2.6 Estimating above ground biomass and carbon stock
Above ground biomass (AGB) is an important function that a forested land offer, and plays an important role in the study of carbon cycle and climate change (Li et al. 2020). This indicator can be highly useful to discern quality of an ecosystem in terms of habitat condition and biodiversity hotspot (Zolkos et al. 2013). AGB and carbon stock in this work are determined, both in space and time, to understand stresses that Cox’s Bazar–Teknaf forest ecosystem is experiencing due to massive influx of Rohingya. Since the study area is inaccessible as being hilly and this study is constrained by logistics, biomass data for selected forest classes are obtained from an earlier inventory (IOM and FAO, 2017). In total, 57 subplots within 15 major plots, covering a total sample area of 6.48 ha, were used to collect AGB parameters, e.g., diameter at breast height (DBH), and height for trees and saplings. Five major LULC were considered by the inventory of IOM and FAO (2017). It is important to note that four major forest covers such as shrubs, mixed forest, planted trees and canopy forest are considered in this work, due to their greatest role in regulating ecosystem function (Li et al. 2020; Panja, 2020). A 100x100 grid is used to estimate area of each four categories which is then multiplied with AGB (ha) values of the respective forest classes (viz., 2, 17,003, 2 and 180,038 kgs for shrubs, mixed forest, planted forest and canopy forest). The values are subsequently summed to get total biomass in kilogram (kg) per grid. To obtain total carbon (in kg/grid), derived biomass values are divided by two (2). A maximum of 180,038 kg AGB or 90,019 kg carbon per grid is possible, if a grid contains 100% canopy forest. In contrast, 0 kg of biomass and carbon/grid is possible, if a grid has no forest, i.e., camps.