OPP-PRF: Freeze-thaw effect on Biogeochemistry and Nutrient Cycling in Arctic Soils

OPP-PRF：冻融对北极土壤生物地球化学和养分循环的影响

• 批准号: 2138937
• 负责人: Erin Rooney
• 金额: $ 34.63万
• 依托单位: University of Tennessee Knoxville
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-07-01 至 2024-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2138937&HistoricalAwards=false
• 关键词: OPP; PRF; Freeze; thaw; effect

Warming air temperatures are thawing frozen ground (permafrost) in the Arctic at a rapid rate. As frozen ground thaws it undergoes temperature fluctuations above and below freezing, known as freeze-thaw cycles. Freeze-thaw can impact the availability of important nutrients such as nitrogen and phosphorus, the activity of microorganisms, soil moisture and associated changes in oxygenation, and the release of greenhouse gases from thawing ground. The implications of freeze-thaw in thawing permafrost are amplified in the Arctic, which stores just under half of all soil carbon across the globe. This research will determine how exposure of previously frozen ground to freeze-thaw alters soil function and nutrient availability. This project supports one postdoctoral scholar and will fund freeze-thaw research and the development of an educational R/RStudio module for an Arctic dataset.Freeze-thaw is a disruptive, temperature driven process with direct impacts to both abiotic and biotic soil properties and their coupled interactions. Rising air temperatures expose previously unavailable compounds to plant uptake, microbial activity, and mineral sorption and precipitation while also altering biogeochemical processes within thawed soil. Freeze-thaw has been recorded to influence the migration of soil solutes (such as P, N, and Fe) through cryosuction in non-permafrost soils. In permafrost-affected soils, freeze-thaw triggered solute migration may coincide with nutrient pulses to the soil environment following microbial cell lysis and death or soil aggregate instability and breakage. In alpine and grassland systems, cryosuction during freeze-thaw can increase anoxic soil conditions with varying levels of Fe reduction and result in subsequent impacts to soil aromatics and dissolved organic carbon concentrations. The number of freeze-thaw cycles, freezing rate, and spatial distribution of freeze-thaw may vary, altering the degree of transport during cryosuction as well as informing microbial adaptation and resiliency. The proposed work will combine field data with freeze-thaw experiments to investigate temporal and spatial variations in freeze-thaw and the direct impacts to critical processes of soil biogeochemistry across a hillslope gradient in Alaskan tundra permafrost at the Toolik Field Station. The investigator will test the hypothesis that permafrost soil chemistry will be altered during the first freeze-thaw cycle, resulting in continuous changes in redox and nutrient availability throughout subsequent freeze-thaw. The study aims to restructure our understanding of permafrost thaw to include responses of the soil nutrient regime, redox chemistry, and microbial communities to freezing rate, repeated freeze-thaw, and spatial variation of freeze-thaw cycling.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

变暖的气温正在迅速融化北极的冻土层。当冻土融化时，它会经历高于和低于冰点的温度波动，称为冻融循环。冻融可以影响氮和磷等重要营养物质的可用性，微生物的活性，土壤水分和相关的氧合变化，以及解冻土壤中温室气体的释放。在北极，永久冻土层融化中冻融的影响被放大了，北极储存了地球仪近一半的土壤碳。这项研究将确定以前冻结的地面暴露于冻融如何改变土壤功能和养分供应。该项目支持一名博士后学者，并将资助冻融研究和北极数据集教育R/RStudio模块的开发。冻融是一个破坏性的，温度驱动的过程，对非生物和生物土壤特性及其耦合相互作用产生直接影响。气温上升使以前无法获得的化合物暴露于植物吸收、微生物活性、矿物吸附和沉淀，同时也改变了解冻土壤中的地球化学过程。冻融作用影响了非冻土区土壤溶质（如P、N和Fe）通过低温抽吸的迁移。在受多年冻土影响的土壤中，冻融引发的溶质迁移可能与微生物细胞裂解和死亡或土壤团聚体不稳定和破碎后营养素脉冲到土壤环境相一致。在高山和草原系统中，冻融期间的低温抽吸会增加土壤缺氧条件，导致不同程度的铁还原，并导致随后对土壤芳香族化合物和溶解有机碳浓度的影响。冻融循环的次数、冷冻速率和冻融的空间分布可能会有所不同，从而改变冷冻抽吸过程中的运输程度，并为微生物的适应性和弹性提供信息。拟议的工作将结合联合收割机现场数据与冻融实验，以调查冻融的时间和空间变化和直接影响的关键过程的土壤地球化学在阿拉斯加冻土带永久冻土在图利克野外站的山坡梯度。研究人员将测试的假设，即永久冻土土壤化学将在第一次冻融循环中发生变化，导致在整个后续冻融过程中氧化还原和养分供应的持续变化。该研究旨在重新构建我们对冻土融化的理解，包括土壤养分状况，氧化还原化学和微生物群落对冻结速率，反复冻融和冻融循环空间变化的反应。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

项目成果

Topography and canopy cover influence soil organic carbon composition and distribution across a forested hillslope in the discontinuous permafrost zone

• DOI: 10.1002/ppp.2200
• 发表时间: 2023-07
• 期刊: Permafrost and Periglacial Processes
• 影响因子: 5
• 作者: Erin C. Rooney;V. Bailey;Kaizad F. Patel;A. Kholodov;H. Golightly;R. Lybrand