Help:

What is a stand?

Is an area of a forest or a forest property with variable surface area but with the same productivity or Site Index and with uniform trees, which means that it is populated by trees of the same species (at least in a 90%), the same age and have suffered the same silvicultural treatments.

Before making calculations with EucaTool®, a given forest or forest property must first be divided into all possible existing stands.

Subsequently, in order to properly estimate the growth, volume, biomass and carbon content of each of the forest stands of the forest or forest property, it will be necessary to determine the following variables: age, dominant height, number of trees per hectare and basal area at different sampling points of each stand, depending on its surface.

What is the age of a stand and how is it measured?

The age (in years) required to use EucaTool® corresponds to the years elapsed since the plantation was made (without adding the years that the plants have grown in the nursery before being moved and planted in the land).

What is the number of trees per hectare and how is it measured?

The number of trees per hectare needed to use EucaTool® corresponds to the number of trees that actually exist on one hectare (10,000 m2), which may not correspond to those that were initially planted if there were losses in the plantation, if some trees have died since then or if, less frequently in eucalyptus, some were extracted.

The number of trees per hectare that correspond initially to the plantation is easily calculated by knowing the spacing, in meters, between rows of trees (in the two perpendicular directions, a and b) by the following equation: (10,000) / (a • b)

To this previous value, we must subtract an estimate of dead or cut trees from the moment of planting.

What is the dominant height and how is it measured?

The dominant height (in meters) required to use EucaTool® is defined as the average of the heights of the hundred thickest trees (of larger normal diameter) per hectare, which are considered dominant trees. A proportional number of dominant trees should be selected based on the stand surface, measuring their heights and making the average, but for practical purposes it would be sufficient to select a minimum of 3-4 trees nearby each sampling point that are really dominant, that is to say, those that have the largest normal diameters and that present an entire crown that dominates or outstands the rest, avoiding choosing trees located on the edges or isolated (which normally have a non-dominant height but a diameter raised by having developed without competition somewhere or in low density conditions). Measure their total height and calculate the average.

To measure the total height of a tree, you can use very different methodologies, which can be consulted in the book Dasometry Practices. A simple procedure, although less precise when it comes to trees taller than 15 m, is to use the so-called Christen hypsometric rule, following the instructions indicated therein, and for which it is necessary to have a stick or reference stick of 2 m in length.

What is the basal area and how is it measured?

The basal area (in m2 / ha) required to use EucaTool® is defined as the sum of the normal sections of the trees in one hectare. The normal section of a tree is the surface of the intersection of its trunk with a plane perpendicular to its longitudinal axis at a height of 1.30 m from the ground (normal height or chest height), which is measured from upstream of the tree in the case of sloppy terrain.

To calculate the normal section of a tree, the diameter is usually measured at that same height of 1.30 m from the ground (called normal diameter or chest height), in two cross or perpendicular directions, and the average of these two values is calculated. Then, the normal section of the tree (in m2) is calculated as: (π / 4) • (average normal diameter) 2.

To measure the basal area at a sampling point, various methodologies can be used, which can be consulted in the book Dasometry Practices. A simple, highly accurate procedure is to measure the normal diameter of all trees in a circular plot (of known radius and, therefore, of known surface, in m2) centered on each sampling point, calculate its normal sections (in m2), add them and use the following formula:

(10,000 • Sum of the normal sections of all the trees in the plot) / (Area of the plot)

How to choose the number of sampling points for a stand and how to distribute them in the field?

In order to properly estimate the growth, volume, biomass and carbon content of each of the stands of a forest or forest property, it is necessary to determine the age, dominant height and basal area at different sampling points of each stand, depending on its surface, and obtain the average value of each of these variables, values that will be introduced in EucaTool® to obtain the average results of the stand. The minimum number of sampling points to be measured in each stand is shown in the following table.

Area (ha) Minimum number of sampling points per stand

<3	3
3-5	4
6-10	5
11-25	6
>25	6 + 1 for every 25 hectares

After 25 ha, a sampling point will be added for every additional 25 ha of surface of the stand.

What is the Site Index?

The Site Index can be defined as the productive potential of an specific land for the growth of trees of a certain species in response to the totality of existing environmental conditions, but certain human interventions can modify that inherent productive capacity of a land, such as fertilizations, tillage, drainage, etc.