White Pine Decline in Maine - The University of Maine - School of ...

A Risk Map for Hemlock Woolly Adelgidrelated
Damage in the Northeast.
Stacy Trosper 1 , William Livingston 1 , Jennifer Pontius 2
1 School of Forest Resources, University of Maine, Orono, ME, USA.
2 University of Vermont, RSENR, Burlington, VT, USA.

Need for HWA Risk Map
• Hemlock Woolly Adelgid
(HWA, Adelges tsugae)
infestations appeared in
Maine during 2000’s
• Future of hemlock
uncertain
• Provide some guidance
on what is at risk

HWA Impacted by Cold Temperatures
Hemlock Impacted by Drought
Kathleen S. Shields and Carole A. S-J. Cheah.
USDA Forest Service, Hamden, CT
Connecticut Agricultural Experiment Station, Windsor, CT
Drought results in mortality spike
Number of -25C events in Sanford, ME
20
190
15
10
5
Sanford
180
170
160
150
0
1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000
140
2010

January Minimum Temperature
Related to Range

Hypotheses
• Cold temperatures and
site factors related to
drought stress
determining factors in
HWA incited decline
• Tree ring growth
trends can be used to
quantify HWA incited
decline

Sampling Plots Along Edge of
Infestation
Calibration Plots Validation Plots
Infested Non-infest Infested
Region Region Region
41 (276) 7 (45) 15 (103)

• Composite score
– % new growth
– % transparency
– % fine twig dieback
– Live crown ratio
Crown Health Rating
• Scale of 1 (no damage)
to 10 (dead)
• Related to % HWA
infestation on twigs
(r=0.87)

Quanifying Increment Growth Trends:
t-score and Percent Decline
• Percent Decline
(PD) is
100 X (Initial_BAI-
Narrowest_BAI)/
Initial_BAI.
• Related to %HWA
infestation (r=0.77)
• Related to CDR
(r=0.86)
• Not related to years
of infestation
(r=0.47)
BAI
t-score
BAI
(3 Year Running Means)
5 10 15 20 25 30
-2 0 2 4 6 8 10
5 10 15 20 25
3 year windows
used to calculate
t-scores
1985 1990 1995 2000 2005
1985 1990 1995 2000 2005
Bavg
Tmax
1985 1990 1995 2000 2005
year
year
Bmin
Rmax

Declining Trees Require High Levels of
Damage

High Crown Damage Related to HWA
Infestation > 10%

• Calculates probability
of location being a
decline site
• Uses stepwise
procedures
• Selected
– January Minimum
Temperature (avg)
– Slope
– Hillshade
Logistical Regression
Predicted Actual
Decline
Actual
Nondecline
Actual
Total
Decline 19.00000 1.00000 20.00000
Non- 1.00000 20.00000 21.00000
decline
Predicted 20.00000 21.00000 41.00000
Total
Correct 0.95000 0.95238
Total Correct = 0.95122%

Validation Plots
• 15 plots in central
Massachusetts
• Percent Decline
measured
• Used cluster groups
from calibration plots
– PD47% = Decline
Coefficients
Used
50 th
percentile
95 th
percentile
Logistic Model Coefficients and
Prediction Success
Decline
Plots
Nondecline
Plots
4 (3) 6 (0) 2
7 (0) 2 (4) 2
Correct (Incorrect)
Uncertain

Non-declining hemlock stands
not likely outside of blue area
HWA incited decline not
likely in blue areas
HWA Probability
of Decline

Risk Map Consistent with Recent
Observations

Thanks To:
Conclusions
•Northern spread of HWA will be limited by
cold temperatures
•Increment trends calculated as Percent
Decline can quantify HWA damage
•Hemlock growing on steep slopes with high
solar exposure are more vulnerable to
decline
• US Forest Service STDP
• Massachusetts Department of Conservation
and Recreation