Tree species diversity increases the temporal stability of multitrophic forest beetle communities

As key members of the terrestrial food webs and vital contributors to wood decomposition, beetles play essential roles in ecosystem services but are experiencing widespread declines under climate change. While protecting and restoring forests with high tree species diversity is widely acknowledged as a nature‐based solution for climate change mitigation, it remains uncertain whether it helps maintain the stability of higher trophic communities (e.g. beetles) under climate change. Here, we used the comprehensive forest and ground‐dwelling beetle inventory dataset spanning the entire latitudinal range of the Japanese archipelago, monitored from 2004 to 2018, to investigate how tree species diversity affects the temporal stability of beetle biomass. We found that tree species diversity increased beetle biomass and its temporal stability. Specifically, higher tree diversity supported greater beetle and trophic diversity, which enhanced the asynchronous population dynamics across species and trophic levels (i.e. species and trophic asynchrony). Meanwhile, higher beetle and trophic diversity promoted temporal stability at the species level (i.e. species stability). Higher asynchrony and species stability jointly increased temporal stability within beetle communities. Our results underscore the potential of conservation efforts targeting forest diversity to uphold the ecosystem functions of higher trophic level communities (e.g. beetles) under climate change.