Henry Lansdell - 3706
ECOSYSTEMS: NATURAL PLANT SUCCESSION
The composition of vegetation depends on the interaction between all of the components that make up
the ecosystem/environment, both biotic and abiotic factors. These include natural factors including
climate, relief and soils in addition to human influence through such activities of deforestation, forest
fires, and livestock grazing. Plants shall ultimately survive under suitable conditions for that specific
species, dependant on plant characteristics, environmental factors and competition. The population if
plants vary from one area to another, and become increasingly complex over time, this change in a
plant community named conclusively as a succession.
Definitions
Succession: A series of changes that take place in a plant community over time.
Sere: An individual stage within a plant succession.
Primary Succession: Primary succession occurs on surfaces that have had no previous vegetation
(such as bare rock and sand dunes).
Secondary Succession: A succession taking place upon land that was formerly vegetated, but has
experienced previous loss of this vegetation. Common influence of vegetation loss involves external
physical and human factors including landslides and wind damage or perhaps deforestation or forest
fires for agricultural grazing.
Fig 1. An example of a plant succession
upon a bare rock, otherwise known as a
lithosere.
Development of a Succession
A plant succession progresses through a series of stages (known as seres) in which each have
differentiations regarding composition of biotic and abiotic conditions, these stages being connected
to each other in a chronological order. These seres involve the processes of invasion, colonisation,
competition, domination and decline respectively.
1. Invasion (Pioneer Stage)
This initial process of invasion involves the introduction of the pioneer species through dispersal
methods, and initially triggers the plant community succession. This introduction can be performed in
Henry Lansdell - 3706
a variety of ways, such as; wind dispersal of seeds into a new area, faecal matter from animals or
potentially tide introduction (clearly dependant on the topography of the area). The pioneer species
are particularly ‘hardy’ plants, adapted to survive and develop within the harsh environment through a
range of physical characters; these varying upon the species and environment. Furthermore, the roots
of the pioneer plants aid in enhancing the soil formation; by breaking it up and weathering the surface.
Pioneers compete for available space, light, nutrients; and as they decay modify the soil quality with
the addition of nutrient within organic matter through a process of humification.
2. Colonisation
As the soil quality is enhanced (added nutrients) through the decomposition of plants (creating
organic matter), other plants have the ability to colonise and alter the existing balance of species, thus
broadening the biodiversity of the area. As each stage of colonisation progresses, the soil condition is
gradually improved for plant growth than the previous through the organic matter; specifically
through improving its physical structure and water retention qualities. Additionally, taller and more
aggressive species which are more demanding of nutrients are introduced with time in which shall
provide shade, potentially establishing other plants in which are tolerated to such conditions.
3. Competition
As the expansive range of plant species are developed within a succession, it can be presumed that all
of these plants shall be competing for light, space and nutrients. These plants require sufficient
nutrients, light and space in order to survive and develop; though with so many plants competing for
the same requirements within the same region, there is a deficit of each variable.
4. Domination
In each stage of a plant succession, there are dominant plants, and are typically the tallest plants in
which cover the most ground, and clearly height. These tend to overpower those other minor species
due to the correct environmental conditions, and can therefore utilise this in mass growth of more
profit. This specific species shall continue to compete with the other species, however have the
significant advantage due to the height (being able to take sunlight and water before lower-lying
plants).
5. Decline (Climatic Climax Stage)Lastly, as the domination proceeds of the species, it will enter
stage where the predominant plant out-competes all of the others due to their tall nature; through
shade, space, light and water. This then enters a stage called the climatic climax, defined as being
the stage where the vegetation is in equilibrium with the environment. This therefore means that
the natural vegetation has reached delicate yet stable balance with the climate and soils of an area.
The climatic climax on this basis features relatively few species of plant, that have out competed
those others due to being best adapted to the environment (typically being the taller and larger
species).
Fig 2. An image of a “climatic
climax”, as portrayed with the
tall and large species of tree.
These are able to reach
sunlight and water through the
canopy layers prior to other
plants, and thus evidently outcompeting smaller species of
plant.