Ash Phloem Reduction
Model Tutorial
Version 1.1
Tara L.
Eberhart, Andrew J. Storer, Linda M. Nagel
© Michigan
Technological University
1400 Townsend Dr.
Houghton
MI, 49931
Updated July 5, 2006
Abstract
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.
Introduction
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?
The
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 Michigan and northern Wisconsin in 2005 and 2006.
The equations to find the percent surface area by diameter of ash in a
stand were built from surface area’s that were estimated using entire ash tree
surface areas including the stump, bole, and all branches until they were less
than 1” in diameter. This represents all
the surface area (phloem) of a tree that is available to emerald ash borer.
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.
Getting Started
Input Requirements Version 1.1
You
will need the following information to run the Ash Reduction Model:
- The model input webpage
found at http://ces.mtu.edu/ashmodel/ Or go
to www.michiganash.org or www.emeraldashborer.org and
click on the link
- Number of Trees per Acre of ash (Fraxinus)
species
- This is a
measurement of tree density and can be determined from stock and stand
tables. Use only ash species in
the stand, not the total stand Trees/Acre. Contact your local forester for more
information. Diameter class can be
2” or (for more specific outputs) 1” classes.
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.
Entering Data
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
The
example in Figure 4 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 4 – Input Page with Example
data filled in
Interpreting
Outputs of the Model
% 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 by the program 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
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
Summary
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
- Do all diameter classes need to have trees per
acre?
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.
- Where can I get trees per acre information from
if I don’t have a stand table?
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.
- Will my remaining ash trees be protected from
emerald ash borer?
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.
