极洲的生物地球化学循环，因此本研究的一个主要重点是确定细菌、真菌和古细菌对变暖的反应。这是通过一种尖端的稳定同位素技术，定量稳定同位素探测（qSIP）来实现的，该技术由提议的研究小组开发，可以识别活跃的和参与加工新碳的分类群。该技术可以识别积极参与营养物质生物地球化学循环的单个微生物类群（通过联合使用18o -水和13c -碳酸氢盐），从而可以与那些简单存在（冷保存）的微生物类群区分开来。该研究进一步评估了植被的光合作用对碳的吸收及其对变暖的敏感性。研究成果将推动气候变化、植物和土壤微生物生态学以及生态系统建模等方面的研究。科学传播将通过提供信息的视频系列、每日南极博客以及对美国学校的在线和亲自访问来实现。该奖项反映了美国国家科学基金会的法定使命，并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，被认为值得支持。

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.