Lecture 16- Disturbance Flashcards
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
