Morley Lucy M, Crofts Sam J, Cole Ella F, Sheldon Ben C
Department of Biology, Edward Grey Institute of Field Ornithology University of Oxford Oxford UK.
Ecol Evol. 2025 Sep 2;15(9):e71821. doi: 10.1002/ece3.71821. eCollection 2025 Sep.
The extent to which phenological synchrony between trophic levels may be disrupted by environmental change has been a topic of increased focus in recent years. Phenological associations between deciduous trees, phytophagous insects, and their consumers (e.g., passerine birds) have become one of the model systems for understanding this process. However, most existing research reports population-level associations rather than examining the smaller spatial scales at which these trophic interactions occur. Furthermore, a variety of methods have been used to measure phenology, particularly on producers and primary consumers, with little formal comparison. To investigate how different methods of measuring producer and primary consumer phenology influence our understanding of these biological relationships at the appropriate scale, we quantified phenological metrics for individual host trees and the phytophagous insects that depend on them in a deciduous woodland during spring 2023. We sampled 170 trees from six deciduous species in Wytham Woods, UK, deriving nine metrics of phenology from five distinct field methods: multispectral drone imaging (NDVI), hemispherical canopy photography, and bud-scoring observations to track tree phenology, as well as water traps and frass traps to monitor insect herbivore phenology. We assessed the reliability of these methods within both trophic levels and across tree species. We further evaluated the extent to which tree phenology metrics correlated with herbivore phenology at the level of individual trees and links to variation in subsequent herbivory rates across a subsample of 72 oak trees (). Our results illustrate how methodological choices can affect our ability to study the timing of trophic interactions and reveal fine-scale spatiotemporal variation in phenology across both trophic levels. We discuss the implications of these results for considering how the scale-dependence of trophic interactions may stabilize populations and shape broader-scale responses to environmental change.
近年来，营养级之间的物候同步在多大程度上可能被环境变化打乱，已成为一个越来越受关注的话题。落叶树、植食性昆虫及其消费者（如雀形目鸟类）之间的物候关联，已成为理解这一过程的模型系统之一。然而，大多数现有研究报告的是种群水平的关联，而非考察这些营养相互作用发生的较小空间尺度。此外，人们使用了多种方法来测量物候，尤其是针对生产者和初级消费者，且很少有正式的比较。为了研究测量生产者和初级消费者物候的不同方法如何在适当尺度上影响我们对这些生物关系的理解，我们在2023年春季对一片落叶林地中依赖宿主树的个体宿主树和植食性昆虫的物候指标进行了量化。我们从英国怀瑟姆森林的六个落叶树种中采样了170棵树，通过五种不同的野外方法得出了九个物候指标：多光谱无人机成像（归一化植被指数）、半球形树冠摄影和芽评分观测来跟踪树木物候，以及水陷阱和粪便陷阱来监测昆虫食草动物物候。我们评估了这些方法在两个营养级内以及不同树种间的可靠性。我们进一步评估了树木物候指标在个体树木水平上与食草动物物候的相关程度，以及与72棵橡树子样本后续食草率变化的联系。我们的结果说明了方法选择如何影响我们研究营养相互作用时间的能力，并揭示了两个营养级物候在精细尺度上的时空变化。我们讨论了这些结果对于考虑营养相互作用的尺度依赖性如何稳定种群以及塑造对环境变化更广泛尺度响应的意义。
