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Stoichiometry of Forest Nutrient Limitation Stoichiometry of Forest Nutrient Limitation Melany Fisk, Miami University

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Stoichiometry of Forest Nutrient LimitationStoichiometry of Forest Nutrient Limitation

Melany Fisk, Miami University

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Bormann et al. 1977

Stoichiometry of Forest Nutrient LimitationStoichiometry of Forest Nutrient Limitation

Dynamic context:Interacting elementsResource optimization by organismsSpecies traits Disturbance and ecosystem developmentHeterogeneous landscape

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Rethinking limitation Rethinking limitation What limits productivity in northern hardwood forests?

− Theory predicts N limitation

− Has N deposition induced P limitation?

− Recent syntheses predict co-limitation

Does a resource allocation framework explain patterns of limitation or co-limitation?

At what time scales can resource allocation processes operate to minimize single-element limitation?

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Rethinking limitation Rethinking limitation Regional approach incorporates forest succession, soil variation

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Rethinking limitation Rethinking limitation Regional approach incorporates forest succession, soil variation

parent material, succession

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Rethinking limitation Rethinking limitation Regional approach incorporates forest succession, soil variation

Short-term experimental responses evaluated in context of longer-term pattern

parent material, succession

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Rethinking limitation Rethinking limitation Regional approach incorporates forest succession, soil variation

Short-term experimental responses evaluated in context of longer-term pattern

N x P fertilization experiment:

13 sites30 kg N/ha/yr10 kg P/ha/yr parent material, succession

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Examples of Resource Allocation Across SitesExamples of Resource Allocation Across Sites

Above vs belowground

• Total soil respiration is negatively related to N availability (Bae et al. submitted)

Belowground: N vs P

• N and P availability are coupled by phosphatase activity (Ratliff 2012)

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Examples of Resource Allocation Across SitesExamples of Resource Allocation Across Sites

Above vs belowground

• Total soil respiration is negatively related to N availability (Bae et al. submitted)

Belowground: N vs P

• N and P availability are coupled by phosphatase activity (Ratliff 2012)

• Fine root allocation to acquire N vs P depends on N availability (Naples and Fisk 2010)

• P enhances C mineralization, while N depresses it (Santangelo et al, in prep)

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Rastetter et al. 2013

Predictions of the multiple-element limitation modelPredictions of the multiple-element limitation model

• Allocation shifts between N and P after large-scale disturbance

• Colimitation occurs when allocation to N and P equilibrates

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Rethinking limitation Rethinking limitation What limits productivity in northern hardwood forests?

Geohydrologic template

Available nutrients

Decomposer microbes mycorrhizae

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Rethinking limitation Rethinking limitation What limits productivity in northern hardwood forests? Does a resource allocation framework explain patterns of

limitation or co-limitation?

Geohydrologic template

Available nutrients

Decomposer microbes mycorrhizae

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Rethinking limitation Rethinking limitation What limits productivity in northern hardwood forests? Does a resource allocation framework explain patterns of

limitation or co-limitation?

Geohydrologic template

Available nutrients

Decomposer microbes mycorrhizae

Allocation feedbacks

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Rethinking limitation Rethinking limitation What limits productivity in northern hardwood forests? Does a resource allocation framework explain patterns of

limitation or co-limitation?

Geohydrologic template

Available nutrients

Decomposer microbes mycorrhizae

Enzymatic feedbacks

Allocation feedbacks

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Rethinking limitation Rethinking limitation What limits productivity in northern hardwood forests? Does a resource allocation framework explain patterns of

limitation or co-limitation?

Geohydrologic template

Available nutrients

Decomposer microbes mycorrhizae

Enzymatic feedbacks

Allocation feedbacks

Page 16: Fisk lter comp

Rethinking limitation Rethinking limitation What limits productivity in northern hardwood forests? Does a resource allocation framework explain patterns of

limitation or co-limitation?

Geohydrologic template

Available nutrients

Decomposer microbes mycorrhizae

Enzymatic feedbacks

Allocation feedbacks

Maintain consistent N:P

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Rethinking limitation Rethinking limitation What limits productivity in northern hardwood forests? Does a resource allocation framework explain patterns of

limitation or co-limitation?

Geohydrologic template

Available nutrients

Decomposer microbes mycorrhizae

Enzymatic feedbacks

Allocation feedbacks

Maintain consistent N:P

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Rethinking limitation Rethinking limitation What limits productivity in northern hardwood forests? Does a resource allocation framework explain patterns of

limitation or co-limitation?

Geohydrologic template

Available nutrients

Decomposer microbes mycorrhizae

Enzymatic feedbacks

Community or ecosystem level?

Allocation feedbacks

Maintain consistent N:P

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Rethinking limitation Rethinking limitation What limits productivity in northern hardwood forests? Does a resource allocation framework explain patterns of

limitation or co-limitation? Is co-limitation a long-term outcome of ecosystem development?

Geohydrologic template

Available nutrients

Decomposer microbes mycorrhizae

Enzymatic feedbacks

Community or ecosystem level?

Allocation feedbacks

Maintain consistent N:P

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Rethinking limitation Rethinking limitation What limits productivity in northern hardwood forests?

Does a resource allocation framework explain patterns of limitation or co-limitation?

Is co-limitation a long-term outcome of ecosystem development?

Or, is it a transient part of long-term, ultimate limitation, mediated by shifting resource allocation?

Geohydrologic template

Available nutrients

Decomposer microbes mycorrhizae

Enzymatic feedbacks

Community or ecosystem level?

Allocation feedbacks

Maintain consistent N:P