Succession

Página 1

Succession

Net Primary Productivity (NPP) – The total amount of energy transferred from sunlight to chemical potential energy (biomass) less any used in respiration.

Gross Primary Productivity (GPP) – The total amount of energy transferred from sunlight to chemical potential energy (biomass) by plants.

Ecology – The study of the interactions between the environment and the organisms that inhabit it.

Succession = When changes to the environment causes the plant and animal species to change. Or… Transition in the species composition of a biological community, often following ecological disturbance to the community; the establishment of a biological community in an area virtually barren of life.

Changes at a predictable rate and predictable species.

Primary succession = Bare rock. Need erosion, wind and rain for soil. = No soil, life has to re-establish.

Secondary succession = Disturbance but soil remains. E.g. forest fires. Pioneer organisms come into an area after disturbance. E.g. large pole pines. Climax species = what happens after succession.

Series of steps where life comes back.

Each step of succession is called seral stages/seres:

Pioneers

Intermediate

Climax

Primary = no soil.

Secondary = soil but no plants or animals.

Pioneer species

Dispersion of seeds/spores carried by wind or animals.

Aren’t reliant on native species.

Lots of seeds/spores. They need to be very light.

Good at germinating

Need to be extremophiles – dry, low nutrients, extreme temperatures.

Penetrate rock.

Biological weathering

Decomposition producing humus.

So mosses and ferns can grow.

Intermediate species

Complex plants

Vascular species

Insects

Pollination

Mosses and ferns cast shade. Stop growth of lichens.

Roots break up rock.

More organic matter as plants die.

More water retained by grasses.

Animals move in changing soil and light conditions.

Shading killing smaller plants.

Climax sere

Colonised by dominant species

Less biodiversity

More stable

E.g. oak woodland in the UK

Heathland management – stops succession

Deflected succession

Climax not reached

E.g. due to agriculture – chalk grasslands of the south downs do not develop into woodland because of the grazing of sheep placed there by man.

Used for conservation

Also due to limiting factors. E.g. around lead mines due to lead in soil.

Called plagioclimax.

Factors which increase as succession increases

Time

Plant and animal diversity

Biomass

Complexity of ecosystem

Stability

Productivity

Height of plants

Number of layers of vegetation

Number of habitats

Number of niches

Soil depth

Soil fertility

Soil organic matter

Soil water holding

Complexity of food webs

Página 2

Additional Information

Succession occurs as a result of changes to the environment, this is caused by the abiotic factor causing the plant and animal species present to change.

Primary succession occurs on land which has been newly formed or exposed such as bare rock. There is no soil present.

Secondary succession occurs on land where soil is present but it contains no plant or animal species.

Primary succession is still taking place.