Describe the various stages of Hydrarch succession.
When the succession takes place in a moist area progressing from hydric to mesic conditions, then it is called Hydrarch.
It is further of two types:
- Hydrosere: When the succession is in fresh water ecosystem like ponds, lakes, etc.
- Halosere: When the succession starts in saline water, for example esturies, mangroves, etc.
When the succession occurs in a’ dry area progressing from the xeric to mesic conditions, it can be further classified as:
- Lithosere: When the succession is on a barock.
We take an example of hydrarch succession in pond, it being a fresh water eco-system the succession can also be called Hydrosere. The succession in the pond begins when it gets occupied by the phytoplanktons.
At this stage the pond water is deficit in nutrients and does not support life. As their population dies the decomposing organisms like bacteria and fungi become the pioneer in the eco-system. This decomposition results in mineralization and because of the silt deposition the pond becomes shallow and the mud at its -bottom is enriched in nutrients. This is called as a pytoplankton’ stage.
In the submerged state a comparatively richer soil is available and it supports growth of rooted, submerged hydrophytes, like Elodea, Utricularia, etc. As the time passes the vegetation expands and there is a gradual change in the habitat. The submerged plants are replaced by the floating types of plants. They are rooted in the mud, but their leaves have buoyancy and reach the water surface to float. For example Nelumbo, Trapa, Nymphea, etc. Due to the growth, death and decay the pond becomes
much shallow and water level decreases. This stage is not suited for the floating plants, so the amphibious plants take their place. This is called Reed-Swamp stage.
The plants of this community are rooted, but their shoots are exposed to the air. For example Typha, Sagittaria, Phragmites, etc. These plants possess a strong root system and form a patchy, dense vegetation. They do not allow the sunlight to pass through the water. After sometime the water level reduces considerably and it becomes unsuited for these plants also.