3.2.5 - succession

What is succession

The process by which an ecosystem changes over time

What are the two different types of succession

Primary and secondary

What is primary succession

This happens on land that is newly formed or newly exposed e.g. from a volcanic eruption

What is secondary succession

Happens on land that has been cleared of al plants but the soil remains

What is the first stage o succession

• bare rock

• Harsh conditions

• Difficult for any species to colonise

• Pioneer species e.g. mosses survive

What is the second stage of succcession

• Pioneer species e.g. mosses an survive (serial stage 1)

• When they die and decompose they add more nutrients to the soil which allows for more vegetation

What is the third stage of succession

• basic soil formed by decomposed mosses allows grass to grow

• Grass outcompetes moss and are the dominant species - serial stage 2

What is the fourth stage of succession

• grasses die and add utter nutrients to the soil meaning shrubs and buses can colonise - serial stage 3

• Biodiversity increases

What is the fifth stage of succession

• eventually we reach climatic climax community which is the end point and final serial stage

• The greatest species richness and biodiversity is present

What is a sub climax

When succession is interrupted by a change in local natural factors e.g. fires which returns succession to stage 2

What is a plagioclimax

When human activity has permanently changed an ecosystem and succession is interrupted

What type of biome is the uk

Temperate deciduous woodland

What trees are we likely to find in the uk

• pine

• Birch

• Oak

What are causes of plagio climax

• deforestation

• Animal grazing

• Clearance by fire

• Afforestation

How does deforestation affect the climatic climax

We clear forests for things like timber or settlements which reduces soil quality as it takes nutrients out of the soil therefore reducing the number of species that can grow there - hardy shrubs e.g. heather

How would animal grazing affect the climatic climax

We put animals on farms so they can eat grass grow and we ca eat them but they are then eating the grass so it can’t die and add more nutrients and they also trample the land so only grasses and weeds can grow

How does clearance by fire affect climatic climax

We clear areas for urbanisation which would remove all biodiversity and return succession to stage 2 so there would only be plants there if there roots hadn’t been affected by the fire

How would afforestation affect climatic climax

We would do this to counteract deforestation or plant trees for timber however this would lea to a monoculture which means that humans have controlled the plagioclimax

What is the lithosere

When a new rock surface begins to be colonised and he habitat changes this could be due to volcanic eruption or glacial retreat

What is the hydrosere

A wet fresh water environment that gradually becomes drier as plants grow, die and decay

What is halosere

Occurs in slat water on things like mudflats or salt marshes or lagoons

What is the psammosere

A beach where sand dunes start to be stabilised as plants colonise the surface and change he nature of the dune system

What happens as you move further into the dune system

• humus increases which is nutrient rich soil which means there can be more vegetation and biodiversity

• The types of species change from things like marram grass and couch to pine trees

Which plants can survive in beach envrionments

Xerophytes and halophytes such as mosses and grasses can survive in the dry and salty conditions due to adaptations such as a lack of leaves and long narrow stems which helps protect them from high wind speeds and salty conditions

How do these plants allow other plants to colonise in the area

Pioneer plants bind the soil together making it stronger and able to house a wide variety of plants - they then die and decompose adding humus to the soil and plants like grasses help to reduce the wind speeds which means more species can colonise

Give fur causes of sand dune erosion

• Fire’s

• Animals burrowing

• Winds

• Dredging = increased wave action

Give 3 pacts that pine plantations have had on Sefton dunes

• less sun means that other plants can’t colonise and due to the needles from the trees the soil becomes more and more acidic which changes the PH of the soil so it reduces the variety of plants

How would the removal of pine trees affect the local ecosystem

• succession would return to stage 2 and species e.g. red squirrels would be in danger