Ash Phloem Reduction Model Tutorial
Tara L. Eberhart, Andrew J. Storer, Linda M. Nagel
© Michigan Technological University
Houghton MI, 49931
The Ash Phloem Reduction Model is a website intended to help forest resource managers reduce the amount of ash resource available to emerald ash borer (Agrilus planipennis) and thereby reduce the insect’s potential population density. Version 1.0 of the model was formulated with morphology data collected from over 500 ash trees in order to find the average surface area of any given ash (Fraxinus spp.) tree within a desired size class. The entire bole above ground and all branches down to 2.5 centimeters (1 inch) in diameter are considered, as emerald ash borer has not been indicated to exploit branches smaller than this.
The phloem tissue is the critical resource utilized by emerald ash borer. Ash Reduction Model 1.1 takes into consideration ash tree surface area, which is a good indicator of the relative amount of phloem available to emerald ash borer. Version 1.1 includes more size classes than 1.0 and used more trees for constructing the equations used in the model. Using Trees per Acre as the input data, managers can view the model outputs which include the diameter limit for removal of ash to achieve the specific reduction target percentage.
Use of the model will limit the population potential of emerald ash borer, thereby reducing its impacts and potential spread. Using diameter limit cutting on ash trees in a stand allows for retention of some trees in order to help preserve ash genetics and maintain it as a viable part of our forest. The model shows outputs for retaining small trees as well as for retaining large diameter ash trees, depending on the manager’s decision. This manual demonstrates an example model using real stand information that shows where to find the model online, how to input data, and read the results. Future models will incorporate phloem widths throughout the tree, ash species, growing conditions and location, and remaining tree basal area of the stand.
Welcome to the Ash Reduction Model – a website created to help with management decisions in removal of ash trees to reduce the population densities of emerald ash borer. This tutorial provides background on the model, instructions for inputting data, and how to use the information given by the model.
The model is designed to work with diameter-limit harvesting silvicultural proscriptions. This short tutorial will be useful to first time users of the model for reading the outputs and to see what data they need to enter into the model. As the model versions progress with additional factors taken into consideration, the tutorials will be updated.
Why use this type of model?
At high population densities, emerald ash borer is capable of attacking and killing green, black and white ash. Long-term prospects for management include biological control to reduce population densities of the insect, and resistance or tolerance of ash trees to reduced population densities of the pest. In the short term, reduction of pest populations in local areas is achievable by removal of its breeding substrate.
Removal of ash from stands such as those in close proximity to outlier populations will reduce the population density of this insect, thereby reducing EAB impacts and potential spread. The amount of tree surface area and phloem available to the insect in a forest stand containing ash can be estimated from tree cores and samples removed from down trees. Models of the amount of ash tree removal necessary to reduce EAB breeding substrate by a target percentage can be developed from these data.
How does the model work?
Ash Reduction Model Version 1.1 is based on specific morphology of ash (Fraxinus spp.) trees. The data used to calibrate the model comes
from 580 ash trees in a variety of rural sites throughout
Limitations to the model
The model is only intended to aid in determining a diameter limit for removal of ash trees. If an area is inaccessible or not large enough to harvest in, it is up to the manager’s discretion to determine whether or not it is feasible to remove the ash. The model will not eliminate emerald ash borer from our forests, but it can be used as a silvicultural tool to manage the insects’ population and reduce its damaging effects.
Input Requirements Version 1.1
You will need the following information to run the Ash Reduction Model:
Note: This model only works with the ash component of a stand regardless of total stand size, other tree species occurrence, or how much total ash there is present.
Using the Model
The model can be found at multiple websites, specifically http://ces.mtu.edu/ashmodel/ which is on the Center for Exotic Species at Michigan Tech website, or the user may find the model webpage by going to www.michiganash.org or www.emeraldashborer.org and clicking on the link Ash Reduction Model.
Figure 1 – Ash Reduction Model homepage
At the bottom of the page is a link to this manual and below that a link for more examples of data input without the tutorial explanations. Click on either the 1” or 2” Diameter class link to enter Trees per Acre data.
The Input Page
Once the input page is open, the user can scroll down and see information about the model, two tables of target percentages, two empty charts, and to the left a column of diameter classes and empty green cells for the user’s Trees per Acre data.
Figure 2 – Top of Model input page
Notice the buttons at the top and bottom of the page:
Update – after data has been entered in the green columns, Update will refresh the page to reflect the correct % Surface Area and Diameter Limit to cut
Reset – will erase data in the green columns and start the page blank
Print – will print the outputs
1 or 2 inch Diameter Classes
The user will also notice that the page for the one inch diameter class has more categories for entering Trees/Acre data but otherwise should appear exactly the same as the 2 “ Diameter Size Class page. To switch from one page to the other, use your browsers back button.
The Ash Reduction Model will automatically start with 0.0 in each of the green Number Trees/Acre cells. This is where the user will enter their data. After all of the numbers have been entered the user may click update to refresh the page or hit the Tab key on their keyboard after each entry to update the page automatically. The Tab key will automatically make the cursor go to the next row, not Return.
Figure – 3 Empty input page
example in Figure 4 shows real stand data that has been entered, with the % Surface
Area that the Trees per
Figure 4 – Input Page with Example data filled in
Interpreting Outputs of the Model
Area Column - The column to the
right of the green Trees per
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 5 – 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 DBH. 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 4. 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 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, as shown in Figure 6. 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.
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.
Figure 6 – Bottom output chart to Retain Large Diameter Trees
This model is available to forest resource managers so that it may be used to determine a diameter limit to retain ash trees as a component of our forests. This management strategy will not eliminate emerald ash borer from our forests but it may reduce their population impacts on our remaining trees after the diameter limit harvest. The model can be used with 1 or 2 inch diameter classes and to find diameter limits to retain large or small ash trees.
Future models will be available soon that incorporate species, location, and growing conditions to find the % surface areas and % phloem in a forested stand.
Common Questions about the Ash Reduction Model
No, a diameter class with no trees in it may be left blank and the model will still work. A straight line may appear in the chart output; however this has no negative effect on the calculations and a target % may still be found.
Contact your local county or state forester, a forestry extension official from a university, or a consulting forester. Trees per Acre is a measure of stand density that is calculated from stand basal area.
No, that is not the purpose of the model. Using target ash reduction as a management tool will reduce the population potential of eab by taking away a targeted % of their critical resource, ash phloem. This will reduce the potential for eab population buildup in an area, therefore minimizing its impact and possibly slowing its spread, but not eliminating it completely from our forests or guaranteeing that remaining ash will be uninfested.
for this research was provided by the USDA Forest Service Northeastern Area and
was conducted at the
Links for more information on Emerald Ash Borer and Ash Trees
Tara L. Eberhart
Andrew J. Storer
Linda M. Nagel
About the Authors
Tara Eberhart is a Graduate Research Assistant, Andrew Storer is Associate Professor of
Forest Insect Ecology, Linda Nagel is
Assistant Professor of Forest Silviculture, and Mike Hyslop is a GIS analyst in the
Fax: (906) 497 – 2915
Cover photo by Jessica Metzger
EAB photo by Andrew Storer