COS 283-5 - Estimation of tree and soil organic carbon stock and their variation along with stand parameters in Ratargul Swamp Forest Ecosystem, Bangladesh

Background/Question/Methods

Wetlands cover 6% of the world’s land surface and contain about 12% of the global carbon pool, playing an essential role in the global carbon cycle. As wetland characteristics vary geographically, understanding the local dynamics of tree carbon stocks and associated drivers is critical for sustainably managing forest carbon sinks. The Ratargul Swamp Forest (RSF), located in northeastern Bangladesh, is the only freshwater swamp forest in the country. The 1345 ha forest houses a pool of endemic trees and plants and offers several ecosystem services. However, the carbon storage capacity of RSF has remained unexplored and, thus, lacks a national policy for its climate-smart management. To that end, this study aimed to estimate above- and below-ground tree carbon and soil organic carbon stocks and explore their key drivers at RSF. From a total of 50 randomly selected plots (20 m x 20), all live trees ≥ 5 cm diameter at breast height were identified, their diameters were measured, and soil samples from 10-30 cm depth were collected to determine the bulk density and organic carbon (SOC). Tree biomass was estimated using a pan-tropical allometric equation known as Brown’s equation. Loss on ignition method was used to quantify SOC.

Results/Conclusions

The study revealed that Pongamia pinnata stores the highest (101.94 ton/ha) and Streblus asper (0.095 ton/ha) stores the lowest carbon stock in the study area. Among the 11 diameter classes recognized, the 80–90 cm diameter class contributed most (14.35%) of the total carbon stock estimated for the RSF, followed by 70–80 cm (13.89%), 60–70 cm (13.8%), 40–50 (13.4%), and 30–40 cm (9.68%) classes. The Average SOC stock up to 30 cm depth at RSF was estimated to be 436.87 tC/ha. We estimated SOC stock to be 170.27 t/ha for the 0–10 cm depth, 145.08 tC/ha for 10–20 cm depth, and 121.51 tC/ha for 20–30 cm depth. Results from the regression analysis showed that the total tree carbon stock had no significant impact on species richness (P > 0.05). On the other hand, soil organic carbon stock had a significant positive relationship with tree density (P < 0.001) and had no significant relation with species richness (P > 0.05). The current study emphasizes the importance of freshwater swamp forest ecosystems in mitigating climate change. It also highlights that swamp forests could contribute substantially to the national carbon budget and offer co-benefits of biodiversity conservation under the REDD+ program.