ESS 2.5 - Zonation & Succession

define zonation

change in a vegetation community along an environmental gradient

describe the types of zonation [6]

• altitude

  • elevation from sea level

  • higher altitude = lower temperatures, shorter growing seasons, higher insolation, stronger winds

  • influences the types of organisms

• latitude

  • angular distance from the equator

  • affects insolation, average temperature, precipitation

  • determines the development of different communities

• stratification

  • vertical zones in the landscape based on the height of the trees

• tidal levels

  • regular increase and decrease of sea levels due to the moon's gravitational pull

  • creates specific abiotic conditions

• deep ocean

  • species are adapted to different environmental conditions, forming distinct communities

  • light levels

  • pressure

  • temperature

• soil horizons

  • layers within the soil with different characteristics

  • different physical/chemical/biological properties

  • supports various communities

describe 2 ways that zonation can be measured

• transect lines

  • line - observations are made at specific intervals along the line

  • belt - quadrats are established along the line

• kite diagrams

  • # of animal/%cover forplants against distance along a transect

  • gradual changes in species distribution

define succession

the predictable change in a vegetation community over time

distinguish the differences between primary and secondary succession

primary succession - occurs on bare abiotic surfaces

secondary succession - occurs when an established ecosystem is destroyed

the process in secondary succession is usually quicker as there is established biomass

outline the stages of primary succession

1. colonization

   • bare inorganic surface

   • pioneer species (small size, short life cycle, rapid growth, production of offspring)

   • shallow soil, poor nutrients, erratic water supply

2. establishment

   • improvement in soil depth + quality

   • increased organic matter + nutrients

   • more plant species

3. competition

   • increased density of plants

   • competition for light/water/nutrients

   • complex root systems

   • soil stabilisation

   • newer plant species

4. stabilisation

   • complex food webs

   • niche development

5. climax community

   • stable + self perpetuating

   • steady state equilibrium

   • max possible development

provide an example of primary succession

Surtsey Island, Iceland

• formed after a volcanic eruption in 1963

• island of bare rock and no soil

• introduction of bacteria, fungi, microorganisms

• birds and gulls began nesting on the island

• nutrient cycling + soil formation

• became a climax community in the 2000s

  • seabird colonies, insects, variety of plant species

provide an example of secondary succession

High Line Urban Park in New York

• elevated + abandoned railway line that was repurposed into an urban park

• human induced introduction of plant species

• species adaptation to high line conditions (i.e. birds)

explain how stages of succession can impact an ecosystems diversity and resilience

resilience - an ecosystems capacity to tolerate disturbances and maintain equilibrium

newly formed pioneer community = simple communities with short food chains = limited resilience

define a sere/seral community

the collective communities in a single stage of succession

one community changes the environmental conditions so that another community can establish itself and replace the first through competition

often loosely defined and can overlap over time