TY - JOUR

T1 - Spatial Distribution of Bioavailable Inorganic Nitrogen From Thawing Permafrost

AU - Hansen, Hans Frederik Engvej

AU - Elberling, Bo

N1 - CENPERMOA[2023] Publisher Copyright: © 2023. The Authors.

PY - 2023

Y1 - 2023

N2 - Arctic permafrost contains large amounts of nitrogen (N), which may be bioavailable upon permafrost thaw. Here, we have compiled inorganic N data from published studies on the active layer and permafrost layers combined with new data to quantify the spatial variability of bioavailable inorganic N in permafrost-affected ecosystems across the Northern Hemisphere. Ammonium (NH4+) and nitrate (NO3−) are typically extracted from samples using different agents and strength. The results of an extraction experiment are here used to recalculate published concentrations on NH4+ and NO3− to a “water extractable fraction.” The results show that upper permafrost across all sites and samples contains significantly more NH4+ compared to the root zone and was significantly and positively correlated with an increasing water/ice content despite a surprisingly high variation within and between sites. Based on the average reported permafrost thaw rates (0.4–0.8 cm y−1) for wet and dry landscape types, the average release of inorganic N (NH4+ and NO3−) from wet tundra ecosystems was calculated to be 2.0 [1.13–2.61] kg N ha−1 decade−1 and 1.3 [0.78–1.81] kg N ha−1 decade−1 for dry ecosystems. This brings permafrost-derived inorganic N on the same order of magnitude as biological nitrogen fixation in relatively dry tundra ecosystems but only marginally compared to nitrogen fixation in wet ecosystems. These landscape-specific variations highlight the need for improving the understanding of N mobilization linked to permafrost thawing, but also that N transfer from well-drained slopes to lower parts of the landscape can be important for the potential plant growth (greening) downslope from surrounding landscape types with faster permafrost thawing.

AB - Arctic permafrost contains large amounts of nitrogen (N), which may be bioavailable upon permafrost thaw. Here, we have compiled inorganic N data from published studies on the active layer and permafrost layers combined with new data to quantify the spatial variability of bioavailable inorganic N in permafrost-affected ecosystems across the Northern Hemisphere. Ammonium (NH4+) and nitrate (NO3−) are typically extracted from samples using different agents and strength. The results of an extraction experiment are here used to recalculate published concentrations on NH4+ and NO3− to a “water extractable fraction.” The results show that upper permafrost across all sites and samples contains significantly more NH4+ compared to the root zone and was significantly and positively correlated with an increasing water/ice content despite a surprisingly high variation within and between sites. Based on the average reported permafrost thaw rates (0.4–0.8 cm y−1) for wet and dry landscape types, the average release of inorganic N (NH4+ and NO3−) from wet tundra ecosystems was calculated to be 2.0 [1.13–2.61] kg N ha−1 decade−1 and 1.3 [0.78–1.81] kg N ha−1 decade−1 for dry ecosystems. This brings permafrost-derived inorganic N on the same order of magnitude as biological nitrogen fixation in relatively dry tundra ecosystems but only marginally compared to nitrogen fixation in wet ecosystems. These landscape-specific variations highlight the need for improving the understanding of N mobilization linked to permafrost thawing, but also that N transfer from well-drained slopes to lower parts of the landscape can be important for the potential plant growth (greening) downslope from surrounding landscape types with faster permafrost thawing.

KW - ammonium

KW - Arctic

KW - bioavailable nitrogen

KW - permafrost

U2 - 10.1029/2022GB007589

DO - 10.1029/2022GB007589

M3 - Journal article

AN - SCOPUS:85148751621

VL - 37

JO - Global Biogeochemical Cycles

JF - Global Biogeochemical Cycles

SN - 0886-6236

IS - 2

M1 - e2022GB007589

ER -