Comparative seed biology of European temperate forest herbs

Herbaceous species of European ancient woodland understories are affected by land use and climate change. Their distribution can be at risk because of their poor capacity to colonize isolated forest patches. The objective of this thesis was to compare the regeneration strategies of those species, with a focus on their germination traits. A database of ancient woodland seed traits was created by reviewing published information for 208 indicator species. The database included seed germination traits, embryo:endosperm ratio and other traits related to the plant regeneration strategy. Field surveys were conducted to compare the understories of old and recent woodlands in Spain and England. Community-weighted means of several seed traits were calculated to assess the functional regeneration ecology of the species that naturally colonize mature and recent forest patches. Two groups of understory species were described according to their regeneration traits. The first group included late flowering species possessing seeds with physiological dormancy that germinated in spring and had a requirement for light, cold stratification and high germination temperatures. Those species produced many small seeds and were taller, suggesting a good colonizing capacity. Species of the second group had seeds with morphophysiological dormancy, and were able to germinate in absence of light following a warm stratification. They produced few big seeds on short stems, suggesting a poor colonizing capacity. Species of the first group were abundant in the recent plantation sites while species of the second one characterized the plots on mature forests. Forest specialists can be differentiated from other forest species on the basis of their germination traits. The identification of regeneration strategies characteristic of poor colonizing understory species provided the basis for planning restoration interventions for European temperate forest understories according to species germination strategies.