Many forms of regression equations have been by different workers.

• For single stemmed, W = a + b D²H
• For multiple stemmed, W = a + b NS D²H

Where, W = weight in kg, D is diameter in decimeters, H is height in decimeters, N is number of samples, a is regression constant, b is regression coefficient, r is correlation coefficient, S is number of shoots, F is variance ratio.

Percentage of biomass

Kaul et al suggested following percentage of biomass for different parts of plant for Poplar trees:

• Above ground: Wood 58%, Bark 13%, Branches 9%, Twigs 4%, Leaves 6%, Roots 20%
• Under ground= 20% of AGB

How to measure biomass?

1. By direct measurement
2. Taking the data directly from the field and preparing the equation and biomass table
3. Indirect (By using the biomass table)
4. Biomass table shows the fresh wt not dry wt

Biomass Equations

For spp. (in Nepal), which have a very low branching habit or species in a coppiced broadleaf natural forest, dia is measured at 0.30m from the ground level.

Model equations
Following equation has been found suitable for calculating biomass.

ln y = a+b ln x

where y = oven dry wt. in kg (Biomass), x = dbh

For plantation spp. equation selected is

Weight = a+b ln x

where x variable is either dia at breast height at (1.3m) or basal diameter

Pukkala (1990) has proposed following equation for biomass:

ln (BRA) =-1.567+1.146* ln DBH (Eucalyptus)

where, BRA-Branch Biomass

Biomass Tables

i) For plantation speces

ii) For natural forest types (Katus-Chilaune) (for fresh green wt.)