Temporal dynamics of insect herbivory in understory trees across temperate and tropical forests

Insect herbivory shapes forest ecosystems by affecting plant growth, nutrient cycling, and regeneration. It is commonly believed that tropical forest understories face greater insect herbivory pressure than their temperate counterparts. Yet, the magnitude of this tropical–temperate contrast remains debated. To address this gap, we examined how insect herbivory accumulates over time on understory woody plants across six temperate and tropical forests in Germany, Japan, China, Papua New Guinea, and Australia. We initiated the sampling during the early growing season in temperate forests and the onset of the wet season in tropical forests, and followed it by resampling. We quantified both standing herbivory and its temporal accumulation over 1‐month and 4‐month intervals on 44 understory tree species. Early in the growing season, standing herbivory was higher at low‐latitude, aseasonal tropical sites than at higher‐latitude temperate sites. However, herbivory accumulated more rapidly in temperate forests during the first month, consistent with intense feeding during spring leaf flush. As a result, initial tropical–temperate differences diminished rapidly, with standing herbivory converging within 1 month and remaining similar after 4 months. In tropical forests, herbivory accumulation was more stable through time, likely reflecting continuous leaf production and sustained herbivore activity. In summary, insect herbivory was primarily shaped by contrasting temporal dynamics of accumulation across forest types. Herbivory varied with latitude early in the season, accumulated rapidly in temperate forests, and converged across sites after 4 months, resulting in no consistent difference between tropical and temperate understories later in the season. These results demonstrate that herbivory accumulation over time is a key driver of observed patterns, which differ during the annual cycle. These findings highlight the importance of multi‐temporal assessments of insect herbivory and caution against inferring broad‐scale herbivory patterns from single time‐point surveys.