Topdown and bottomup controls on ecosystem

Question 1

bottom up vs top down

Answer 1

• Bottom up - pp drive the system
  
  • Top down - quaternary consumers drive the system

Question 2

evidence for bottom up?

Answer 2

• Atudy in canada
  
  • Adding nutrients increases productivity
  • Broader scale - fert. Added on a large scale
  • Doubling of PP with increase of fertilizer
  • Another study:
    ○ Phosphorous added to one slide of a lake
    ○ Side where it was not limiting had a boom in algae growth
  • Across many biomes -

Question 3

evidence for top down

Answer 3

• If we removed the top predator, assuming top down control, what should happen to pp?
  
  • Commonly demonstrated in aquatic systems, but some examples in terrestrial systems
• moose study