Increased Arctic NO 3 − Availability as a Hydrogeomorphic Consequence of Permafrost Degradation and Landscape Drying

• Published in: Nitrogen
• Main Authors: Carli A. Arendt, Jeffrey M. Heikoop, Brent D. Newman, Cathy J. Wilson, Haruko Wainwright, Jitendra Kumar, Christian G. Andersen, Nathan A. Wales, Baptiste Dafflon, Jessica Cherry, Stan D. Wullschleger
• Format: Article in Journal/Newspaper
• Language: English
• Published: MDPI AG 2022
• Subjects: polygonal permafrost; climate change; Arctic; nutrient availability; nitrate; soil moisture; Ecology; QH540-549.5; Climate change; permafrost; Tundra
• Online Access: https://doi.org/10.3390/nitrogen3020021; https://doaj.org/article/39d66e730cc34018a7ef8177b62c2466

Climate-driven permafrost thaw alters the strongly coupled carbon and nitrogen cycles within the Arctic tundra, influencing the availability of limiting nutrients including nitrate (NO 3 − ). Researchers have identified two primary mechanisms that increase nitrogen and NO 3 − availability within permafrost soils: (1) the ‘frozen feast’, where previously frozen organic material becomes available as it thaws, and (2) ‘shrubification’, where expansion of nitrogen-fixing shrubs promotes increased soil nitrogen. Through the synthesis of original and previously published observational data, and the application of multiple geospatial approaches, this study investigates and highlights a third mechanism that increases NO 3 − availability: the hydrogeomorphic evolution of polygonal permafrost landscapes. Permafrost thaw drives changes in microtopography, increasing the drainage of topographic highs, thus increasing oxic conditions that promote NO 3 − production and accumulation. We extrapolate relationships between NO 3 − and soil moisture in elevated topographic features within our study area and the broader Alaskan Coastal Plain and investigate potential changes in NO 3 − availability in response to possible hydrogeomorphic evolution scenarios of permafrost landscapes. These approximations indicate that such changes could increase Arctic tundra NO 3 − availability by ~250–1000%. Thus, hydrogeomorphic changes that accompany continued permafrost degradation in polygonal permafrost landscapes will substantially increase soil pore water NO 3 − availability and boost future fertilization and productivity in the Arctic.