2.5: Zonation, Succession And Change In Ecosystem Flashcards
(11 cards)
What is zonation?
The gradual change in the composition of species and communities across an environmental gradient (a change in abiotic factors through a space)
Creates distinct zones/bands of organisms
- result of interaction between abiotic and biotic components
What are examples of an environmental factor?
Altitude
Latitude
Tidal level
Soil horizon
Distance from water source
Distance from a given human impact
Temperature
Moisture
Light
What is succession?
The predictable change in the composition and complexity of a community over time
What is primary succession?
The process that occurs when NEWLY FORMED/EXPOSED LAND is gradually colonized by an increasing number of species
Uninhabited, inorganic surface can be created many ways:
Magma from volcano -> new rock surface
Sea level drop/drying of lake -> bare rock
Glacial retreat -> leave bare rock
(Doesn’t have to be bare rock - any barren terrain ex sand dunes)
What is secondary succession?
Happens on bare soil where there WAS a pre-existing community
- restoration of a community following a disturbance
Ex: forest area after forest fire
What is a seral community?
A temporary/intermediate stage in the ecological succession of an ecosystem
- each seral community in succession -> change in environmental conditions
- allow for next community to replace it until stable community is reached
What are the stages of succession?
Seeds/spores carried by wind to bare rock -> start to grow
- forest species to colonize -> pioneer species
- as they die/decompose -> dead organic matter -> basic soil
Seed of small plant/grass carried by wind/transported another way
- seed + basic soil -> growth
- small plants die/decompose -> soil is deeper and more nutrient rich
- roots form network -> hold soil
Larger plant and shrub + small trees
- can now grow -> deeper + more nutrient soil
- also need more water - stored in deeper soil
Soil sufficiently deep + enough nutrients + hold enough water -> growth of large tress
- final species to colonize -> dominant species
- relatively complex ecosystem
- final community
= CLIMAX COMMUNITY
How does energy flow change during succession?
How does productivity change during succession?
ENERGY FLOW:
- Early stages of succession -> energy flow is low
-> only few species, most energy used for growth
- ecosystem increase complexity -> increases
PRODUCTIVITY:
Gross productivity:
- early stages -> gross primary productivity low
-> only few species present -> overall gain in energy+biomass/area/time is small
- ecosystem more complex -> gross primary productivity increase
Net productivity:
- early stages: net primary productivity high
-> very little plant growth -> less energy on respiration
- ecosystem evolve -> more plants need to grow more -> more respiration
-> most glucose used in respiration -> glucose leftover small
How does species diversity change during succession?
How does nutrient cycling change during succession?
SPECIES DIVERSITY:
- Early stages -> diversity low
-> only few species present
- increased complexity -> more niches -> more species can coexist -> more diversity
NUTRIENT CYCLING:
- Early stages -> very simple
-> only few species, abiotic processes dominate
- more complex ecosystem -> more complex cycling
-> more species -> each species has unique requirements and cycling processes
What is diversity?
What is resilience?
Diversity:
The variety of species, genetic variation, habitats and ecological functions within an ecosystem
Resilience:
The ability of an ecosystem to recover after a disturbance
Greater diversity = greater resilience
- species redundancy: many species similar roles -> one lost others can fill
- genetic variation: more genetic diversity in a species -> adapt
How does human impact affect succession?
Human impact -> divert progress of succession to an alternative stable state
- modify ecosystem: burning, agriculture, grazing pressure, resource use
Many impacts - changes to abiotic and biotic components altering course of succession temporarily or permanently:
Ex:
Controlled fires to clear land
- kills plants
- reduce soil fertility
- alter nutrient cycling
Agriculture and grazing
- soil erosion
- loss of vegetation cover
- alter nutrient cycling
= important to consider environmental impact of human activities -> minimize negative effects
