Assessment of Biomass and Total Carbon Stock in a Tropical Wet Evergreen Rainforest of Eastern Himalaya along a Disturbance Gradient

Rainforests of North-East India in the Eastern Himalaya forms a part of the Himalayan biodiversity hotspot with rich biodiversity accompanied with dense vegetation of trees, thus making rainforest ecosystems a major carbon sink. Despite the biological richness, forest degradation is a matter of serious concern in this region. Considering disturbance as a major factor, a study was carried out to assess the biomass and carbon allocation pattern in the different compartments of the rainforest. The study area was stratified into least disturbed (LD), mildly disturbed (MD) and highly disturbed (HD) sites based on visual assumption, and later disturbance index of the sites were calculated. Vegetation analysis for various ecological indices was carried out. Biomass and carbon stock in different pools were estimated adopting suitable regression equations developed earlier for similar ecological regions. The total plant biomass showed a gradual decrease from LD to HD site and was 425.70 ± 29.71 Mg ha-1 in the LD site, followed by 236.08 ± 5.82 Mg ha-1 in the MD site and 127.38 ± 4.74 Mg ha-1 in the HD site. Amongst the different pools, aboveground biomass constituted the largest compartment in all the three sites for C stock and biomass. Tree density and basal area were highest in the LD sites. Soil organic Carbon (SOC) stock in 0 - 45 cm depth was also recorded maximum in the LD (72.48 ± 5.11 Mg C ha-1) followed by MD (40.13 ± 2.50 Mg C ha-1) and HD (32.38 ± 1.66 Mg C ha-1) sites. Total carbon stock was also found highest (306.61 ± 17.14 Mg C ha-1) in the LD site followed by 169.97 ± 2.59 Mg C ha-1 in the MD and 102.43 ± 3.18 Mg C ha-1 in HD site. Forest disturbance thus showed a significant inverse relation with carbon storage in all the pools. Thus it can be concluded that carbon sequestration in forest ecosystems was influenced by the anthropogenic disturbances in the present study.