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.

温暖的空气温度是在北极融化的冷冻地面（多年冻土），速度很快。当冷冻的地面解冻时，它在冰冻上方和下方经历温度波动，称为冻融周期。冻融会影响重要营养素的可用性，例如氮和磷，微生物的活性，土壤水分和相关的氧合变化以及从融化地面释放温室气体的释放。在北极地区放大了冻融中冻融中冻融的含义，该北极储存在全球所有土壤碳的一半以下。这项研究将确定以前冷冻地面冻结的暴露如何改变土壤功能和养分的可用性。该项目支持一位博士后学者，并将为北极数据集的教育R/RSTUDIO模块提供资金。Freeze-thaw是一种破坏性的，温度驱动的过程，对非生物和生物土壤及其耦合相互作用产生直接影响。空气温度的升高暴露于以前无法获得的化合物，可植入摄取，微生物活性以及矿物质吸附和降水，同时还改变了融化的土壤中的生物地球化学过程。已经记录了通过非冻土土壤的冷冻作品来影响土壤溶质（例如P，N和FE）的迁移。在由多年冻土影响的土壤中，冻融触发的溶质迁移可能与微生物细胞裂解和死亡或土壤骨料骨料不稳定性和破裂后，可能与养分脉冲到土壤环境相吻合。在高山和草地系统中，冻融期间的冷冻作用可以增加缺氧的土壤条件，而Fe降低的水平变化，并导致对土壤芳香剂和溶解有机碳浓度的影响。冻融周期的数量，冻结速率和冻融的空间分布可能会有所不同，从而改变了冷冻过程中的运输程度，并告知微生物适应性和弹性。拟议的工作将将现场数据与冻融实验相结合，以研究冻结的时间和空间变化，以及在Alaskan tundra permafrost跨越Toolik Field站的阿拉斯加苔原（Alaskan Tundra）跨越山坡梯度的土壤生物地球化学的关键过程的直接影响。研究者将检验以下假设：在第一次冻融周期中，多年冻土土壤化学将改变，从而导致整个随后的冻结 - 盘中的氧化还原和养分可用性的持续变化。这项研究旨在重组我们对永久冻结融化的理解，包括土壤养分制度，氧化还原化学和微生物群落对冻结率，重复冻结的反应以及冻结自行车的空间变化。这一奖项奖励NSF的法律任务和范围的范围，这是通过评估的范围来弥补的。

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