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Box B: Aboveground live dry biomass calculation for a sample plot.
Table 5.1 contains estimates of AGB for each of the 28 trees contained in the
example sample plot shown in Figure 5.2. The estimates were calculated using
the Chave et al. (2005) allometric equation for moist tropical forest species as
explained in Box A.
The AGB values calculated for each tree can be added together to obtain an estimate of the total AGB for the sample plot. In this example, the total AGB for
the plot is estimated to be 24.5 metric tons (see Table 5.1).
Typically, AGB is reported on a per hectare basis. Figure 5.3 illustrates the spatial relationship between the 40 m x 40 m sample plot and a one-hectare parcel.
The formula for converting from a per plot estimate of AGB (in metric tons) to
a per hectare estimate (in metric tons per hectare) can be calculated as:
AGBh = (Ah/Ap) * AGBp
where AGBh is the estimate of aboveground biomass in metric tons per hectare,
Ah is the area of one hectare in square meters, Ap is the area of the plot in square
meters and AGBp is the plot level estimate of aboveground biomass in metric
tons.
Thus, in this example where the area of one hectare is 10,000 m2, the area of the
plot is 40 m x 40 m or 1600 m2, and the above-ground live dry biomass in the
plot is approximately 24.5 metric tons, the per hectare estimate of biomass is
calculated as:
AGBh = (10,000/40*40) * 24.5
AGBh = (10,000/1600) * 24.5
AGBh = (6.25*24.5)
AGBh = 153.13 metric tons/hectare
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Field Guide for Forest Biomass and Carbon Estimation