Lecture 15-17: Consumer-Resource Interactions & Community Structure Flashcards
Effect of fish in river food webs; NorCal
Exp. 1: Effect of top predator on algal structure
* 3 groups for 4 cages
* permeable to insects and fish fry; X predatory adults
* measure algal heights and biomass, insect biomass @ beginning vs. after 5 weeks & count fish fry
* less algal inside enclosures after weeks, more algal outside
Dominant fish effect on turbidity?
- Bass reintroduction –> planktivore abundance down & zooplankton mostly efficient grazers (vs. weak grazer dominance in absence)
- Bluegill reintroduction –> stabilize planktivore densities
- P pollution may reverse transition to turbid state
Given impossibility of complete niche overlap, how to enable more species to coexist in ecological community?
More species or restrict niche widths
* increasing habitat diversity (resource availability) –> more niches –> higher diversity
Tolerance
early species don’t modify the environment to favor any other species; any species that tolerates the current conditions may be present
Inhibition
one species decreases ability of another to establish or persist
Facilitation
modification of the environment by earlier species that allows establishment of other species
Primary succession
bare rock, no soil
Secondary succession
starting from soil after disturbances removes vegetation
* faster due to existing soil (maintains nutrients, some organic matter, moisture, seed banks)
Climax community concept (historical)
- ecological community as analagous to organismal development (“superorganism”)
- suggested each community progresses towards a single climax community state (deterministic and directional)
- climax is stable and disturbance infrequent
Individualistic concept of plant association
- communities are random assemblages of similar physical habitat requirements
- stochastic process of assembly
Current ecological depictions
Disturbance is the norm
