Ecological Succession 2

Ecological succession is the gradual process by which ecosystems change and develop over time.

For example, a bare patch of ground will not stay bare. It will rapidly be colonized by a variety of plants.

Recently cleared ground to the front of the log cabin. The bare ground is now covered by a great variety of different grass species and  other  herbaceous flowers.

A recently cleared patch of ground (in Britain).

The same ground 2 years later,
now covered in grasses and low flowering plants.

In the process of succession, the species present in an area will gradually change.

Succession takes place because the environmental conditions in a particular place change over time. Each species is adapted to thrive and compete best against other species under a very specific set of environmental conditions. If these conditions change, then the existing species will be replaced by a new set of species which are better adapted to the new conditions.

As an example, the environmental conditions present on the bare patch of ground above would have been quite different 2 years later. Some of these differences are highlighted below.

Bare Ground Two Years Later

No plant competition for light, space, nutrients or water.

Soil mobile and liable to erosion and loss.

A more extreme surface microclimate because the bare soil both absorbs and reflects heat more than soil covered in vegetation.

A drier environment because there is no plant cover to hold moisture above ground and little humus to hold it in the soil.

Lower nutrient levels in the soil.

Intense plant competition for space and other resources.

Soil bound by roots and plant cover.

The plant cover provides a certain amount of ground insulation from extremes of temperature. There are now also a variety of microclimates within the vegetation.

Plant cover and increasing humus levels help to retain water.

The nutrient levels in the soil will have increased.

The bare ground conditions favour pioneer plant species. These are often species which grow best where there is little competition for space and resources.

Mosses are often pioneer species. Mosses are often pioneer species. Most moss species are low growing, carpeting the ground and with little height. As a result of this growth form, many mosses are unable to successfully compete for space amongst taller, dense ground cover.

This makes bare ground ideal for the establishment of a number of different moss species. These mosses then provide a microhabitat equivalent to a miniature forest for a variety of invertebrates such as mites and spiders. The moss also acts like a sponge when wet, in some cases providing a semi-aquatic microhabitat.

Dandelion - Taraxacum officinalis agg. Pioneer species are often also 'opportunist' species which are able to rapidly exploit a sudden new opening in ground plant cover.


Left: Dandelion


Typical examples in the UK would be dandelion, Foxglove and willowherb.



Seeds arrive, germinate and grow quickly, rapidly reproducing themselves before other slower-colonizing species arrive to outcompete them.

Along with the plants will come the animals which feed on them or use them for shelter.



Left: Bee on Foxglove

Bumble Bee on Foxglove - Digitalis purpurea
Ragwort seed. Pioneer species are often characterized by having light seeds, which are easily transported by the wind. Many of them belong to the flowering plant family 'Compositae'

Such plants produce large numbers of seeds with parachutes of fine hairs which help to keep them afloat in air currents.


(Left: Ragwort seed)




Succession Contents