1. Intro to the co-limitation study: synergistic effects of N+P

2. Elser et al. (2007) Ecology Letters Co-limitation

3. General Project Questions Is productivity in the northern hardwood forest co-limited by N and P? Do mechanisms of resource optimization contribute to co-limitation in changing environments?

4. Mid-age forestMature forest Young: 15-20 yrs Mid-age: 35-40 yrs Mature: 100+ yrs Study Sites

5. 3 sites: Jeffers Brook HBEF BEF 2 stands per site: 1 mid-age 1 mature 9 stands at BEF: 3 young 3 mid-age 3 mature Study Sites

6. 4 (sometimes 5) plots per stand

7. Treatments (And sometimes Ca) N (30 kg/ha/yr) P (10 kg/ha/yr) N+P Control

8. Nutrient availability assayed with resin strips 2 weeks after 2 nd fertilization Inserted in Oa horizon Retrieved after 2 weeks First year’s question Does excess of one nutrient influence the availability of the other?

9. Young Mid-age Mature

10. Conclusions First year of treatment successfully elevated nutrient availability No evidence that adding one nutrient reduces availability of other Synergistic effect of N+P raised N availability We hypothesize that N+P reduced microbial allocation of N to phosphatase production