Forest stands ©

Stands are made-up from a number of trees. We could just list all the individual tree measurements, but unless the stand is very small, it is impossible to grasp an understanding of the patterns involved. Therefore a number of stand parameters are defined for measurement:

Stand Table - frequency of trees in diameter classes
Stand height - the average height of a defined component of the stand
Stand Height Curve - relationship between tree diameter and height
Stand Density - a measure of competition within the stand
- Stand Basal Area
Site Index - a measure of the potential quality of the site.
Stand volume - a measure of the volume and yields from a stand

Various factors influence what stand variables are measured and how they are measured, the main factors being:-

purpose of measurement
location, size and value of population
stand characteristics (including variability)
time, labour and money
market conditions .

Purpose of measurement

Stands are measured for three main purposes:

to provide data for policy planning
to provide data for management planning
to obtain measurements from which conclusions of a research nature can be drawn.

The detail of measurement increases progressively from 1 to 3.

Location, size and value of population

Forests generally are too expensive to measure every tree. They also differ in accessibility and intrinsic value. Hence, the first decision to make is how many trees to measure and in what detail. This decision, which is not independent of the other factors, largely determines the sampling method.

Stand characteristics/structure

The general structure of a forest has an important influence on stand measurement. As an example of the influence of stand structure on measurement, contrast stands in a rainforest and coniferous forest respectively, viz:

Item                  Rainforest              Coniferous Plantation

Species and pattern Range of species in       Single species
                    irregularpattern          regularly laid out

Access              Impeded by ground         Easy,
                    vegetation and fallen     as little vegetation
                    trees                     or rubbish on forest floor

Stand age           Uneven age                Even aged and age known
                    and determining age
                    of any stem may be 
                    difficult or impossible

Utilisation         Not all species and       Limited range of 
                    sizes are commercial.     size classes. 
                    Many trees are not        With few exceptions
                    utilisable due to defect  all trees are
                    and this is not readily   utilisable
                    discernible

Time, labour, money

In practice, time, labour and money largely determine what measurements are made. An insufficiency of any one of the three limits the measurement programme.

Market factors

Relevant factors are the quantity and quality of produce available for sale and the precision of the estimates. In general:

the more produce available for sale, the lower the cost of measurement /unit.
the more precise the estimate required of a quantity of produce available for sale, the higher the cost of measurement and the higher the selling price.
for a given quantity of produce available for sale, the higher its quality (and hence its sale price), the more money can be spent on measurement /unit of product while optimising the net sale price.

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Document URL	http://online.anu.edu.au/Forestry/mensuration/GROUPS.HTM
Editor	Cris Brack ©
Last Modified Date	Fri, 9 Feb 1996