Investigation into Succession in Sand Dunes.
Succession is a long-term direction of change in the composition of a community, brought about by the organisms themselves. Primary succession occurs when a community develops on bare/uncolonised ground, which has never had vegetation growing on it. A good example of primary succession is that of succession on sand dunes. Secondary succession occurs on ground that has previously been colonised but is now available because the previous community has been destroyed. Such ground will not be ‘virgin’ as there will be remnants of soil and organic matter, seeds and possibly some resistant plants. For example, an area destroyed by forest fire. The first plants to colonise the area are called the pioneer species. These will have special adaptations to survive in difficult conditions. The pioneer species are able to tolerate extreme abiotic conditions, they have good means of seed/spore dispersal, they germinate quickly and they do not depend on animal species. These species may be able to fix nitrogen, by the nitrogen fixing bacteria found in the root nodules, so to help build up soil nutrients where there is little nitrate to grow. Also, these species are usually photosynthetic so are not dependant on other organisms for energy. As the pioneer species are photosynthetic, there are a few limiting factors that affect the rate of photosynthesis: 1. Light Intensity: As light intensity increases, the rate of light-dependent reactions that take place during photosynthesis, and therefore photosynthesis, generally increases proportionately. However, as the light intensity is increased, another factor will eventually limit the rate of photosynthesis 2. Carbon Dioxide Concentration: An increase in the carbon dioxide concentration increases the rate at which carbon is incorporated into carbohydrate in light-independent reactions. Therefore, the rate of photosynthesis generally increases until once...
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