Chapter 19: Community Dynamics Flashcards
1
Q
What is succession?
A
- gradual and seemingly directional change in community structure over time
- sequence of species replacements that occurs after habitat has been opened up for colonization
- shifting pattern of species dominance and diversity (birth and death rates cause this)
2
Q
What is community dynamics?
A
- the changing pattern within the community of its structure
- changing structure over time is community dynamics
- succession is HOW that occurs
3
Q
Explain the colonization of concrete blocks in intertidal zone Sousa study with respect to succession!
A
- intertidal zone in Cali
- noted that if you were to look at rocky intertidal areas action of waves will move rocks and turn them over stripping algae off them. Over time the algae comes back and colonizes. The author looked at the colonization..which species come first..who competes etc
- they monitored algae succession on the blocks over time
- they noted early, mid and late succession of the algae.
- they found a general pattern of colonization and extinction. Basically species like Ulva (green algae) come in early succession and take over but they don’t compete well so they decrease as others come in. The late colonizers were the better competitors (Gigartina canaliculata)
- *done over two years
4
Q
Explain the characteristics you would expect to see in initial or early successional species (pioneer species)! What type of species would these be classified as?
A
- fast growing, high reproductive rates, high mortality rates, small size, high degree of dispersal
- R Species
5
Q
Explain the characteristics you would expect to see in late successional species. Also, what type of species would these be classified as?
A
- low rates of dispersal, s;ow growth rate, larger in size, longer lived, produce fewer offspring, nurture them, out compete other species such as the early successional ones
- K Species
6
Q
What is primary succession?
A
- it occurs on a site previously unoccupied by a community
- aka an area that nothing ha lived on before
ex: newly exposed surface
7
Q
Explain the coastal sand dune example for primary succession!
A
- costal sand dune is created by the action of waves washing up sand and creating a new substrate..succession occurs over time..beach grass colonizes it which stabilizes the area. Aft this k-sekected secures ca come in and colonize the area since it has been stabilized by the r-selected species.
8
Q
Explain the changes in wood species at Glacier Bay with respect to primary succession!
A
- When a glacier melts it isn’t just water..it is filled with silt
- silt builds up creating a new substrate that organisms can live on
- glacier use to cover the whole area and over the past 200 years it has been retreating exposing new areas that a variety of species can now come in
- over time 550500 years after the retreat we have seen alders, willow and cotton wood that are colonizers come in and stabilize the area making it more habitat for other species….
- after this spruce have now come in (no longer just shrubs). They can grow and start shading shrub species which will die off. They make the area better for hemlock since they are shade tolerant and can grow under the spruce
- now the spruce cannot live bc hemlock shades them out and they cannot tolerate it …fucking hemlock - what a douche
9
Q
What is secondary succession?
A
- succession that occurs on a previously occupied site following a disturbance
- the amount and composition of surviving community influence successional dynamics
10
Q
Explain the secondary succession example with respect to the salt marsh and ice scrapping!
A
- ice scrapping the salt marsh will wipe out life. Then secondary succession occurs. If there is still some of the older k-selected species they can stay and the pioneer species that come in may not be the same as if it was primary succession
11
Q
Explain the secondary succession example about a cleared forest!
(fyi theres a fucking ton on this)
A
- the forest was deforested and turned into a field which was then abandoned. During the first year the field was filled with annual crab grass which took over. By next spring, horse weed took over the field from crab grass . During that second summer other plants cam in such as white aster and rag weed. By the third summer there was broom sedge which is a perennial bunch grass and it coloized the area which out competed the earlier pioneers. Around this same time pine seedlings began to invade. Within 5-10 years the trees were taller enough to shade out the broom hedge since they grow quite quickly
- over time the hardwoods come in (lat successional species..slowly growing ) - they start slowly and build up. As the pine builds up they start to decline via competition with the hardwoods as they get big enough because there is not enough room for all the seedlings. Over time the hardwoods will out compete the pines. As the pine seedlings reach maturity they will die out because the hardwoods have shaded out the forest flower and the seedlings cannot grow anymore.
12
Q
What are the three models of succession?
A
- Facilitation
- tolerance
- inhibition
13
Q
Explain the facilitation model of succession( aka establishment, recruitment, replacement, continuation and long-term/steady state)!
A
- Disturbance opens space
- Establishment: only certain early succession species can establish themselves
- Effect go early occupants on Recruitment: environment becomes less suitable for early succession and more suitable for late succession species
- Replacement: Early succession species facilitate later succession species. In time the earlier species are eliminated
- Continuation: continues until the resident species no longer facilitate other species
14
Q
Explain the tolerance model of succession aka establishment, recruitment, replacement, continuation and long-term/steady state)!
A
- Disturbance opens a space
- Establishment: any that are able to survive there as adults can establish themselves
- Effect go early occupants on Recruitment: environment becomes less suitable for early species, little or no effect on late species
- Replacement: Juveniles of later species invade despite early species. In time, earlier species are eliminated
- Continuation: continues until now species exist that can invade and grow in the presence of residents
15
Q
Explain the inhibition model of succession aka establishment, recruitment, replacement, continuation and long-term/steady state)!
A
- disturbance opens up space
- Establishment: any that are able to survive there as adults can establish themselves
- Effects of early occupants on Recruitment: environment becomes less suitable for recruitment of both early and late successional species
- Replacement: earlier colonists exclude, suppress or inhibit subsequent colonists
- *no continuation period**
