Chapter 17: Change in Communities

Question 1

Communities are always ____

Answer 1

changing

Question 2

What are the strongest forces behind community change?

Answer 2

human actions

Question 3

What types of changes have happened to coral reefs in the Indian Ocean?

Answer 3

-Slow, subtle changes: gradual turnover of dominant species due to competition, predation, and disease
-Catastrophic Change: bleaching events and the 2004 tsunami

Question 4

Succession

Answer 4

change in species composition in communities over time, resulting from both biotic and abiotic factors

Question 5

Do abiotic factors vary?

Answer 5

Yes. Over daily, seasonal, decadal, and longer time scales

Question 6

Disturbance

Answer 6

events that injure or kill some individuals and create opportunities for other individuals

Question 7

Stress

Answer 7

abiotic factors that reduce growth, reproduction, or survival of individuals

Question 8

Biotic agents of change

Answer 8

-species interactions can result in species replacements
-diseases can cause death or slow growth of a species
-ecosystem engineers or keystone species

Question 9

____ and ____ factors often interact to produce community change

Answer 9

abiotic and biotic

Question 10

What does succession involve due to abiotic and biotic agents of change?

Answer 10

colonization and extinction

Question 11

Climax Stage

Answer 11

a stable end point that changes little

Question 12

Primary Succession

Answer 12

colonization of habitats devoid of life
-can be very slow. initial conditions are very inhospitable
-the first colonizers tend to be stress-tolerant

Question 13

Secondary Succession

Answer 13

reestablishment of a community in which some, but not all, organisms have been destroyed
-occurs after fires, storms, logging
-legacy of the preexisting species and their interactions with colonizing species play larger roles than in primary succession

Question 14

Henry Cowles (1899)

Answer 14

studied succession on sand dunes along Lake Michigan
-he assumed that plant assemblages farthest from the lake’s edge were the oldest; the ones nearest the lake were the youngest, representing a time series of successional stages (a space for time substitution)

Question 15

Climax Community

Answer 15

dominant species persist over many years and provide stability that can be maintained indefinitely

Question 16

Are communities predictable or repeatable?

Answer 16

No

Question 17

Connell and Slayter (1977)

Answer 17

reviewed the literature on succession and proposed three models

Question 18

Facilitation Model

Answer 18

inspired by Clements-early species modify the environment in ways that benefit later species. The sequence of species facilitations leads to a climax community

Question 19

Tolerance Model

Answer 19

assumes early species modify the environment in neutral ways that neither benefit nor inhibit later species

Question 20

Inhibition Model

Answer 20

assumes early species modify conditions in negative ways that hinder later successional species

Question 21

Pioneer Stage

Answer 21

dominated by lichens, mosses, horsetails, willows, and cottonwoods

Question 22

Dryas Stage

Answer 22

at 30 years, dominated by the shrub Dryas, other tree species start to appear

Question 23

Alder Stage

Answer 23

at 50 years, alder dominates

Question 24

Spruce Stage

Answer 24

at 100 years, a mature Sitka spruce forest

Question 25

Chapin et al. (1994)

Answer 25

studied mechanisms for succession in Glacier Bay

Question 26

Bertness and Shumway (1993)

Answer 26

manipulated wrack patches after they had been colonized

Question 27

Sousa (1979)

Answer 27

studied algal succession on boulders that were overturned by waves in the rocky intertidal zone

Question 28

Do any succession models fit all communities?

Answer 28

No

Question 29

What interactions are often important in early succession?

Answer 29

facilitative interactions

Question 30

What plays a more dominant role later in succession?

Answer 30

competition

Question 31

Lewontin (1969)

Answer 31

sometimes different communities develop in the same area under similar environmental conditions
-alternative stable states

Question 32

When is a community thought to be stable?

Answer 32

when it returns to its original state after perturbation

Question 33

What does stability depends on?

Answer 33

scale of observation, both spatial and temporal

Question 34

Sutherland (1974)

Answer 34

studied marine fouling communities that grow on ships and docks

Question 35

Hysteresis

Answer 35

an inability to shift back to the original community type

Question 36

Connell and Sousa (1983)

Answer 36

believed that alternative stable states could be driven only by species interactions and not by physical changes in the community