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| Hydrosere |
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| Stages of ecological succession in a hydrosere |
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| Hydrosere, also called hydrarch involves the ecological succession in the newly formed pond or lake. |
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| a) Plankton stage |
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| Germination of encysted spores in the newly formed water body forms the pioneer community, Spores could have reached the water body through wind or animals. Planktonic stage includes minute autotrophic diatoms, phytoflagellates, cyanobacteria etc. Population of phytoplankton is regulated by zooplanktons. Their dead and decomposed organic matter mixes with silt and forms soft mud at the bottom of the pond. |
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| b) Rooted submerged stage |
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| Rooted submerged hydrophytes like Hydrilla, Vallisneria, Utricularia, etc. grow on the soft mud. Due to death and decay of these plants and deposition of sand and silt, leads to a slow rise in the bottom level (soil layer) of the pond. Buried older plants form good humus for next seral stage. |
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| c) Rooted floating stage |
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| Area is now invaded by species of floating, leaved, anchored plants like Nymphea, Trapa, Monochoria, Nelumbo etc, which help the water become rich in mineral and organic matter. Later free floating species like Azolla, Lemna, Pistia, Eichornia, etc. appear. This rapid growth of plants builds up the pond bottom and makes the water shallower. |
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| d) Reed swamp stage |
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| 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 amounts of water by transpiration. Addition of organic matter raises the substratum of the pond and becomes unsuitable for growth of amphibious plants. |
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| e) Sedge meadow stage |
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| Also called marsh meadow stage where the area is now made up of plant species like Carex (Sedge), Juncus, Diochanthium and herbs like Caltha, Polygonum, etc. They form a mat like vegetation with their much branched rhizomatous system. Finally the marshy vegetation disappears due to the development of mesic conditions. |
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| f) Wood land stage |
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| First the peripheral part of the area is invaded by some shrubby plants, which can tolerate bright sunlight and water logged conditions. Plants that grow are Cornus (Bogwood), Cephlanthus (Button brush), etc. The next to invade trees are Populus (Cottonwood), Almus (Alder), etc. Further fall in the water table, along with mineralisation and soil buildup favours the arrival of plants for next seral community. |
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| g) Forest stage |
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| It is the formation of climax community, which depends upon the climatic conditions. For e.g., 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. |
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| Stages of Plant Succession of Plant Succession in a Lake or Pond (Hyrosere) |
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| Ecological succession is of great importance as |
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| i) It provides information, which help to have control on the growth rate of one or more species in a given geographical area. |
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| ii) It helps in reforestation and forest management programmes. |
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