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

2. Bormann et al. 1977 Stoichiometry of Forest Nutrient Limitation Dynamic context: Interacting elements Resource optimization by organisms Species traits Disturbance and ecosystem development Heterogeneous landscape

3. 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?

4. 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 sites 30 kg N/ha/yr 10 kg P/ha/yr parent material, succession

5. Examples 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)

6. Examples 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)

7. Rastetter et al. 2013 Predictions 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

8. 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

9. 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

10. Forest Nutrient Limitation Collaborators: Multiple element interactions in northern hardwood ecosystems Joel Blum, geochemistry Tim Fahey, trees Melany Fisk, soil biota and processes Christy Goodale, soils and nutrients Ed Rastetter, modeling Ruth Yanai, trees and modeling And many others