EDI Data Portal
Includes: denitrification enzymatic activity (denitrate), N2O production potential, relative production of N2O (fN2O), AFDM, extractable, stream water and pore water NO3, NH4, DOC, thaw depth of upland sites, bulk density. A warming climate causes permafrost to thaw, especially in the region of discontinuous permafrost, where soil temperatures may only be a few degrees below 0 degC. Permafrost thaw may be exacerbated by more frequent and severe fires that remove insulating organic layers above permafrost. Soil thaw releases carbon and nitrogen (N) into the actively cycling pools, and whereas carbon emissions following permafrost thaw are well documented, the fates of N remain unclear. Denitrification could release thawed N as nitrous oxide (N2O) or nitrogen gas (N2), but the contributions of these processes to the high-latitude N cycle remain uncertain. We quantified microbial capacity for denitrification and N2O production in boreal soils, lakes, and streams, and assessed correlates of denitrifying enzyme activity (DEA) in Interior Alaska. Across all landscape positions, DEA under anoxia and nitrate and organic carbon amendment was 4.15 microgram N2O-N /kg dry soil*h (range -6.39 to 479.94). Riparian soils and stream sediments supported the highest potential rates of denitrification, upland soils were intermediate, and lakes supported lower rates, whereas deep permafrost soils supported little denitrification. Time-since-fire had no effect on denitrification potential in upland soils. Across all landscape positions, DEA was negatively correlated with ammonium pools. Within each landscape position, potential rate of denitrification increased with soil or sediment organic matter content. Widespread N loss to denitrification in the boreal forest could constrain the capacity for N-limited primary producers to maintain carbon stocks in soils following permafrost thaw.
