In eastern North America, many deciduous forest ecosystems grow at the northernmost extent of their geographical ranges, where climate change could aid or impede their growth. This region experiences frequent extreme weather conditions, allowing us to study the response of these forests to environmental conditions, reflective of future climates. Here we determined the impact of seasonal and annual climate variations and extreme weather events on the carbon (C) uptake capacity of an oak‐dominated forest in southern Ontario, Canada, from 2012 to 2016. We found that changes in meteorology during late May to mid‐July were key in determining the C sink strength of the forest, impacting the seasonal and annual variability of net ecosystem productivity (NEP). Overall, higher temperatures and dry conditions reduced ecosystem respiration (RE) much more than gross ecosystem productivity (GEP), leading to higher NEP. Variability in NEP was primarily driven by changes in RE, rather than GEP. The mean annual GEP, RE, and NEP values at our site during the study were 1,343 ± 85, 1,171 ± 139, and 206 ± 92 g C m⁻² yr⁻¹, respectively. The forest was a C sink even in years that experienced heat and water stresses. Mean annual NEP at our site was within the range of NEP (69–459 g C m⁻² yr⁻¹) observed in similar North American forests from 2012 to 2016. The growth and C sequestration capabilities of our oak‐dominated forest were not adversely impacted by changes in environmental conditions and extreme weather events experienced over the study period.

中文翻译：

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季节性和年度气候变化对加拿大大湖区落叶林碳吸收能力的影响

在北美东部，许多落叶林生态系统在其地理范围的最北端生长，在此气候变化可能有助于或阻碍其生长。该地区经常遇到极端天气条件，使我们能够研究这些森林对环境条件的反应，以反映未来的气候。在这里，我们确定了2012年至2016年，季节性和年度气候变化以及极端天气事件对加拿大安大略省南部橡树林为主的森林吸收碳（C）的影响。我们发现5月下旬至5月下旬的气象变化7月中旬是确定森林碳汇强度的关键，影响了生态系统净生产力（NEP）的季节和年度变化。总体，较高的温度和干燥条件所导致的生态系统呼吸（RE）下降远超过生态系统总生产率（GEP），从而导致更高的NEP。NEP的可变性主要是由RE而不是GEP引起的。研究期间，我们站点的年平均GEP，RE和NEP值分别为1,343±85、1171±139和206±92 g C m^-2  yr ^-1。即使在经历高温和高压的多年中，森林也是一个碳汇。从2012年到2016年，在我们类似的北美森林地区，我们站点的年均NEP处于NEP范围内（69–459 g C m ^-2  yr ^-1）。我们以橡树为主的森林的生长和固碳能力没有在研究期间受到环境条件变化和极端天气事件的不利影响。