EFFECT OF DISTURBANCE ON PLANT SPECIES DIVERSITY, FOREST STRUCTURE AND REGENERATION IN COMMUNITY FORESTS OF DEUKHURI, DANG, NEPAL

Abstract

Disturbance are the major drivers of forest ecosystem. Disturbance both natural and human disturbances affect forest characteristics and biodiversity of the local area. This study investigated the effect of disturbance in plant species diversity, forest structure and regeneration in Durga community forest (undisturbed) and Mahadewa community forest (disturbed) of Deukhuri, Dang Nepal. Disturbance was estimated by visual observation of the study area on the basis of different disturbance parameters. Altogether 60 plots were laid for the study. Each of 30 quadrats of 20m×20m for tree, 2 sub plots of 5m×5m for shrubs and 3 sub plots of 2m×2m for herbs within each tree plot were laid in disturbed and undisturbed forest. A total of 106 plant species under 44 families were recorded from study area. Among the recorded species, 69 plant species under 35 families were found in undisturbed forest and 81 plant species under 35 families were found in disturbed forest. Whereas, 44 species under 26 families were common to both. Fabaceae was the richest family in undisturbed forest while Poaceae dominated in disturbed forest. Shorea robusta was the dominant tree species in both forests with higher IVI value (i.e, 212.127 in undisturbed and 256.201 in disturbed). The grasses like Cynodon dctylon Eragrostis sp., Cyperus rotundus, Imperata cylindrica etc. dominated disturbed forest while Hemidesmus indicus, Dioscorea alata, Cynodon dactylon etc were found more in undisturbed forest. Some of the herb and shrub species were added up during rainy season. Shrub Clerodendrum infortunatum dominated both forest types. The overall plant biodiversity was higher in disturbed forest. The herb density (per hectare) was higher in disturbed forest while the tree and shrub density was higher in undisturbed forest during both (rainy and dry) season. The Diameter- density relation was reverse J shape i.e, with increase in diameter the number of trees decreases which show that trees are at intermediate stage of growth. Similarly, the height class distribution showed that in disturbed forest highest frequency was at 20-25m with very few young trees while in undisturbed forest there were more frequency at 15-20m height. The regeneration pattern in undisturbed forest was comparatively good as the number of seedlings were higher followed by number of saplings and trees. Whereas, in disturbed forest there were more trees than seedlings and saplings. Shorea robusta had the higher regeneration compared to other species in both forest.