Plants acclimate to temperature by adjusting their photosynthetic capacity over weeks to months. However, most evidence for photosynthetic acclimation derives from leaf-scale experiments. Here we address the scarcity of evidence for canopy-scale photosynthetic acclimation by examining the correlation between maximum photosynthetic rates (A_max,2,000) and growth temperature (\(\overline{{T}_{\rm{air}}}\)) across a range of concurrent temperatures and canopy foliage quantity, using data from >200 eddy covariance sites. We detect widespread thermal acclimation of canopy-scale photosynthesis, demonstrated by enhanced A_max,2,000 under higher \(\overline{{T}_{\rm{air}}}\), across flux sites with adequate water availability. A 14-day period is identified as the most relevant timescale for acclimation across all sites, with a range of 12–25 days for different plant functional types. The mean apparent thermal acclimation rate across all ecosystems is 0.41 (−0.38–1.04 for 5th–95th percentile range) µmol m⁻² s⁻¹ °C⁻¹, with croplands showing the largest acclimation rates and grasslands the lowest. Incorporating an optimality-based prediction of leaf photosynthetic capacities into a biochemical photosynthesis model is shown to improve the representation of thermal acclimation. Our results underscore the critical need for enhanced understanding and modelling of canopy-scale photosynthetic capacity to accurately predict plant responses to warmer growing seasons.

植物通过在数周到数月内调整其光合作用能力来适应温度。然而，大多数光合驯化的证据来自叶尺度实验。在这里，我们通过使用来自 >200 涡度协方差站点的数据，检查最大光合速率 （A_max，2,000） 和生长温度 （\（\overline{{T}_{\rm{air}}}\）） 之间的相关性，解决了冠层尺度光合适应证据的稀缺性。我们检测到了冠层尺度光合作用的广泛热驯化，在较高的 \（\overline{{T}_{\rm{air}}}\） 下，在具有足够水可用性的通量位点上，增强的 A_max，2,000 证明了这一点。14 天的时间被确定为所有地点最相关的驯化时间尺度，不同的植物功能类型为 12-25 天。所有生态系统的平均表观热适应率为 0.41（第 5-95 个百分位范围为 -0.38-1.04）μmol ^{m-2 s-1} °^C-1，农田的驯化率最高，草原的适应率最低。将基于最优性的叶片光合能力预测纳入生化光合作用模型已被证明可以改善热驯化的表示。我们的结果强调了加强对冠层尺度光合作用能力的理解和建模的迫切需求，以准确预测植物对温暖生长季节的反应。