Lecture 30: Community Change

Question 1

Define chronosequence

Answer 1

A series of communities representing a range of ages or times since disturbance

Question 2

Why do we see change in species composition?

Answer 2

Species have different adaptations that allow them to colonize, compete and persist

Question 3

What are some examples of temporal scale of succession?

Answer 3

Primary succession - 1,500 years
Secondary forest - 200 years
Succession in intertidal communities - 1.5 years
Succession in desert streams - few weeks

Question 4

Long-term succession: What happens after sedimentation has filled up a lake?

Answer 4

1. Becomes a bog/fen - organic sediment prevails, high water availability
2. terrestrial vegetation - abiotic sediment prevails, low water availability

Question 5

How does succession occur?

Answer 5

Facilitation model: early species modify the environment in ways that hinder themselves and benefit later species

Tolerance model: early species modify the environment, but it doesn’t affect later species

Inhibition model: early species modify conditions that hinder later species

Question 6

What is the climax community outcome of each of the 3 models?

Answer 6

Facilitation: early successional species die out and late successional species persist

Tolerance: Species become the most tolerant to changes made by earlier species

Inhibition: early successional species persist until disturbed