Community Ecology Exam Flashcards
Succession
A gradual change in plant and animal communities in an area following disturbance
- the disturbance can be small or large, there are a removal of few to many individuals or a creation of an entirely new habitat
pioneer community
organisms that colonize area immediately following disturbance
primary succession
newly exposed substrates and not significantly modified by organisms
ex. glacier retreat, lava flows, sediment deposition (river/stream outflow)
secondary succesion
following disturbance that does not destroy soil
ex. fire, flood, abandoned agriculture land
what occurred in the greenbelt corridor?
plant community responded to flooding and drought
- species richness declined after flood and drought occurred over years, then increased past original and declined slightly and stabalized
climax community
late successional community that remains stable until disrupted by disturbance
disclimax community
maintained only through continual disturbances
ex. grazing, drought, fires, flood (centrifugal organization)
community structure and ecosystem process may change in a predictable manner or not ending in one of few to many _________ ________
alternative states
does disturbance impact all communities equally?
no
stability
the tendancy to resist or recover from disturbance
what was Sousas definition of disturbance?
Discrete, punctuated, killing, displacement, or damaging of one or more individuals (or colonies) that directly or indirectly creates an opportunity for new individuals (or colonies) to be established.
what was white and pickets definition of disturbance?
Any relatively discrete event in time that disrupts ecosystem, community, or population structure and changes resources, substrate availability, or the physical environment
what are some spatial and temporal considerations for for disturbance?
- disturbance to bryophyte on a rock near a stream may occur at spatial and temporal scales irrelevant to surrounding forest communities
- a disturbance for one species may be inconsequential to another
- the nature of a disturbance may be environment specific
biotic vs abiotic disturbance:
biotic - disease and predation
abiotic - fire, hurricane, flood, wind, ice storm
intermediate disturbance hypothesis (Connell)?
proposed disturbance is a prevalent feature that influences community diversity
- proposed high diversity consequences of continually changing conditions
- predicted intermediate levels of disturbance promote higher diversity
if disturbance is too frequent and intense only _______ species will be present
pioneer, can complete life cycle between disturbance
if disturbance is too infrequent or minor only _____ species will be present
climax
- most effective competitors
as frequency and intensity increases there is a shift from in species composition from ________ to _______
competitors to colonizers
competitive exclusion
At intermediate levels of disturbance there is sufficient time for competitors to establish but not enough to outcompete early colonizers
what was Sousas study on disturbance ands diversity in intertidal zones?
- studied effects of disturbance on diversity of algae and invertebrates growing on boulders in the intertidal zone
- Disturbance comes mostly from wave action during winter storms.
– Predicted level of disturbance depends on boulder size. Classified boulders into three disturbance levels based on size and force required to move - most boulders subject to high disturbance had one species
- modal number of species on boulders subject to low disturbance was two
- most number of species was highest 4 on boulders subject to intermediate disturbance, boulders that experiences to intermediate rates of disturbance supported more species
one of the most important and ubiquitous sources of disturbance in grasslands is ________ _________
burrowing mammals
describe disturbance of paradise dogs
- creates distinctive patches of vegetation, the areas around the mounds support communities distinct from surrounding grassland
- species diversity highest at intermediate levels of prairie dog disturbance
- grass diversity decreases
intermediate disturbance allows persistence of species that are good _________ and species that are good ________
colonizers and competitors
stability
absence of change