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

北极最近无疑正在经历迅速变暖，这很可能对其生态系统的结构和功能产生重大影响。作为一名陆地生态系统生态学家和生物地球化学家，我在未来15年的研究的长期目标是大幅提高我们对加拿大北极苔原生态系统如何运作的生物学理解，以及它们可能如何受到气候变化的影响。在接下来的五年研究期间，我将充分研究我们最新发现的机制和影响，以便显著提高我们对支配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，这些假设围绕着我以前的研究得出的以下三个相互关联的主要目标：*1.确定我们发现的苔原植物生长可能受到氮(N)和磷(P)共同限制的生物地球化学和生态学意义。*2.预测不仅气候变化，而且驯鹿和其他哺乳动物草食动物数量下降对苔原落叶和常绿灌木丰度的可能影响。*3.为了评估植物、土壤和土壤微生物之间的化学计量差异在理解冻土带生态系统对气候变化响应方面的生物地球化学意义。*我的实验室团队将使用我于2004年在加拿大中低北极的达令湖研究基地发起的实验基础设施来测试创新的研究假设。这些完全重复的(n=5-10)实验操作包括高水平和低水平因子恩智浦年产量增加、夏季塑料温室、雪栅栏和驯鹿围栏。此外，我还对魁北克北部第二个试验性施肥研究地点--大令湖景观中各种生境类型的植被变化进行了长期观测研究，正在阿拉斯加的图利克和瑞典的阿比斯科进行积极的研究合作，我还领导着几项泛北极调查，这些调查基于同事们来自52个高纬度冻土带地点的叶片和土壤样本。*开展这些调查将在生态化学计量学和草食动物-植物-土壤养分相互作用等新兴概念、开发和使用新的/最新技术方面，如用于测量冻土带植物有效养分的离子交换膜、用于分别测定P通量和N固定的磷酸盐Pδ18Op和15N同位素的开发和使用，以及土壤酶学方面，提供HQP的前沿培训。最终，我希望这项研究将导致北方的适应性土地管理，以及更多的公众对北极生态价值的欣赏，从而为整个加拿大更有效和更可持续的环境政策和实践敲响警钟。

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 δ18Op 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.