29. Succession

Question 1

succession

Answer 1

the outcome of ecological processes (not a process itself): shifts in

• species dominance
• species evenness
• species diversity
• species composition
• soil amount and composition
• nutrient reservoirs/flows

Question 2

processes involved in succession

Answer 2

• dispersal
• niche requirements
• competition
• exploitation
• associated mutualists

Question 3

primary succession at Glacier Bay

Answer 3

• succession after glacial disturbances can take centuries to millennia - chronosequence created using 8 study sites - rapid increase in first years since disturbance and eventually almost levels out

Question 4

chronosequence

Answer 4

a series of communities or ecosystems representing a range of ages or times since disturbance - plot number of plant species against years since disturbance

Question 5

differences in colonization

Answer 5

can be attributed to the life histories of species - ex. lichens can colonize earlier than trees

Question 6

secondary succession in boreal forest

Answer 6

community is already established and soil remains in disturbance (forest fires) - aspen roots generally survive fires, jack pines release seeds –> able to live in disturbed habitat better - chronosequence shows basal area (density) of species against time since fire

Question 7

succession in rocky intertidal communities

Answer 7

intermediate-sized boulders have the greater diversity - after storm, first green algae, then red algae - rapid succession

Question 8

time scale of succession

Answer 8

• primary succession (glacial bay) can require 1500 years
• secondary (forest fire) succession can require 200 years
• succession in intertidal communities can require 1.5 years
• succession in desert streams can occur in weeks

Question 9

succession in shallow lakes

Answer 9

succession on two time scales - lakes also experience succession over geological time scales (more obvious in shallow organic lakes) - sediment slowly settles and fills lake into a marsh - can become bog or land

Question 10

ecosystem properties that change in succession

Answer 10

• biomass
• primary production
• respiration
• nutrient retention

Question 11

ecosystem changes at glacier bay

Answer 11

depth of all major soil layers changed with different times during succession and overall increased

Question 12

ecosystem changes on Hawaiian islands

Answer 12

• primary succession on lava flows
• total soil nitrogen and carbon peaks about 100 years after and then declines due to leaching of nutrients into groundwater

Question 13

ecosystem change after deforestation

Answer 13

sites with logging had sharp decrease in biomass, but once succession was allowed to proceed, biomass increased

Question 14

model of ecosystem recovery

Answer 14

1. reorganization phase
2. aggradation phase
3. transition phase

Question 15

reorganization phase

Answer 15

(10-20 years) forest loses biomass and nutrients, despite accumulation of living biomass

Question 16

aggradation phase

Answer 16

(>100 years) ecosystem accumulates biomass, eventually reaching peak

Question 17

transition phase

Answer 17

biomass declines somewhat from the peak

Question 18

steady-state phase

Answer 18

biomass fluctuates around a mean level

Question 19

3 models for mechanisms of success

Answer 19

1. facilitation model
2. tolerance model
3. inhibition model

Question 20

facilitation model

Answer 20

many species attempt to colonize newly available space but only species with particular characteristics can establish (pioneer species), replacement of early successional stages until resident species no longer facilitate colonization by other species

Question 21

pioneer species

Answer 21

capable of colonizing new sites, modify environment so it becomes less suitable for them but more suitable for species found in later successional stages

Question 22

tolerance model

Answer 22

• initial stages not limited to pioneer species
• juveniles of dominant species at climax establish in earliest successional stages
• species colonizing in early succession do not facilitate colonization by other species
• climax community established when no more species tolerant of the environmental conditions colonize

Question 23

inhibition model

Answer 23

• any species can colonize during early succession
• early occupants modify environment to make it less suitable for any species
• early colonizers inhibit colonization by later arrivals
• climax community long-lived species resistant to damage by physical or biological factors