Question

What is ecological succession? Mention its different steps. Explain Hydrarch and Xerarch succession with diagrammatic representation.

Answer 1

All the abiotic (climatic conditions, water availability, etc.) and biotic (plants, animals, etc.) elements in a given area make up an ecosystem. These elements have to interact with one another for an ecosystem to thrive. The study of these elements and their interactions is called ecology. In ecology, the word community refers to different species of organisms that inhabit a geographical area at a given period.

Complete Answer:-
Ecological succession can be referred to as the changes that occur in a particular ecosystem, over some time, brought about by the communities that reside there. A stable climax community is established as a result of these successive changes.
The species that are initially present at the beginning of succession are called the pioneer species. The ones present in the intermediate stages are called seral communities. These seral communities get replaced with each succession. The species found at the very end of the successive process are called climax communities. The species of the climax community are not affected by the changes that they cause.

The steps that are involved in succession includes:
- The first step is called nudation which is the formation of a new area with no life forms.
- New species may migrate to or invade the area.
- These species will now try to survive and reproduce in this new area, this is called ecesis.
- Their number increases as a result of reproduction. Now the species can aggregate in this given area.
- This aggregation of various species in the area will lead to competition among the species and within the species for resources such as water, nutrients, etc.

The presence of some of these species will bring about some changes in their environment. For example changes in soil conditions, temperatures, etc. These modifications might not favour a particular species or an already existing community. They may either migrate to another area or die. A new community or species, able to survive in this new environment, will replace them. All the above steps except the first step are repeated over time till the establishment of a climax community. Any other community does not replace this community. They are relatively stable.

Hydrarch succession is plant succession that takes place in areas with abundant water supply. Phytoplanktons are producers of the aquatic ecosystem.

Xerarch succession is a plant succession that takes place in an area/ land which is dry or has limited water availability. Lichens can absorb water from the atmosphere hence, they thrive in this area.

Note:- Both hydrarch and xerarch succession proceed to a mesic condition. At this stage water availability is moderate. If succession starts in dry land it progresses to a stage where there is now a forest cover. The same happens in case the succession begins in a water body. The amount of rainfall in the region is also a factor that determines the type of forest cover or vegetation in the area whether the succession is xerarch or hydrarch.