Unit 1 - Interdependance & Succession - (Week 4)

Question 1

Define “succession”.

Answer 1

the process by which plants naturally occupy a site and over time bring about changes in plant and animal communities, and therefore changes in the level of biodiversity.

A sequence of changes in the types
of species present in a community.

Question 2

Describe the influence of climatic and
edaphic factors on succession.

Question 3

Define “primary succession”

Answer 3

the establishment of communities on bare ground (no soil) eg lava fields, glaciated landscapes, mountain scree, concrete/tarmac, newly created pond etc.

Takes place in an environment that
has no vegetation nor soil; can take
1000+ years.

Question 4

Define “secondary succession”.

Answer 4

is the most common type.
soil is present but vegetation has been removed eg fire, flood, deforestation, pollution, weeding.

Question 5

Describe Primary Succession

Answer 5

Start off with bare rocks something small such a lichen (primarycoloniser or pioneer species) that breaks down rock to soil as they are able to live in these harsh and unfavourable conditions.

Once there is soil small flowering plants and shrubs arise which increase soil depth & fertility. These outcmpete the primary colonisers for water, light, space, nutrients.

Herbs/Bigger shrubs start to form which outcompete the small plants. eventually a forest (climax community) is reached

Question 6

State features associated with a climax community

Answer 6

• Is stable and can recover well from external disturbances eg strong winds which affect mostly the exterior trees, leaving the inner trees
  protected
• Has a well developed and organised community structure complex food web and soil base
• Supports a high biodiversity
• Produces a high volume of biomass ie lots of leafy growth

Question 7

Describe Secondary Succession

Answer 7

takes place in an environment that was
once inhabited and has become barren,
but still contains soil nutrients. Occurs
more rapidly than primary succession.

Occurs where soil is already present but vegetation has beenremoved (eg weeding, forest fire)
the ‘seed bank’ is present in the soil, just needs the chance to germinate.

This type of succession tends to miss out colonisers and go straight to herbaceous species (weeds!) and then continues
through shrubs  trees  climax community.

Much shorter process as does not have to wait until soil develops.

Question 8

What is a plagioclimax community and give examples?

Answer 8

a stable plant community that arises as a result of human intervention in the natural succession of communities.

examples:
* Mowing the grass
* Weeding
* Grazing by livestock
* Muirburn