Characterizing Production of Nitrous Oxide in High Arctic Polar Desert.

Nitrous oxide (N₂O) is a major greenhouse gas released from different types of soil by microbes, and High Arctic is a region where N₂O emissions are observed. In this region, nitrification was shown to be main process in which N₂O is produced. Soil properties including soil nutrients and pH control nitrification. However, how main soil properties in High Arctic influence production of N₂O in nitrification is not clearly characterized. In this region, it is important to take cryoturbation caused by freeze-thaw cycle into account. A type of cryoturbation causes upward movement of soil materials from above permafrost to occur in soil, which results in diapir formation. Therefore, nitrifier may receive key nutrients necessary to nitrification provided from bottom part of soil by diapir formation. Soil sampling was performed at Alexandra Fjord, Ellesmere Island, Nunavut Territory, Canada (78°53’N, 75°55’W). Soil sampling was done in two different types of polar desert, i.e. the dominant general vegetation type in High Arctic. Soil samples were taken from both soils affected by diapir formation and without the formation in the deserts. Gross rates of nitrification and mineralization were performed using stable isotope dilution techniques. While gross nitrification rates and mineralization rates were significantly different between the two types of polar desert, neither gross nitrification rates nor mineralization rates were significantly different between presence and absence of diapir formation. To interpret the results, we are currently investigating key soil properties including soil organic carbon, nitrogen, phosphorous, and pH. Those data will be assessed if there is the relationship between the soil properties and the observed gross rates of nitrification and mineralization.