2016 Hubbard Brook Annual Meeting- July 13-14

1. Aboveground growth responds more to P than N
Shinjini Goswami, Miami University
Team Shoestring:
Kikang Bae
Joel Blum
Tim Fahey
Melany Fisk
Christy Goodale
Shinjini Goswami
Mariann Johnston
Ed Rastetter
Craig See
Matt Vadeboncoeur
Adam Wild
Ruth Yanai
And many more!

2. Nutrient limitation of productivity
• Ecosystem theory predicts N limitation
Time (millions of years)
N
P
Totalnutrients

3. Nutrient limitation of productivity
Elser et al. (2007) Ecology Letters
• Ecosystem theory predicts N limitation
• Recent syntheses predict co-limitation

4. Nutrient limitation of productivity
• Ecosystem theory predicts N limitation
• Recent syntheses predict co-limitation
• Has N deposition induced P limitation?

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

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

7. 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

8. Study Sites
4 (sometimes 5) plots per stand

9. Treatments
(And sometimes
Ca)
N (30 kg/ha/yr)
P (10 kg/ha/yr)
N+P
Control
• DBH (trees > 10 cm) quantified pre-treatment and after 5 years of treatment
• Relative growth rate estimated as relative basal area increment per individual
tree

10. Forest growth response
• No co-limitation
response detected
• Response to N in
young forests and to P
in mid-age and mature
forests
Relativebasalareaincrementperindividualtree

11. Conclusions
P limits productivity in mature and mid-age stands whereas
N limits productivity in young stands
N+P co-limitation may be developing; allocation responses
may take time to influence treatment responses