Abstract Climate change projections for the Mediterranean basin predict a continuous increase in extreme drought and heat episodes, which will affect forest dynamics, structure and composition. Understanding how climate influences the maximum size-density relationship (MSDR) is therefore critical to designing adaptive silvicultural guidelines based on the potential stand carrying capacity of tree species. With this aim, data from the Third Spanish National Forest Inventory (3NFI) and WorldClim databases were used to analyze climate-related variations of the maximum stand carrying capacity for 15 species from the Pinus, Fagus and Quercus genera. First, basic MSDR were fitted using linear quantile regression and observed size-density data from monospecific 3NFI plots. Reference values for maximum stocking, expressed in terms of the Maximum Stand Density Index (SDImax), were estimated by species. Then, climate-dependent MSDR models including 35 annual and seasonal climatic variables were fitted. The best climate-dependent models, based on the Akaike Information Criteria (AIC) index, were used to determine the climatic drivers affecting MSDR, to analyze general and species-specific patterns and to quantify the impact of climate on maximum stand carrying capacity. The results showed that all the selected climate-dependent models improved the goodness of fit over the basic models. Among the climatic variables, spring and summer maximum temperatures were found to be key drivers affecting MSDR for the species studied. A common trend was also found across species, linking warmer and drier conditions to smaller SDImax values. Based on projected climate scenarios, this suggests potential reductions in maximum stocking for these species. In this study, a new index was proposed, the Q index, for evaluating the impact of climate on maximum stand carrying capacity. Our findings highlight the importance of using specific climatic variables to better characterize how they affect MSDR. The models presented in this study will allow us to better explain interactions between climate and MSDR while also providing more precise estimates concerning maximum stocking for different Mediterranean coniferous and broadleaf tree species.

中文翻译：

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气候对 15 种地中海针叶和阔叶树种最大林分承载力的潜在影响

摘要 地中海盆地的气候变化预测预测极端干旱和高温事件将持续增加，这将影响森林动态、结构和组成。因此，了解气候如何影响最大尺寸密度关系 (MSDR) 对于根据树种的潜在林分承载能力设计适应性造林指南至关重要。为此，使用来自第三次西班牙国家森林清单 (3NFI) 和 WorldClim 数据库的数据分析了松、山毛榉和栎属 15 个物种的最大林分承载力与气候相关的变化。首先，使用线性分位数回归拟合基本 MSDR，并从单特异性 3NFI 图中观察到的大小密度数据。最大库存的参考值，以最大林分密度指数 (SDImax) 表示，按物种估计。然后，拟合了包括 35 个年度和季节性气候变量的气候相关 MSDR 模型。基于 Akaike 信息标准 (AIC) 指数的最佳气候依赖模型用于确定影响 MSDR 的气候驱动因素，分析一般和特定物种的模式，并量化气候对最大林分承载能力的影响。结果表明，所有选定的气候相关模型都提高了基本模型的拟合优度。在气候变量中，发现春季和夏季最高温度是影响所研究物种 MSDR 的关键驱动因素。在物种间也发现了一个共同的趋势，将温暖和干燥的条件与较小的 SDImax 值联系起来。根据预测的气候情景，这表明这些物种的最大放养量可能会减少。在这项研究中，提出了一个新的指标，即 Q 指数，用于评估气候对最大林分承载力的影响。我们的发现强调了使用特定气候变量来更好地描述它们如何影响 MSDR 的重要性。本研究中提出的模型将使我们能够更好地解释气候与 MSDR 之间的相互作用，同时还提供关于不同地中海针叶树和阔叶树种的最大蓄积量的更精确估计。我们的发现强调了使用特定气候变量来更好地描述它们如何影响 MSDR 的重要性。本研究中提出的模型将使我们能够更好地解释气候与 MSDR 之间的相互作用，同时还提供关于不同地中海针叶树和阔叶树种的最大蓄积量的更精确估计。我们的发现强调了使用特定气候变量来更好地描述它们如何影响 MSDR 的重要性。本研究中提出的模型将使我们能够更好地解释气候与 MSDR 之间的相互作用，同时还提供关于不同地中海针叶树和阔叶树种的最大蓄积量的更精确估计。