Rapp vmc maple_121713
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Maple syrup production declines following masting Joshua Rapp Tufts University and Harvard Forest [email protected]
description
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.
Transcript of Rapp vmc maple_121713
Maple syrup production declines
following masting Joshua Rapp
Tufts University and Harvard Forest
Acknowledgements
People Elizabeth Crone
Dash Donnelly
Casey Mangnall
Natalie Kerr
Data and Support
Masting as a reproductive
strategy
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
Definition:
Masting as a reproductive
strategy
Density-dependent benefits to
fitness
Escape seed predators
Attract seed dispersers
Pollination efficiency
Why not just make the same number of seeds each year?
Masting as a reproductive
strategy
Resource Budget Model (RBM)
Proximate mechanisms variable reproduction
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
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
Reproductive litter fall can equal or exceed vegetative litter fall in mast years
Resource Budget Model
6CO2 + 6H2O C6H12O6 + 6O2 light
Resource Budget Model
6CO2 + 6H2O C6H12O6 + 6O2 light
Resource Budget Model
6CO2 + 6H2O C6H12O6 + 6O2 light
Resource Budget Model
6CO2 + 6H2O C6H12O6 + 6O2 light
Resource Budget Model
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
Does masting affect syrup
production?
1. Resource stores
(NSC) should be
high just before
flowering.
2. Masting should
deplete NSC
Resource Budget Model -
Predictions
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 R2 (below) best model including seed production in the previous year only, weather only, or both seeds and weather.
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
The take
home… NSC =
Theory informs practice
Importance of life history in considering climate change effects on maple syrup industry
