Increased Arctic NO3− Availability as a Hydrogeomorphic Consequence of Permafrost Degradation and Landscape Drying

• Published in: Nitrogen (Basel, Switzerland) Switzerland), 2022-06, Vol.3 (2), p.314-332
• Main Authors: Arendt, Carli A., Heikoop, Jeffrey M., Newman, Brent D., Wilson, Cathy J., Wainwright, Haruko, Kumar, Jitendra, Andersen, Christian G., Wales, Nathan A., Dafflon, Baptiste, Cherry, Jessica, Wullschleger, Stan D.
• Format: Article
• Language: English
• Subjects: Arctic; Availability; Carbon cycle; climate change; Coastal plains; Drainage; Drying; ENVIRONMENTAL SCIENCES; Evolution; Fertilization; geomorphic evolution; geospatial scaling of nutrient inventories; Hydrology; Integrated approach; Landscape; Limiting nutrients; Moisture content; Moisture effects; nitrate; Nitrates; Nitrogen; Nitrogen fixation; Nitrogenation; Nutrient availability; Nutrients; Permafrost; polygonal permafrost; Polygons; Pore water; Production increases; Shrubs; Soil degradation; Soil moisture; Soil water; Taiga & tundra; Topography; Tundra; Vegetation
• ISSN: 2504-3129; 2504-3129
• DOI: 10.3390/nitrogen3020021

Climate-driven permafrost thaw alters the strongly coupled carbon and nitrogen cycles within the Arctic tundra, influencing the availability of limiting nutrients including nitrate (NO3−). Researchers have identified two primary mechanisms that increase nitrogen and NO3− 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 NO3− 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 NO3− production and accumulation. We extrapolate relationships between NO3− and soil moisture in elevated topographic features within our study area and the broader Alaskan Coastal Plain and investigate potential changes in NO3− availability in response to possible hydrogeomorphic evolution scenarios of permafrost landscapes. These approximations indicate that such changes could increase Arctic tundra NO3− availability by ~250–1000%. Thus, hydrogeomorphic changes that accompany continued permafrost degradation in polygonal permafrost landscapes will substantially increase soil pore water NO3− availability and boost future fertilization and productivity in the Arctic.