Tree mortality significantly influences forest structure and function, yet our understanding of its dynamic patterns among a range of tree sizes and among different plant functional types (PFTs) remains incomplete. This study analysed size-dependent tree mortality in a temperate forest, encompassing 46 tree species and 32,565 individuals across different PFTs (i.e., evergreen conifer vs. deciduous broadleaf species, shade-tolerant vs. shade-intolerant species). By employing all-subset regression procedures and logistic generalized linear mixed-effects models, we identified distinct mortality patterns influenced by biotic and abiotic factors. Our results showed a stable mortality pattern in evergreen conifer species, contrasted by a declining pattern in deciduous broadleaf and shade-tolerant, as well as shade-intolerant species, across size classes. The contribution to tree mortality of evergreen conifer species shifted from abiotic to biotic factors with increasing size, while the mortality of deciduous broadleaf species was mainly influenced by biotic factors, such as initial diameter at breast height (DBH) and conspecific negative density. For shade-tolerant species, the mortality of small individuals was mainly determined by initial DBH and conspecific negative density dependence, whereas the mortality of large individuals was subjected to the combined effect of biotic (competition from neighbours) and abiotic factors (i.e., convexity and pH). As for shade-intolerant species, competition from neighbours was found to be the main driver of tree mortality throughout their growth stages. Thus, these insights enhance our understanding of forest dynamics by revealing the size-dependent and PFT-specific tree mortality patterns, which may inform strategies for maintaining forest diversity and resilience in temperate forest ecosystems.

中文翻译：

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温带森林植物功能类型 （PFT） 之间树木死亡率的差异：对大小依赖性和 PFT 特异性模式的见解


树木死亡率对森林结构和功能有显著影响，但我们对其在各种树木大小和不同植物功能类型 （PFT） 之间的动态模式的理解仍然不完整。本研究分析了温带森林中大小依赖性的树木死亡率，包括 46 种树种和 32,565 个个体，涉及不同的 PFT（即常绿针叶树与落叶阔叶树种，耐阴树种与不耐阴树种）。通过采用全子集回归程序和 logistic 广义线性混合效应模型，我们确定了受生物和非生物因素影响的不同死亡模式。我们的结果表明，常绿针叶树物种的死亡率模式稳定，而落叶阔叶树种和耐阴物种以及不同大小类别的物种死亡率下降模式则呈下降模式。随着规模的增加，常绿针叶树种对树木死亡率的贡献由非生物因素转变为生物因素，而落叶阔叶树种的死亡率主要受生物因素的影响，如胸高初始直径 （DBH） 和同种负密度。对于耐阴物种，小个体的死亡率主要由初始 DBH 和同种负密度依赖性决定，而大个体的死亡率则受到生物（来自邻居的竞争）和非生物因素（即凸性和 pH 值）的综合影响。至于不耐阴的物种，研究发现来自邻居的竞争是树木在整个生长阶段死亡的主要驱动因素。 因此，这些见解通过揭示大小依赖性和 PFT 特异性的树木死亡模式来增强我们对森林动态的理解，这可能为维持温带森林生态系统中森林多样性和复原力的策略提供信息。