Is the gradual replacement of the community of organisms in one area or another. It may take millions of years . Once the plant have qst themselves eg will attract animals since they are the producers . succession occurs in stages known as SERAL STAGES .
The first community of plants is refered to as the PIONEER COMMUNITY . This keeps its self under harsh conditions . this place has very low rainfall very high temperature nutrients are scarce and the surface on which it grows lacks soil (rocks) eg lichens which are highly adopted to these un favourable conditions .As the successive communities colonise the area in the prvious community has made the conditions more favourable for for growth.
It weathers the surface to form soil ,it conserves and traps moisture and as they die ,they decay and contributes nutrients to the soil. In the process of succession there is a transition from simpler communities to more complex communities and this occurs through the process of colonization.
Colonization is mainly by disposal of seeds, spirals ,fruits and any vegetative part of a plant.
Types of succession
1) Primary succession
The primary community colonizes and establishes on a bare surface which has never had any community existing. It has got several stages
First stage (Gutose lichen’s stage). It is a thin layer of lichens on the surface.
Stage two. (Foliase lichen) .This means leafy
Stage three. (The moss). It is plenty with a lot of rain
Stage four (Herb) it’s anon woody eg dood
Stage five (shrub) it’s made up of woody plants.
Stage six (climax forest community) it’s made up of highly developed big trees. It starts in a few trees which are scattered and have started growth due to unfertile soils. Their leaves fall and decay and this increase the soil fertility. The forests trap rain water using their leaves. Invertebrates and rodents are attracted hence braking down the little. New species of trees colonise the area and have a faster rate of growth. The trees grow closer to form a forest. A typical forest has got a number of layers. The big trees form the emergent layer followed by the canopy layer and then the under growth (shrubs and herbs).
The temperatures are moderate with enough rainfall and high humidity. The litter becomes a habitat for invertebrates e.g. earth worms and termites which improve the soil with their droppings. When they die, decay and add humus to the soil. They create tunnels in the soil improving the soil drainage and aeration. They mix the soil, earth worms break down plant materials as they feed.
2) Secondary Succession:
It occurs when a previously existing community is completely destroyed and a new community re-establish its self.
Natural pests attacks, fire out break, volcanic eruption, flooding, droughts.
Human hazards include; – Bush clearing and burning
Wars,
Deforestation
Excavations (mining and constructions)
No comments:
Post a Comment