Although forest fires are one of the main natural disturbance types in boreal forests, there is limited information regarding surface fires (dominant in Northern Europe), and how surface fires of different severities could affect post-fire soil greenhouse gas emissions. The results of our study show that fire severity, time since fire and post-fire changes in soil temperature were the main factors driving soil carbon dioxide (CO) flux (forest floor ecosystem respiration) from burned boreal forest soils. Approximately two hours after the fire, soil CO emissions from burned areas were significantly higher compared to pre-fire conditions, and areas with high-severity fires had significantly higher soil CO emissions compared to those with low-severity fires. Later (days, months) after the fire, the unburned control areas always had higher soil CO emission values compared to burned areas. In the case of methane (CH), time since fire and post-fire changes in soil temperatures were the main factors driving soil CH fluxes. Unburned study areas were sinks of CH through the entire measurement period, while immediately after the fire, the burned areas turned from CH sink to CH source. For nitrous oxide (NO) measurements, time since fire was the only factor that significantly affected soil NO fluxes. Shortly after the fire, NO emissions increased significantly from both low- and high-intensity study plots. Two days after the fire, post-fire soil C and N content decreased in the O-horizon and increased within the first 5 cm of the soil mineral layer, and the trend was visible both in low- and high-severity fire plots. Samples collected four months after the fire, showed similar total soil C and N content as there was before the fire.

中文翻译：

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北方欧洲赤松林火后土壤温室气体通量——它们是否受到不同严重程度的地表火灾的影响？

尽管森林火灾是北方森林的主要自然干扰类型之一，但有关地表火灾（主要在北欧）以及不同严重程度的地表火灾如何影响火灾后土壤温室气体排放的信息有限。我们的研究结果表明，火灾严重程度、火灾发生后的时间和火灾后土壤温度的变化是驱动烧毁的北方森林土壤二氧化碳（CO）通量（林地生态系统呼吸）的主要因素。火灾发生后约两小时，与火灾前相比，过火地区的土壤二氧化碳排放量明显更高，而火灾严重程度较高的地区的土壤二氧化碳排放量明显高于火灾程度较低的地区。火灾发生后（几天、几个月），与燃烧区域相比，未燃烧控制区域的土壤二氧化碳排放值始终较高。就甲烷 (CH) 而言，火灾发生后的时间和火灾后土壤温度的变化是驱动土壤 CH 通量的主要因素。在整个测量期间，未燃烧的研究区域都是 CH 汇，而火灾发生后，燃烧区域立即从 CH 汇转变为 CH 源。对于一氧化二氮 (NO) 测量，火灾发生后的时间是显着影响土壤 NO 通量的唯一因素。火灾发生后不久，低强度和高强度研究区的二氧化氮排放量均显着增加。火灾两天后，火后土壤C和N含量在O水平线内下降，在土壤矿物层前5厘米内增加，并且在低严重度和高严重度火灾地块中都可以看到这种趋势。火灾四个月后收集的样本显示，土壤总碳和氮含量与火灾前相似。