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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

基本信息

批准号：
1724868
负责人：
Aleksey Sheshukov
金额：
$ 10.59万
依托单位：
Kansas 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=1724868&HistoricalAwards=false
关键词：
Collaborative Research Hydrologic Permafrost Changes

项目摘要

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，北极一直在加速变暖，与此同时，树木和灌木正在入侵阿拉斯加，加拿大和俄罗斯极地地区的苔原。植被的这些变化反过来可能会影响区域水文和气候。这个合作项目的目标是联合收割机的方法来研究水，能源和碳循环，以了解森林和苔原之间的相互作用，包括永久冻土。研究人员将在西伯利亚北极地区一个未充分研究的森林-冻土带边界考察树木扩张或侵占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。研究人员将与俄罗斯的科学家和学生合作，美国研究生将接触跨学科研究，在俄罗斯进行实地考察，并有机会发展国际合作。各种外联活动将向公众介绍这项研究的结果，并更广泛地介绍北极在全球环境变化中的作用。这些活动包括：在自然历史博物馆（密歇根州）、奥顿地质博物馆（俄亥俄州）、Prairifire博物馆（堪萨斯州）举办博物馆展览;举办有亚马尔土著人民参加的公共研究研讨会（俄罗斯）;该项目的目标是研究与树木扩张到苔原地区相关的水文和永久冻土的变化，实地观测计划和区域西西伯利亚平原。基本假设是，树木入侵过程1）改变了土地与大气之间热交换的季节性，2）增加了地表蒸散量，3）随着土壤厚度的逐渐增加，导致地下变暖季节性解冻深度。这项研究建立在对俄罗斯乌拉尔极地和亚马尔半岛南部落叶松和云杉入侵地区50年的观测基础上。研究人员将使用一种新的理论，结合全面的实地观测数据和遥感分析，揭示苔原和森林土地覆盖之间的热交换差异。将确定成对的实地监测地块，其中一个地块的落叶松和云杉的扩张，而另一个地块的落叶松和云杉没有被侵占。实地观测将包括以下测量：微气象学、雪况和辐射通量;树级液流;雪水当量;土壤温度、湿度和热通量;活动层厚度;和土壤成分。现场数据将为模型提供信息，以获得表面能量收支和热通量。从20世纪80年代至今的遥感数据将从这些实地观测推断出的当地趋势与西西伯利亚平原的区域特征联系起来。观测到的和模拟的热通量将用于一个综合物理模型，以研究植被侵蚀对当地和区域尺度的永久冻土动态的影响，对不确定性的分析将评估项目结果的可靠性。