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.

若要精准预测未来气候情景下的多年冻土（permafrost）碳反馈过程，针对多年冻土生态系统热量交换开展面向非专业受众的写实表征十分必要。本项目将针对植被与景观特征对多年冻土热状态的影响开展泛北极（pan-arctic）定量评估。通过跨生态系统、景观特征与区域的研究，本研究将识别出通用规律；而密集型能量平衡站点将从机制层面解析生态系统对多年冻土响应气候变化的影响。

本研究的影响将通过以下途径得以强化：将研究成果整合至区域及特定站点的多年冻土模型，并开展综合研究，以解析生态系统对能量平衡以及多年冻土气候变化脆弱性的影响。此项工作将对科学界与公众产生广泛影响，因其整合了全球环境中的关键议题，并提升了人们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人员与美国国家科学基金会（National Science Foundation, NSF）资助的本科生野外研究体验项目的合作，为本科生提供培训机会。研究人员将在本拟议工作中指导多名学生，同时还将在一所以本科生为主体的院校开设两门北极系统科学课程。本项目将通过持续与教育中心、当地社区，尤其是与教师和外联协调人员开展合作，提升科学传播与认知水平。

**技术层面**：气候变暖将导致多年冻土分布显著缩减，但在未来气候情景下明确多年冻土的演化命运仍存在巨大不确定性。这些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驱动。对多年冻土温度的长期监测已证实了这些局地条件的重要性，但目前尚未有泛北极项目协同开展生态与景观变量监测以及多年冻土温度监测工作。

本项目将结合野外实测与遥感数据，解答植被与景观因子如何调控多年冻土温度对气候变化的响应这一科学问题。为解答该问题，研究人员将把泛北极植被-多年冻土动态的大范围评估，与灌丛和树木冠层覆盖对生态系统能量平衡影响的密集型定点研究相结合。

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，即本提案拟设立的植被-能量平衡站点，将在西伯利亚的灌丛-树木冠层覆盖梯度带开展——该区域分布着全球绝大多数多年冻土区。这些密集型研究的能量平衡站点将提升我们对生态系统组分及其相互作用对生态系统能量平衡以及多年冻土气候变化脆弱性影响的机制性认知。反过来，这些机制性认知将助力解释通过泛北极多年冻土温度监测站点采样所观测到的大范围格局。