Question

Primary mechanisms that cause differences in succession rates in forests, rocky intertidal, and stream communities are:

1. The type of ecosystem

2. The type of species and species interaction involved in the succession.

3.The parameters of the species population

4. Availability of propagules

5.The type of disturbance tbefore succession

6. The presence of survivors after the disturbance.

Explain how each mechanism would lead to a different succession rate versus the other.

Answer 1

Primary succesion is a succession on a newly exposed geopgraphical substrates which is a gradual change in the plant and animal communities. And succession followed by a disturbance is secondary succession where soil is not destroyed. The succession rates varies in forests,rocky intertidal and stream communities.

In the forests the species are all kinds of plants such as tall short, grasses,shrubs,lichens,algae,fungi etc are present. But due to disturbance such as hot wildfires. Then the trees, tall shrubs,mosses,liverworths and lichens grow quickly and propagules enables the plants to grow quickly. The woody plants species increases and bird diversity increase as these plants increase. There will be species richness at the initial stage but competition among these arises and this leads to supression of short trees or shrubs. The fertility of the soil increases and nitrogen fixing bacterial species increase which shows a species interaction of mutualism. This enables many insects, birds and animals to attract the area after succession.

At rocky intertidals the species available are red algae,green algae and barnacles. The disturbances in this area is caused due to short generation time of dominant species. The species such as red algae are dominant which do not allow other species to grow and this species interaction is called predation. So when a boulder overturns by a wave then this species will be killed and a new species develops and prevents red algae from growing. The presence of the survivors depends on the disturbance caused to a specific species.

Stream communities have small animals, insects, algae and plants. The disturbances caused is due to heavy rainfalls which increase the volume and speed of the water and the rocks tumble dowstream killing many plants,animals and algae. Then the stream would be colonized by diatoms and then algae develops slowly which provides insects to lay eggs in the streams. The species interaction involved in succession is Mutualism where both the species are benefited.