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

Elser et al. (2007) Ecology Letters

Co-limitation

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?

Mid-age forest Mature forest

Young: 15-20 yrsMid-age: 35-40 yrsMature: 100+ yrs

Study Sites

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

Study Sites

4 (sometimes 5) plots per stand

Treatments

(And sometimesCa)

N (30 kg/ha/yr)

P (10 kg/ha/yr)

N+P

Control

Nutrient availability assayed with resin strips

• 2 weeks after 2nd fertilization

• Inserted in Oa horizon

• Retrieved after 2 weeks

First year’s question

Does excess of one nutrient influence the availability of the other?

Young Mid-age Mature

Young Mid-age Mature

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