Collaborative Research: Vegetation And Ecosystem Impacts On Permafrost Vulnerability

Nontechnical Realistic representations of heat exchange in permafrost ecosystems are necessary for accurate predictive understanding of the permafrost carbon feedback under future climate scenarios. This project will provide a quantitative pan-arctic assessment of the effects of vegetation and landscape characteristics on permafrost thermal regimes. By working across ecosystems, landscape characteristics, and regions, the research will identify broad trends, and intensive energy balance sites will provide a mechanistic study of ecosystem impacts on permafrost response to climate change. The impacts of this study will be enhanced through integration of research results into regional and site-specific permafrost models and synthesis activities that will examine ecosystem impacts on energy balance and permafrost vulnerability to climate change. This work will have broad impacts on the scientific community and general public because it brings together important issues in the global environment and raises awareness of the connection between ecosystem dynamics and permafrost thaw. The proposed project will provide training opportunities for undergraduate students through collaboration between the researchers and an NSF funded field research experience for undergraduates. The researchers will mentor several students as part of this proposed work and will also teach two arctic system science courses at a predominantly undergraduate institution. This project will enhance scientific understanding through continued work with education centers, local communities and, in particular, with teachers and outreach coordinators. Technical Significant declines in permafrost distribution are expected as the climate warms, but large uncertainties remain in determining the fate of permafrost under future climate scenarios. These uncertainties are driven, in large part, by vegetation and ecosystem properties that modulate the effect of climate on permafrost temperatures. Long-term monitoring of permafrost temperatures demonstrates the importance of these local conditions, yet there has been no pan-arctic effort to measure ecological and landscape variables in concert with permafrost temperature monitoring. This project will use a combination of field and remotely-sensed data to address the question of how vegetation and landscape factors modulate permafrost temperature response to climate change. To address this question the researchers will couple an extensive pan-arctic assessment of vegetation-permafrost dynamics with an intensive study of shrub and tree canopy cover effects on ecosystem energy balance. The first component of this research will be conducted at long-term permafrost temperature monitoring sites in Siberia and Alaska, and the second component, the vegetation-energy balance sites that will be established as part of this proposal, will be conducted at a shrub-tree canopy cover gradient in Siberia, where most permafrost regions are located. These intensively studied energy balance sites will provide an improved mechanistic understanding of the effects of ecosystem components, and interactions among these components, on ecosystem energy balance and permafrost vulnerability to climate change. This mechanistic knowledge will, in turn, support interpretation of broad patterns observed through a pan-arctic sampling of the permafrost temperature monitoring sites.

为在未来气候情景下精准预测多年冻土（permafrost）碳反馈，亟需获取寒区生态系统热交换过程的非技术写实表征。本项目将针对植被与景观特征对多年冻土热状况的影响开展量化泛北极（pan-arctic）评估。研究将覆盖不同生态系统、景观特征与区域，以识别宏观趋势；同时将通过重点能量平衡观测站点，从机制层面解析生态系统对多年冻土响应气候变化的调控作用。
本研究成果可通过整合至区域及站点专属多年冻土模型，并结合相关合成分析工作得到强化——这些合成分析将聚焦生态系统对能量平衡的影响，以及多年冻土对气候变化的脆弱性。本项工作将对科学界与公众产生广泛影响：它将全球环境领域的核心议题加以整合，并提升大众对生态系统动态与多年冻土融化之间关联的认知。
本拟议项目将通过研究者与美国国家科学基金会（National Science Foundation, NSF）资助的本科生野外研究实践项目合作，为本科生提供培训机会。研究者将指导多名学生参与本项研究工作，同时将在一所以本科教育为主体的院校开设两门北极系统科学课程。本项目还将通过持续与教育机构、当地社区，特别是教师与外联协调员开展合作，进一步深化科学认知。

技术层面：随着气候变暖，多年冻土的分布预计将大幅缩减，但在未来气候情景下，多年冻土的演变趋势仍存在较大不确定性。这类不确定性在很大程度上由调控气候对多年冻土温度影响的植被与生态系统属性所导致。长期多年冻土温度监测工作已证实了这些局地条件的重要性，但目前尚无泛北极尺度的研究同时开展生态与景观变量监测及多年冻土温度监测。
本项目将结合野外与遥感数据，解答植被与景观因子如何调控多年冻土对气候变化的温度响应这一科学问题。为解答该问题，研究者将结合两项研究内容：一是对植被-多年冻土动态开展广泛的泛北极评估，二是针对灌丛与林冠覆盖对生态系统能量平衡的影响开展重点研究。
本研究的第一部分将在西伯利亚与阿拉斯加的长期多年冻土温度监测站点开展；第二部分即本提案拟新建的植被-能量平衡观测站点，将在西伯利亚存在多数多年冻土分布的灌丛-林冠覆盖梯度区域开展。这些重点研究的能量平衡观测站点将帮助我们从机制层面更深入理解生态系统组分及其相互作用对生态系统能量平衡及多年冻土气候变化脆弱性的影响。反过来，这类机制性认知将助力解读通过泛北极尺度多年冻土温度监测站点采样所观测到的宏观格局。