Ecological succession is the orderly progression of a vegetation community through developmental stages over time, eventually reaching a climax community. The key stages are: 1) Pioneer species first colonize the bare ground, exploiting the lack of competition. Moss and other low-growing plants are common pioneers. 2) After a few years, competition and environmental changes increase as the number of species grows. Soil develops, temperatures moderate, and nutrients rise with more complex food webs and larger herbivores present. 3) Further successional stages occur until a stable climax community is reached that is in equilibrium with the local climate and environment. In the UK, deciduous oak woodland is a common climax community

1. ECOLOGICAL
SUCCESSION
the orderly progression of a vegetation
community, through a series of
developmental stages, reaching equilibrium
in a climax community.

2. Volcanic island

3. Forest fires in Australia

4. Abandoned parking area

5. Glacial retreat/moraine

6. Pioneer Species
bare ground conditions favour pioneer plant species.
Species which grow best where there is little
competition for space and resources. (moss)
moss are low growing, carpeting the ground
and with little height. Mosses are unable to successfully
compete for space amongst taller, dense
ground cover.
often have light seeds, which are easily
transported by the wind.
seeds which rapidly germinate and do not require
dormancy.
grow quickly, reproducing themselves before slow other slower-
colonising species arrive to out compete them.
often ‘opportunist’ species which are able to rapidly
exploit a sudden new opening in ground plant
cover.

7. QUICK QUESTION
How would bare ground which has just started to be
colonised by pioneer species differ after 2 years in:
competition, soil structure, ground temperature and
nutrient levels?

8. In the process of succession, the
species present in an area will
gradually change.
Bare ground Two years later
No plant competition for light, space, nutrients or water. Intense plant competition for space and other resources.
Soil mobile and liable to erosion and loss. Soil bound by roots and plant cover
A more extreme surface microclimate because the bare The plant cover provides a certain amount of ground
soil both absorbs and reflects heat more than soil covered insulation from extremes of temperature. There are now
in vegetation also a variety of microclimates within the vegetation.
A drier environment because there is no plant cover to
Plant cover and increasing humus levels help to retain
hold moisture above ground and little humus to hold it in
water.
the soil.
Lower nutrient levels in the soil. The nutrient levels in the soil will have increased.

9. environmental conditions on the same patch of ground are very different to the
conditions when the first pioneers arrived.
a variety of longer-lived, slower colonisers have displaced many of the species in the
early pioneer community.
plants are not the only colonisers. Herbivorous invertebrates which feed on those
particular plant species have arrived. These then attract a range of carnivorous
invertebrates to feed on them.
larger herbivores such as rabbits and deer will also graze this area.
the soil will be enriched as the dung is recycled by the dung-dwelling community.
the simple food chains of the earliest pioneer stage, when few species were present,
have developed into more complex foodwebs.
many, if not all of the environmental changes have been brought about by the
communities living there. During the processes of living, growing and reproducing,
species interact with and modify their habitat.
in 2 years, the biodiversity (variety of life) on the bare patch of ground has soared,
as it has been colonised by fungi, plants and animals. The ecosystem has developed
from a very simple one with few interactions, to a much more complex system with
a staggering number of interactions going on between individuals, species and the
habitat itself.

10. Climax Community
If left undisturbed, the area will pass through a number of
further different successional stages, each with
its own characteristic mix of species. All of n these
different successional stages are known as a collectively as a
sere.
Each new community will be better adapted to the the
changed environment which has been provided provided by the by
the previous community.
Eventually, a climax or ‘final’ community is reached. At
reached. At this point, succession will not er
further.
Climax community is in a stable equilibrium
with prevailing climate. Abiotic factors such as
climate determine dominant species of that
community.
In the UK, this is most likely to be deciduous
oak woodland.

11. Primary Succession
is found on a new land surface or in water and various
seral stages are passed through before climatic climax is
reached. It is an orderly sequence of events where one
community is replaced by another. Biomass is created
via decomposition and provides more nutrients for the
soil allowing for greater and variety of plants and
animals to exist at each successive seral stage:

12. Secondary Succession
if succession is halted before reaching dynamic
equilibrium a secondary succession occurs.
Interruptions include fire, disease, climate change and
deforestation.
more rapid - spores and seeds remain in soil.
does not begin with pioneer species, but one of the
subsequent successional stages.
land alteration will mean some of the species in the
climax community will be different.

13. Polyclimax
If sub-climax is due to local variations in soil etc.

14. Plagioclimax
If sub-climax is a consequence of human activity.
Management practices of humans (burning, clearing
and grazing of land, urban and transport
developments).

15. Hydrosere
Succession which starts in fresh
water.
A wetland, which is a
transitional area between open
freshwater and dry land,
provides a good example of this
and is an excellent place to see
several stages of a hydrosere at
the same time.

16. Halosere
Succession which
starts in salt water.
A salt marsh

17. Lithosere
Succession which starts on
newly exposed rock surface.
Examples, one left bare as a
result of glacial retreat or
volcanic eruptions.

18. Psammosere
Succession which
starts on sand surface.
Sand dunes