Succession in ecosystem

Introduction

As the generations move, organisms tend to evolve. The essence of evolution relies on the entry of new species and the extinction of older species. However, the rate at which the new ones enter and the older ones die-off depends upon the interaction between the species with their habitats  As a general rule the survival capacity of the organisms declines. Over the longer time horizons, many organisms die leaving behind similar species. For instance, the extinction of Dinosaurs has left its impression by giving way to crocodiles and snakes. You might have noticed a gradual decline in the tiger population or a sudden increase in the number of new types of birds. These are the consequences of ecological succession. In an ecological succession is linked with multiple factors. Some of them are drastic changes in the environmental conditions, adverse human activities, Destruction of habitats. In some cases, ecological succession is a normal phenomenon. For example, assume that there is a sharp spike in the number of tigers. This can result in 2 scenarios, first is that all the deer might die as a result of predation or the tigers might start searching for alternative options to feed themselves. In the second scenario, other herbivores such as cows and sheep might become the target for tiger population resulting in a gradual decline in the cows and sheep population. In a real sense, succession is a need for the system when changes happen in an orderly and sequential manner. “Ecological succession is the term used for gradual and fairly predictable changes in the composition of all or few species of a given ecosystem”.

 

Seasonal succession 

On the contrary, few species might colonize in an area resulting in a sudden increase in their numbers. For example, in a domestic environment, the number of cockroaches see a rise during summer. The term sere/s is used when the entire sequence of communities undergoes a successive change in a given area and such transitional communities are known as seral stages or seral communities. Seral stage results in the diversity and changes in the number of species as well as the total biomass.

 

Types of succession 

Primary succession 

Primary succession is the systematic process of how the individual species enter the ecosystem and slowly help others to evolve. It was started when the barren areas such as bare rocks have exposed by a retreating glacier. Primary succession progress through, pioneer, intermediate and climax phases. Pioneer organisms are the first inhabitants such as some plants and lichens successfully survived against the adverse environmental conditions.  Centuries later, these “pioneer species” were able to convert the rock into the soil in order to nourish other simple plants such as grasses; they were simply called intermediate organisms. Furthermore, the grass has modified the soil over a time period to help in colonizing different types of plants and trees(such as oak and hickory). These were called the climax species.

Secondary succession 

Plant’s succession depends upon the availability of water and other resources in an area. The terms used for such succession is hydrach (if there is plenty of water) and xerarch (if the area is dry), respectively. Secondary succession is the result of dramatic changes happened in a given community. Some of them are massive deforestation, destruction of farmlands, burnt and cut forests, flooded areas, areas with earthquakes and huge soil degradation, etc. Followed by a secondary succession,  new classes of species and a variety of habitats have erupted to bring novelty into the composition of biomass and types of organisms. Secondary succession is directly linked with vegetation changes affecting the food and shelter required for various animals. You can see an example of primary and secondary succession in the image below. 

 

Succession in a forestSuccession of a forest-image source- wiki commons

 

Further reading 

1          

Introduction to ecosystem

2

Succession in ecosystem

3

Trophic levels in ecosystem

4

 Productivity in ecosystem

 

Questions

  1. What is succession in an ecosystem?

  2. What is the difference between primary and secondary succession?

  3. Is succession necessary? Give reasons.

  4. What are the consequences of uncontrolled succession?

  5. What are climax species?

 



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