The next step: Capitalizing on long-term experimental manipulations to understand and predict arctic terrestrial ecosystem responses to climate warming

毫无疑问，北极最近正在经历快速变暖，这很可能对其生态系统的结构和功能产生重大影响。作为陆地生态系统生态学家和生物地球化学家，我的研究在未来15年的长期目标是大幅推进我们对加拿大北极苔原生态系统功能的生物学理解，因此它们如何受到气候变化的影响。在接下来的5年的研究期间，我将充分调查我们最近发现的机制和影响，从而大大提高我们对控制北极陆地生态系统功能的生物控制和相互作用的理解。我的建议描述了多个具体的假设，这些假设围绕着以下三个主要的相互关联的目标，这些目标是我以前的研究中产生的：确定本研究发现的中等冻土带植物生长受氮(N)和磷(P)共同限制的生物地球化学和生态学意义。预测气候变化以及北美驯鹿和其他食草哺乳动物减少对冻土带落叶和常绿灌木丰度的可能影响。3. 评估植物、土壤和土壤微生物化学计量差异对了解冻土带生态系统对气候变化的响应的生物地球化学意义。我的实验室小组将使用我于2004年在加拿大中部低北极地区的大胆湖研究基地发起的实验基础设施来测试创新的研究假设。这些完全重复（n = 5-10）的实验操作包括高因子和低因子恩智浦每年添加，夏季塑料温室，雪栅栏和驯鹿的禁闭。此外，我还对达林湖景观中各种生境类型的植被变化进行了长期观察研究，魁北克北部的第二个试验施肥研究地点，在阿拉斯加的图里克和瑞典的阿比斯库进行了积极的研究合作，我还领导了几项基于同事从52个高纬度苔原地点采集的叶子和土壤样本的泛北极调查。开展这些研究将提供前沿的HQP培训，包括生态化学计量学和草食-植物-土壤养分相互作用等新兴概念，以及开发和使用新的/最新技术，如用于测量冻土带植物有效养分的离子交换膜，分别用于测定磷通量和氮固定的磷酸p18op和15N同位素，以及土壤酶学。最终，我希望这项研究将导致北方的适应性土地管理，以及公众对北极生态价值的更多认识，从而为整个加拿大敲响更有效和可持续的环境政策和实践的警钟。

The Arctic is undoubtedly experiencing rapid recent warming that is very likely to substantially affect the structure and functioning of its ecosystems. As a terrestrial ecosystem ecologist and biogeochemist, the long-term goal of my research over the next 15 years is to substantially advance our biological understanding of how Canadian arctic tundra ecosystems function, and therefore how they may be affected by climate change. This next 5 year research period is the time for me to fully investigate the mechanisms and implications of our recent discoveries, so as to significantly improve our understanding of the biological controls and interactions that govern arctic terrestrial ecosystem functioning. My proposal describes multiple specific hypotheses that are centered on the following three major interconnecting objectives which have arisen from my previous research:1. To determine the biogeochemical and ecological significance of our discovery that mesic tundra plant growth can be co-limited by nitrogen (N) and phosphorus (P).2. To predict the likely impacts of not just climate change, but also declining caribou and other mammalian herbivory, on tundra deciduous and evergreen shrub abundances. 3. To evaluate the biogeochemical significance of the stoichiometric differences among plants, soils, and soil microbes in understanding tundra ecosystem responses to climate change.My lab group will test innovative research hypotheses using the experimental infrastructure that I initiated at our Daring Lake research site in central low arctic Canada in 2004. These fully replicated (n = 5-10) experimental manipulations include both high and low-level factorial NxP annual additions, summer plastic greenhouses, snowfences, and caribou exclosures. In addition, I have a long-term observational study of vegetation change across the full range of habitat-types in the Daring Lake landscape, a second experimental fertilization research site in Northern Quebec, ongoing active research collaborations at Toolik, Alaska and Abisko, Sweden, and I am leading several pan-Arctic investigations based on colleagues' leaf and soil samples from 52 high latitude tundra sites. Undertaking these investigations will provide cutting-edge HQP training in emerging concepts such as ecological stoichiometry and herbivore-plant-soil nutrient interactions, and in the development and use of novel/recent techniques such as ion exchange membrane for measuring plant available nutrients in tundra, phosphate P 18Op and 15N isotope use for determining P fluxes and N fixation respectively, and soil enzymology. Ultimately, I hope that this research will lead to adaptive land management in the North, as well as greater public appreciation of the ecological value of the Arctic, and therefore serve as a wake-up call' to more effective and sustainable environmental policies and practices for Canada as a whole.