Hydrosere(long questions 8 marks) botany

 Process of Succession in hydrosere

Succession means the natural development of a series of biotic communities one after the other in the same area, till a permanent climax community is reached.

Hydrosere is an ecological succession that occurs in aquatic environment. If the body of water is large and very deep and other powerful factors are at work the succession results in stable aquatic community in which any considerable further change is hardly recognizable.Succession takes place in artificial small and shallow ponds, lake etc. where wave actions speed up the process by allowing the erosion of soil towards the edges. In this way, the filling process also speeds up quickly and water disappears within few years time. The process of aquatic succession completes in following steps.—

Phytoplankton stage In the initial stage of succession algal spores is brought in the body of water. All these organisms add large amount of organic matter and nutrients due to their various life activities and after their death, they settle at the bottom of pond to form a layer of muck.
when a loose layer of mud is formed on the bottom of the pond, some rooted submerged hydrophytes begin to appear when water depth is about 10 feet or more. The plants appearing at his stage are 1.hydrilla 2. potamogeton, 3.utricularia, 4.vallisneria 5. chara etc. When these plants die, their remains are deposited at the bottom of the ponds. The eroded soil is also deposited
Floating stage–

when the depth of water reaches about 4 to 8 feet, the submerged vegetation starts disappearing and floating plants make their appearance. Important floating plants are:-

• Trapa 2. Pistia 3. Nymphaea  4. Nelumbo. More water and air borne soil and dead remains of plants are deposited at the bottom.

4. Reed swamp stage– when the ponds and lakes become too shallow the habitat is changed so the floating plants start disappearing and their places are occupied by amphibious plants. Important plants are- 1.typhia 2. Sagittaria 3. Phragmites

5. Sedge marsh or meadow stage– The filling process finally results in a marshy soil which may be too dry for the plants of pre existing community. The plants well adopted to marshy habitat start to appear. Important plants of marshy habitat are the member of cyperacae and garminae like- 1. Juncus Cyperus 3. Iris 4. Caltha

These plants are than replaces by mesic(moderately moist habitat) communities.

6. Woodland stage– IN the beginning some shrubs and medium sized trees from open vegetation or woodland. These plants produce more shade and absorb and transpire varying quantity of water. Important plants are-1. Salin  2.cornus 3. Terminalia

Climax forest (forest stage)– after a very long time the hydrosere may lead to the development of climax vegetation . As the level of soil is raised much above the water level the habitat becomes more dry and in such a habitat well adopted self maintaining and self reproducing nearly stable plant community of woody trees develop.

• important question botany grade 11