Vegetation succession and disturbance

Question 1

Primary succession

Answer 1

occurs in lifeless area where the conditions are extreme and are barely suitable of sustaining plant life

Question 2

sere

Answer 2

a stage in succession sequence of colonisation by which the vegetation develops over a period of time

Question 3

prisere

Answer 3

is the complete sequence of events beginning with the first plants to occupy the area and finishing with the climatic climax vegetation

Question 4

psammosere succession

Answer 4

develops in sand and a transect across a dine system illustrates this evolution of plant communities over time

Question 5

secondary succession

Answer 5

occurs in areas where the existing ecosystem has been removed but soil and nutrients remain and succession can being once more

Question 6

hydosere succession

Answer 6

in recently formed ponds and lakes

Question 7

tolerance model

Answer 7

• fast growing, shade intolerant species dominate first
• slow growing shade tolerant species dominate later
• late successional species arrive together with early successional species

Question 8

facilitation model

Answer 8

• Henry Cowels and Fredric Clements
• operating on the assumption that there is not external disturbance (constant climate)
• primary succession sequence (pinoeer, intermediate and climax stage)
• based on initial conditions, this can indicate what vegetation may grow

Question 9

inhibition model

Answer 9

• first come first served

- early arrivals dominate and inhibit establishment of late arrivals

Question 10

nice theory but is it true?

Answer 10

theories don’t always stand up to vigorous testing

• autogenic processes consistent with facilitation model in pioneer stages
• allogenic and random processes dominate in further climax stage

Question 11

Fire disturbance

Answer 11

• wildfires >100,000 ha
• wildfires vary year to year, usually depending on climate
• adaptations, thick bark, serotinous cones produce open during fire event
• 1990: 8 million ha burned in Canada
• Savannas are used to fires,thick barked trees and semi-open landscape
• destruction in rainforest environment (Deforestation is creating a huge issue in frequency0

Question 12

Disease disturbance

Answer 12

• Dutch elm disease
• caused by beetle
• introduces fungus that starves the tree
• happens very quickly

Question 13

Natural Disturbance

Answer 13

• flood

- avalanche

Question 14

Natural Disturbance

Answer 14

• flood

- avalanche

Question 15

crown/canopy fire

Answer 15

whole tree goes up in flames, severe, destroys ecosystem

Question 16

surface fire

Answer 16

just the surface of the ground burning, less severe

Question 17

what controls fire

Answer 17

• ignition source (lightning or humans)
• fuel (wood, dead branches on ground)
• flammability (dry summer, fuel is easy to burn)

Question 18

1980 Yellowstone national park wildfire

Answer 18

• 2/3 of the forest burnt down
• dead wood has built up over the years (due to policy to stop every small fire)
• fire is a natural park of Yellowstone national parks ecosystem
• scale of fire was much greater than it should have been

Question 19

fire benefits

Answer 19

• soil, releases nutrients
• part of some ecosystems cycle
• specially adapted organisms, help to reproduce