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Succession
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Succession
Succession is the name given to the replacement of a plant species, by another species,
or a group of species over time. In simple terms it refers to how plant communities
change with distance away from ‘something’. This ‘something’ could be bare rock, a
water body or a number of other things. There are many different types of succession
and although you may not realise it, succession is occurring all the time in a variety of
circumstances.
Types of succession
Lithosere – Rock
Hydrosere - Water
Xerosere – Dry conditions
Halosere – Salty conditions
Psammosere – Sandy conditions
No matter what type of succession you are studying, they all start and end in the same
way. Diversity, stability, and soil depth all start being sparse or nonexistent and then
move to a flourishing community of different species due to more pleasurable growing
conditions. In biological terms succession starts with a pioneer species and ends up in
with a climax community.
Copyright ©2012
Naturalinfo.co.uk
Author: Liam Ring
Succession
Naturalinfo.co.uk
Lithosere
I’ll start off by explaining the changes which occur within a ‘lithosere’ (Succession from
bare rock). The picture above shows a transect being laid out in a rocky environment.
The transect starts in the ‘bare’ rock and ends in the woodland at the bottom of the
slope. I have used the word ‘bare’ rock as if you look closely you can see that the rock
isn’t actually ‘bare’ at all. Species of Lichen are living on the rocks and these are the
pioneer species in this particular rocky environment. Lichen is a symbiotic relationship
between algae and fungi, this means that although it may not look particularly exciting it
is a living organism which is respiring, photosynthesising, and it will eventually die. The
death of lichen brings an extremely primitive soil to the lithosere. This primitive soil
however can hold water and has some nutrients and therefore certain mosses can start
to grow. Mosses are a more ‘substantial’ organism than lichens and therefore when they
die they leave behind more soil which allows grass species to move in. The grass species
have root systems which enter the soil and bind it together meaning that it stays in
place. As the soil is now not going to move anywhere it means that other organisms that
die will be adding to the soil formation meaning that soil can start to build up. As the
Copyright ©2012
Naturalinfo.co.uk
Author: Liam Ring
Succession
Naturalinfo.co.uk
soil builds and builds it becomes less acidic or alkaline (depending on the ‘bare’ rocks’
original composition), more nutrient rich, and stabilised, which allows woodland
species, and trees to grow. It is theses changes in abiotic (non-living) factors which lead
to a change in species diversity and presence. pH, light availability, soil depth, soil
moisture, wind speed, and a host of other abiotics will change as succession occurs.
Different plant species thrive in different conditions and therefore they either grow at
the top, middle, or bottom of the successive sequence.
Hydrosere
The same principles occur no matter where succession is happening however it is worth
explaining how hydrosereal succession is different from lithoseral etc..
Hydroseral succession refers to how plant species change within a water environment.
This normally refers to freshwater ponds, lakes, rivers, or streams. Hydroseral
succession like all types of succession happens naturally over time. The pioneer species
with hydroseral succession is mainly algae. When algae die they sink to the bottom of
the ‘hydro’ environment. For the sake of example I have chosen a lake to explain the on
goings of a hydrosere. When the algae reach the bottom of the lake they break down and
form a ‘soil’ at the bottom of the lake, this then allows submerged plants to grow, also
Copyright ©2012
Naturalinfo.co.uk
Author: Liam Ring
Succession
Naturalinfo.co.uk
known as hydrophytes. These plants then die leading to a larger build up of organic
matter at the bottom of the lake, which in turn allows more plant species to grow. This
process continues until the land and the water body (lake) become ‘joined’. This will
occur at the edge of the lake as species such as mosses, and bedstraws stabilise the area.
When the species at the edge of the lake die this leads to more soil being built up, this in
turn leads to a woodland community forming due to the changes in abiotic conditions
brought on by the species dominating the environment previously.
Copyright ©2012
Naturalinfo.co.uk
Author: Liam Ring