8.2

The Process of Colonization

and Succession

An introduction

• Ecosystem is defined as a self-suporting system of organisms interacting with each other and also with the non-living organisms

Colonization and Succession

Human activities (e.g. : mining) and natural disasters

(e.g. : earthquake)

Barren land with non-living organisms

Colonization

Climax community

Succession

First species to arrive

at the new habitat is called the

PioneerSpecies

Colonization?

• The arrival of organisms to live, reproduce and take over the new habitat

Phytoplanktons

Hydrilla sp.

Elodea sp.

Submergent Plants

• These plants spend their entire lives underwater. Bladderworts and horntails are examples. Submergent plants provide structure for aquatic insects to climb on and food for animals, such as ducks and snails.

Submerged plants

• Submerged plants spend their entire life cycle beneath the surface of the water. Nearly all are rooted in the substrate. Submerged plants take up dissolved oxygen and carbon dioxide from the water column.

Succession?

• The process where the pioneer species change the conditions of the habitat making it more suitable for other species to take over

Floating plants

Floating-leaved plants

• Floating-leaved plants have leaves that float on the water’s surface while the roots are anchored in the substrate. Stems connect the leaves, which are circular or oval and have a tough leathery texture, to the bottom.

Emergent plants

Emergent plants

Emergent

• Emergent wetland plants are rooted in soil with basal portions that typically grow beneath the surface of the water, but whose leaves, stems (photosynthetic parts), and reproductive organs are aerial. Examples of emergent plants include cattails and rushes.

Floating Plants

• These plants float on the surface film of the water. Some, the duckweeds, float freely, with tiny roots dropping down into the water.

• Others, like lily pads, have wide leaves that float on the surface and long stems that reach all the way down to the pond bottom where roots lay in the mud.

• Lilies grow in huge colonies and can sometimes cover the entire surface of a pond. Floating plants provide cover for fish and other underwater creatures.

Climax community?

• A stable and mature community which undergoes little or no change in species structure

Shrubs and bushes?

• A shrub or bush is a horticultural rather than strictly botanical category of woody plant, distinguished from a tree by its multiple stems and lower height, usually less than 5-6 m (15-20 ft) tall.

Shrubs

Shrubs

Bushes

Pond succession

Part II

Mangrove swamp

mangrove swamp?

• –noun – a coastal marine swamp of tropical or

subtropical regions that is dominated by mangrove trees.

• Mangrove swamps are mostly found in the tropical and subtropical region where fresh-water meets salt water.

•They have muddy soft soil and are a hostile environment for normal plants. This is because the soil has very low levels of oxygen and a high concentration of salt.

• In addition, mangrove swamps are exposed to high intensities of sunlight and strong winds.

The green tunnel of mangrove in

Sihcao, Tainan, Taiwan

The root systems of mangrove plants

The root systems of mangrove plants

Pneumatophores?• Specialised aerial roots that enable plants to breathe air

in habitats that have waterlogged soil.

• The roots may grow down from the stem, or up from typical roots.

• Some botanists classify these as aerating roots rather than aerial roots, if they come up from soil.

• The surface of these roots are covered with lenticels which take up air into spongy tissue which in turn uses osmotic pathways to spread oxygen throughout the plant as needed.

•Black mangrove is differentiated from other mangrove species by its pneumatophores.

Above and below water view at the edge of

the mangrovel

Pneumatophore penetrates the sand surrounding the mangrove tree.

Mangroves have evolved a special mechanism to help their offspring

survive.

Salt crystals formed on

grey mangrove leaf

A mangrove of the genus Sonneratia,

showing abundant pneumatophores

Types of mangrove tress

Avicennia sp.

Sonneratia sp.

• The pioneer species of a mangrove swamp are the Sonneratia sp. and Avicennia sp.

• The presence of this species gradually changes the physical environment of the habitat.The extensive root systems of these plants trap and collect sediments, including organic matter from decaying plant parts.

• As time passes, the soil becomes more compact and firm. This condition favours the growth of Rhizophora sp. Gradually the Rhizophora sp. replaces the pioneer species.

Rhizophora sp.

• The prop root system of the Rhizophora sp. traps silt and mud, creating a firmer soil structure over time.

• The ground becomes higher. As a result, the soil is drier because it is less submerged by sea water.

• The condition now becomes more suitable for the Bruguiera sp., which replaces the Rhizophora sp.

Bruguiera sp.

• The buttress root system of the Bruguiera sp. forms loops which extend from the soil to trap more silt and mud.

• As more sediments are deposited, the shore extends further to the sea. The old shore is now further away from the sea and is like terresterial ground.

• Over time, terrestrial plants like nipah palm and Pandanus sp. begin to replace the Bruguiera sp.

---------Water-------------------------------

Avicennia sp.

Sonneratia sp.

Rhizophora sp. Bruguiera sp.

---------Water-------------------------------

Avicennia sp.

Sonneratia sp.

Rhizophora sp. Bruguiera sp.

---------Water-------------------------------

Avicennia sp.

Sonneratia sp.

Rhizophora sp. Bruguiera sp.

Pneumatophore

Prop roots

Buttress roots