TY - JOUR

T1 - Nitrous oxide surface fluxes in a low Arctic heath

T2 - Effects of experimental warming along a natural snowmelt gradient

AU - Kolstad, Elisabeth

AU - Michelsen, Anders

AU - Ambus, Per Lennart

N1 - CENPERM[2021]

PY - 2021

Y1 - 2021

N2 - Climate change is profound in the Arctic where increased snowfall during winter and warmer growing season temperatures may accelerate soil nitrogen (N) turnover and increase inorganic N availability. Nitrous oxide (N2O) is a potent greenhouse gas formed by soil microbes and in the Arctic, the production is seen as limited mainly by low inorganic N availability. Hence, it can be hypothesized that climate change in the Arctic may increase total N2O emissions, yet this topic remains understudied. We investigated the combined effects of variable snow depths and experimental warming on soil N cycling in a factorial field study established along a natural snowmelt gradient in a low Arctic heath ecosystem. The study assessed N2O surface fluxes, gross N mineralization and nitrification rates, potential denitrification activity, and the pools of soil microbial, soil organic and soil inorganic N, carbon (C) and phosphorus (P) during two growing seasons. The net fluxes of N2O averaged 1.7 μg N2O–N m−2 h−1 (range −3.6 to 10.5 μg N2O–N m−2 h−1), and generally increased from ambient (1 m) to moderate (2–3 m) snow depths. At the greatest snow depth (4 m) where snowmelt was profoundly later, N2O fluxes decreased, likely caused by combined negative effects of low summer temperatures and high soil moisture. Positive correlations between N2O and nitrate (NO3−) and dissolved organic N (DON) suggested that the availability of N was the main controlling variable along the snowmelt gradient. The maximum N2O fluxes were observed in the second half of August associated with high NO3− concentrations. The effect of growing season experimental warming on N2O surface flux varied along the snowmelt gradient and with time. Generally, the experimental warming stimulated N2O fluxes under conditions with increased concentrations of inorganic N. In contrast, warming reduced N2O fluxes when inorganic N was low. Experimental warming had no clear effects on soil inorganic N. The study suggests that if increased winter precipitation leads to a deeper snow cover and a later snowmelt, total emissions of N2O from low Arctic heath ecosystems may be enhanced in the future and, dependent on dissolved N availability, summer warming may stimulate or reduce total emissions.

AB - Climate change is profound in the Arctic where increased snowfall during winter and warmer growing season temperatures may accelerate soil nitrogen (N) turnover and increase inorganic N availability. Nitrous oxide (N2O) is a potent greenhouse gas formed by soil microbes and in the Arctic, the production is seen as limited mainly by low inorganic N availability. Hence, it can be hypothesized that climate change in the Arctic may increase total N2O emissions, yet this topic remains understudied. We investigated the combined effects of variable snow depths and experimental warming on soil N cycling in a factorial field study established along a natural snowmelt gradient in a low Arctic heath ecosystem. The study assessed N2O surface fluxes, gross N mineralization and nitrification rates, potential denitrification activity, and the pools of soil microbial, soil organic and soil inorganic N, carbon (C) and phosphorus (P) during two growing seasons. The net fluxes of N2O averaged 1.7 μg N2O–N m−2 h−1 (range −3.6 to 10.5 μg N2O–N m−2 h−1), and generally increased from ambient (1 m) to moderate (2–3 m) snow depths. At the greatest snow depth (4 m) where snowmelt was profoundly later, N2O fluxes decreased, likely caused by combined negative effects of low summer temperatures and high soil moisture. Positive correlations between N2O and nitrate (NO3−) and dissolved organic N (DON) suggested that the availability of N was the main controlling variable along the snowmelt gradient. The maximum N2O fluxes were observed in the second half of August associated with high NO3− concentrations. The effect of growing season experimental warming on N2O surface flux varied along the snowmelt gradient and with time. Generally, the experimental warming stimulated N2O fluxes under conditions with increased concentrations of inorganic N. In contrast, warming reduced N2O fluxes when inorganic N was low. Experimental warming had no clear effects on soil inorganic N. The study suggests that if increased winter precipitation leads to a deeper snow cover and a later snowmelt, total emissions of N2O from low Arctic heath ecosystems may be enhanced in the future and, dependent on dissolved N availability, summer warming may stimulate or reduce total emissions.

KW - Climate change

KW - Greenland

KW - NO

KW - Snowbed

KW - Soil nitrogen cycling

KW - Tundra

U2 - 10.1016/j.soilbio.2021.108346

DO - 10.1016/j.soilbio.2021.108346

M3 - Journal article

AN - SCOPUS:85108422289

VL - 160

JO - Soil Biology & Biochemistry

JF - Soil Biology & Biochemistry

SN - 0038-0717

M1 - 108346

ER -