Lecture 16- Disturbance Flashcards Preview

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What is disturbance?

-any event that creates a gap in a community


What is a gap?

-a patch where one or more species have gone extinct
-gap size depends on the species you're looking at


What are the five main types of disturbance?

-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.)


What is a biological community?

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


What are differences in time scales in terms of disturbance?

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


What are three things that are associated with patch dynamics?

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


What is founder controlled patch dynamic?

-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


What is dominance controlled patch dynamic?

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


Is a community controlled by founder or dominance patch dynamic?

-no it is a continuum


What happens when a patch is vacated?

-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


What happens in primary succession?

-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


Give an example of primary succession.

e.g. sand dunes= blank slate
-first grass stabilising it, then praire grass and shrubs and then mature forest


What is a secondary succession?

-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)


What are characteristics of early succession species in secondary succession?

-good dispersers (lot and small seeds)
-grow quickly
-consume resources quickly
-"live fast, die young species"


What are characteristics of late succession species in secondary succession?

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


What happens in an environment with low frequency of disturbance?

-superior competitors dominate= lower species richness


What happens in an environment with high frequency of disturbance?

-colonisers dominate= lower species richness
-the frequent disturbances kill off everyone and only the colonisers have time to get in


What happens in an environment with medium frequency of disturbance?

-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


What are the practical applications of Intermediate disturbance hypothesis?

-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


What is an endemic species?

-species found only in that one particular area


What is the crazy ant example about?

-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