Wildfire is one of the most important disturbances affecting boreal forests. Most previous research on boreal forest fires has occurred in North American forests which have different fire regimes, tree species and are less intensively managed than their Eurasian counterparts. Recent extreme fire years have highlighted the vulnerability of the Nordic boreal forest to climatic shifts that are increasing forest fire frequency and severity. The Ljusdal fire (2018) was one of the largest wildfires in recorded history in Sweden. We established eddy covariance flux towers to track the impacts of this fire on the carbon balance of two sites subject to different fire severities and forest management strategies 1–4 years post-fire. The ‘SLM’ site was a mature stand that experienced low-severity fire (trees survived) followed by salvage-logging and reseeding, whilst the ‘HY’ site was 10 years old when it experienced high-severity fire (all trees killed) then was replanted with seedlings. During the study period, both sites were net carbon sources at the annual scale. It took up to 4 years after the fire until the first day of net CO uptake was recorded at each site. We estimated that it will take 13 years (8, 21; mean ± 95 % confidence intervals) after the fire until the sites reach a neutral annual carbon balance. It will take up to 32 years (19, 53) at HY and 46 years (31, 70) at SLM to offset the carbon lost during and after the fire and salvage-logging. In addition, our measurements showed that more carbon was emitted in the first 4 years after the fire compared to the carbon lost from combustion during the fire. Quantifying carbon fluxes during the initial years after fire is therefore crucial for estimating the net impact of wildfire on the carbon budget of boreal forests.

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野火对管理的北欧北方森林碳预算的影响

野火是影响北方森林的最重要的干扰之一。此前大多数关于北方森林火灾的研究都发生在北美森林，与欧亚森林相比，北美森林的火势、树种不同，管理程度也较低。最近的极端火灾年份凸显了北欧北方森林对气候变化的脆弱性，气候变化导致森林火灾的频率和严重程度不断增加。吕斯达尔火灾（2018 年）是瑞典有记录以来最大的野火之一。我们建立了涡流协方差通量塔，以跟踪这场火灾对两个地点碳平衡的影响，这些地点受到不同火灾严重程度和火灾后 1-4 年的森林管理策略的影响。 “SLM”场地是一个成熟的林分，经历了低度火灾（树木幸存），然后进行了抢救性伐木和重新播种，而“HY”场地已经有 10 年历史了，当时经历了高度严重的火灾（所有树木都被烧死），然后被重新种植了幼苗。研究期间，两个地点均为年规模净碳源。火灾发生后长达 4 年的时间才在每个地点记录到二氧化碳净吸收量的第一天。我们估计火灾发生后需要 13 年（8 年、21 年；平均值 ± 95% 置信区间）才能使这些地点达到中性年度碳平衡。 HY 需要长达 32 年（19、53）的时间，SLM 需要长达 46 年（31、70）的时间才能抵消火灾和抢救伐木期间和之后的碳损失。此外，我们的测量结果表明，与火灾期间燃烧损失的碳相比，火灾后头 4 年排放的碳更多。因此，量化火灾后最初几年的碳通量对于估计野火对北方森林碳预算的净影响至关重要。