Abstract Key message Flower production in three Acer species is primarily determined by individual size, with local light exerting secondary effects depending on species-specific responsiveness. Abstract Reproductive and growth strategies of long-lived trees depend on both the timing of reproductive onset and the regulation of reproductive allocation, which are shaped by internal and external factors. We investigated how flowering in three Acer species— Acer mono , Acer japonicum , and Acer amoenum —is influenced by individual size, light conditions, and position within the crown. Tree height and diameter at breast height (DBH) were measured along with light metrics (relative photosynthetic photon flux density RPFD, canopy layer, and gap status), and their effects were evaluated at the individual, branch, and shoot levels. Statistical analyses showed that reproductive onset in A. mono and A. japonicum was primarily determined by tree size, whereas light conditions additionally influenced A. amoenum . Although tree-level flowering intensity was similarly affected by size and light across all species, species-specific trends appeared at the shoot and branch scales. A. mono , a light-demanding species, produced more flowers on current-year shoots with greater relative length (RL). No shoot-level trend was evident in A. japonicum , a shade-tolerant species. By contrast, A. amoenum produced more flowers on relatively short current-year shoots in partially shaded, growth-demanding trees, while flowering was more uniform in isolated trees. A light-manipulation experiment further supported the light-sensitive flowering of A. amoenum , highlighting the role of the red-to-far-red (R: FR) ratio, in contrast to the minor response of A. mono . Overall, size establishes the threshold for reproductive onset, while light regulates reproductive allocation; flowering patterns reflect species-specific strategies linking growth, reproduction, and light use.
Fujioka et al. (Sun,) studied this question.