In summer 2018, Europe experienced a heatwave that impacted the forest carbon cycle. We assessed the influence of elevated temperatures on the carbon exchange of three forest stands of different types (coniferous, deciduous, and conifer-broadleaved) and a clear-cut area located in the geographical vicinity within a hemiboreal zone. The carbon fluxes were calculated using the eddy-covariance technique. Over the period of anomaly high temperatures, the NEE of a deciduous (alder) forest was similar to the previous year due to the reduction of both GPP and ER of the same magnitude. Warm days in spring and autumn allowed for the GPP offset, and the total NEE of vegetation season 2018 was more negative than of 2017. Coniferous (pine and spruce) forest carbon uptake decreased during the temperature anomaly as a result of GPP reduction being higher than the decrease in ER. Spring warming had almost no effect on the carbon exchange, while ER and GPP increased in autumn warm days. As a result, annual ER was higher in 2018 than in 2017, and the NEE was smaller. The coniferous forest was most resistant to the heatwave, most probably because of its adaption to low soil water content. Contrary to our expectations, a mixed conifer-broadleaved forest (pine, spruce, birch, clear-cuts) was more affected by the heatwave than a pine-dominated forest. It switched from net carbon sink during the vegetation season of 2017 to net carbon source in 2018. Almost three times higher amount of carbon was released in 2018 as a result of GPP reduction. The clear-cut area carbon exchange was the most vulnerable to the heatwave influence out of all study sites. A more prominent reduction of GPP resulted in smaller NEE. Warm days in spring and autumn did not offset the temperature anomaly impact, as was observed for the forested ecosystems.

2018 年夏天，欧洲经历了一场影响森林碳循环的热浪。我们评估了升高的温度对三种不同类型（针叶、落叶和针叶阔叶）林分和位于半寒带带内地理附近的空旷区域的碳交换的影响。使用涡度协方差技术计算碳通量。在异常高温期间，落叶（桤木）林的 NEE 与上一年相似，因为 GPP 和 ER 均降低了相同幅度。春秋暖日允许 GPP 抵消，2018 年植被季总 NEE 比 2017 年负值更大。由于 GPP 减少高于 ER 减少，针叶（松树和云杉）森林碳吸收在温度异常期间减少。春季变暖对碳交换几乎没有影响，而秋季温暖日ER和GPP增加。因此，2018 年的年度 ER 高于 2017 年，NEE 较小。针叶林对热浪的抵抗力最强，这很可能是因为它适应了低土壤含水量。与我们的预期相反，针叶阔叶混交林（松树、云杉、桦树、砍伐林）比以松树为主的森林更容易受到热浪的影响。它从 2017 年植被季节的净碳汇转变为 2018 年的净碳源。由于 GPP 的减少，2018 年的碳排放量几乎增加了三倍。在所有研究地点中，明确区域的碳交换最容易受到热浪的影响。GPP 的更显着降低导致更小的 NEE。正如在森林生态系统中观察到的那样，春季和秋季的温暖日子并没有抵消温度异常的影响。