Setting targets on patch accounts

Now that we have defined a number of patch targets in the PIN file, lets look at how to get target values to control the spatial distribution of disturbance patches across the landscape.

Patch size targets calculate the amount of area in the size class as a percent of the total patch criteria present in the entire forest. Setting targets on these accounts encourages the scheduler to make allocations that result in patch size distributions matching the target charts. This provides direction for the scheduler to attempt a solution that will satisfy the individual patch category objectives.

For example, with 5 size categories we could divide the patch distribution evenly by percent area amoung the size class targets:

0_50     = 20% minimum
50_150   = 20% minimum
150_250  = 20% minimum
250_2500 = 20% minimum
2500+    = 20% minimum
      

These targets can be set by entering '20' into the minimum target values for each of the size sub-accounts. Be sure to activate the accounts and the minimum targets. Defining patch size objectives in this way will direct the scheduler to find a solution that had just as much area in the 2500ha+ size class as the 0-50ha size class.

Having targets for each size class category provides flexibility and control over the resultant landscape patterns. Defining meaningful categories in the PIN file means targets can be used to help the model meet specific landscape level goals.

Let's look at another example where we change the distribution of area between patch size classes. In this example, we will limit the number of disturbance patches in the two largest size classes by setting a maximum area objective of zero and weighting this target very high to prioritize the objective to the scheduler. This will instruct the scheduler that we do not want to see any disturbances in the 2500+ and 250-2500 range. If fully achieved, this will distribute 100% of the disturbance to the smaller patch size classes. Furthermore, we would like the disturbances spread across the 0-50, 50-150 and 150-250 size classes according to a 20%, 40% and 40% distribution.

0-50 = 20%
50-150 = 40%
150 - 250 = 40%
250 - 2500 = 0 %
2500+ = 0%
      

Setting up this type of scenario would resemble the target charts below:

The two largets patch sizes have a maximum set to 0.1%, essentially asking the scheduler to avoid creating disturbances in these size categories. The other targets on the left have minimum objectives set to direct the distribution of disturbances over the landscape. 20% of the patches should be 0-50ha, 40% should be 50-150ha and the remaining 40% should be 150-250ha in size.