Plant community structure and regeneration of Quercus Semecarpifolio Sm.Forests in disturbed and undisturbed areas

Abstract

Regeneration behavior of tree species is characterized by their population structure which depends upon the presence of adequate number of seedlings and saplings. Quercus semecarpifolia is a main forest forming evergreen tree species from upper temperate to lower sub alpine regions of the Himalaya. Vegetation structure and regeneration of Quercus semecarpifolia were studied in two forests of midhills of Central Nepal with different disturbance levels; one was distrubed forest at Simbhanjyang, Makawanpur, and another was undisturbed forest in Shivapuri National Park, Kathmandu. A systematic random sampling method, using square quadrats, was used for vegetation and soil sampling. Soil was collected from each quadrat and their physicochemical characteristics (soil pH, organic carbon and total nitrogen) were analysed. In each quadrat, presence/absence of herbs and shrubs; and the total number of individuals of tree species, sapling and seedling were recorded. Community attributes such as importance value index, species richness and species diversity were determined for both forests and compared. Density-diameter relations for trees, and the spatial pattern of distribution of seedlings and saplings were analyzed to understand regeneration pattern. Altogether 86 and 57 species of flowering plants were found in disturbed and undisturbed forests, respectively. Tree species diversity was higher in undisturbed forest while herb and shrub diversity was higher in disturbed forest. There was significant (p<0.05) difference in soil pH, soil nitrogen, soil organic carbon, litter coverage, total tree density, density of Quercus semecarpifolia tree, sapling and seedling of Quercus semecarpifolia, density of seedlings of all tree species, and total species richness between two forests. Sapling density of Quercus semecarpifolia declined with increasing tree basal area in both forests and seedling density was also decreased with increasing basal area in undisturbed forest whereas no relation was found in disturbed forest. Significant increase in regeneration of Quercus semecarpifolia along with other tree species in disturbed forest might be due to disturbances in the canopy of trees.