Question

What is a keystone species and how are they different from foundation species?

What is the difference between primary and secondary succession? Explain in detail.

How does the Biomass Accumulation Model describe succession of ecosystems following disturbances?

Answer 1

Ans,)

a) Keystone Species is a plant or animal that plays a unique and crucial role in the way a ecosystem functions. Without keystone species, the ecosystem would dramatically fall. Its presence and role within an ecosystem has disproportionate effect on other organisms within a ecosystem. Often a keystone species is a apex predator whose removal will lead to unexceptional growth of prey species.

A foundation species is that species of ecosystem which have strongest role in structuring a community. A foundation species can occupy any trophic level in food web. The activities of foundation species is to physically modify the environment and produce and maintain habitats that benefit other other organisms using that benefit. The presence of foundation species has the ability to either reduce or increase species diversity depending on a particular role in a specific ecosystem. These include mostly producers.

b) Difference between Primary and Secondary Succession

Primary succesion is the type of ecological succession leading to formation of a community (plant community) in area where no previous sign of any existed community occured i.e which were totally devoid of any vegetation. It occurs in barren area, cooled lava, newly formed dunes, rocks left from retreating glacier, coral leaf. It requires very long period of time to completely grow into climax community from a mere pioneer community.

However, secondary succession is the type of ecological succession leading to formation of well developed plant community in area where vegetation was present previously but vegetation was destroyed due to natural or artificial causes. It occurs in area which were disturbed fire, flood, sudden climatic change; and climax community establishment donot take much longer period of time.

c) Biomass accumulation model explains the phases in recovery of an ecosystem after the disturbances. The recovery is usually divided into four phases. As follows:

• Reorganizational phase ( 10-20 years) - It includes loss of biomass and nutrients and also accumulation of biomass starts in last stageof this phase.
• Aggradation (100+ years) - Longest phase, community expands exponentially without any hindrance and biomass reaches a peak level
• Transition - Biomass declines from peak during this phase due several effects
• Steady- stable : No much fluctuation in biomass level. It just fluctuates around mean.