Ecological Succession

to differentiate the types of ecological succession

is the sequence of community and ecosystem changes after a disturbance

ecological succession

occurs where no soil exists when succession beings

primary succession

where does the primary succession begin/start?

starts from the primitive substratum, where there was no previously any sort of living matter

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

begins in an area where soil remains after a disturbance

• starts from previously built up substrata with already existing living matter. The action of any external force, as a sudden change in climatic

• describes the return of an area to its natural vegetation following a disturbance such as fire, tree fall or forest harvesting

secondary succession

what causes the community to disappear in secondary succession

factors, biotic intervention, fire etc. causes the existing community to disappear

what are the stages of ecological succession

1. pioneer community

2. secondary community

3. climax community

what do you call the organisms which first colonize the region?

the organisms which first colonize the region are called pioneer species or primary colonizers

pioneer species must be able to?

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

is driven by biological changes within the ecosystem itself

• as plant grow, they change soil conditions (e.g adding organic matter, altering pH), allowing new species to establish

autogenic succession

is driven by external environmental factors like floods, climate change, or human activity which force changes in the ecosystem

allogenic succession

what’s the difference between autogenic and allogenic succession

organisms modifying their environment (autogenic) from changes caused by external forces (allogenic)

is dominated by producers (autotrophs) like plants and algae, which convert sunlight into energy

• it typically happens in nutrient-poor environments where plants establish first, supporting herbivores and later carnivores

autotrophic succession

is dominated by consumers (heterotrophs) like bacteria, fungi, and decomposers

• this often occurs in environments rich in organic material, such as after a mass die-off (e.g a dead tree decomposing)

heterotrophic succession

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

• substrate has been occupied by aggregate of organisms

second community

• the 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

climax community

• there is no net annual accumulation of organic matter in a climax community. The annual production and use of energy is balance in such a community

what are the types of succession based on nature of environment

• hydrosere

• xerosere

• mesosere

• halosere

• if the successi9on begins from a water body

• for example in a lake, pond, stream, bog, or swampy area

hydrosere or hydrarch

if succession begins from the dry conditions with very little moisture content, for example, a desert area, sandy areas, rocks

xerosere or xerarch

starts in rocky areas

Xerosere or Xerarch: Lithosere

starts in a sand dune

Xerosere or Xerarch: Psammosere

is the succession starts in an area with adequate moisture conditions and temperature

mesosere or mesarch

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

halosere

examples of succession

a. terrestrial primary succession

b. aquatic primary succession

• begins in a place without any soil

• in the beginning there is only rock, sand, volcanic ash

• since there is no soil, there is no community

terrest5rial primary succession

in order for there to be soil there must be nutrients like?

like nitrogen

what are lichens?

lichens begin growing on the rocks. Over many years lichens break down rock into sand

• weathering and erosion break down rock into sand

do lichens need soil to survive

• lichens that do not need soil to survive

• in this case lichens are the pioneer species

• lichens grow larger. Some die. Decomposers arrive and break down the lichens. The dead lichens and waste materials of the decomposers enrich the sand. Nitrogen cycle begins. Eventually enough nutrients enter the sand and it becomes soil

what simple plants can grow in the new soil

• seeds are blown in by the wind or carried in by animals. Simple plants like mosses can grow in the new soil

• the plants grown and the soil gets enriched as plants die

can grown in the thicker, enriched soil

herbs and weeds

• the simple plants die, adding more organic material

• the soil layer thickens, and grasses, wildflowers, and other plants begin to take over

is a mature, stable community that is the final stage of ecological succession

climax community

• in an ecosystem with a climax community, the conditions continue to be suitable for all the members of the community

• any particular region has its own set of climax species, which are the plants that are best adapted for the area and will persist after succession has finished, until another disturbance clears the area

what are the climax communities

1. maintains 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

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

hydrosere

unicellular floating algae such as?

Phytoplankton stage: unicellular floating algae such as diatoms, blue-green algae and bacteria are pioneer species in a water body

• followed by zooplanktons

• they settle down to the bottom of the water body after their death and decay and add organic matter and nutrients

• as soil builds up, the pond becomes shallower and favors the growth of the next seral stage

phytoplankton stage

aquatic plants with roots but remain under water

rooted submerged hydrophytes

• like Hydrilla, Utricularia, Elodea, Vallisenaria and Potamogeton invade when the pond is a bit shallower and contains organic matter

what is rooted floating stage

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

• these are Nelumbo, Nymphaea, Trapa and Monochoria

• These become associated with other free-floating plants like Lemna, Salvinia, Azolla and Wolffia. With the dense growth of these plants, the water level of the pond further decreases and become rich in salts and organic matter

what is the reed-swamp stage

• this stage is dominated by plants Typha, Sagittaria and Scirpus

• 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

the species that colonize such areas are the grasses and sedges

sedge-meadow stage