19.6 Succession

Succession:

• Succession is a term that is used to describe changes which happen over time in the species that occupt a particular area. It's essentially the gradual replacement of one community by another, leading to a more complex and stable ecosystem.

Stages of succession:

First stage of this type of succession is:

Pioneer species make up a pioneer community and often have features that suit them to colonisation: These may include -

During succession there are a number of common features that emerge:

What is succession?

• A term to describe the changes in an ecosystem that occur over time in the species that occupy a particular area

Pioneer species

• These make up the pioneer community

• They are able to tolerate hostile abiotic conditions

• Other common features include.

• Asexual, wind-dispersal of seeds or spores, rapid germination

• Photosynthetic, nitrogen-fixing

• Tolerant of extreme conditions

Early colonisers

• These very simple plants are able to take advantage of the improved

abiotic conditions provided by the shallow soil.

• Mosses are able to increase in size and as they erode the rock and die

to produce a greater soil volume, more water can be held and more

nutrients become available. These allow larger plants like ferns to

grow

Features of a climax community

Same species present over a long time 

Abiotic factors are constant/ stable

- Populations stable (around carrying capacity)

Competition

• As more plants area able to thrive in the less hostile conditions,

earlier plants are unable to compete effectively for resources and are

likely to fall in number or disappear completely.

• In a succession, earlier species are replaced by more successful

competitiors once the abiotic conditions are improved.

• This causes the changes in the species found in the ecosystem.

Animals

• Once there are plants growing the animals will come

• Dead lichen provide food for detritus feeding mites

• Mosses & grasses provide food & habitats for insects, millipedes and

worms

• These will then allow predators such as centipedes to feed

• Trees attract many larger organisms, including reptiles, mammals &

birds.

Things that effect succession

• Early colonisers outcompete the pioneers since they are better adapted for the new conditions. Each successive plant outcompetes the previous one.

• Land mass, weather

During a succession

• Abiotic environment becomes less hostile

• Increase in number & variety of habitat & niche

• Increase in biodiversity...peak mid succession

• More complex food webs

• Increase in biomass...peak mid succession