A standardized photographic guide to woody plant spring phenology

Measuring plant phenology--the timing of recurring life history events such as leafout and flowering--sounds tantalizingly simple, but is complicated by the reality that different people often interpret the same event (e.g., budburst or leafout) differently. Researchers have worked to overcome this with a series of guides that explicitly describe each phenological event in great detail. One of the most widely-used scales is the BBCH (Biologische Bundesanstalt, Bundessortenamt und CHemische Industrie), which defines several principal growth stages and breaks down each stage into events within stages (e.g., first leaves separated). Yet, even with clearly described stages aimed at standardizing measurements of the same events taken by different observers, there can still be variation in observers' interpretation of events. Thus, photographs of each defined stage, for each species of interest, can help standardize observations further. Here we present a photographic guide to the BBCH stages of 31 woody species common to northeastern North American temperate forests.

测定植物物候学（plant phenology）——即展叶、开花等周期性生活史事件的发生时间——看似简单直观，实则操作复杂：不同研究者对芽萌动、展叶等同一物候事件的解读往往存在差异。为解决这一问题，研究者们开发了一系列详尽明确的物候事件描述指南。目前应用最广泛的分期标准之一是BBCH（Biologische Bundesanstalt, Bundessortenamt und CHemische Industrie，德国联邦生物研究所、联邦品种局与化学工业协会），该标准定义了多个主要生长阶段，并将每个阶段进一步细分为阶段内的具体事件（如首叶展开）。即便制定了清晰的分期标准以统一不同观测者对同一事件的测定结果，观测者的解读仍可能存在偏差。因此，为目标物种的每个已定义生长阶段配套拍摄对应的照片，可进一步标准化观测流程。本研究提供了北美东北部温带森林常见的31种木本植物的BBCH分期摄影指南。