Blumesche formula

The Blum formula is used to determine the real value of a forest or tree population using age value factors . It provides the age value expressed in units of value per unit area, e.g. B. euros per hectare .

The formula is ${\displaystyle A_{i}=((A_{u}-c)\cdot f+c)\cdot bf\cdot ha}$

It mean

A _i : Material value at the age of the forest stand at age i (years since the stand was established )

A _u : downforce at the age of the rotation period of a tree species (part of a forest )

c : Culture costs (planting and planting costs)

f : applicable age value factor for tree species, mass production of this tree species and tree species age (at age i )

bf : tillering factor [number between 0 and 1]: comparison of the actual stock of land with the stock of land that should be available according to a forestry yield table, capped at 1.0. (In contrast to this, the static tillage level is not capped)

ha : area, usually expressed in hectares

This formula corresponds to the specifications of the forest assessment guidelines of the BDR (status 2007).

In practice, the formula has been modified and further developed.

1. The hectare value is provided with percentage surcharges or deductions ( w  %). This is often easier than a complicated re-determination of the A _u value (value branches, stubborn stands, non-commercial forests). The modified Blum formula is

${\displaystyle A_{i}=((A_{u}-c)\cdot f+c)\cdot bf\cdot w\%\cdot ha}$

2. In the case of stands with a statically degree of tillage above 1.0, the output value of the excess wood mass is added to the age value (value of the excess mass).

3. The cultures are assessed dynamically; H. the cultural market value is derived from c and A _u . The exchange value ratio A _u to c is taken into account (= KAT  %).

The formula for spruce, fir and Douglas fir is:

${\displaystyle A_{i}=\left((A_{u}-c\right)\cdot f+\left(c+{\frac {A_{u}}{100}}\cdot {\frac {KAT\%}{2}}\right))\cdot w\%\cdot bf\cdot ha}$

for other tree species:

${\displaystyle A_{i}=\left((A_{u}-c\right)\cdot f+\left(c+2\cdot {\frac {A_{u}}{100}}\cdot {\frac {KAT\%}{3}}\right))\cdot w\%\cdot bf\cdot ha}$

In the case of unripe stands, the output value must be taken as a basis if the output value is greater than the age value, possibly together with the value of the excess mass.