Active management promotes plant diversity in lowland forests: A landscape-scale experiment with two types of clearings

•Study shows important role of location of forest clearings within forest matrix.•Plant richness substantially increased after canopy opening.•Clearings connected with migration corridor were richer in functional strategies.•Threatened species of relict open forests tended to establish in isolated clearings.•Light-demanding plants were more diverse in connected while threatened species in isolated clearings.