What is plant succession brought about by?
The changes in the microoenvironment which occur due to the supply of new species, the competition between the species and changes in habitat.
A number of different successions occur within a habitat.
What factors influence the types of plants that can colonise on a particular site? 6
- Slope - horizontal/gentle slopes - debris accumulates to make soil.
- Moisture availability - gentle slopes - rainwater accumulates/drains away slowly; steep slopes, faster runoff creates dry areas.
- Aspect - south-facing slopes are warmer/drier,
- Porosity (the ability to hold water) - surfaces that can hold water are colonised more quickly.
- Surface roughness - allowing plants to get a hold e.g. glass is too smooth for most plants.
- Pollution levels - depends on the previous site use. Substances that are toxic to plants may contaminate the ground.
What is the FIRST plant succession stage for an abandoned industrial sit? 1/5
Mosses/lichens on bare surfaces.
Able to exist with little water - obtain nutrients from photosynthesis.
Concrete - slowly weathered by the production of acids.
When plants die, they provide a thin mat of organic matte.
Mixed in with the weathered mineral matter, a protosoil is produced - other plant species can root into.
What is the SECOND plant succession stage for an abandoned industrial sit? 2/5
Cracks - provide shelter for seeds to germinate/retain moisture/dust - helps root plants.
Windblown seeds - Oxford Ragwort (180 days - long flowering season - millions of seeds produced.
Dandelions and perennial rye-grass.
Known as ruderal species - able to tolerate waste ground/rubbish/debris.
What is the THIRD plant succession stage for an abandoned industrial sit? 3/5
Higher plants die - thicker/more nutrient-rich soil.
Taller plants established e.g. rosebay whillowherb.
Spread by seeds and then rhizomes - extend up to 1m per year.
Michaelmas daisy and Jacob’s ladder.
These gradually shade out smaller plants - stops them from photosynthesising.
What is the FOURTH plant succession stage for an abandoned industrial sit? 4/5
Soil enrichment continues - grass increases.
Smaller meadow grasses are replaced by taller species.
Appearance of grassland containing scattered clumps of tall herbs.
E.g. Japanese knotweed - 3m in height - dense canopies can shade out most of the species beneath them.
What is the FIFTH AND FINAL plant succession stage for an abandoned industrial sit? 5/5
Continued soil enrichment/competition.
Taller herbaceous plants are replaced by shrubs, and eventually trees.
Woody plant colonists e.g. birch possess light, wind-bourne seeds - but thick herbaceous vegetation makes it difficult for establishment - unless in a case of a fire.
Larger seeded trees e.g. sycamore and hawthorn are established.
Dense thickets of bramble develop.
Able to complete as they can grow roots into deeper crevices in the rock/concrete.
What changes to the fauna are made as the plant succession develops?
Soil fauna e.g. earthworms, increase in number as the soil improves.
Increase in the number/diversity of the insect population.
These then provide food for small mammals - allows predators such as kestrels/urban foxes.
Tree arrivals may be squirrels.
What are sub-stratum variations?
Variations caused by differences in the nature of the surface being colonised.
Can lead to several parallel successions developing.
Surfaces can be acid/alkaline.
Can include wetland, concrete, tarmac and rubble.
SHEFFIELD EXAMPLE OF SUB-STRATUM VARIATIONS. 3
Different successions on different types of rubble.
Three sub-strata present:
1. Crushed brick and mortar rubble.
2. Several metres of whole and half-bricks on a slight slope.
3. A granular layer of ash and slag.
How do railway lines serve as habitats?
Enables animals to move around cities.
Steam days - frequent fires on the lines burnt off tall species and allowed light through - encouraging light-demanding species to establish e.g. primroses.
Windbourne seeds e.g. Oxford ragwort.
Tracks fenced off - lack of human interference,
Wildlife e.g. badgers and urban foxes, encouraged.
Bramble-filled areas - nesting site for birds.
How do roads serve as habitats?
Nitrogen-rich exhaust fumes boost the growth of some wild flowers.
Increases the presence of insects and animals further up the food chain.
Number of flowers reduced by mowing.
Some roadsides are managed e.g. London streets - London plane tree is planted.
How do canals serve as habitats?
Act like long ponds.
Provides for a variety of aquatic plants e.g. yellow flag iris.
Waterfowl e.g. moorhens and ducks.
Water-loving insects e.g. dragonflies.