herbivores and NPP

Question 1

plant defense feedbacks?

Answer 1

• Terrestrial systems have a funnel effect
  
  • Figure of plant defense feedbacks
    ○ More investment in leaves - herbivores prefer them usually
    ○ High soil fertility - tends to accelerate growth, leads to lower plant defense bc nutrients that go into investing into leaves are more abundant - higher herbivory

Question 2

poplar system ex

Answer 2

• Two types: narrow leafed, broad leafed
  
  • Two species able to hybridize where their distributions overlap
  • More expression of tannins in the one that is located higher up (more north)
  • hybrid plant F1 has lower tannins, backcross has even more tannins
    Different genetics

Question 3

look at ecosystem genetics graph + notes

Answer 3

ok

Question 4

positive impacts of herbivory?

Answer 4

• Minor in comparison to negative aspects
  
  • Consumption of seeds and fruit = dispersal
  • Overcompensation
  • Increase in nutrient cycling

Question 5

over comp?

Answer 5

• Anything below the zero line = suggests plant growth is decreasing with herbivory
  ○ Anything above = suggests plant growth is increasing with it
  
  • At some level, herbivory is always bad
    Low or moderate amounts of herbivory can increase productivity (growth and fitness) of some plants rather than cause harm

Question 6

test of overcomp

Answer 6

• Approx 35% of plants studied showed compensation (2) or overcompensation (3)
  
  • e.g. jefferies et aal snow goose grazing on arctic marshes
    Snow geese clearly reduce standing biomass of the arctic plant communities