Plant diversity and free carbon stock in Swyambhu and Dakshinkali........

Abstract

Species diversity is the combination of species evenness and species richness. Sacred groves play significant role in conservation of rare and endemic species due to taboos and prohibitions. Nepal has centuries old traditions of establishing sacred groves of various size devoted to a particular deity. The relationship of tree diversity and carbon stock, an important concern of climate change mitigation and biodiversity conservation has been less studied in sacred groves of Nepal. This study aimed to assess the plant diversity and carbon stock in Swayambhu sacred grove (SSG) and Dakshinkali sacred grove (DSG) of Kathmandu district. To study diversity, IVI, regeneration, tree and soil carbon stock, altogether 77 plots were sampled in 9 parallel transects in SSG (30 plots) and 10 parallel transects in DSG (47 plots) by using systematic random sampling method. Circular plot of 10 m radius was laid for trees and within it, one concentric plot of 5 m radii for shrubs and 3 subplots of 1 m radius for herbs was laid. Soil samples were collected from surface upto 15 cm depth using core sampler (volume 356.5179 cm3 ) from the plot centre for estimation of bulk density and composite soil sample (one in the plot centre while other four in N, E, W and S directions) for estimation of soil organic carbon. Regeneration was assessed by using Density-Diameter (D-D) curve and calculating density of each tree species in seedling, sapling and tree phases. Tree biomass was calculated using allometric equation developed for moist forest and later converted into carbon stock using default factor. Altogether 115 species belonging to 57 families and 104 genera were recorded in the SSG and in DSG total 184 species belonging to 77 families and 159 genera were recorded. Shannon-Weiner diversity index (H) of plant species was found to be higher in DSG (H = 3.975) than in SSG (H = 3.213). The D-D curve showed reverse J shaped size class distribution in DSG. Density of seedling, sapling and tree was higher in DSG than that of SSG. Tree carbon stock (113.76 t/ha) and soil carbon stock (18.31 t/ha) of SSG (113.76 t/ha) was found higher than tree carbon stock (79.87 t/ha) and soil carbon stock (17.93 t/ha) of DSG. Tree carbon stock showed non-signicant weak positive correlation with species richness (r = 0.290, p = 0.120) and diversity index (r = 0.219, p = 0.246) in SSG but it showed non-significant weak negative correlation with species richness (r = - 0.077, p = 0.607) and diversity index (r = - 0.201, p = 0.177) in DSG. The findings of this study will be helpful to direct implication for the management and policies related to sacred groves for climate change mitigation and biodiversity conservation.