Center for Permafrost, Department of Geosciences and Natural Resource Management, University of Copenhagen, 1350 Copenhagen K, Denmark.
Center for Permafrost, Department of Geosciences and Natural Resource Management, University of Copenhagen, 1350 Copenhagen K, Denmark.
Sci Total Environ. 2022 Feb 10;807(Pt 3):150990. doi: 10.1016/j.scitotenv.2021.150990. Epub 2021 Oct 15.
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 (NH-N and NO-N) to trace the post-fire mineral N pools. The partitioning of N 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 N 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 N recovery to bulk soil N 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 N 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 N enrichment of Betula nana leaves while higher N 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.
气候变化增加了北极苔原地区火灾的频率和严重程度。我们评估了火灾与夏季变暖相结合对土壤生物地球化学氮和磷循环的影响，重点是在格陵兰西部干旱石南荒原经历了一场实验性火灾后的两年内，追踪矿质氮的变化。我们应用稳定同位素（NH-N 和 NO-N）来追踪火灾后的矿质氮库。确定了土壤中氮的分配情况，包括土壤溶解有机氮（TDN）、微生物和植物（根和叶）中的氮。火灾后一年和两年，微生物磷库分别增加了四倍。火灾后两年，未燃烧样地的土壤全氮恢复率下降到 10.4%，而燃烧样地的恢复率相对较高（30%），表明火灾后土壤氮保留量增加。微生物氮恢复对土壤全氮恢复的贡献从火灾后 21 天的 11.2%增加到两年后的 31.5%，表明火灾后氮保留量的增加主要是由于微生物生物量中氮的含量增加。火灾还增加了根中的氮恢复，无论是在火灾后一年还是两年，但仅在夏季变暖的情况下。这表明，在未来更温暖的气候下，火灾后氮的更高保留量可以大大增加恢复植物吸收氮的潜力。与对照样地相比，燃烧样地的柳兰叶片氮富集程度显著降低，而越橘叶片氮富集程度更高（三年后）。这表明，火灾可以在该苔原生态系统中不同地改变主要灌木物种的氮吸收，这意味着野火可能会在更长的时间内改变植物物种组成。
