2.5 Zonation, Succession And Change In Ecosystem Flashcards
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
