Primary Succession vs Secondary Succession
Biotic communities are changing according to internal factors or external factors. This process, which a biotic community undergoes a series of recognizable and predictable stages following colonizing in a new habitat such as in land or water or following major disruption, is called the succession. The changing time scale of succession is highly variable.
Succession gives an opportunity to increase the amount of biomass in given community. By modifying the environment, it invites for new organisms. It leads high species diversity in a given area. Interactions between organisms become more complex. Size of the organisms becomes large. Later specialist species becomes common than opportunistic species.
What is Primary Succession?
When a succession process is initiated with the bare rock surface or water body that lacks soil or vegetation, it is called primary succession. So, communities are gradually growing over a long period. The primary succession occurs rarely, because of rare opportunities. Primary succession occurs when land or lakes form during glacier retreat or emerging new island by a volcanic eruption.
A bare rock surface gives more hostile environment for most organisms. So, as primary colonizers, such as lichens algae and blue green algae, which are called autotrophs can tolerate this hard environment. They excrete chemicals, which help in breaking the rock surface and absorb inorganic materials, which they need for their growth. After the death of these primary colonizers, decaying organic material will be a good source for the decomposers. This is the initial stage for the soil formation, and it is full of nutrients for the plant growth. Then it will be colonized with tolerant plants with good seed dispersal mechanisms (Taylor et al, 1998).
What is Secondary Succession?
When communities are established after a major disruption such as fire, severe wind throw or logging is called secondary succession. This type of succession process is more common than the primary succession.
In secondary succession, the natural succession process has disrupted by the human activity or natural process. Already soil is present and primary colonizers do not need for the initial stage. So, the initial stage of forming soil does not occur. Some vegetative parts, which helps in colonizing the niche, will remain, and they regenerate new plants. The existing soil is well structured and modified by previous vegetation. The new generation will slowly arise. Secondary succession is initiated by several mechanisms such as facilitation and inhibition as well as trophic interaction.
What is the difference between Primary and Secondary Succession?
- When a succession process initiated with the bare rock surface or water body that lacks soil or vegetation, it is called primary succession, while communities are established after a major disruption such as fire, severe wind throw or logging is called secondary succession.
- Primary succession is rarer than the secondary succession.
- Primary colonizers are involved in primary succession, whereas no need of primary colonizers in secondary succession.
- Soil is already present in secondary succession, but in primary succession, primary colonizers involve in creating soil.
- Existing soil is well structured and is modified by previous plants, whereas soil is newly formed during the succession process.
- Some vegetative parts, which helps in colonizing the niche, will remain, and they regenerate in secondary succession, but in primary succession after the soil formation it is colonized with plants with good dispersal mechanisms, which ensure the arrival of the plant to the site.
References
Taylor, D.J., Green N.P.O., Stout, G.W., (1998), Biological Science. Cambridge University Press, Cambridge