Week 11 Wednesday

Question 1

what is a succession?

Answer 1

gradual change in plant and animal communities in an area following a disturbance

Question 2

what is primary succession?

Answer 2

colonization of newly exposed geological substrates

Question 3

what is secondary succession?

Answer 3

initial growth of plant community following disturbance that does not destroy soil

Question 4

what is a pioneer community?

Answer 4

made of early successional species; plants that colonize area first, shortly after initial availability

Question 5

what is a climax community?

Answer 5

made late successional species that remains stable until disrupted by disturbance

Question 6

what is a disclimax community?

Answer 6

maintained only thru continual disturbances

Question 7

what is an example of primary succession?

Answer 7

• Volcanoes
• Glaciers

Question 8

what is an example of secondary succession?

Answer 8

• Lightning strike fires
• Windthrow or blowdowns
• Floods

Question 9

what are some effects of fires in forests?

Answer 9

• Kill plants
• increased nutrient availability
• fire tolerant-species regrow quickly from living root systems, while others may have seeds dispersed as a result of the fire and regrow more slowly

Question 10

time scales of the successions?

Answer 10

• Primary succession (Glacier Bay) ~1500 yrs
• Secondary succession (Boreal forest post-fire) ~ 200 yrs
• Succession in intertidal zone ~ 1.5 yrs

Question 11

what are the hypotheses of mechanisms of succession?

Answer 11

• Relay Floristics Hypothesis
• Initial Floristics Hypothesis

Question 12

what is the initial floristics hypothesis?

Answer 12

Different species dominate at different time periods following disturbance, but great deal of overlap in species occurrence.

Question 13

what is the relay floristics hypothesis?

Answer 13

one wave of species being replaced by next until climax. Very little overlap in species distributions at different successional stages.

Question 14

Describe Facilitation with the Connell-Slatyer Model of ecological succession

Answer 14

• Many species attempt to colonize newly available space, but only species with particular characteristics can establish
• Successful colonizers are pioneer species
• Pioneer species modify the ecosystem so that it becomes less suitable for them but more suitable for species found in later successional stages.
• Replacement continues until resident species no longer facilitate colonization by other species

Question 15

Describe Tolerance with the Connell-Slatyer Model of ecological succession

Answer 15

• Initial stages of colonization are not limited to a few pioneer species. Juveniles of species dominant at climax can establish early in succession.
• Species colonizing early in succession do not facilitate colonization by other species, those that persist are simply those tolerant of conditions
• Climax community is established when there are no more colonizing species tolerant of environmental conditions

Question 16

Describe Inhibition with the Connell-Slatyer Model of ecological succession

Answer 16

• Like in the tolerance model, any species can colonize the area during early stages of succession
• Early occupants modify the environment to make it less suitable for any species; early colonizers inhibit colonization by later arrivals
• New species move in only when space opens
• Climax community consists of long-lived species resistant to damage by physical or biological factors.