Diversity and functional differentiation of renewal buds in temperate herbaceous plants

Spring regrowth in temperate perennials relies on renewal buds, which form a key component in the shoot growth cycle. Still, we possess almost no information on these renewal buds, which is becoming more pressing with the current climate change. Most existing studies concentrated on easy-to-study aboveground buds of woody plants, whose morphology has largely been linked to frost protection. It is not clear to what extent these findings apply also to herbaceous species. We therefore examined protective traits and preformation of winter renewal buds in 379 species of temperate herbs, and tested how these traits are distributed across the phylogeny and related to other bud bank and whole-plant traits. We identified a major gradient from few, large, highly preformed, scale-covered buds associated with larger belowground storage organs deep in the soil, to small, numerous, less preformed, and naked buds near the soil surface. Belowground renewal buds of temperate herbs show several distinct strategies for winter survival and spring regrowth that might affect their response to changing winter and early spring conditions. Renewal bud traits are driven not only by frost protection but also by protection of the apical meristem from mechanical disturbance in the soil.