The carbon sequestration of plants through photosynthesis is responsible for removal of a substantial amount of the man-made CO₂ emissions to the atmosphere. In recent years this so-called land-sink has removed about 30% of the man-made emissions to the atmosphere, with forests being the most important sinks. The land-sink is, however, vulnerable to changes in the environment, such as the atmospheric composition, climate change, and extreme events like storms and droughts. It is therefore important to study the effects of such change on terrestrial ecosystems to provide the basis for predicting the future of the sink.

We here report the results of continuous CO₂ flux measurements over a Danish beech forest during the years 1996–2019. Over the years the forest acted as a sink of CO₂ with a net carbon sequestration ranging from about zero to 400 g C m^–2 yr^−1. We found significant trends in net ecosystem exchange (NEE) (increasing in absolute terms with 15 g C m^–2 yr²), gross ecosystem exchange (GEE) (increasing with 25 g C m^–2 yr^–2), and ecosystem respiration (RE) (increasing with 10 g C m^–2 yr^–2). A prolonged growing season explained 73% of the increase in NEE. The increasing CO₂ concentration in the atmosphere and a subsequent increase in photosynthetic capacity together with warming are the most likely main causes of the increased carbon uptake. The severe drought in the summer of 2018 resulted in a reduction of the annual NEE of 25%.

通过光合作用将碳固存在植物中，这是消除了向大气中排放的大量人造CO ₂的原因。近年来，这种所谓的“陆地沉没”消除了约30％的人为排放物，其中森林是最重要的汇。但是，汇陷区容易受到环境变化的影响，例如大气成分，气候变化以及暴风雨和干旱等极端事件。因此，重要的是研究这种变化对陆地生态系统的影响，为预测汇的未来提供基础。

我们在这里报告了1996–2019年间丹麦山毛榉森林中连续CO ₂通量测量的结果。多年来，森林一直是CO ₂的汇入区，其净碳固存范围从大约零到400 g C m ^–2 yr ^-1。我们发现净生态系统交换（NEE）（绝对值增加15 g C m ^–2 yr ²），生态系统总交换量（GEE）（增加25 g C m ^–2 yr ^–2）和生态系统呼吸的显着趋势（RE）（增加10 g C m ^–2 yr ^–2）。生长季节延长解释了NEE增长的73％。不断增加的CO ₂大气中的高浓度和随后的光合作用能力增加以及变暖是最可能的碳吸收增加的主要原因。2018年夏季的严重干旱导致年度NEE降低了25％。