Disturbance Flashcards
What is succession?
Gradual community change in an area following a disturbance
What is a disturbance?
Any relatively discrete event that disrupts an ecosystem, community, or population structure and changes resources, substrate availability, or the environment
What are examples of disturbances?
Forest fire
Windstorms
Pest outbreaks
Roadside construction
What is a short-term disturbance?
Windstorms
Wind can destroy vegetation within only minutes to hours
What is a long-term disturbance?
Glaciation
Glaciation can destroy vegetation and keep area devoid of life within thousands of years
What is a local disturbance?
Off-road vehicle use
What is a regional disturbance?
Drought
What does disturbance lead to?
Succession
The type of succession that occurs depends n how extreme the disturbance was
What is primary succession?
Gradual change in communities on newly exposed geological substrates
What is secondary succession?
Gradual change in communities where the disturbance has destroyed a community without destroying the soil
What are some characteristics of primary succession?
Existing vegetation is destroyed, new substrate created
No soil, no soil seed bank
Colonization via dispersal
Pioneer organisms are lichens, mosses, and vascular plants
What are some characteristics of secondary succession?
Colonization by pioneer organisms but existence of soil gives succession a head start T
There is a seed bank, soil nutrients, and substrate for roots
What are the stages of succession?
Disturbance
Annual plants
Grasses and perennials
Grasses, shrubs, pines, young oak and hickory
Mature oak and hickory forest
What is a climax community?
A community that occurs late in succession and whose state remains stable until disrupted by a disturbance
What is a disclimax community?
A community whose species composition is maintained through frequent disturbances
What is the intermediate disturbance hypothesis?
The theory that intermediate levels of disturbance allow for the greatest species diversity
What are levels of disturbance defined by?
Frequency of the disturbance
Severity of the disturbance
What happens at high disturbance?
Lots of change
To little time for many species to colonize
Contain mostly organisms that are good colonizers
r-selected species
What happens at low disturbance?
Little change
Competitive exclusion by species that are good competitors
K-selected species
Many are climax species
What happens at intermediate disturbance?
A moderate amount of change
Sufficient time between disturbances for species to colonize, but not enough time to allow competitive exclusion
Community contains organisms that are good competitors and organisms that are good colonizers = higher diversity than at high or low disturbances
What is the evidence supporting the intermediate disturbance hypothesis?
Intertidal pools
How much evidence is there for the intermediate disturbance hypothesis?
Some ecologists have no found support when looking at different ecosystems because ecosystems are complex
Effect of the disturbance depends on the biology of the organisms in the system and the details of the disturbance
Why would communities not change when disturbed?
Community stability
What is stability?
The persistence of a community of ecosystem in the face of disturbance
