Ash Phloem Reduction Model Examples

Version 1.1

Tara L. Eberhart, Andrew J. Storer, Linda M. Nagel

 

 

Examples of Data Entry

 

The example in Figure 1 shows real stand data that has been entered, with the % Surface Area that the Trees per Acre in that stand represent. The Cumulative Percent Surface Area in the chart shows what Diameter Limit corresponds with the cumulative percent. The Target Percentage tables at the top show specific diameter limits for target percentages of surface area that may be chosen to remove.

Figure 1 Input Page with Example data filled in

 

% Surface Area Column - The column to the right of the green Trees per Acre column shows what percent of the total surface area in the stand that that particular diameter size class represents. This information is used to compile the cumulative surface area that is graphed in the charts.

 

Relationship Cumulative Surface Area and DBH charts & Target % tables Notice there are two output charts given with cumulative surface area, one descending (on top) and one ascending (on bottom of the page).

 

Figure 2 2 Output charts

 

The first chart corresponds with most common type of diameter limit harvesting of retaining small trees, which is removing all trees above a specified diameter at breast height. This chart matches up with the first table on the top left Retaining Small Trees that shows what the specific diameter limit is when targeting a certain percent removal of ash surface area as shown in Figure 1. In this example, to remove 95 % of the surface area available to EAB, all ash trees greater than 4.4 inches should be removed.

 

The second chart (Figure 3) has a positive slope with the cumulative surface area ascending. This chart uses the same data as the first one, but is showing what the diameter limit harvest would be to remove smaller trees and retain large diameter trees. The user will see that the diameter limits shown in the top table on the right to retain large trees are much larger than in the table to retain small trees.

 

Figure 3 Bottom output chart to Retain Large Diameter Trees

With this type of harvesting, the forest manager can still remove a target amount of surface area or phloem available to emerald ash borer but retain seedlings (trees to small to be cut at all) and the larger diameter trees. The diameter limit given for this type of harvesting indicates the size at which trees are left rather than cut, so all trees less than the specific diameter are removed. Using this example, to retain large trees and still remove 95 % of the ash surface area, all trees less than 18.8 inches should be removed.

 

The same data entry applies to the 1 diameter class model. In Figure 4, the 1 inch diameter classes have been filled in using Trees per Acre data. Notice that there can be empty classes and the model will still calculate the % surface area. In this example, to remove 95% of the ash surface area, remove all trees greater than 3.7 inches. To retain large trees and remove 95% of the surface area, remove all trees less than 21 inches.

 

Figure 4 Example using 1 inch class

 

 

Figure 5 Examples using 1 inch class for large tree retention