Discuss the relative importance of physical and human factors in accounting for changes to vegetation over time within ecosystems in the British Isles (40 marks)

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Discuss the relative importance of physical and human factors in accounting for changes to vegetation over time within ecosystems in the British Isles.

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Robyn Moore
Discuss the relative importance of physical and human factors in accounting for changes to vegetation over
time within ecosystems in the British Isles (40 marks)
The British Isles, located in the northern hemisphere is home to a mild climate and varied soils, giving rise
to a diverse pattern of vegetation and a climatic climax community of deciduous woodland. Over time,
there have been substantial changes to vegetation as a result of a combination of both natural, physical
factors and human interference. This essay aims to identify ways in which vegetation has transformed over
time, and to evaluate the importance of both human and physical factors.
The composition of vegetation depends upon the interaction between all of the components that make up
the specific environment. Some of the core physical components of a habitat include climate, relief,
drainage, geology soils and competition. Plant populations gradually become more complex over time ­ a
process that is known as succession. Over time, sometimes even thousands of years, a period of relative
stability is reached in which the vegetation has reached its climatic climax - the state in which the species
will be in dynamic equilibrium with its environmental conditions. In the British Isles, the climatic climax
community at the end of succession is temperate deciduous woodland. As succession develops, it passes
through a series of stages called seres, and it is here that the natural processes of invasion, colonisation,
competition, domination and decline influence the composition of the vegetation. The way in which the
vegetation naturally changes over time in accordance with these physical processes can be seen in the
transformation from pioneer species to the climatic climax community. In primary succession, the plants
that first invade the bare ground through dispersal and migration become established. Such plants are
known as pioneer species, as they are extremely hardy plants that are adapted to living in harsh conditions.
Pioneer species are of great significance, as they can affect the microclimate of the area ­ in terms of wind
speed at ground level, shelter, temperature and humidity ­ but most importantly, these plants add organic
matter to the developing soil when they die, creating more favourable conditions for the growth of more
complex plants. Each stage of colonisation provides better conditions for plant growth than the one before
due to the improvements in soil, so an increasing number of species can be found. The process of natural
succession has been of great importance in accounting for natural changes to vegetation over time, as the
British Isles is an example of lithosere succession, in that it began as bare rock from glacial retreat ­ the
most recent being the Devensian glaciation.
Climate is arguably the most important abiotic factor with the greatest influence upon vegetation within an
ecosystem, particularly the seasonal pattern of temperature and precipitation. Some bio geographers
believe that, within one climate, local factors such as drainage, geology, relief and microclimate can create
variations in the climatic climax community; an idea which is known as polyclimax theory. The climate of
the British Isles has changed significantly since the Pleistocene Ice Age which ended around 10,000 or
11,000 years ago. At the end of the Pleistocene, during the time known as the pre-Boreal, the climate
began to warm up, and that trend has continued ever since, with only minor fluctuations for short periods.
There are several theories regarding physical factors that may have instigated such changes. Suggestions
have included: variations in solar or sunspot activity, meteorite impact, changes in the Earth's orbit and

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Robyn Moore
axial tilt and changes in atmospheric composition (namely greenhouse effect.) All of these processes would
be classified as natural processes - even the greenhouse effect is part of the natural process of heat
balance in the atmosphere.…read more

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Robyn Moore
how important human management has always been. On the other hand, physical factors are also of great
importance, particularly precipitation in heather moorland ecosystems. Average recordings for this
particular area show that there are roughly 100 wet days per year, along with moist westerly winds. The
wet climate is one of the vital growing conditions for heather, as it leads to the formation of acid soils in
which heather is able to grow best.…read more

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Robyn Moore
successions may take place within urban areas, depending on the type of habitat initially colonised. One
example of succession within an urban area is the lithosere-type succession that occurs on an abandoned
or neglected area. It follows the same basic course as normal succession, with pioneer species being the
first to colonise and establish and the final stage being woodland. One interesting difference is that the
second stage often involves foreign or invasive species, such as Oxford ragwort and buddleia.…read more

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Robyn Moore
determine the type of vegetation that exists, as well as the overall structure of an ecosystem and the way
in which things work within it. The natural process of succession shows the fundamental importance of
physical factors, and yet all of the other examples, particularly plagioclimaxes and urban ecology indicate
that human factors have overtaken physical factors in terms of importance in modern times.…read more




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