Fire increases soil nitrogen retention and alters nitrogen uptake patterns among dominant shrub species in an Arctic dry heath tundra

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Climate change increases the frequency and severity of fire in the Arctic tundra regions. We assessed effects of fire in combination with summer warming on soil biogeochemical N- and P cycles with a focus on mineral N over two years following an experimental fire in a dry heath tundra, West Greenland. We applied stable isotopes (15NH4+-N and 15NO3-N) to trace the post-fire mineral N pools. The partitioning of 15N in the bulk soils, soil dissolved organic N (TDN), microbes and plants (roots and leaves) was established. The fire tended to increase microbial P pools by four-fold at both one and two years after the fire. Two years after the fire, the bulk soil 15N recovery has decreased to 10.4% in unburned plots while relatively high recovery was maintained (30%) in burned plots, suggesting an increase in soil N retention after the fire. The contribution of microbial 15N recovery to bulk soil 15N recovery increased from 11.2% at 21 days to 31.5% two years after the fire, suggesting that higher post-fire N retention was due largely to the increased incorporation of N into microbial biomass. Fire also increased 15N recovery in bulk roots after one and two years, but only under summer warming. This suggests that higher retention of post-fire N can strongly increase the potential for N uptake of recovering plants under a future warmer climate. There was significantly lower 15N enrichment of Betula nana leaves while higher 15N enrichment of Vaccinium uliginosum leaves (after three years) in burned than control plots. This shows that fire can alter the N uptake differently among dominant shrub species in this tundra ecosystem, and implies that wildfires may change plant species composition in the longer term.

Original languageEnglish
Article number150990
JournalScience of the Total Environment
Issue numberPart 3
Number of pages11
Publication statusPublished - 2021

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© 2021 The Authors

    Research areas

  • N tracing, Microbial biomass phosphorus, Shrub cutting, Tundra fire, Warming

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