Ecological Succession

Ecological succession

sequence of community and ecosystem changes after a disturbance.

Primary succession

occurs where no soil exists when succession begins.

primitive substratum

Primary succession starts from the

Primary succession

refers to colonization of a newly exposed landform, such as sand dunes or lava flows after a volcanic eruption

Secondary succession

begins in an area where soil remains after a disturbance.

previously built up substrata with already existing living matter.

Secondary succession starts from

Secondary succession

describes the return of an area to its natural vegetation following a disturbance

1. Pioneer community

2. Secondary community

3. Climax community

Stages of Ecological Succession

pioneer species or primary colonizers.

organisms which first colonize the region

Pioneer species

must be able to withstand the adverse climatic and edaphic conditions existing in the area.

Secondary community

• Intermediate communities that appear for a shorter time and are replaced in succession.

• Substrate has been occupied by aggregate of organisms.

Climax community

• final stable community formed at the end of succession exists for a longer period and is self-perpetuating and in equilibrium with the physical habitat.

• no net annual accumulation of organic matter

Hydrosere, Xerosere, Mesosere, Halosere

Types of Succession Based on Nature of Environment

Hydrosere or Hydrarch

succession begins from a water body. (lake, pond, stream, bog or swampy area.)

Xerosere or Xerarch

succession begins from the dry conditions with very little moisture content, (desert area, sandy areas, rocks.

Lithosere

starts in rocky areas

Psammosere

starts in a sand dune

Mesosere or Mesarch

succession starts in an area with adequate moisture conditions and temperature.

Halosere

occurs in a saline area i.e. where concentration of salt in the substratum is very high.

without any soil

Terrestrial Primary Succession Begins in a place

nitrogen

In order for there to be soil there must be nutrients like

1. maintain their mix of species for a long time

2. tend to have many specialized niches

3. Have many more kinds of organisms and kinds of interactions among organisms

4. recycle nutrients and maintain a relatively constant biomass

Climax Communities

Hydrosere

succession starts in a water bodies like pond and ends in a climax community as a forest.

Phytoplankton Stage

Unicellular floating algae such as diatoms, blue-green algae and bacteria are pioneer species in a water body.

Submerged Stage

Rooted submerged hydrophytes (aquatic plants with roots but remain under water) like Hydrilla, Utricularia, Elodea, Vallisenaria and Potamogeton invade when the pond is a bit shallower and contains organic matter.

Rooted Floating Stage

Several root bearing plants and having large floating leaves invade the pond, when it is about 2-5 feet deep

Reed-Swamp Stage

The roots of these plants remain buried in the muddy soil while their above ground parts are exposed to air. This stage is also known as amphibious stage since plants are found in the semi-aquatic conditions.

Sedge-Meadow stage

The pond becomes very shallow with reduced water and accumulated soil rich in salts and organic matter.

Woodland Stage

With the pond becoming constantly drier, many terrestrial plants invade the area and establish there.

Forest Stage

When the pond is completely turned into land, many tree species invade the area depending upon the climatic conditions.

Eutrophication

• Occurs when excessive nutrients enter an aquatic ecosystem and stimulate rapid producer growth.

• Natural process, but humans ACCELERATE. (Fertilizers such as N and P)

Algal bloom

Excess Nitrogen and Phosphorus enter lake causing

hypoxic

starved of oxygen

dead zones

Hypoxic zones harbor bacteria that emit dihydrogen sulfide (rotten-egg gas), a poison for other life. These areas are sometimes called