A clear understanding of the relationship between two photosynthetic capacity parameters, maximum carboxylation rate (Vcmax) and maximum electron transport rate (Jmax), is expected to reveal plant photosynthetic physiology strategies and is critical in determining the carbon and water cycle in the terrestrial biosphere. Increasing evidence in recent suggests the relationship is unstable in spatiotemporal contexts, casting a doubt on deriving Jmax solely from a single linear function of Vcmax as in most gas exchange models do. In this study, we have examined the instability of the relationship in terms of seasonal and interannual courses (from 2006 to 2014) as well as at different altitudes (550, 900, and 1500 m a.s.l.) and in different leaf types (sunlit and shaded) of the only dominant species of Fagus crenata Blume in typical cool temperate forests in Japan based on a long-term field dataset. Our results clearly indicated that there is not only remarkable seasonal variability in the two parameters themselves but also large variations in their ratios. The slope parameter of the best fitted single linear function for estimating Jmax from Vcmax varied also in different seasons and different years and different leaf types, as well as at different sites. Further exploration of the slope parameter with internal leaf traits and external climatic drivers revealed that the leaf chlorophyll content had a significant correlation with the slope parameter (R² = 0.72, RMSE = 0.08, RPD = 2.00) but the impacts of climatic drivers were rather versatile. Our findings should hence advance understanding of the dynamics of photosynthetic capacity and the instability of the Jmax–Vcmax relationship, which should be considered explicitly in the future in order to substantially improve model predictions in terrestrial carbon cycle models.

清楚地了解最大羧化速率 ( V cmax) 和最大电子传递速率 ( J max) 这两个光合能力参数之间的关系，有望揭示植物的光合生理策略，并且对于确定陆地碳和水循环至关重要。生物圈。最近越来越多的证据表明这种关系在时空环境中不稳定，因此对仅从V的单个线性函数推导出J max表示怀疑cmax 与大多数气体交换模型一样。在这项研究中，我们研究了季节和年际过程（从 2006 年到 2014 年）以及不同海拔（550、900 和 1500 米 asl）和不同叶型（阳光照射和阴影)基于长期野外数据集的日本典型凉爽温带森林中唯一的Fagus crenata Blume优势物种。我们的结果清楚地表明，这两个参数本身不仅存在显着的季节性变化，而且它们的比率也存在很大差异。用于从V估计J max的最佳拟合单线性函数的斜率参数cmax 在不同季节、不同年份、不同叶型以及不同地点也有所不同。对坡度参数与叶片内部性状和外部气候驱动因素的进一步探索表明，叶片叶绿素含量与坡度参数有显着相关性（R ²  = 0.72，RMSE = 0.08，RPD = 2.00），但气候驱动因素的影响相当大多才多艺的。我们的研究结果应当因此推进的光合能力的动态和不稳定的理解Ĵ MAX- V的C max的关系，这应该以明确地被认为在将来显着改善在陆地碳循环模式模型预测。