Collaborative Research: Hydrologic and Permafrost Changes Due to Tree Expansion into Tundra

合作研究：树木扩展到苔原导致的水文和永久冻土变化

• 批准号: 1724786
• 负责人: Desheng Liu
• 金额: $ 18.02万
• 依托单位: Ohio State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-09-01 至 2022-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1724786&HistoricalAwards=false
• 关键词: Collaborative; Research; Hydrologic; Permafrost; Changes

The Arctic has been warming at an accelerating rate over the last several decades, and at the same time, trees and shrubs have been invading into tundra across the polar regions of Alaska, Canada, and Russia. These shifts in vegetation may, in turn, have the potential to influence regional hydrology and climate. The goal of this collaborative project is to combine approaches to study water, energy, and carbon cycling to understand inteactions between forest and tundra, including permafrost. The investigators will examine the effects of tree expansion, or encroachment, on movement of water between earth and air in an understudied forest-tundra boundary in the Siberian Arctic. The methods will include collection and analysis of field data, use of remote sensing, and modeling. The investigators will collaborate with scientists and students in Russia, and U.S. graduate students will be exposed to interdisciplinary research, perform field work in Russia, and have the opportunity to develop international collaborations. Various outreach activities will inform the public about results of this research and more generally, about the role of the Arctic in global environmental change. These activities include development of museum exhibits at the Museum of Natural History (MI), Orton Geological Museum (OH), Museum of Prairiefire (KS); public research seminars engaging indigenous people of Yamal (Russia); and documentaries showcasing this study in social and news media.The objective of this project is to study changes in hydrology and permafrost associated with tree expansion into tundra areas at the scales of both the field observational program and the regional Western Siberian Plain. The underlying hypotheses are that the tree encroachment process 1) alters the seasonality of heat exchange between the land and the atmosphere, 2) increases surface evapotranspiration, and 3) leads to warming of the subsurface with a progressive increase of thickness of soil seasonal thaw depth. The research builds on fifty years of observations in the areas with documented larch and spruce encroachment in the Polar Urals and southern Yamal Peninsula of Russia. The investigators will use a novel theory combined with comprehensive field observational data and remote sensing analyses to reveal the differences in heat exchange between the tundra and forest land covers. Pairs of field monitoring plots will be identified, with expansion of larch and spruce in one plot and no encroachment in the second of the pair. Field observations will include measurements of: micrometeorology, snow conditions, and radiative fluxes; tree-scale sap flows; snow water equivalent; soil temperature, moisture, and heat fluxes; active layer thickness; and soil composition. Field data will inform a model to derive surface energy budgets and heat fluxes. Remote sensing data from 1980s to present will connect local trends inferred from these field observations with regional characertistics of the Western Siberian Plain. Observed and modeled heat fluxes will be used in a comprehensive physical model to study the impact of vegetation encroachment on permafrost dynamics at both local and regional scales, and analysis of uncertainty will assess the reliability of the project findings.

在过去的几十年里，北极一直在以加速的速度变暖，与此同时，树木和灌木一直在入侵阿拉斯加、加拿大和俄罗斯等极地地区的苔原。反过来，植被的这些变化可能会对区域水文和气候产生影响。这个合作项目的目标是将研究水、能源和碳循环的方法结合起来，以了解森林和冻土之间的相互作用，包括永久冻土。研究人员将在西伯利亚北极未被研究的森林-冻土带边界上，研究树木扩张或侵蚀对土壤和空气之间水分运动的影响。这些方法将包括收集和分析实地数据、使用遥感和建模。调查人员将与俄罗斯的科学家和学生合作，美国研究生将接触到跨学科研究，在俄罗斯进行实地考察，并有机会开展国际合作。各种外展活动将向公众通报这项研究的结果，以及更广泛地说，关于北极在全球环境变化中的作用。这些活动包括开发自然历史博物馆(MI)、奥顿地质博物馆(OH)、草原火博物馆(KS)的博物馆展品；参与(俄罗斯)亚马尔原住民的公共研究研讨会；以及在社会和新闻媒体上展示这项研究的纪录片。该项目的目标是在野外观测计划和区域西西伯利亚平原的尺度上研究与树木扩展到冻土地区有关的水文学和永冻土的变化。其基本假设是：1)树木入侵过程改变了陆地和大气之间的热量交换的季节性；2)增加了地表蒸散量；3)随着土壤季节融化深度的增加，次表层变暖。这项研究建立在对俄罗斯极地乌拉尔和亚马尔半岛南部有记录的落叶松和云杉入侵地区50年来的观察基础上。研究人员将使用一种新的理论，结合全面的现场观测数据和遥感分析，揭示冻土带和森林土地覆盖之间的热交换差异。将确定成对的田间监测地块，其中一块地块有落叶松和云杉的扩张，第二块地块没有被侵占。野外观测将包括以下测量：微气象、雪条件和辐射通量；树木尺度树液流量；雪水当量；土壤温度、水分和热通量；活动层厚度；以及土壤成分。现场数据将为模型提供信息，以求出地表能量收支和热通量。从20世纪80年代到现在的遥感数据将把这些实地观测得出的地方趋势与西西伯利亚平原的区域特征联系起来。观测和模拟的热通量将在一个综合的物理模型中使用，以研究植被侵蚀对当地和区域尺度上的永久冻土动力学的影响，不确定性分析将评估项目结果的可靠性。

项目成果

Decreasing rainfall frequency contributes to earlier leaf onset in northern ecosystems

• DOI: 10.1038/s41558-022-01285-w
• 发表时间: 2022-02
• 期刊: Nature Climate Change
• 影响因子: 30.7
• 作者: Jian Wang;Desheng Liu;P. Ciais;J. Peñuelas

Vegetation green‐up date is more sensitive to permafrost degradation than climate change in spring across the northern permafrost region

• DOI: 10.1111/gcb.16011
• 发表时间: 2021-12
• 期刊: Global Change Biology
• 影响因子: 11.6
• 作者: Jian Wang;Desheng Liu

Reconstructing Digital Terrain Models from ArcticDEM and WorldView-2 Imagery in Livengood, Alaska

• DOI: 10.3390/rs15082061
• 发表时间: 2023-04
• 期刊: Remote. Sens.
• 作者: Tianqi Zhang;Desheng Liu

Spatiotemporal dynamics of encroaching tall vegetation in timberline ecotone of the Polar Urals Region, Russia

• DOI: 10.1088/1748-9326/ac3694
• 发表时间: 2021-11
• 期刊: Environmental Research Letters
• 影响因子: 6.7
• 作者: Wenbo Zhou;V. Mazepa;S. Shiyatov;Yulia V. Shalaumova;Tianqi Zhang;Desheng Liu;A. Sheshukov