Examples of Other Relationships to be Characterized
     Relationships between phloem thickness and surface area and:
•Geographic location
•Crown ratio
•Light
•Dieback
•Hydrology, soils
•
   Initial Data
           Strong relationships exist between diameters at breast height and surface area as well as diameter and phloem width.  We are refining these relationships as more relationships are determined with other tree factors.
    Examples of curvilinear relationships between diameter at breast height and bark surface areas of the boles and branches greater than 2.5 cm for Fraxinus spp. throughout Michigan and northern Wisconsin.  Surface Area is used as an indicator of amount of phloem available in a tree to emerald ash borer.
Living with Emerald Ash Borer: Modeling Phloem
Reduction to Reduce Resource Availability
Tara L. Eberhart, Andrew J. Storer, Linda M. Nagel
School of Forest Resources and Environmental Science, Michigan Technological University, Houghton, MI 49931
• Introduction
•      The exotic insect, emerald ash borer (Agrilus planipennis), is established in Michigan and in some surrounding states.  At high population densities, all green, black and white ash trees are apparently susceptible to attack and can be expected to die.  Long-term prospects for management of this beetle include biological control to reduce population densities of the insect, and resistance or tolerance of ash trees to reduced populations of the pest.
•      Removal of ash from high priority areas such as those stands in close proximity to outlier populations will reduce the population density of this insect.  Emerald ash borer larvae develop in the phloem of ash trees in stems and branches above approximately 2.5 cm (1”) in diameter.  We can estimate the amount of phloem available to the insect in a forest stand containing ash and develop models of the amount of ash tree removal necessary to reduce the breeding substrate by a target percentage. 
Methods
 Data were collected over the summer of 2005 to describe ash tree morphology for standing ash to estimate the surface area and to measure phloem thickness.  Additional data on the condition and position of the tree in the forest canopy and in relation to forest edge have also been collected.  Ash trap trees were also felled and diameter and phloem thickness of the trees and their branches was determined during fall 2005.  These data enable us to describe the surface area of the tree for all material greater than 2.5 cm in diameter.
Model Utilization
The model interface will be web-based through www.michiganash.org. Forest resource managers can view % ash surface area and phloem to find the diameter limit for removal of ash to achieve the reduction target.
By reducing emerald ash borer populations through phloem reduction, and decreasing the removal of the smaller trees in a stand, this model will enable the genetic diversity of ash to be maintained by allowing for the retention of trees under the diameter limit.
Emerald Ash Borer Photos by Andrew Storer
Photos by Jessica Metzger and Brandon Bal
Acknowledgements
      We would like to thank the USDA Forest Service Northeastern Area for funding provided for this project.  We would also like to thank the survey crews working on this project for their time and effort in helping collect data.
An example of a large phloem ring (indicated by arrow).  Phloem widths on wedges or cookies cut from ash trees are measured twice at 90o angles, from the vascular cambium to the cork cambium.
Green ash with many smaller
 branches showing example
 tree form.
Emerald ash borer larva in a
gallery found in a peeled tree
feeding on the phloem and etching
the sapwood.  
•Canopy position
•Species of Ash
•Tree height
•Bark thickness
•Basal area
Measuring ash trees at Fayette State Park 11/4/05.
Text Box: Photos by Brandon Bal.
Photos by Brandon Bal.
Example Model With Real Data
•Ash Species Trees per Acre is calculated from Stand Table.
•The following are real data of Fraxinus spp. in a 102 acre stand in the Upper Peninsula.
Note: Data are ash trees only.
•Therefore in this stand, to retain small trees and remove 90% of the phloem the diameter limit would be 6.7” (Remove all ash trees above 6.7 inches to take out 90% of the ash surface area).
•
•
•
•
3.02%
0.5
20
9.93%
2
18
20.40%
5.1
16
12.59%
4.0
14
14.47%
6.0
12
8.24%
4.6
10
13.75%
10.7
8
11.40%
12.7
6
6.21%
10
4
% Surface Area
No. Trees/Acre
Diameter Class”
2" Size Class Increments
4.3”
99%
5.6”
95%
9.1”
75%
Diameter Limit
To Cut
% Surface Area Removed
Collecting data from a felled tree.
The main boles and all branches
greater than 1” had their diameters
measured every 3’ up the tree.
•Other removal percentages can be targeted
as shown, using the graph as a guide.
•The model may also be used to retain a target %
of large trees or using 1” diameter class depending on management goals.
•
    We also anticipate making the data on ash tree morphology available to other research groups developing models of emerald ash borer population dynamics in relation to ash tree characteristics.