TREE DIVERSITY, CARBON STOCK AND REGENERATION  PATTERN IN SHOREA ROBUSTA GAERTN. FORESTS ALONG  THE ALTITUDINAL GRADIENT IN EASTERN NEPAL

Chaudhary, Sujan

TREE DIVERSITY, CARBON STOCK AND REGENERATION PATTERN IN SHOREA ROBUSTA GAERTN. FORESTS ALONG THE ALTITUDINAL GRADIENT IN EASTERN NEPAL

Publisher

Amrit Campus

Abstract

The forest with good regeneration can store a sufficient amount of carbon. The Shorea robusta Gaertn. (Sal) forests of Nepal are facing the problem of poor regeneration. The present study aimed to find out the tree diversity, carbon stock and regeneration status of Shorea robusta forests along an altitudinal gradient in eastern Nepal. The study was conducted in three community forests of Sunsari and Dhankuta District. The forests were Ramdhuni Kalijhora community forest (82-170 m a.s.l.), Patrangbari community forest (440-695 m a.s.l.) and Khanidada Malbase community forest (650-990 m a.s.l.) which were regarded as lower, middle and upper altitudinal range forest respectively in the present study. The stratified random sampling method was used for the sampling. Altogether, 90 circular plots (30 in each forest) were laid for trees and saplings each and 180 plots were (60 in each forest) laid for seedlings. Physico-chemical parameters (Nitrogen, potassium, phosphorus, organic matter, moisture, pH and bulk density) were analyzed from all 90 plots. The present investigation has recorded 43 tree species under 25 families and 35 genera. The Dominance-Diversity curve (DD curve) showed the highest IVI of Shorea robusta in all three altitudinal ranges. The value of Shannon Diversity index was higher in high altitudinal range (1.078) followed by low (0.966) and middle altitudinal range (0.833). Species richness increased with increasing altitudes (from 82 m to 990 m a.s.l). The tree carbon stock ranged from 134 – 372 t ha–1 .Similarly soil carbon stock was higher in high altitudinal range (60.03 t ha–1 ) and lower in middle altitudinal range (27.69 t ha–1 ). The seedling of Shorea robusta was higher in low altitudinal range and lower in high altitudinal range. Contrast results were obtained for sapling i.e. lower in low and middle altitudinal ranges and higher in high altitudinal range. The regeneration of Shorea robusta was affected by various edaphic factors and anthropogenic activities. The regeneration status of seedlings and trees in the forests was healthy but poor in terms of saplings. Organic matter, nitrogen and sand percentage were positively correlated to altitudinal range. However, potassium, pH, silt and clay content showed a negative correlation with altitudinal ranges. Bulk density and moisture content were negatively correlated. Therefore, the establishment of seedlings to saplings in the study areas was very crucial for the sustainability of forests.