Lecture 16- Disturbance

Question 1

What is disturbance?

Answer 1

-any event that creates a gap in a community

Question 2

What is a gap?

Answer 2

• a patch where one or more species have gone extinct

- gap size depends on the species you’re looking at

Question 3

What are the five main types of disturbance?

Answer 3

• natural disaster(fire, flood, windstorm, earthquake)
• ecological engineers(organisms that change the habitat)
• predation and disease
• senescence(old age- old tree falls and kills…)
• anthropogenic (people caused such as climate change=biggest one, hunting etc.)

Question 4

What is a biological community?

Answer 4

-the assemblage of populations of all species that occur together in SPACE and TIME

Question 5

What are differences in time scales in terms of disturbance?

Answer 5

• communities can change over different time scales (glaciation vs leaf decomposition)
• scale is important when thinking of disturbance temporally

Question 6

What are three things that are associated with patch dynamics?

Answer 6

• nature is heterogenous(patchy= looks different in different places)
• dispersal links patches
• scale of patchiness depends on species of interest

Question 7

What is founder controlled patch dynamic?

Answer 7

• when all species are good colonisers and equal competitors
• species composition is determined by a competitive lottery
• no predictable pattern of takeover= results in high degree of diversity
• when a patch disturbed and vacated= who gets here first takes hold

Question 8

What is dominance controlled patch dynamic?

Answer 8

• species differ in competitive ability

- species composition changes over time in a predictable sequence (=succession)

Question 9

Is a community controlled by founder or dominance patch dynamic?

Answer 9

-no it is a continuum

Question 10

What happens when a patch is vacated?

Answer 10

• first pioneer species come in and colonise (those grow quickly)
• then mid-successional species
• and lastly the climax species= they take over in the end

Question 11

What happens in primary succession?

Answer 11

• when after volcano or sth with a blank slate, it’s a start from the beginning, nobody lives there
• pioneer species take off= start to develop soil etc
• then more species come and develop and eventually get more species richness= succession
• get completely new species, but predictable sequence

Question 12

Give an example of primary succession.

Answer 12

e. g. sand dunes= blank slate

- first grass stabilising it, then praire grass and shrubs and then mature forest

Question 13

What is a secondary succession?

Answer 13

• when after a disturbance some of the original species remain but significant portion dies off
• new species can come in but not as common
• remnants of previous occupiers start over (from seeds, spores and mats)

Question 14

What are characteristics of early succession species in secondary succession?

Answer 14

• good dispersers (lot and small seeds)
• grow quickly
• consume resources quickly
• “live fast, die young species”

Question 15

What are characteristics of late succession species in secondary succession?

Answer 15

• poorer dispersers (larger seeds)
• slower growers
• tolerate low resource levels( as some of it has already been used)
• better at lower light levels

Question 16

What happens in an environment with low frequency of disturbance?

Answer 16

-superior competitors dominate= lower species richness

Question 17

What happens in an environment with high frequency of disturbance?

Answer 17

• colonisers dominate= lower species richness

- the frequent disturbances kill off everyone and only the colonisers have time to get in

Question 18

What happens in an environment with medium frequency of disturbance?

Answer 18

• many species become established (succession)
• higher species richness
• have some disturbance so the superior competitors won’t completely dominate but not too much disturbance to kill the late succession species too much

Question 19

What are the practical applications of Intermediate disturbance hypothesis?

Answer 19

• management of nature
• e.g. fires = controlled fires= have more species then if there were no fires= then fewer species and implications for animal species as well

Question 20

What is an endemic species?

Answer 20

-species found only in that one particular area

Question 21

What is the crazy ant example about?

Answer 21

-how an invasive species changed an environment
-crazy ant (villain invader) versus crabs (locals)
-due to the invader fewer crabs
-as ants release formic acid and debilitates them= don’t move and the ants kill them when they don’t get out of the way
-when crabs disappear more understory plants= as no crabs to eat them
predation: eating the crabs, birds
interference competition: with other ants and insects
mutualism= with scale insects
many indirect effects= in the habitat
kill ants with fibronil= bad for the bats