Gerenser 1 Potential Impacts of Emerald Ash Borer (Agrilus planipennis) on Plant Community and Biomass
Dynamics in Mature Ash Forests in New York Great Lakes Basin State Parks
Kalie A. Gerenser
SUNY College of Environmental Science and Forestry
Edna Bailey Sussman Foundation Final Report 2011
Description of Research
The main goal of my research was to quantify ecological impacts of emerald ash borer (EAB) on
understory plant community and overstory biomass dynamics in 8 New York State Parks (NYSP) within the
GLB containing high-value, mature ash forest stands. Parks include: Beaver Island, Buttermilk Falls, Chimney
Bluffs, Green Lakes, Harriet Hollister Spencer, Jacques Cartier, Letchworth, and Wellsley Island. Many of the
parks contain forest types that are designated as significant ecological communities by the NY Natural Heritage
Program (NHP) and likewise, they contain relatively high densities of ash.
A complete ecological survey was performed to give insight on the potential destructive behavior EAB
will cause for forests containing either green or white ash species so New York State Office of Parks, Recreation
and Historic Preservation (OPRHP) personnel can proactively prepare a management plan. Essentially, the 8
state parks can be used as a baseline for the remaining state parks that also contain similar high-value ash
forests. By working in conjunction with the OPRHP, the following questions are currently working to be
answered: (1) Within each park, how important is ash for the functioning of the ecosystem and the community?
(2) Within each park, approximately how much biomass will be lost with ash mortality? (3) What species
(native or invasive) will potentially colonize the gaps created by (white, green) ash mortality? (4) Can we
predict what affected green ash and white ash forests will look like in the future?
Narrative of Work Completed
In April 2011, I began sampling in the 8 state parks. 20 x 20 m fixed-area plots were used to sample tree
species importance values and biomass in the different forest types represented in each park. Overstory trees
greater than 10 cm diameter at breast height (DBH) were quantified (species, DBH, height) for use in allometric
equations to predict the biomass loss due to ash mortality. Plots were identified using ArcGIS, and were based
on the presence and species of ash as a canopy layer (by selecting for communities that often contain white ash
and/or green ash). Plots were randomly selected if they were greater than 50 m apart and 50 m away from
human disturbances (roads, buildings, trails). Plots were only sampled if they were located in mature (mid to
late successional) stands with at least 10% ash.
Height was taken for five trees at each site to form a linear regression equation (y = 0.26x + 12.53,
2
R =0.3872) to calculate the remaining tree heights. Within each 20 x 20 m plot, four 3 x 3 m subplots were used
to record the diameter and species of subcanopy shrubs and saplings. Within each subplot, two 50 x 50 cm
microplots were used to record the species and percent cover of both native and invasive herbaceous understory
vegetation. Particular emphasis was placed on identifying invasive species that may benefit from these canopy
gaps and thus, foster further changes.
Gerenser 2 Total aboveground biomass data was analyzed using allometric equations, which requires the measured
DBH and height of each tree. The importance value (IV) was also calculated by taking the average of the
relative density and relative dominance. This value is vital in determining the influence of trees and saplings in
the community to predict which species will potentially replace ash subjected to EAB-induced mortality.
Preliminary Results
Table 1 Summary data for 34 plots deployed in forested stands with a green ash and/or white ash component in
eight NY state parks in the Great Lakes Basin in 2011.
Park
No. plots
No. tree species
Ash IV (%)
Ash Biomass
(%)
No. invasive
plants
Dominant ash
species
Green
White
Green
White
Green
White
Green
White
Green
White
Beaver Island
3
---
8
---
36.9
---
33.8
---
2
---
Buttermilk Falls
4
---
13
---
16.0
---
10.8
---
2
---
Chimney Bluffs
3
2
7
10
39.2
33.0
46.1
39.9
1
1
Green Lakes
---
4
---
6
---
34.5
---
46.0
---
4
Harriet Hollister
---
3
---
7
---
18.9
---
20.8
---
0
Jacques Cartier
3
---
7
---
60.5
---
56.8
---
0
---
Letchworth
3
4
8
12
40.0
37.5
43.3
45.8
3
2
Wellesley Island
3
2
9
9
41.2
22.6
21.2
17.1
1
2
A total of 34 plots were sampled in the eight state parks. Tree species richness was 26 and overall plant
richness was 41. All tree species were native. There were 36 native and 5 non-native herbaceous plants in the
field plots, including garlic mustard, lesser burdock, autumn olive, stinging nettle, and multiflora rose. Nonnative species found within the plots, but not physically inside the measured microplots, include Japanese
barberry, Japanese honeysuckle, common dandelion, and pale swallowwort. There were no non-native plant
species observed within the plots or along the edges of field plots in Jacques Cartier and Harriet Hollister
Spencer State Parks.
Nineteen plots were deployed in forests with green ash as a component in five state parks. Green ash
was the dominant tree species, based on both aboveground biomass (29.6%) and importance value (33.2%). In
terms of biomass, the next most dominant species were sugar maple, eastern cottonwood, and silver maple. With
regards to IV, sugar maple, shagbark hickory, and eastern cottonwood were the most important. Important
sapling species based on IV include sugar maple, American hophornbeam, and green ash. Sixteen plots were
deployed in forests with white ash as a component in 4 state parks. White ash was the dominant tree species on
the basis of aboveground biomass (36.0%) and importance value (31.1%). Sugar maple, white oak, red maple,
and red oak were the next highest species in terms of biomass, which was similar in terms of IV with sugar
maple, red maple, and white oak having the next highest IVs. Important sapling species based on IV include
sugar maple, black cherry and American beech.
Gerenser 3 Preliminary Conclusions
Overall, white ash and green ash both appear to be important overstory tree species in a significant
amount of the surveyed plots located in mature ash forests. The only other species that surpassed this IV is
sugar maple, suggesting that if EAB does destroy all ash trees, sugar maple should be the next species to focus
management efforts. This is also seen in the sapling count, which shows sugar maple as an important understory
species in plots where both white and green ash are a component. The sapling count shows little to no white ash
for replacement, but a small amount of green ash saplings to suggest a possible regeneration, however EAB has
been known to attack even the smallest saplings. There is the question of what understory vegetation will win
the battle for establishment in the canopy gaps created by ash mortality. It may be invasive plants or the
seedlings of native trees, such as sugar maple, green ash, black cherry, and American beech.
As for the biomass estimations, a large amount of biomass is expected to be lost as a result of ash
mortality. In green ash forests, green ash comprises 29.6% of the aboveground biomass, while in white ash
forests, white ash comprises 36.0% of the aboveground biomass. This large decrease in biomass is expected to
alter the forest community structure significantly, and likewise, offset the carbon sink.
Future Work
To complete my thesis, community data will be analyzed using PC-ORD, which will provide graphical
relationships of tree and plant species within the forested communities and elucidate invasive plants current
importance value in these parks as many of them may benefit from the gaps created in the canopy by ash
mortality. Right now, I only identified 5 invasive plants in my plots. However, there appear to be plenty of
potential invaders lurking on the edges. Although they may not be in the forest now, the canopy gaps created by
ash mortality may facilitate their spread to the forest understory. This analysis, combined with the previous
results, will provide the OPRHP with the appropriate information they need to create an EAB plan of action for
the NYSP. Future work could continue by revisiting all of the sites at periodic intervals during and after EAB
hits. It would be interesting to compare the plant community and biomass dynamic data to those taken after an
EAB-induced ash decline in order to gain a better understanding of EAB’s impact at different stages of
infestation.
Acknowledgements
My sincerest appreciation goes to my advisor, Dr. Melissa K. Fierke for believing in my scientific
abilities, despite me not being a typical graduate student. I would also like to thank my two committee
members, Dr. Gregory McGee, at SUNY ESF and Melissa Plemons at the Office of Parks, Recreation, and
Historical Preservation (OPRHP). Melissa Plemons graciously agreed to sponsor this project, which really
helped make it a shining success. I would also like to thank my loving parents, Louis and Mary Ann Gerenser,
who offered to help countless times during my field season. My wonderful fiancé Jeffrey Brady, also deserves
great thanks for not only helping with the field research, but also for sharing and embracing my passion for
nature. Lastly, I would like to thank the Edna Bailey Sussman Foundation for their outstanding contribution to
my research. The foundation has been, and will continue to be acknowledged in all presentations and
publications that may result from this research.
Pictures
One of the 50 x 50 cm microplots
A green ash surrounded by invasive garlic mustard in Letchworth State Park
Gerenser 4