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.

在过去的几十年中，北极一直以加速的速度变暖，与此同时，在阿拉斯加，加拿大和俄罗斯的极地地区，树木和灌木也入侵了苔原。植被中的这些转变反过来可能会影响区域水文学和气候。这个协作项目的目的是结合研究水，能量和碳循环的方法，以了解森林和苔原（包括永久冻土）之间的意见。研究人员将检查树木膨胀或侵占的影响，对西伯利亚北极地区研究研究的森林刺激边界中水之间的水运动。该方法将包括对现场数据的收集和分析，遥感的使用和建模。调查人员将与俄罗斯的科学家和学生合作，美国研究生将接受跨学科研究，在俄罗斯进行实地研究，并有机会发展国际合作。各种外展活动将向公众提供这项研究的结果，更普遍地了解北极在全球环境变化中的作用。这些活动包括在天然历史博物馆（MI），奥尔顿地质博物馆（OH）的博物馆展览开发，草原博物馆（KS）；吸引雅马尔土著人民（俄罗斯）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。该项目的目的是研究与田间观测计划和西西伯利亚区域西伯利亚平原的尺度上的树木扩展到苔原地区相关的水文学和多年冻土的变化。潜在的假设是树侵占过程1）改变土地和大气之间的热量交换的季节性，2）增加表面蒸散液，3）3）导致地下变暖，随着土壤季节性融化深度的厚度逐渐增加。这项研究基于在俄罗斯的极地乌拉尔和南部雅马尔半岛的落叶岩和云杉侵占的地区进行了五十年的观察。研究人员将使用一种新颖的理论，结合了综合的现场观察数据和遥感分析，以揭示苔原和森林土地覆盖率之间的热交换差异。将确定成对的野外监测图，并在一个地块中扩展落叶岩和云杉，而两对中的第二个则没有侵蚀。现场观察将包括：微气流学，降雪条件和辐射通量的测量；树尺度的汁液流；雪水等效；土壤温度，水分和热通量；主动层厚度；和土壤组成。现场数据将告知模型以得出表面能预算和热通量。从1980年代到现在的遥感数据将将这些现场观察结果推断的局部趋势与西伯利亚西部平原的区域特征联系起来。观察和建模的热通量将在一个全面的物理模型中使用，以研究植被侵占对局部和区域尺度上多年冻土动态的影响，不确定性的分析将评估项目发现的可靠性。

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

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

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