The occurrence of herbs and woody juveniles in a hardwood floodplain forest in relation to flooding and light

Abstract. A study of the distribution of herbs, seedlings and vegetative propagules of woody species in a hardwood flood-plain forest along the Upper Rhine in France revealed that the occurrence of most species is significantly correlated to elevation above river level and light transmission in summer. Species confined to higher-lying sites which are only occasionally and briefly flooded in the growing season show most damage upon flooding. Tall herb species occur on sites where more than 5% daylight reaches the herb layer and they only reach a dense cover where flooding is occasional. The occurrence of woody juveniles is negatively correlated with tall herb cover and largely confined to more shaded sites or more frequently flooded sites. The results indicate that both shading and flooding are important for regeneration of woody species and for maintaining species diversity in hardwood flood-plain forests.