2. Audience Poll: How will fine root biomass respond to
nutrient additions?
• Increase
• Decrease
• No change
3. Background: Fine root biomass
Depends upon both root production and root turnover rate
(or root lifespan)
Higher root biomass could represent either or both higher
production or lower turnover rate (longer lifespan)
4. Functional considerations
• Lower soil resource supply should require more roots
• Evidence: high root:shoot ratio in dry or infertile sites
6. Complication of nitrogen-phosphorus colimitation
If N and P are colimiting, then adding only one (N or P) might
create greater demand for the other, stimulating increased
fine root biomass
7. Complication of nitrogen-phosphorus colimitation
If N and P are colimiting, then adding only one (N or P) might
create greater demand for the other, stimulating increased
fine root biomass
However, Shinjini’s results…
12. Why does adding both N and P cause a big increase in
fine root biomass in the young stands?
Hypothesis: Growth of new fine roots might be nutrient
colimited – i.e. new roots require balanced mineral nutrition
13. Why does adding both N and P cause a big increase in
fine root biomass in the young stands?
Hypothesis: Growth of new fine roots might be nutrient
colimited – i.e. new roots require balanced mineral nutrition
Tentative plan: factorial experiment using ingrowth cores to
determine whether root production is colimited