Oak forests are among the dominant vegetations of Himalaya. Understory vegetation of these forests are influenced by structure and composition of upper canopy species and the microenvironment. This study assessed the diversity and species composition of understory species at six different study sites of Quercus glauca forests in lower Himalaya. Sample plots of 20 m × 20 m, 5 m × 5 m and 1 m × 1 m were taken to collect tree, shrub and herb related data, respectively. Importance value index (IVI), Shannon-Wiener biodiversity index, Margalef’s index of species richness and Simpson’s species dominance were calculated for each study sites. The result revealed the presence of 45 shrub species belonging to 25 families and 61 herbages from 27 families. Site III and site V have highest number of shrub species, while site III and site VI have highest number of herbaceous species. The dominant shrub and herbages were Berberis lycium, Caryopteris wallichiana, Sageretia oppositifolia, Viburnum cotinifolium, Carissa carandas, Rhus cotinus, Digitaria cruciata, Paspalum coryphaeum, Oryzopsis hymenoides, Oplismenus composite, Thalictrum foliolosum, Oplismenus composites, and Panicum agrostoides. Diversity, species richness and dominance were related to density of upper canopy trees and the microenvironment. The study concluded that disturbance increased the diversity and species richness of shrubs and herbs. Species richness of shrub and herb decreased with increasing density of trees up to 675 trees ha-1 thereafter it increased up to the density level of 742 trees ha-1. Herbs are less affected by abiotic site conditions than shrubs.

Keywords: herbs, importance value index, Shannon-Wiener index, shrubs, tree density