plant succession

plant succiession with types and summry

1. 2018







Plant succession

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Contents


Introduction………………………… .0-1
History……………………………….0 -2
Types of succession………………… .2-3
Stages of Plant sucession……………4 -7
Process of Plant succession…………8-9
Major trends during Succecssion……0-9
Causes of Plant succession………….9-10
Reference……………………………0 -12

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Plant succession
Introduction
Succession is a directional non-seasonal cumulative change in the types of plant species that
occupy a given area through time. It involves the processes of colonization, establishment, and
extinction which act on the participating plant species. Most successions contain a number of
stages that can be recognized by the collection of species that dominate at that point in the
succession. Succession begins when an area is made partially or completely devoid of vegetation
because of a disturbance. Some common mechanisms of disturbance are fires, wind storms,
volcanic eruptions, logging, climate change, severe flooding, disease, and pest infestation.
Succession stops when species composition changes no longer occur with time, and this
community is said to be a climax community.
The concept of a climax community assumes that the plants colonizing and establishing
themselves in a given region can achieve stable equilibrium. The idea that succession ends in the
development of a climax community has had a long history in the fields of biogeography and
ecology. One of the earliest proponents of this idea was Frederic Clements who studied
succession at the beginning of the 20th century. However, beginning in the 1920s scientists
began refuting the notion of a climax state. By 1950, many scientists began viewing succession
as a phenomenon that rarely attains equilibrium. The reason why equilibrium is not reached is
related to the nature of disturbance. Disturbance acts on communities at a variety of spatial and
temporal scales. Further, the effect of disturbance is not always 100 percent. Many disturbances
remove only a part of the previous plant community. As a result of these new ideas, plant
communities are now generally seen as being composed of numerous patches of various size at
different stages of successional development.
History
Mechanisms of succession has been produced by Connell and Slatyer (1977, American
Naturalist. Connell and Slatyer propose three models, of which the first (facilitation) is the
classical explanation most often invoked in the past, while the ot her two
(toleranceand inhibition) may be equally important but have frequently been overlooked.
The essential feature of facilitation succession, in contrast with either the tolerance or inhibition
models, is that changes in the abiotic environment are imposed by the
developing plant community. Thus, the entry and growth of the later species depends on earlier
species preparing the ground.
The tolerance model suggests that a predictable sequence is produced because different species
have different strategies for exploiting resources. Later species are able to tolerate lower

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resource levels due to competition and can grow to maturity in the presence of early species,
eventually out competing them.
The inhibition model applies when all species resist invasions of competitors. Later species
gradually accumulate by replacing early individuals when they die. An important distinction
between models is the cause of death of the early colonists. In the case of facilitation and
tolerance, they are killed in competition for resources, notably light and nutrients. In the case of
the inhibition model, however, the early species are killed by very local disturbancescaused by
extreme physical conditions or the action of predators.
Types of Succession
1. Primary succession : Lava has streamed down
over the lush landscape for thousands of years,
leaving smooth, black rock behind. However,
life can still take hold here through primary
succession, which starts in a barren environment.
Primary succession usually takes a long time,
since the ecosystem has to start from scratch.

2. Secondary succession:is like primary
succession fast forwarded. It doesn't start from a
barren location, but rather an ecosystem that has
been through a natural or man-made disaster,
such as a fire, clear-cutting, or a flood. The soil
and seeds present aren't destroyed, so species that appear much later in primary
succession, like shrubs and trees appear rapidly. Secondary succession skips the early
stages where rock needs to be broken down into soil.

3. Allogenic succession - is caused by a change in environmental c0onditions which in turn
influences the composition of the plant community. In Cornwall England, observations
on the estuary of the FalRiver suggest that
the deposition of silt may be causing an
allogenic succession from salt marsh to
woodland. Measurements indicate
sedimentation rates of about 1 cm per year
on the mud flats that are found 15
kilometers (9 miles) into the estuary. Over

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the last 100 years, this salt marsh has increased its elevation and has extended itself
seaward by 800 meters (2600 feet). The adjacent woodland has followed the salt marsh
by invading its landward limit.


4. Autogenic succession - is a succession where both the plant community and environment
change, and this change is caused by the activities of the plants over time. Mt. St. Helens
after the last volcanic eruption.

5. Progressive succession - is a succession where the community becomes complex and
contains more species and biomass over time.


6. Retrogressive succession - is a succession where the community becomes simplistic and
contains fewer species and less biomass over time. Some retrogressive successions are
allogenic in nature. For example, the introduction of grazing animals results in
degenerated rangeland.

Depending upon the nature of the habitat on which the plant
succession begins seven types of seres may be distinguished:

A. Hydrosere:
When succession start in aquatic habitat.It is succession occurring in the aquatic environment.
Such a type of succession does not necessarily lead the aquatic communities toward the
development ofl land communities

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A sere beginning on a wet area is often referred to as a hydrosere. It may proceed in open bodies
of water, such as ponds, lakes, and marshes etc.
Stages
Hydrosere consists following six seral stages:
I. Submerged stage:
In this initial seral stage, a number of submerged aquatic plants, such as Hydrilla, Elodea,
Potamogeton, Ceratophyllum, Najas, Vallisnaria, Utricularia, Ranunculus and several algae
occupy the shallow pond or lake, which, accumulating after death and decay, gradually raise the
bottom of the pond or lake. Silting may also be associated with this accumulation. The
inadequate oxidation of flora and fauna remains of the lake results in the formation of humus-
which makes the bottom of the lake firmer.
II. Floating stage:
As the bottom of the lake is raised, a second, or floating, stage follows, characterized by plants
like Nymphaea, Polygonum, Limnanthemum and Castalia etc. These plants are rooted in the
mud, and their broad leaves float on the surface of the water shading the submerged plants
below. Besides these, free floating plants like Azolla, Eichornia and Lemna may also make their
appearance. The death and decay of the submerged and free floating plants further raise the level
of the lake bottom and contribute further to the soil-building process. This initiates the next reed-
swamp stage.

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III. Reed-Swamp stage:
This stage is initiated in extremely shallow waters (i.e., hardly one to four feet deep). The area is
invaded by amphibious plants like Scirpus, Typha, Phragmites etc. These plants remain only
partly submerged in water.
Their rhizomes are profusely branched and they are rooted in the bottom of the lake. These
plants prevent light to reach submerged and floating plants which consequently die, and their
dead remains settle down on the lake bottom raising its level further.
Now a second group of plants, such as Sagittaria, Alisma and Acorus etc., invades the area.
Eventually the habitat is made unfit for the growth of the plants of reed-swamp stage. The soil
becomes dry enough to afford a foothold for terrestrial species.

(4) Sedge meadow stage:
Reed-swamp stage is followed by sedge-meadow stage which is characterized by plants like
Carex, Juncus and Eleocharis. The soil level continues to rise and soil organic matter continues
to increase. More competent and dominant plants, such as Mentha, Caltha, Iris, Galium,
Campanula and Teuricum etc., invade the area. By excessive transpiration and soil binding, these
species make the area too dry for any hydrophytic plant. This eventually leads to other-sub-
climax vegetation.
(5) Woodland stage:

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The sedge-meadow stage leads to the formation of heath land which remains saturated with
water in spring and early summer. A new sub-climax vegetation dominated by shrubs and small
trees make their appearance in this area. Important among these plants are Salix, Cornus,
Cephalanthus, Alnus and Populus etc. Due to shade of these plants grasses and sedges disappear
from the area. Shrubs and trees further lower the water table and bind the soil.
(6) Climax forest stage:
As more and more plants appear in the area, competition among these plants also intensify and
soil organic matter further increases, soil becomes more fertile and consequently the area is
invaded by larger trees. Competition then becomes less intense as the community becomes stable
and a climax state is reached. It may also be pointed out here that succession in water always
does not necessarily lead to land community. When succession starts in deep and large open
water it may lead to a stable aquatic vegetation.
B. Xerosere:
When succession initiates on a dry bare land.The succession occur in dry condition is called
Xerosere. Xerosere is a plant succession that is limited by water availability.
A xerosere usually includes the following six seral stages.

(1) Crustose lichen stage:
Succession on the bare rock surfaces begins with crustose lichens as pioneers. These lichens
migrate to the rocks by means of wind-borne spores and soredia. The lichens grow only when
enough moisture is available, but they can withstand drought conditions for long.
The lichens release carbon dioxide during respiration which after combining with water forms a
weak acid. The mechanical and chemical action of the lichens on the underlying rock, loosens
particles, which, together with decaying lichen remains form a thin layer of soil on the soil

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surface. The requisite nitrogen is brought in by rain and wind-blown dust. These lichen form
pioneer community.
(2) Foliose lichen stage:
Simple crustose lichens may be followed by larger, leafy forms, such as Parmelia,
Dermatocarpon. Umbilicaria, which grow on the slight accumulation of soil and humus Foliose
lichens further loosen the rock particles. They overshadow the crustose lichens which eventually
die and decay thus increasing the amount of humus in the soil.
(3) Moss stage:
Lichens are succeeded by mosses, which, like lichens, are able to survive in dry environment.
These mosses are xerophytic in nature and important among these are the species of Polytrichum
and Tortula.These mosses form an open community connected with a dense rhizoid system
which passes through and binds together a few millimeters of soil particles. Among the shoots of
these mosses wind and water borne soil continues to accumulate. The primary role of these
mosses is to stabilize the soil surface and to increase its water-holding capacity.
(4) Herbaceous stage:
The moss plants increase in number until a close carpet of moss is formed over the soil. The
mosses shade the lichens and successfully compote with them for water and nutrients which
eventually result in the death of the lichens. The death and decay of the lichens and old mosses
add to the amount of organic matter in the soil and still further increases its water- holding
capacity.
In his way the habitat is rendered suitable for the growth of higher plants and consequently a new
community of herbaceous plants, such as Festuca, Verbascum, Poa, Potentilla and Solidago etc.,
invade the area. The herbaceous plants over shadow the mosses, compete successfully with them
for space, water and nutrients. The soil increases in thickness by disintegration of the rock and
the decay of the various plant parts, more nutrients become available and next higher
community, dominated by shrubs, appear.
(5) Shrub stage:
Shruby plants, such as Rhus, Physocarpus, Symphocicarpous, invade the area, erstwhile
dominated by herbaceous plants, by means of seeds and underground rhizomes. The herbaceous
plants of the preceding stage, now shaded, tend to disappear. The death and decay of the
herbaceous plants further enrich the soil. As the shrubs grow in size and number, they continue
to modify the soil and make the habitat more and more suitable for the support of still higher
plants i.e., trees.
(6) Climax forest stage:

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The first tree species to invade the area are usually xerophytic in character, but as the soil
moisture increases, these are gradually replaced by mesophytic ones. The mesophytic species
compete successfully and become dominant because their seedlings are much more shade-
tolerant. Competition gradually becomes less intense as the community becomes stable and a
climax state is reached.
C. Lithosere:
It starts on a bare rock surface.A plantsuccessionthatoriginates on a rocksurface.An ecological
sere originating on rock.
D. Psammosere:
Initiating on sandy habitats. Here the pioneer community comprises sand-binding grasses with
runners, e.g. Spinifex and Ipomoea biloba.
E. Halosere:
It starts in saline soil or water. Here the pioneer plants usually have succulent leaves and stem
e.g., Suaedamaritima, Acanthus ilicifolius, Chenopodium, Basella and some species of
Asclapias.
Differences between Succession on Land and in Water:
Succession on Land:
1. It begins with lichens or blue green algae.
2. Initial succession is a slow process.
3. The whole of the area is involved in formation of climax community.
4. Succession converts xeric environment to mesic environment.
5. It reduces bare land area and converts it into fertile forest area.
Succession in Water:
1. begins with phytoplankton’s.It
2. Initial succession is quite fast.
3. Climax community develops on the edge only.
4. It converts aquatic environment into mesic environment.
5. It fills up water body and changes it into forest land.
Process of Plant Succession:
Major steps in a autotrophic succession are as follows:
1. Nudation:
An area is exposed.
2. Migration:
The process of dispersal of seeds, spores and other structures of propagation of the species to
bare area is known as migration.
3. Germination:
It occurs when conditions are favourable.

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4. Ecesis:
Successful germination of propagules and their establishment in a bare area is known as ecesis.
5. Colonisation and Aggregation:
After ecesis, the individuals of the species increase in number as the result of reproduction.
6. Competition and Co-action:
Due to limited resources, species show both inter and intraspecific competition. This results into
elimination of unsuitable and weaker plants.
7. Invasion:
Various other types of plants try to establish in the spaces left by the elimination of plants due to
competition.
8. Reaction:
The newly arrived plants interrupt with the existing ones. As a result of reaction, environment is
modified and becomes unsuitable for the existing community which sooner or later is replaced
by another community.
9. Stabilisation:
Finally, there occurs a stage in the process when the climax community becomes more or less
stabilized for a longer period of time and it can maintain itself in equilibrium with the climate of
the area. As compared to seral stage community, the climax community has larger size of
individuals, complex organization, complex food chains and food webs, more efficient energy
use and more nutrient conservation.
Major Trends during Succession:
1. There is an increase in structural complexity.
2. Diversity of species tends to increase.
3. Biomass and standing crop increase.
4. There is a decrease in net community production.
5. Increase in non-living matter.
6. Food chain relationship becomes complex.
7. Niche becomes special and narrower.
8. Energy use and nutrient conservation efficiency increases.
9. Stability increases.
Causes of Succession:
The main causes of succession are as follows:
(1) Climatic causes,
(2) Topographic causes, and
(3) Biotic causes.
1. Climatic causes:
Plants cannot adjust with the long range variations in the climate. The fluctuating climate
sometimes leads the vegetation towards total or partial destruction and, as a result, the bare area
develops which becomes occupied by such plants as are better adapted for changed climatic

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conditions. Drought, heavy snowfall, hails and lightning’s are some of the important factors for
the destruction of vegetation. Sometimes new bare ground is formed by emersion of land from
the bodies of water (ponds, rivers etc.).
2. Topographic causes:
These are concerned with the changes in the soil.
The following are two important soil factors which bring about changes in the habitat:
(i) Erosion of the soil:
Sometimes surface soil is removed by a number of agents, such as wind, water currents, and
rainfall. This process is known as soil erosion. In the process of erosion new and bare area is
exposed in which new plant communities begin to appear one after another.
(ii) Soil deposition:
It is one of the important causes that initiates succession. Soil deposition results owing to heavy
storms, glaciers, snowfalls and landslides. If the deposition of soil takes place over an area
already covered with vegetation, the plants occurring over there may be suppressed and
destroyed. Deposition results in a new bare area on which succession of vegetation starts.
3. Biotic causes:
Many biological or living agencies also affect the vegetation in many respects. Grazing, cutting,
clearing, cultivation, harvesting, and deforestation, all caused by living agencies, are directly
responsible for vegetational change. The parasitic plants and animals also affect the vegetation
and destroy it.
Five Stages of Plant Succession
Herb Stage
Herbaceous plants form the first stage of plant succession following a disturbance. Flowering
plants and grasses are usually the first plants to emerge following forest clearing or plowing a
field. Ferns and vines often emerge first following a fire.
Shrub Stage
The shrub stage follows the herb stage in plant
succession. Cane plants such as berries, woody-
stemmed shrubs and small, sun-loving trees
such as cedars spring up from the ground that
has been stabilized by the herbaceous plant
layer. Young white pines, aspens, and birches
begin to appear as the shrub stage transitions to
a young forest.

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Young Forest Stage
The young forest stage is characterized by thick
growth of thin-trunk young trees. Aspens and birch
are followed by specimens of maple, pine, and
other species depending on the forest location and
climate. Young forest trees climb quickly skyward,
attempting to out-compete one another for sunlight.
Slower trees are shaded out by their faster-growing
neighbors and die off as the system moves toward
the mature forest stage.




Mature Forest Stage
A mature forest includes diverse species of diverse
ages, from ground cover and undergrowth plants to
trees with low, mid- and upper-story canopies. Sun-
loving successional varieties such as birch and
aspen will die off, and varieties of hardwoods and
straight-trunk conifers that need protected shade to
germinate and grow will begin to dominate the
forest system.




Climax Forest Stage
A climax or "old growth" forest is not an even-
age forest of enormous old trees. Rather, a
climax forest is the most diverse forest system.
Trees left undisturbed to reach their full life
span will then die and fall, serving as 'nurse
trees' to new growth. This creates sunlit
openings in the canopy that foster herbaceous
growth, starting the stages of plant succession
over again in a patchwork throughout the forest.
Forests rarely reach the climax stage because
disturbances such as fire, clearing, or timber

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management usually interrupt succession at the mature forest stage.

REFERENCE

Pidwirny, M. (2006)."Plant Succession". Fundamentals of Physical Geography, 2nd Edition.
Date Viewed. http://www.physicalgeography.net/fundamentals/9i.html
Allama W.F.1984.Nice gusys finish first.Science 84 5(8):24-32
Axelsod,R.1984.The Evolution of coopration.Basic Books,New York
Clements F.E,and V.E. shelford.1939.Bio ecology.Jhon Wiley,New York
Berkner,N.V. and L.C.Mashall 1965.Histroy of major atmospheric components.Proc.Natal Acad
Sci.USA 53:1215-1226
http://www.biologydiscussion.com/plants/plant-succession-causes-concepts-and-theories/6808
http://www.biology-pages.info/S/Succession.html