Information on changes in the herb layer of unmanaged forest nature reserves may be useful to assess present-day issues of management relating to sustainability and biodiversity in forestry and nature conservation. Selected floristic and vegetation studies from forest nature reserves in the German states of Lower Saxony and Hesse showed that the number of vascular plant species was higher in forests that are managed than in completely unmanaged forests. Species richness declined significantly during a ten-year period after the active management of the forest reserves had stopped. In both cases, species richness was related to non-forest plant species that depend on high light intensity and soil disturbances. Beech (Fagus sylvatica) became dominant in unmanaged forests due to its high shade tolerance, providing it with a competitive advantage over most other species. However, after large-scale disturbances such as windthrow, species richness increased again even in unmanaged forests.