STAGES OF ECOLOGICAL SUCCESSION
In this article, you will today learn about the types and stages of ecological succession which is one of the popular concept of environmental studies:
1. Ecological Succession
Ecological succession is defined as the natural process by which the same locality becomes successively colonised by different groups or communities of plants.
2. Types and Stages of Ecological Succession
Following types of ecological succession are as under:
- HYDRARCH OR HYDROSERE:
The ecological succession taking place in water (pond, lake or saline water) is called hydrarch and the stages through which it occurs collectively constitute the hydrosere. The various stages of hydraarch or hydrosere are:
- Phytoplankton Stage
The passively floating and drifting plants (phytoplanktons) are the pioneers in a hydrosere. They generally comprise green algae, blue algae, diatoms etc.
- Submerged Stage
The humus formed by the decomposition of planktons paves way for the arrival of a new community comprising submerged plants which may or may not have roots anchoring the plant to be bottom soil.
- Floating Stage
As more humus and soil is accumulated, the depth of pond/lake recedes further and a new community of plants is introduced comprising floating forms.
- Reed Swamp Stage
Also called amphibious stage and plants like Typha, Sagittaria, Scripus, etc., replace the floating plants. These plants produce abundant amount of organic wastes and lose huge amount of water by transpiration.
- Sedge Meadow Stage
Also called marsh meadow stage where the area is now made up of plant species like Carex, etc. They form a mat like vegetation with their much branched rhizomatous system. Finally the marshy vegetation disappear due to the development of mesic conditions.
- Wood Land Stage
First the peripheral part of the area is invaded by some shrubby plants, which can tolerate bright sunlight and water logged conditions.
- Forest Satge
It is the information of climax community, which depends upon the climatic conditions. For example., tropical deciduous or monsoon forests are formed in regions of moderate rainfall, tropical rain forests in areas with heavy rainfall, mixed forests in temperate regions.
2. XERARCH AND XEROSERE
The ecological succession taking place in a dry areas is called xerarch. The stages through which occurs constitute xerosere. The various stages are:
- Crustose-Lichen Stage
Lichen forms the pioneer community in a lithosere, as they can tolerate desiccation. Organic acids produced by lichens corrode the rock surface and release minerals for proper growth of lichens.
- Foliose Lichen Stage
They retain more water and accumulate more soil particles, helping in the development of a fine layer of soil on the rock surface.
- Moss Stage
Accumulation of soil and humus leads to the growth of mosses such as Polytrichum and Grimmia. Over a period of time, collection or more soil and organic matter favour the growth moisture loving mosses like Hypnum, Bryum.
- Herb Stage
Death and decay of mosses produce a mat of organic moss on partially fragmented rock help the germination to seeds of hardy grasses.
- Shrub Stage
Further weathering or rocks and death of herbs make the habitat more suitable for the growth of shrubs. Since the shrubs are larger in size and their roots penetrate more deeply in the rocky substratum causes more weathering and soil formation.
- Forest Stage
Many light demanding, stunted and hardy trees invade area. Vegetation finally becomes mesophytic. A steady state is reached between the environment and the biotic community. Type of climax community depends upon the climate.
3. Importance of Ecological Succession
Ecological succession is of great importance as:
- It provides information, which help to have control on the growth rate of one or more species in a given geographical area.
- It helps in reforestation and forest management programmes.