17Mar-PL-Vegetation_Dynamics (1)

17Mar-PL-Vegetation_Dynamics (1) - Vegetation Dynamics:...

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Vegetation Dynamics: Succession There are two types of Vegetation Dynamics or changes: Ø Fluctuations: No change in the composition or overall appearance of the vegetation &/or fauna, but it looks different because of seasonal variations : seasonal growth of various species. (e.g. deciduous species in leaf or not, different seasonal activities of animals species - like migration, hibernation ).
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Rattray Marsh (Mississauga) in Summer, Fall & Winter
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Ø Seral Succession: This is change where a group of plant & animal communities ( Seres ) are related in a particular fashion to replace each other. There is a progression of communities from pioneer assemblages to a climax community in a linear fashion. The vegetation & animals have the ability to change the environment in terms of the soils, microclimate etc. Succession depends on: Competition Persistence of species Availability of species
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As succession occurs there is: Ø Species change in the ecosystem. Ø An increase of biomass as the system matures. Ø An increase in complexity of energy & food webs & biogeochemical cycles. Ø Increasing species diversity because of the increase in niches.
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Ø Increase in the size of organisms. Ø Ø Closure of mineral cycles with maturity (cycles are open in development stages but closed at maturity). Ø Increasing nutrient conservation with maturity (it is poor during development stages but good at maturity) Ø Increasing stability (in terms of outside influences) with maturity.
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These were defined by the American botanist & ecologist Frederic Clements in the early part of the 20th. Century (e.g. 1916). Ø He viewed vegetation & animal communities as being Ø Believed that communities evolved through development stages ( seres ) towards equilibrium with the environment ( climax ). Ø Was criticized from the beginning for his linear, gradualist evolutionary model (very similar to the Davisian view of landscape development) & for the idea that vegetation & animals could reach a state of climax , given that environmental conditions were ever-changing.
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Various types of Climax are recognized: 1) Climatic (emphasized by Clements) 2) Edaphic – dominated by soil conditions. 3) Topographic climatic – influenced by altitude, 4) Disclimax (plagioclimax) – influenced by: •) Burning/Cutting disclimax – burning (natural & man-made). •) Zootic disclimax - grazing (natural or human- induced) •) e.g. of both:
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The Mediterranean Basin was originally covered by evergreen forest. The Pleistocene saw the expansion of deciduous forest mainly in mountainous areas.
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This note was uploaded on 04/06/2012 for the course GEOG 1600 taught by Professor Roger during the Fall '12 term at York University.

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17Mar-PL-Vegetation_Dynamics (1) - Vegetation Dynamics:...

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