River continuum concept (RCC)
Rivers are powered by gravity. The water flow from highland to lowland and in this unidirectional flow there is a pattern of loading and transportations of the nutrients from headwater to the mouth of river. The sizes of the nutrients also change according to size of stream and river beds, velocity of water, width, depth and slope gradient. These specific pattern of nutrients and ecosystem along river length control the distributions of living organisms. From upstream to mouth of river, the sequence is as follows,
Shredders, grazers, collectors and decomposers.
Plankton Ecology Group
It is the seasonal succession of zooplankton and phytoplankton. The composition of the phytoplankton and zooplankton changes due to changes in amount of nutrients, oxygen, light and temperature which are changing by changing seasons.
Succession in plants community:
Soon as a catastrophe like a volcanoe, hurrican, fire or human development leave a bareland behind, the most quick growing plants or grasses invade the land. As time passes the annual plants and shrubs that store more nutrients in their stems and roots replace earlier fast growing plant communities. And then the most slowly growing plants come and replace others by dominating the community. These most slow growing usually harwood plants preserve nutrients in their stems and roots and they can reuse them, so despite they come late but they dominate.
So both spatial and temporal distribution of organisms depend on their strategy of energy usage. Climax community in a plant succession or top predator in ecosystem do not mean they are more successful than other organisms but they are part of the energy cycle. Temporally, a catastrophe repeat the cycle and spatially it is the habitat and climate or microclimates that decide where cycle starts.
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