Nitrogen immobilization could link extreme winter warming events to Arctic browning
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Nitrogen immobilization could link extreme winter warming events to Arctic browning. / Rasmussen, Laura Helene; Danielsen, Birgitte Kortegaard; Elberling, Bo; Ambus, Per; Björkman, Mats P.; Rinnan, Riikka; Andresen, Louise C.
In: Soil Biology and Biochemistry, Vol. 191, 109319, 2024.Research output: Contribution to journal › Journal article › Research › peer-review
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TY - JOUR
T1 - Nitrogen immobilization could link extreme winter warming events to Arctic browning
AU - Rasmussen, Laura Helene
AU - Danielsen, Birgitte Kortegaard
AU - Elberling, Bo
AU - Ambus, Per
AU - Björkman, Mats P.
AU - Rinnan, Riikka
AU - Andresen, Louise C.
N1 - Publisher Copyright: © 2024 The Authors
PY - 2024
Y1 - 2024
N2 - Arctic extreme winter warming events (WW events) have increased in frequency with climate change. WW events have been linked to damaged tundra vegetation (“Arctic browning”), but the mechanisms that link episodic winter thaw to plant damage in summer are not fully understood. We suggest that one mechanism is microbial N immobilization during the WW event, which leads to a smaller release of winter-mineralized N in spring and therefore more N limitation for vegetation in summer. We tested this hypothesis in a Western Greenlandic Low arctic tundra, where we experimentally simulated a 6 day field-scale extreme WW event and 1) used stable isotopes to trace the movement of N as a consequence of the WW event, 2) measured the effect of a WW event on spring N release in top soils in the laboratory, and 3) measured the carry-over effect on summer aboveground vegetation C/N ratio in tundra subject to a WW event. Our results show that soil mineral N released by a WW event followed by soil thaw is taken up by microbes and stored in the soil, whereas vascular plants acquired almost none, and significant amounts were lost to leaching and gaseous emissions. As soils thawed in spring, we saw weak but not significant evidence (P = 0.067) for a larger N release over the first month of spring thaw in Control soils compared to WW event soils, although not significantly. A weak signal (P = 0.07) linked WW event treatment to higher summer C/N ratios in evergreen shrubs, whereas deciduous shrubs were not affected. We conclude that our results did not show significant evidence for WW events causing Arctic browning via N immobilization and summer N limitation, but that we had indications (P < 0.1) which merits further testing of the theory in various tundra types and with repeated WW events. Evergreen shrubs could be especially sensitive to winter N immobilization, with implications for future vegetation community composition and tundra C storage.
AB - Arctic extreme winter warming events (WW events) have increased in frequency with climate change. WW events have been linked to damaged tundra vegetation (“Arctic browning”), but the mechanisms that link episodic winter thaw to plant damage in summer are not fully understood. We suggest that one mechanism is microbial N immobilization during the WW event, which leads to a smaller release of winter-mineralized N in spring and therefore more N limitation for vegetation in summer. We tested this hypothesis in a Western Greenlandic Low arctic tundra, where we experimentally simulated a 6 day field-scale extreme WW event and 1) used stable isotopes to trace the movement of N as a consequence of the WW event, 2) measured the effect of a WW event on spring N release in top soils in the laboratory, and 3) measured the carry-over effect on summer aboveground vegetation C/N ratio in tundra subject to a WW event. Our results show that soil mineral N released by a WW event followed by soil thaw is taken up by microbes and stored in the soil, whereas vascular plants acquired almost none, and significant amounts were lost to leaching and gaseous emissions. As soils thawed in spring, we saw weak but not significant evidence (P = 0.067) for a larger N release over the first month of spring thaw in Control soils compared to WW event soils, although not significantly. A weak signal (P = 0.07) linked WW event treatment to higher summer C/N ratios in evergreen shrubs, whereas deciduous shrubs were not affected. We conclude that our results did not show significant evidence for WW events causing Arctic browning via N immobilization and summer N limitation, but that we had indications (P < 0.1) which merits further testing of the theory in various tundra types and with repeated WW events. Evergreen shrubs could be especially sensitive to winter N immobilization, with implications for future vegetation community composition and tundra C storage.
KW - Climate change
KW - Evergreen shrub
KW - Greenland
KW - Mesic tundra
KW - Nitrogen cycling
U2 - 10.1016/j.soilbio.2024.109319
DO - 10.1016/j.soilbio.2024.109319
M3 - Journal article
AN - SCOPUS:85184021808
VL - 191
JO - Soil Biology & Biochemistry
JF - Soil Biology & Biochemistry
SN - 0038-0717
M1 - 109319
ER -
ID: 382436645