Tracks, treatment options and products


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The next section to add to our ForestModel is the management treatment options. Stands have been associated with feature attributes to describe what is on the ground, succession tells the model what each stand will succeed to naturally, now we can describe what management options are available for selected stands. Management options are described in <track> elements with the use of 'helper' variables. Tracks contain all the management options available for the selection, as tracks are an entirely new bundle of selection statements.

Treatment types are possibilities and do not necessarily imply that any one treatment will be chosen. To create multiple treatment options we must use the <define> element to create an empty field that can be assigned the value of the treatment type temporarily. Later in the ForestModel the treatment field can be queried in a select statement to find the specific products that would result from the application of that particular treatment on the selected stand. Modelling multiple treatment types cannot be done without the helper variable.

The following lines of code could be added to our XML file to describe a simple treatment option named CC.

  <define field="treatment"/>

    <select statement="theme1 in 'P1,ST' and theme2 in 'Y1,Y2,Y3,Y4,Y5,Y6,Y7' and theme3 = 'N'">
      <track>
      <treatment label="CC" minage="90" maxage="300" offset="-5">
        <produce>
           <assign field="treatment" value="'CC'"/>
          </produce>
        </treatment>
      </track>
    </select>

	The helper variable `treatment` should be defined with other variables at the beginning of the ForestModel. Select statements can identify specific stands with unique characteristics and assigned the appropriate treatment options (all treatments found within the track element).
	The treatment element has a number of attributes which can modify the treatment type and supply some operational restrictions. These attributes and their function are discussed in detail in the treatment reference page. In our example, we have defined a CC treatment that can take place if the stand is between 90 and 300 years of age. After the treatment has been applied, a 5 year regeneration delay has been specified (`offset="-5"`).
	Assigning the treatment type to the helper variable is done within a produce element. Assignments within the produce element are temporary and used to locate the associated product attributes in product select statements. If this particular stand was eligible for other management treatments they could be included within this track and searched for in unique product select statements.

Products are very similar to the features we have already discussed in this chapter. Products are attributes describing the results of a management treatment. To find the specific results of treatments, the helper variable treatment is queried with other stand characteristics in a new bundle of select statements. Records that satisfy the product select statements will be associated with various attribute curves to describe the results of a treatment if it is scheduled. For example, the products derived from our treatment above would look like this.

  <select statement="theme2 eq 'Y4' and theme5 eq 'PL' and treatment eq 'cc'">
      <products>
        <attributes idref="Seral.PL"/>
        <attributes idref="Yield.Y4"/>
        <attribute label="product.Treated.CC"/>
          <curve>
            <point x="0.0" y="1.0"/>
          </curve>
        </attribute>
      </products>
    </select>

The section of code above indicates that if a Block with Y4 and PL is treated with a CC treatment type, the following product attribute curves will describe the results. These particular attribute curves relate directly to a CC treatment and not a Thinning for example, because of the helper attribute. If the track had multiple treatments, identical product select statements would be repeated except for a change of treatment type. See the products reference page for additional examples.

What becomes of a stand after a particular management treatment depends on the assignments made in <transition> elements. Transitions can be defined for each treatment in the track, and any number of stand characteristics can be <assign> new values. The treatment element specifies the new average offset of the resulting stand (age), as well as the time between treatments but does not specify any changes in the actual stand characteritiscs.

For example, a management treatment may include a clear cut harvest and plant option for a particular BW stand. The species planted however, may change the composition of the original stand, as well as the recorded silvicultural intensity. Including transition assignments in a treatment indicates to the model that the stand characteristics change as a result of the treatment, and defines the changes.

    <select statement="FU eq 'BW1' and IFM in ifm and SILVINT eq 'Exten'">
      <track>
        <treatment label="Intn1" minage="70">
          <produce>
            <assign field="treatment" value="'Intn1'"/>
          </produce>
          <transition>
            <assign field="FU" value="'PWUS'"/>
            <assign field="SILVINT" value="'Regrowth'"/>
          </transition>
        </treatment>
        ...

In the above example, two fields change as a result of an Intn1 treatment: FU and SILVINT. Additional characteristics could have been changed by adding more assign statements. If a treatment does not change the stand in any other way than age, no transition elements need be included with the treatment. For more information see transition.

	Tip
Tracks contain all the management options available for blocks that match your select statements. Treatment is a helper variable that temporarily stores the value of the treatment type that is selected, based on matching the select statements. Products are very similar to the features. They are attributes describing the results of a management treatment. Blocks that satisfy the product select statements will be associated with various attribute curves to describe the results of a treatment if it is scheduled.

Tip

Tracks contain all the management options available for blocks that match your select statements.
Treatment is a helper variable that temporarily stores the value of the treatment type that is selected, based on matching the select statements.
Products are very similar to the features. They are attributes describing the results of a management treatment. Blocks that satisfy the product select statements will be associated with various attribute curves to describe the results of a treatment if it is scheduled.