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.