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Regeneration from seed in herbaceous understory of ancient woodlands of temperate Europe.

BACKGROUND AND AIMS
European ancient woodlands are subject to land use change and the distribution of herbaceous understory species can be threatened because of their poor ability to colonize isolated forest patches. The regeneration niche can determine the species assembly of a community and seed germination traits may be important descriptors of it.


METHODS
We analysed ecological records for 208 herbaceous species regarded as indicators of ancient woodlands in Europe and, where possible, collated data on seed germination traits, reviewed plant regeneration strategies and measured seed internal morphology traits. The relationship between plant regeneration strategies and ecological requirements was explored for 57 species using ordination and classification analysis.


KEY RESULTS
Three regeneration strategies were identified. Species growing in closed canopy areas tend to have morphological seed dormancy, often requiring darkness and low temperatures for germination, and their shoots emerge in early spring, thus avoiding the competition for light from canopy species. These species are separated into two groups: autumn and late winter germinators. The third strategy is defined by open-forest plants with a preference for gaps, forest edges and riparian forests. They tend to have physiological seed dormancy and germinate in light and at warmer temperatures, so their seedlings emerge in spring or summer.


CONCLUSION
Seed germination traits are fundamental to which species are good or poor colonizers of the temperate forest understory and could provide a finer explanation than adult plant traits of species distribution patterns. Seed dormancy type, temperature stratification and light requirements for seed germination are important drivers of forest floor colonization patterns and should be taken in account when planning successful ecological recovery of temperate woodland understories.