fisk lter comp

Stoichiometry of Forest Nutrient LimitationStoichiometry of Forest Nutrient Limitation

Melany Fisk, Miami University

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

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?

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

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

parent material, succession

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

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

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)

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)

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

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

Geohydrologic template

Available nutrients

Decomposer microbes mycorrhizae

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

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

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

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

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

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

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

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

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