Succession and climatic climax Flashcards
What does the composition of vegetation rely upon?
Natural factors:
Climate, relief and soils.
Human factors:
Clearance, fires and livestock grazing.
What is a plant succession?
Plants become more complex over time.
‘The change in a plant community through time’.
When is a climatic climax achieved?
Undisturbed succession - climatic climax.
Plant species live in a perfect balance with the current environmental conditions.
What factors affect plant growth? 4
Climate.
Drainage.
Geology.
Relief ect.
What is a primary succession?
Occurs on surfaces that have had no previous vegetation.
Includes lava flows, bare rock and sand dunes.
Main types: Xreoseres and Hydroseres.
Where is a Xerosere formed?
Formed on dry land.
Lithoseres - rock.
Psammoseres - sand dunes.
Where is a Hydrosere formed?
Formed in water.
Haloseres - salt water.
Hydroseres - fresh water.
What is a secondary succession/when does it occur?
After the destruction/modification of an existing plant community.
Can occur naturally e.g. fire caused by lightening/deforestation.
What is a sere?
An individual stage in a plant succession.
Invasion, colonisation, competition, domination and decline.
What is the first general stage of plant succession? 7 points.
Pioneer species - can survive harsh conditions.
Invade bare ground (dispersal/migration) = colonies of 2+ species established.
E.g. long-rooted salt-tolerant marram grass in a sand dune.
Compete for space/light/water/nutrients.
Dying - adds organic matter to soil.
Can affect microclimate and soil conditions.
Roots break up/weather the surface - aids soil formation.
What is the second general stage of plant succession? 7 points.
Improved ground by immature soil.
Other plants colonise.
Each stage has improved conditions - more species.
Organic matter improves structure/water-rendition.
Allows taller plants - more in demand of water/nutrients.
Provide shelter from wind/sun - other plants colonise.
Dominant plants - tallest.
What is the third general stage of plant succession?
Thousands of years - stability. Dominants rule over rivals. Species decrease. Community becomes 'closed' - saturation point has been reached with all potential niches occupied. CLIMATIC CLIMAX COMMUNITY.
What is polyclimax theory?
Local factors e.g. drainage/geology, can create variations in a climatic climax community.
What is an example of a lithosere?
Begins life on newly exposed rock surface.
E.g. eruption of a volcano leaves a new, bare lava surface - Surtsey 1963, Iceland.
Raised beaches e.g. west coast Scotland.
What is the FIRST STAGE of succession of a lithosere?
FIRST STAGE:
The bare rock surface - very dry - rapid runoff.
Only bacteria/algae present.
What is the SECOND STAGE of succession of a lithosere?
SECOND STAGE: lichens - withstands the water shortage. Break down the rock/reduce water levels.
E.g. Rinodina lichens.
Wind borne soil particles/organic matter collect in the depressions - soil formation.
Helps growth of foliose lichens e.g. Parmelia.
Retain more water/accumulate more soil particles - develops fine layer of soil on the rock surface.
What is the THIRD STAGE of succession of a lithosere?
THIRD STAGE:
Soil/humus accumulation - moss growth - e.g. Grimmia.
More soil/organic matter accumulation - favour moisture loving mosses e.g. Hypnum (more advanced).
What is the FOURTH STAGE of succession of a lithosere?
FOURTH STAGE:
Decaying mosses - herb layer.
Helps germination to seeds of hardy grasses e.g. Poa.
Decomposition of annual grasses - replacement by perennial grasses e.g. Heteropogon (lives for 2+ years).
Small animals invade.
What is the FIFTH STAGE of succession of a lithosere?
FIFTH STAGE:
Further weathering/herb deaths - shrub growth - e.g. Rhus.
Larger size/deeper roots - more weathering/soil formation.
What are the SIXTH/SEVENTH STAGES of succession of a lithosere?
SIXTH STAGE: fast-growing pioneer trees e.g. willow.
SEVENTH STAGE: slower-growing trees e.g. ash.
Appear in later stages - initially in shrub shade.
Temperate deciduous woodland dominants.
