Seasonal life history events are often interdependent, but we know relatively little about how the relationship between different events is influenced by the abiotic and biotic environment. Such knowledge is important for predicting the immediate and evolutionary phenological response of populations to changing conditions. We manipulated germination timing and shade in a multi-factorial experiment to investigate the relationship between spring and autumn phenology in seedlings of the pedunculate oak, Quercus robur, and whether this relationship was mediated by natural colonization of leaves by specialist fungal pathogens (i.e., the oak powdery mildew complex). Each week delay in germination corresponded to about 2 days delay in autumn leaf senescence, and heavily shaded seedlings senesced 5–8 days later than seedlings in light shade or full sun. Within seedlings, leaves on primary-growth shoots senesced later than those on secondary-growth shoots in some treatments. Path analyses demonstrated that germination timing and shade affected autumn phenology both directly and indirectly via pathogen load, though the specific pattern differed among and within seedlings. Pathogen load increased with later germination and greater shade. Greater pathogen load was in turn associated with later senescence for seedlings, but with earlier senescence for individual leaves. Our findings show that relationships between seasonal events can be partly mediated by the biotic environment and suggest that these relationships may differ between the plant and leaf level. The influence of biotic interactions on phenological correlations across scales has implications for understanding phenotypic variation in phenology and for predicting how populations will respond to climatic perturbation.

季节性生活史事件往往相互依存，但我们对不同事件之间的关系如何受到非生物和生物环境的影响知之甚少。这些知识对于预测种群对不断变化的条件的直接和进化物候反应非常重要。我们在多因素实验中操纵发芽时间和遮荫，以研究有花梗栎 ( Quercus robur ) 幼苗春季和秋季物候之间的关系，以及这种关系是否由专业真菌病原体（即橡树白粉病复合体）对叶子的自然定殖介导。每周发芽延迟相当于秋季叶片衰老延迟约2天，重度遮荫的幼苗比浅色或全日照的幼苗晚衰老5-8天。在幼苗中，在某些处理中，初生枝上的叶子比次生枝上的叶子衰老得晚。路径分析表明，发芽时间和遮荫通过病原体负荷直接和间接影响秋季物候，尽管具体模式在幼苗之间和幼苗内部有所不同。病原体负荷随着发芽较晚和遮荫程度增加而增加。更大的病原体负荷反过来与幼苗的较晚衰老有关，但与单个叶片的较早衰老有关。我们的研究结果表明，季节性事件之间的关系可以部分由生物环境介导，并表明这些关系可能在植物和叶片水平之间有所不同。生物相互作用对跨尺度物候相关性的影响对于理解物候的表型变异和预测种群将如何应对气候变化具有重要意义。