Biomass Equations

Features Biomass estimation equations are also known as allometric equations or regression models. Normally, these models estimate the biomass or volume of above-ground tree components (kg/tree) based on DBH and height data. These equations are derived based on measured values of tree weight related to its DBH and height from sample trees. Regression models are also available for estimating biomass (tonnes) on a per hectare basis, based on estimates of basal area (m2/ha) of all tree stems derived using the DBH values of sample trees which are extrapolated to per hectare value. The method for deriving biomass regression equations is given in Chapter 17. The DBH alone or DBH and height may not always explain all the variation in the weight of the tree, the dependent variable. The suitability of a regression model is explained by the standard error of the regression coefficients and the coefficient of the determination (r2), normally given along with the equation. Normally, each biomass equation can be used within a defined DBH range, for example, a DBH-based equation derived using only large trees (e.g. DBH greater than 30 cm) cannot be used for young trees with low DBH (e.g. smaller than 10 cm). However, most equations can be used for trees within the normal range of DBH, but not for those outside it.

Application Regression models are available for estimating the stocks of different carbon pools, with separate equations for each. These models can be used for estimating the following:

Table 15.1 Comparative features, inputs, outputs and application of carbon estimation and projection models

Model Features Key inputs Key outputs Application

Model Features Key inputs Key outputs Application

Table 15.1 Comparative features, inputs, outputs and application of carbon estimation and projection models

V.

- Biomass stock at Tree parameters

- Biomass stock

- Afforestation,

« =d

C

a given point is

- DBH

estimates kg/tree

avoided deforesta-

c

3

estimated using

- Height

at a given period

tion, roundwood

PC

cu

tree parameters

- Basal area

- Total AGB and BGB stock/ha

production

- Equilibrium

- Area dedicated to activity

- Total carbon

- Projection of

model for

- Planting rate and veg-

stock/ha and total

carbon stocks in

<

estimating car-

etation carbon stock in

project area

forestry mitiga

S c

bon stocks for

base year

- Biomass and soil

tion, afforestation,

Ü

project area

- Rotation period

carbon stock

reforestation,

§ p

- Mean annual increment

- Incremental

avoided deforesta-

in biomass and soil

carbon stocks - Cost-effectiveness

tion projects

- Simulates car-

- Simulation length

- C stocks and

- Forestry and

bon dynamics of

- Max. biomass in stand

fluxes

plantation projects

single/multiple

- Carbon content

- Total biomass and

- Projection of C

£

species, forest

- Wood density

soil carbon

stocks in for-

stands with trees

- Initial carbon

- AGB and BGB,

estry projects for

cf o

of varied ages

- Yield tables

deadwood, litter

selected species

and agroforestry systems

- Temperature

and SOC production or stocks

- Precipitation

- LGP

- Simulates long-

- Monthly mean maxi-

Soil outputs

- Forest, grassland,

term dynamics

mum and minimum air

- Total C

savannah and

of C, N, P and

temperature and total

- Soil water

cropping systems

t pi

S for different

precipitation

dynamics

or projects

plant soil sys-

- Plant N, P and S content

Plant outputs

- Can be applied

E—

tems

- Soil texture

- Commercial crop

at plot, project,

AK

- Atmospheric and soil

yield

regional or

Ü

N inputs - Initial soil carbon, N, P and S levels

- Total dry matter products

- Carbon input in plant debris

national level

C: carbon, N: nitrogen, P: phosphorus, S: sulphur, AGB: above-ground biomass, BGB: below-ground biomass, SOC: soil organic carbon, LGP: length of the growing period (season)

C: carbon, N: nitrogen, P: phosphorus, S: sulphur, AGB: above-ground biomass, BGB: below-ground biomass, SOC: soil organic carbon, LGP: length of the growing period (season)

• Above-ground biomass (kg/tree) based on DBH or DBH and height

• Above-ground biomass (t/ha) based on basal area (m2/ha)

• Below-ground biomass (t/ha) based on above-ground biomass

The above-ground biomass equations based on DBH variable are the most commonly used biomass equations. The application of biomass equations along with examples is demonstrated in Chapter 17. These models can be used for estimating carbon stocks or changes in carbon stocks in biomass and in soil for

• Afforestation and reforestation projects under Clean Development Mechanism (CDM) of the Kyoto Protocol

• Industrial roundwood or bioenergy plantation projects

• Community forestry and agroforestry projects

• National greenhouse gas inventory

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