Hydrosere

The early changes are allogenic as inorganic particles such as sand and clay are washed from catchment areas and begin filling the basin of the water body.

They settle down to the bottom of the pond after death, and decay into humus that mixes with silt and clay particles brought into the basin by run off water and wave action and form soil.

Inorganic sediment is still entering the lake and is trapped more quickly by the net of plant roots and rhizomes growing on the pond floor.

The large and broad leaves of floating plants shade the water surface and conditions become unsuitable for growth of submerged species which start disappearing.

[1][3] The pond is now invaded by emergent plants such as Phragmites (reed-grasses), Typha (cattail), and Zizania (wild rice) to form a reed-swamp (in North American usage, this habitat is called a marsh).

[1] Successive decreases in water level and changes in substratum help members of Cyperaceae and Graminae such as Carex spp.

The habitat becomes suitable for invasion of herbs (secondary species) such as Mentha, Caltha, Iris, and Galium which grow luxuriantly and bring further changes to the environment.

These plants react upon the habitat by producing shade, lower the water table still further by transpiration, build up the soil, and lead to the accumulation of humus with associated microorganisms.

It may be a forest if the climate is humid, grassland in case of sub-humid environment, or a desert in arid and semi-arid conditions.

A forest is characterized by presence of all types of vegetation including herbs, shrubs, mosses, shade-loving plants and trees.

The center is occupied by floating and submerged plants with reeds nearer the shores, followed by sedges and rushes growing at the edges.

[3] Sweetmere is one of many small kettle lakes which formed at the end of the last glacial period when the temperatures began to increase.

As the climate slowly began to warm this allowed algae, water lilies and floating aquatic plants to begin to colonise the lake.

Once these began to die it provided organic matter to the lake bed sediment and therefore increased fertility and reduced depth.

Because the bulrushes and reeds have relatively deep roots, this encouraged bioconstruction which traps more sediment, allowing sedges, willow and alder to become established.

The lake exhibits characteristic features of a hydrosere, the succession from a fresh water surface with small pioneer plant species to a sub-climax vegetation of alder and willow.