Discuss various stages occurring in a hydrosere formation.

Explanation

Biotic Succession In Newly Form. Pondflake (Hydrosere). Serve of biotic communities that develop in a newly formed pond or lake is called hydrosere. It starts as soon as the muddy water becomes clear. The various successional or send stages of hydrosere are :—
1. Plankton Stage. It is the pioneer stage of hydrosere. Spores of this stage reach the water body through wind or animals. The first to appear are minute autotrophic organisms called phyloplankton, e.g., diatoms, green flagellates, single- celled colonial or filamentous green algae as well as blue-green algae. They multiply rapidly. Soon a balance is created by the appearance of zooplankton which feed on phytoplankton. Death and decomposition of plankton produce organic matter. The latter mixes up with clay and silt at the bottom tb form soft mud favourable for growth of next sera stage.
2. Submerged Stage. The bottom lined by soft mud having organic matter is favourable for growth of submerged plan. like Hydrilla Potamogeton and Najas .limy are rooted in the mud and form dense growth. As a result sand and silt get deposited around the plants. The bottom level, therefore, rises slowly. The older plants and buried parts of other plants form humus on their death .d decay. llns enriches the newly built up bottom and makes it favourable for growth of next stage.
3. Floating Stage. Floating leaved anchored plan. (e.g., Nymphae. Nelumbo, Nuphar)appear where water becomes shallow. These plants have subterranean stems like rhizome and tub. The plants make the water rich in mineral and organic natter. It becomes suitable for growth of tree floating plan. like Lemna, Spirodela, Wholfiila Azolla, Eichhoria , etc. They cover the water quickly. Rapid growth of floating stage further builds up bottom so that water becomes shallow .
4. Reed Swamp Stage. Amphibious plants grow where the water body becomes shallow (0:3-1.0 m), e.g.. Phragmites ,Typha,scirpus,sagittaria The plants of Reed swamp stage transpire and produce abundant organic matter and their growth accumulates silt.
5 Sedge or Marsh Meadow Sage. The shores built by above stage arc invaded by Carex (Sedge). fences, Cyperus, Cgrasses . Dlchantium and herbs like Polygonum, companule etc. he plants transpire and add enormous humus. So soil is built up and create condition for invasion of next stage.
6. Woodland Stage. The periphery of sedge meadow stage is invaded by some rhizome bearing shrubby plants which can tolerate bright sunlight as well as water logged conditions, e.g.. cornus, (Bogwood), Cephalanthus (Button Brush). The shrubs shade away the plants of sedge meadow stage. They invite invasion by trees capable of bearing bright sunlight and waterlogging, e.g., Popular (Cottonwood), Alms (Alder). The plants of woodland stage lower the water table by their transpiration. They also built up more soil. Shade loving plants come to grow below them.
7. Climax Forest. New trees invade the area They have shade loving seedlings. These trees grow to greater heights.l. trees and shrubs of woodland stage disappear. The climax forest depends upon the climate— rain forest in moist tropical area and mixed coniferous or deciduous forest in temperate area. A mixed temperate forest includes broad leaved trees like Quercus (Oak), Ulmus (Elm) and Aces and gymnosperms like Able: (Fir), Taxus (Yew) and Picea (Spruce).