Fire regimes in many fire-prone temperate forest landscapes are intensifying under changing climates. More frequent and severe fires are threatening plant diversity, vegetation structure, and regeneration. Nonetheless, fire responses of understory communities, including both extant understory vegetation and soil seed banks (SSBs) remain under-evaluated. After a systematic search of published literature, we reviewed 55 temperate forest studies (668 individual effects), that assessed fire effects on understory richness and abundance across life forms, species origin, fire response strategies, fire regime components, and climatic zones. Overall effects of fire relative to unburned conditions were negative, but statistically non-significant, for the richness and abundance of both extant vegetation and SSBs. Statistically significant negative fire effects on extant vegetation were indicated for richness of non-woody perennial species and seeder species, and for resprouter abundance. In contrast, negative fire effects in SSBs were detected for resprouter and native richness and exotic abundance. Statistically significant decreases in species richness and/or abundance in extant vegetation were associated with prescribed fire, short time since fire, autumn fire and short-interval fires. By comparison, SSB richness and/or abundance were only clearly influenced by high-severity and short-interval fires. Our analyses underscore the essential yet different contributions of extant vegetation and SSB communities to post-fire recovery, and the importance of understanding interactions among plant traits and fire regime components to anticipate and manage fire impacts on understory plant diversity in temperate forests. • Fire had non-significant negative effects on understory richness and abundance. • Understory responses vary with plant traits and fire regime components. • In extant vegetation, fire reduced richness of non-woody perennials and seeders. • In SSB, fire decreased resprouter and native richness, and exotic abundance. • Short-interval fires are critical considerations for managing temperate understory.
Chaulagain et al. (Fri,) studied this question.