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Maple syrup production declines
following masting
Joshua Rapp
Tufts University and Harvard Forest

rapp@fas.harvard.edu
Acknowledgements
Data and Support
People
Elizabeth
Crone
Dash
Donnelly
Casey
Mangnall
Natalie Kerr
Masting as a reproductive
strategy
Definition:
 Episodic and synchronous
production of seeds across a
population

Sugar m...
Masting as a reproductive
strategy
Why not just make the same number
of seeds each year?
 Density-dependent benefits to
f...
Masting as a reproductive
strategy
Proximate mechanisms variable
reproduction
 Resource Budget Model (RBM)
Reproductive litter fall
can equal or exceed
vegetative litter fall in
mast years
Reproductive litter fall
can equal or exceed
vegetative litter fall in
mast years

Flowering before leaves come
out requir...
Reproductive litter fall
can equal or exceed
vegetative litter fall in
mast years

Flowering before leaves come
out requir...
Resource Budget Model

6CO2 + 6H2O

light

C6H12O6 + 6O2
Resource Budget Model

6CO2 + 6H2O

light

C6H12O6 + 6O2
Resource Budget Model

6CO2 + 6H2O

light

C6H12O6 + 6O2
Resource Budget Model

6CO2 + 6H2O

light

C6H12O6 + 6O2
Resource Budget Model
Why Sugar
Maple?
• Bimodal seed
production
• Maple syrup
production as a
potential proxy of
carbohydrate stores
• Potentia...
Does masting affect syrup
production?
Resource Budget Model Predictions
1. Resource stores
(NSC) should be
high just before
flowering.
2. Masting should
deplete...
Sugar Maple Seed Production in Vermont
Maple syrup production in Vermont –
detrending the data
Masting and syrup production in Vermont
What about the weather?
What about the weather?
Relative importance (left, top) and shrinkage-adjusted
coefficients (left, bottom) from model averaging
analysis.
Adjusted...
Summary – masting and maple
syrup
• Masting depletes sap sugar
and leads to lower maple
syrup yields

• Seed production is...
The take
home…

 NSC =

 Theory informs
practice
 Importance of life
history in considering
climate change
effects on m...
Rapp vmc maple_121713
Rapp vmc maple_121713
Rapp vmc maple_121713
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Rapp vmc maple_121713

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Maple syrup production declines following masting

Joshua Rapp and Elizabeth Crone
Department of Biology
Tufts University

Flowering and seed production are energetically costly, which is hypothesized to play a role in driving masting dynamics. For spring-flowering species, energy is drawn from non-structural carbohydrate (NSC) stored in woody tissues. We hypothesized these same NSC stores provide the sugar in xylem sap that is tapped to produce maple syrup, and that maple syrup yields and seed production should be coupled. Specifically, we expected that in sugar maple, a masting species: 1) carbohydrate stores as measured by soluble sugars in xylem sap would be depleted after masting; and 2) seed production would increase after a resource threshold is reached. We tested these predictions at the landscape scale using monitoring data on seed production from the North American Maple Project provided by the Vermont Monitoring Cooperative, and maple syrup production from the United States Department of Agriculture National Agricultural Statistics Service. Maple syrup production data, detrended to remove a decade-long increase in syrup production reflecting greater harvesting effort, declined in the year following a mast year, demonstrating a cost of reproduction to trees, and maple syrup producers. We also found evidence for a resource threshold beyond which trees attempt reproduction, and a positive relationship between seed and syrup production in the same year. In addition, even though weather during the sugaring season is a strong predictor of sap flow, seed production was a stronger predictor of maple syrup production than climate alone, although a model containing both seed production and climate best predicted syrup production. Our results show that reproduction-driven internal resource dynamics of trees can have impacts on economic activity, and the importance of long-term monitoring data for testing ecological theory.

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Rapp vmc maple_121713

  1. 1. Maple syrup production declines following masting Joshua Rapp Tufts University and Harvard Forest rapp@fas.harvard.edu
  2. 2. Acknowledgements Data and Support People Elizabeth Crone Dash Donnelly Casey Mangnall Natalie Kerr
  3. 3. Masting as a reproductive strategy Definition:  Episodic and synchronous production of seeds across a population Sugar maple seed fall in The Bowl Natural Area, White Mountain National Forest Graber and Leak, 1992
  4. 4. Masting as a reproductive strategy Why not just make the same number of seeds each year?  Density-dependent benefits to fitness  Escape seed predators  Attract seed dispersers  Pollination efficiency
  5. 5. Masting as a reproductive strategy Proximate mechanisms variable reproduction  Resource Budget Model (RBM)
  6. 6. Reproductive litter fall can equal or exceed vegetative litter fall in mast years
  7. 7. Reproductive litter fall can equal or exceed vegetative litter fall in mast years Flowering before leaves come out requires stored resources Non-structural carbohydrates: energy reserves of a tree
  8. 8. Reproductive litter fall can equal or exceed vegetative litter fall in mast years Flowering before leaves come out requires stored resources Non-structural carbohydrates: energy reserves of a tree
  9. 9. Resource Budget Model 6CO2 + 6H2O light C6H12O6 + 6O2
  10. 10. Resource Budget Model 6CO2 + 6H2O light C6H12O6 + 6O2
  11. 11. Resource Budget Model 6CO2 + 6H2O light C6H12O6 + 6O2
  12. 12. Resource Budget Model 6CO2 + 6H2O light C6H12O6 + 6O2
  13. 13. Resource Budget Model
  14. 14. Why Sugar Maple? • Bimodal seed production • Maple syrup production as a potential proxy of carbohydrate stores • Potential effect of seed production on maple syrup yield 2011 2012
  15. 15. Does masting affect syrup production?
  16. 16. Resource Budget Model Predictions 1. Resource stores (NSC) should be high just before flowering. 2. Masting should deplete NSC
  17. 17. Sugar Maple Seed Production in Vermont
  18. 18. Maple syrup production in Vermont – detrending the data
  19. 19. Masting and syrup production in Vermont
  20. 20. What about the weather?
  21. 21. What about the weather?
  22. 22. Relative importance (left, top) and shrinkage-adjusted coefficients (left, bottom) from model averaging analysis. Adjusted R2 (below) best model including seed production in the previous year only, weather only, or both seeds and weather.
  23. 23. Summary – masting and maple syrup • Masting depletes sap sugar and leads to lower maple syrup yields • Seed production is a better predictor of syrup production than weather during the tapping season
  24. 24. The take home…  NSC =  Theory informs practice  Importance of life history in considering climate change effects on maple syrup industry

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