Ecosystems In The British Isles Over Time Flashcards
What is succession
The process by which an ecosystem changes over time (change in plant community). The biotic conditions change as as abiotic conditions change
What is primary succession
Occurs on land that’s been newly formed or exposed eg where a volcano erupts and forms new rock surface.
Abiotic conditions harsh eg no soil, seeds spores blown by wind
What is secondary succession
Happens on land that’s been cleared of all plants but soil remains eg after forest fire
What happens during each stage of a succession
Different plants and animals are better adapted for improved conditions move in and outcompete plants and animals already there to become dominant species. Ecosystem becomes more complex over time, species diversity increases
Describe primary succession
On land that’s newly formed or exposed.abiotic conditions harsh. First species to colonise are pioneer species they adapted to harsh conditions. They change abiotic conditions, die and decompose to form a soil so conditions less hostile eg soil retain water, new organisms grow, die and decompose soil is deeper and richer so larger plants can grow
What are the stages in a succession called?
Sere -a community of plants that forms a stage in the development of vegetation over time.
Example of a succession
Lithosere (raised beach) created by falling sea level or by isostatic uplift of land from sea
Raised beach succession stages
Seral stage 1- colonisation Seral stage 2- establishment Seral stage 3 - competition Seral stage 4 - stabilization Seral climax
During raised beach succession what happens at stage 1 - colonisation
Pioneers begin to colonise eg lichen, are adapted to severe(dry,windy,soil free) conditions. They die and add dead organic matter to weathered rock - simple soil, water retention improved Mosses grow. More soil so more advanced plants begin to grow
During raised beach succession what happens during stage 2 - establishment
Soil develops furthur, ferns, small herbaceous plants and grasses begin to grow. Species diversity increases. Humus created and improves soil fertility. Soil holds more water.
During a raised beach succession what happens during stage 3 - competition
Larger plants establish themselves eg shrubs (gorse) and small trees, use up water and shade ground. Some of earlier colonisers unable to compete and die out
During a raised beach succession what happens during stage 4 - stabilization
Fewer new species colonise, larger pioneer trees dominate such as willow, birch, and Rowan
During a raised beach succession what happens during the seral climax stage ( final stage)
Slower growing tree ps develop eg ash, oak. They are dominant soft climatic climax community -temperate deciduous woodland
Where is temperate deciduous woodland biome found ?
In mid latitudes where there’s adequate moisture
Climate of temperate deciduous woodland -Ave winter and summer temps -Total precipitation -winds Which weather system dominates?
- Winter temp 2-7c Summer - 13-17c
- Total precipitation 500-2000mm per yr
- On shore westerly wind predominate - moderates temperature, bring moist air
- low pressure weather systems dominate
Vegetation In temperate deciduous woodland
- Characterised by Seasonal colour change
- Broadleaved deciduous tree set oak,ask beech ,birch shed leaves in Autumn before Cold temp
- Soil temp fall so growth retarded - can’t absorb much water
- Heat loss reduces transpiration and demand for water during cooler months.
Soil of temperate deciduous woodland
- Brown earth, fertile, 1.5m deep , well drained
- Leaf litter accumulates during autumn and is quickly decomposed the following year
- Soil well mixed by earthworms so layers unclear
- Mild leaching occurs so soil slightly acidic ideal for plant growth
Oak woodland characterised by 4 layers
- Tall tree canopy - Oak, beech, sycamore, ash. Loose leaves I winter reduce transpiration, light limited? Reduce species
- Shrub layer - small trees eg hazel, hawthorn , rowan
- Field layer- woodland flowers eg bluebell,primrose
- Ground layer - mosses,tree seedlings. Fallen and decaying wood and leaf litter important for fungi
What are interfering or arresting factors
Those that stop a plant community from reaching climatic climax
What is a plagioclimax
The plant community that exists when human interference prevents the climatic climax vegetation being reached
Examples of types of human activity that stop succession or redirect it towards a different climax
Deforestation - reduces soil quality fewer plants can grow
Animal grazing- small plants/ saplings eaten or trampled
Clearance by fire - all plants destroyed ,fastest growing types recolonise
Afforestation - trees cleared to make way for new saplings, only one species planted and managed (monoculture)
Example of a plagioclimax in the uk
Heather moorland
Describe Heather moorland plagioclimax
Upland of Britain was covered in deciduous woodland (oak forest) Heather in small amounts. Forests gradually removed + soil deteriorated + hardy plants (Heather dominate ). Sheep grazing prevented regeneration of climax woodland as destroyed young saplings. Managed burning used to control uplands to encourage new Heather shoots , less fire resistant species eliminated Heather shoots dominate.
How often is Heather burnt In Heather moorland
On average every 15 years if left longer there’s too much woody tissue and nutrients lost in smoke
