We aimed to study the composition of herb layer in old Estonian boreonemoral forests (Aegopodium and Hepatica forest site-types) and estimate factors that influence the vegetation. Besides forest management and other anthropogenic disturbances, stand age, geographic location and tree species composition were analysed as potential driving factors. We surveyed 169 forests, mostly as a contrasting pair of intensively managed and possibly near-natural forest within each sub-region of a forest site-type. Later, for analyses, we reclassified forests into three groups by weighted summing of the observed signs of disturbances. Analyses revealed the distinction in herb layer composition among forest site-types and dominant-tree species. Geographic location of a stand also appeared to affect the understorey, while stand age had no statistically significant impact on herb layer in old and over-matured forests. We did not detect explicitly the direct effect of forest management and disturbances on herb layer composition and diversity. However, indirectly, only in Hepatica site-type, the management increased herb layer species richness and the proportion of graminoids, by providing more light via reduced closure of a stand. Species characteristic of managed stands were mostly light-demanding, dry soil tolerant and apophytic species. Undisturbed stands were characterized by presence of nemoral and vernal herbs that typically grow in broad-leaved or mixed stands. Consequently, the dominance of conifers in managed forest, can limit the growth of characteristic species of boreonemoral forest site-types. Therefore, to improve the state of plant diversity in boreo-nemoral forests, tree species diversity and small-sized gap-initiation should be supported.
