Wildfires are the major disturbance in boreal ecosystems and are of great importance for the biogeochemical cycles of carbon (C) and nutrients. However, these fire-induced impacts are hard to quantify and are rarely assessed together at an ecosystem level incorporating both aquatic and terrestrial environments. Following a wildfire in Sweden in an area with ongoing monitoring, we conducted a pre-fire (9 years) and post-fire (4 years) multi-catchment investigation of element losses (combustion and leaching) and impacts on water quality. Direct C and nitrogen (N) losses through combustion were ca. 4500 and 100 g m⁻², respectively. Net CO₂ loss associated with soil and biomass respiration was ∼ 150 g C m⁻² during the first year, but the ecosystem started to show net CO₂ uptake in June 3 years post-fire. Aquatic C and N losses the first 12 months post-fire were 7 and 0.6 g m⁻², respectively. Hence, soil respiration comprised a non-negligible part of the post-fire C loss, whereas aquatic C losses were minor and did not increase post-fire. However, other elements (e.g. Ca, S) exhibited ecologically relevant increases in fluvial export and concentration with large peaks in the immediate post-fire period. The temporal dynamics of stream concentrations (Ca²⁺, Mg²⁺, K⁺ ,SO${}_{\mathrm{4}}^{-\mathrm{2}}$, Cl⁻ ,NH${}_{\mathrm{4}}^{+}$, total organic N) suggest the presence of faster- and slower-release nutrient pools with half-lives of around 2 weeks and 4 months which we attribute to physicochemically and biologically mediated mobilization processes, respectively. Three years after the fire, it appears that dissolved fluxes of nutrients have largely returned to pre-fire conditions, but there is still net release of CO₂.

中文翻译：

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野火对北方集水区生物地球化学通量和水质的影响

野火是北方生态系统的主要干扰，对碳 (C) 和养分的生物地球化学循环非常重要。然而，这些火灾引起的影响很难量化，并且很少在包含水生和陆地环境的生态系统水平上一起评估。在瑞典持续监测的地区发生野火后，我们对元素损失（燃烧和浸出）和对水质的影响进行了火灾前（9 年）和火灾后（4 年）多流域调查。通过燃烧直接损失的碳和氮 (N) 约为 分别为4500和100g m ^-2。与土壤和生物量呼吸相关的CO ₂净损失 约为 150 g C m ^-2在第一年，但生态系统在火灾后的 6 月 3 年开始显示净 CO ₂吸收。火灾后前 12 个月的水生 C 和 N 损失分别为 7 和 0.6 g m ^-2。因此，土壤呼吸是火灾后碳损失不可忽略的一部分，而水生碳损失很小，火灾后没有增加。然而，其他元素（例如钙、硫）表现出与生态相关的河流出口和浓度增加，并在火灾后立即达到峰值。流浓度 (Ca ²⁺ , Mg ²⁺ , K ⁺ ,SO${}_{\mathrm{4}}^{——\mathrm{2}}$, Cl ^- ,NH${}_{\mathrm{4}}^{+}$，总有机氮）表明存在更快和更慢释放的营养池，其半衰期约为 2 周和 4 个月，我们分别将其归因于物理化学和生物介导的动员过程。火灾发生三年后，营养物质的溶解通量似乎已基本恢复到火灾前的状态，但仍然有 CO _{2 的}净释放。