Presentation on theme: "Section 2: Plant Succession Plant communities develop through a succession of changes. Key Ideas: - Seral Stages - Climatic Climax Vegetation - Plagioclimax."— Presentation transcript:
Section 2: Plant Succession Plant communities develop through a succession of changes. Key Ideas: - Seral Stages - Climatic Climax Vegetation - Plagioclimax Vegetation Case study : Psammoseres (sand dunes) e.g. Murlough Nature Reserve outside Newcastle
Biogeography: The study of the distribution of plants and animals over the earth’s surface. ‘Nature abhors a vacuum’ i.e. if plants die something will always replace them. When new land is created, e.g. a lava flow, new species will move into that area and take over. Algae & lichen will colonize rock and break it down (weather it) to form soil. The formation of soil then allows other plants to take over.
What is vegetation succession? PRISERE is the term for vegetation succession. It is the complete chain of successive seres beginning with a pioneer community and ending with a climax vegetation. Vegetation succession occurs because the environmental conditions change. This happens gradually for lots of plants to develop. Each stage is called a SERAL STAGE. Each stage sees the development of species which cause the micro environment to change which in turn lets new species move in and become dominant.
The MONOCLIMAX CONCEPT F.E. Clements (1916) said that for each climatic zone only one type of climax vegetation could evolve. He called this the climatic climax vegetation. It is now more commonly known as the monoclimax concept. This occurs when the vegetation is in harmony with the local environment. As seral stages develop the number of species and height of the plants increase. Each sere tends to be named after the dominant species ( the largest or most numerous species). The Monoclimax Concept Pioneer Community Climatic climax (natural vegetation) prisere Seral stages: temporary conditions which develop over time (plant succession)
What is Britain’s Biome? P.306
Britain’s Climate Cool temperate due to our island position Cool summers (winds off Atlantic cooling influence– water slower to heat up than land) Mild winters (winds off Atlantic warming influence – water holds its heat for longer & warm ocean current North Atlantic Drift) Rain in all seasons HOW DOES THIS INFLUENCE VEGETATION?
Britain’s Vegetation Our natural Climatic Climax Vegetation is broad leaved deciduous forest. The dominant vegetation is influenced by soil type, rock type and climate if people do not interfere. So why is Britain not covered in woodland? Human activities have cut down many trees (farming & urban growth). Trees do not exist on mountains – relief, soils & climatic factors. Coniferous trees (fast growing) are planted which are not native.
Britain’s Vegetation: The vegetation cover in much of Britain is a PLAGIOCLIMAX VEGETATION. This is a deflected climax vegetation that occurs when people have damaged the natural climatic climax so much that regeneration is not possible. In the UK you now have grassland instead of woodland.
Possible interruptions: Natural interruptionsHuman interruptions Tectonic activity e.g. volcanic eruptions Temporary climatic changes e.g. drought, colder conditions e.g. deforestation Plagioclimax Vegetation (if permanent)
The Polyclimax Theory The monoclimax concept has been replaced by the polyclimax theory. This theory acknowledges the importance not only of climate, but of several (poly) local factors including : - drainage - parent rock - relief - microclimate - human activity
The polyclimax theory (p.287)
New or previously sterile land surface, or in water Land on which previous management has been discontinued e.g. abandoned farmland due to shifting cultivation in the tropical rainforest Primary Succession Secondary Succession
Ecosystem Evolution Bare surface Subclimax Ecosystem Relic Ecosystem X Climatic Climax Ecosystem Plagio Climax Ecosystem Deflected Succession e.g. relief restricts development Deflected Succession e.g. severe disturbance fire, hurricane Primary succession Sudden displacement e.g. logging Secondary succession e.g. natural regrowth Secondary succession e.g. development of a farmed ecosystem Partial displacement e.g. grazing
Primary Successions (p.284)
Transect across sand dunes to show a PSAMMOSERE.
Primary succession on a psammosere. Colonisation of fore-dunes.
Transect showing a primary succession in a HALOSERE (river estuaries where silt deposited by the ebbing tides and inflowing rivers)
Primary succession in a halosere.
Primary succession in a HYDROSERE (lakes and ponds – sediment carried into the lake will enrich the water and begin to infill it)
Primary succession in a hydrosere
Field sketch of a LITHOSERE on a newly emerging rocky coastline (raised beach), Arran.
Primary succession in a LITHOSERE Lichens, mosses and grasses on a rocky coastline