Succession and Stability

Question 1

In Alaska, the prevailing species over time of a glacial retreat are…

Answer 1

20 years: PIONEERS [lichen mosses grasses –> horsetail willow herb cotton wood]
30 years: Dryas dwarf shrubs
40 years: Alnus shrubs
50-70 years: Picea [STIKA SPRUCE] and Populus [ALDER]
75-100: Picea dominates –> Tsuga hemlock

Question 2

Succession

Answer 2

formation and development of a community overtime from pioneer to climax; return to “normal” conditions after a disturbance;
determined by PLANT succession

Question 3

Primary vs Secondary Succession

Answer 3

Primary: r-selected species on a barren land
Secondary: dormant species [r and k selected] in a partially cleared land

Question 4

Unit of Succession

Answer 4

SERE / SERAL

Question 5

3 Types of Succession

Answer 5

1. Facultative: r-selected species paves the way for successors [first 3 seres then competition]
2. Inhibition: r-selected species prevent succession from thriving
3. Tolerance: any species can start succession [only for secondary succession]

Question 6

How do biotic processes influence succession? [3]

Answer 6

1. Seed dispersal important to initiate primary succession; dormant seeds is important for secondary succession
2. Stochastic [chance] events have greater influence in early stages
3. Competition more important in later seres

Question 7

Important Terraforming Notes

Answer 7

1. Greenhouse gas emissions to induce an atmosphere closer to Earth
2. Rainfall once enough CO2 has been released to raise the atmosphere pressure and warm the planet above freezing
3. R-selected plant species: microbes algae lichens, would prepare the way for future successions

Question 8

First biomes to take place in Mars post-terraforming?

Answer 8

Boreal Forests & Tundra

Question 9

Community Stability

Answer 9

No apparent changes in population size and # of species;
Ability of a community to resist changes and return to normal quickly

Question 10

Resistance

Answer 10

Ability to withstand change

Question 11

Resiliency

Answer 11

Ability to return to equilibrium after disturbance

A. Elasticity: how quickly it can return
B. Amplitude: disturbance threshold allowing return

Question 12

of Alternative Stable States and Stability

Answer 12

Greater # of alternative stables states = lesser comparitive stability

Question 13

Most important mechanisms of community stability [3]:

Answer 13

1. Strength of interactions among species
2. Mode of interaction [food-web topology]
3. How individual species experience the perturbations

Question 14

Why is there no link between diversity and stability?

Answer 14

• The presence of a few key species > overall diversity in terms of importance and stability

DIRECTLY PROPORTIONAL:
- Increase in # of species = increase in predation = increase in diversity
- Increase in diversity means more niches filled = greater stability

INDIRECTLY PROPORTIONAL:
- As diversity decreases, stability increases