plant succession

1. Plant Sucession
Hydrosere
Dr. Vasanta Kahalkar
Assistant Professor
Department of Botany
M. G. Arts, Science & Late N. P.
Commerce College, Armori

2. Plant Succession
• Definition :- Plant succession is an orderly
change of communities of plant which occur
over a period of time at the same place.
• Sere :- The stages in the communities that
appear and disappear during course of
succession are called sere and the communities
area called seral communities or seral stages.

3. Causes of Successions
• Main causes of successions are follows :-
• (1) Physiographic processes :- Producing mostly primary bare area
• A) Erosion :- By wind, water, gravity or by glaciers.
• B) Deposition :- By water, wind and volcanoes.
• (2) Climatic phenomena :- Producing mostly secondary bare area.
• A) Wind :- Removing previous vegetation. B) Drought :- Death and
wilting of weak species. C) Snow :- Killing previous vegetation D).
Lighting :- Causes fire in the forest.
• (2) Biotic agents :- Producing mostly secondary bare area.
• A) Man :- Destroying natural vegetation B). Animals :- Overgrazing
C) Bacteria, Fungi, insects :- Eliminating plant species by disease or
by eating.

4. Hydrosere
• It is succession occurring in the aquatic
environment. Hydrosere are well studied in ponds,
lakes etc. Hydrosere, originated in a ponds start
with the colonization of some phytoplanktons
which form the pioneer plant community and finally
terminates into a forest which is a climax
community together with their chief component of
vegetation.
• The plant succession which start in the aquatic
environment is called hydrarch. A series of changes
taking place in the vegetation of hydrarch is called
hydrosere.

5. The process of aquatic succession completes in
the following stages :-
• 1. Phytoplankton stage:
• In the initial stage of succession the simple forms
of life like bacteria, algae and many other aquatic
plants (phytoplankton) and animals (zooplankton)
floating in water are the pioneer colonizers. All
these organisms add large amount of organic
matter and nutrients due to their various life
activities and after their death, they settle at the
bottom of pond to form a layer of muck.

6. • 2. Rooted Submerged stage:-
• The phytoplankton stage is followed by submerged plant
stage. When a loose layer of mud is formed on the bottom
of the pond, some rooted submerged hydrophytes begin to
appear on the new substratum. The submerged aquatic
vegetation develops in the regions of ponds or lakes where
water depth is about 10 feet or more. The pioneers are
Hydrilla, Potamogeton, Myriophyllum, Ranunculus,
Utricularia, Ceratophyllum, Vallisnena, Chara, etc.
• These plants bring about further build up of the substratum
as a result of their death and decay. When these plants die
their remains are deposited at the bottom of the ponds or
lakes. The eroded soil particles and other transported
materials are also deposited at the bottom. As this process
of stratification progresses the body of water becomes more
and more shallow, consequently the habitat becomes less
suited for the submerged vegetation but more favourable for
other plants.

8. • 3. Rooted Floating stage: -
• When the depth of water reaches about 4 to 8 feet, the
submerged vegetation starts disappearing from its original place
and then the floating plants make their appearance gradually in
that area. In the beginning the submerged and floating plants
grow intermingled but in the course of time the submerged
plants are replaced completely. The most tolerant species in the
area are able to reproduce and perpetuate. Their broad leaves
floating on the water surface check the penetration of light to
deeper layer of water.
• This may be one of the main causes responsible for the death of
submerged plants. Due to continuous interaction between plant
communities and aquatic environment, the habitat becomes
changed chemically as well as physically. More water and air
borne soil and dead remains of plants are deposited at the
bottom. Thus, the substratum rises up in vertical direction.
Important floating plants that replace the submerged vegetation
are Nelumbmm, Trapa, Pistia, Nymphaea, and Limnanthemum
etc.

9. 4. Reed-swamp stages:-
• This stages is also known as amphibious stages
as the plant of the community are rooted but
most part of their shoot remain exposed to air.
Species like of Scirpus, Typha, Phragmites etc
are the chief plant of this stages. They have well
developed rhizome and form a very dense
vegetation. The water level is by now very
much reduced and finally becomes unsuitable
for the growth of these amphibious species.

10. 5. Sedge meadow stage
• Also called marsh meadow stage where the area is
now made up of plant species like Carex (Sedge),
Juncus, Diochanthium and herbs like Caltha,
Polygonum, etc. They form a mat like vegetation
with their much branched rhizomatous system. As
result of high rate of transpiration, there is much
rapid loss of water, & latter the mud is exposed to
air as a result which the nutrient like ammonia,
sulphides etc. become oxidized to nitrate and
sulphates. Finally the marshy vegetation disappears
due to the development of mesic conditions.

11. 6. Wood land stage:-
• By the time, of disappearnce marshy vegetation, soil
become drier and drier for most time of the year. This area
is now invaded by terrestrial plant. Which are some herbs,
shrub & tree. By this time there is much accumulation of
humus with rich flora of micro-prganism. Thus
minerlization of the soil favours the arrival of new tree
species in the area.
7. Forest stage :-
• It is the formation of climax community, which depends
upon the climatic conditions. For e.g., tropical deciduous or
monsoon forests are formed in regions of moderate rainfall,
tropical rain forests in areas with heavy rainfall, mixed
forests in temperate regions.
• Thus, in hydrosere stages 1 is pioneer community, stage 7 is
climax community & 2-6 stage are seral community.

12. Diagram showing different plant
community appearing different stages of a
hydrosere in apond

13. • Thank You

14. Xerosere :
Dr. Vasanta Kahalkar
Assistant Professor
Department of Botany
M. G. College, Armori

15. Xerosere :
• This is a type of xerosere originating on bare
rock surfaces. The original substratum is
deficient in water and lacks any organic matter,
having only minerals in disintegrated
unweathered state. The pioneers to colonise this
primitive substratum are crustose type of lichens,
and through a series of successive seral stages
the succession finally terminates into a forest
which constitutes the climax community.

16. Crustose lichens :-
Stages In Xerosere Can Be Enumerated as Follows
A bare rock consists of solid surface or very
large boulders and there is no place for rooting
plants to colonize. The crustose lichens like
Licanora, Rhinodina can adhere to the surface
of rock and absorb moisture from atmosphere.
Therefore these colonize the bare surfaces of
rocks fast. The Propagulis of these lichens are
brought by air from the surrounding areas.
These lichens produce acids which weathering
the rocks. The dead organic matter of lichens
becomes mixed with the small particle of rocks.
However, this process is very slow. These
lichens are then replaced by foliose and
fruticose type of lichens.

18. Stage 2: Foliose and
Fruitcose Lichen Stage
•
Foliose have leaf like thalli while the fruticose lichens are
small bushes. They are attached by the substratum at one
point only. Therefore do not cover the soil completely.
They can absorb and retain more water and are able to
accumulate more dust particles. Their dead remains are decomposed to humus
which mixes with soil particles and help building substratum and improving soil
moisture contents further. The shallow depreciation in the rocks and crevices
become filled with sold and top soil layers increases further. These autogenic
changes favor growth and establishment of mosses. This community includes
Permelia and Dermatpcarpom etc which have large leaf like thalli.

19. Stage 3: Moss Stage
• The development of thin soil layer
on rock surface, especially in the
crevices, favours the growth of
some such xerophytic mosses as
species of Polytricum, Tortula. At their successful
growth they compete with the lichens. The
bodies of mosses are rich in organic and inorganic
compounds. When these die they add these
compounds, to the soil to increase the fertility of
the soil. The thickness of the soil layer now
increases.

20. Stage 4: Herb Stage
The thickness of the soil layer now
increases. This changed habitat favors
the growth of some herbaceous plant
mostly annuals, in turn being followed by some
biennial and perennial plant. Due to their growth
and decay there is much more accumulation of
humus in soil together with further weathering of
rock. Thus, habitat changes with decreasing xeric
condition. This stages is constituted by such
shallow rooted grasses as Aristida, Poa etc. which
in turn are replaced by shrubs.

21. Stage 5: Shrub Stage:
Due to accumulation of soil the habitat becomes
suitable for shrub species which start migrating
in the area such as Rhus and others. They
overshadow the harbaceous vegetation. The soil
is further enriched by this dense shruby growth.
These in turn are finally replace by trees which
make up the climax community.

22. Stage 6:-Tree Stage
Change in environment favors colonization of tree species. The tree saplings begin
to grow among the shrubs and establish themselves. The kind of tree species
inhabiting the area depends upon the nature of the soil. In poorly drained soils
oaks establish themselves. The trees form canopy and shade the area. Shade
loving shrubs continue to grow as secondary vegetation. Leaf litter and
decaying roots weather the soil further
and add humus to it making the habitat
more favorable for growth to trees.
Mosses and ferns make their
appearance and fungi
population grows abundantly.

23. Stages 7 : Forest stages or climax stages :-
Some xerophytic tree species invade the area.
Further weathering of rocks and increasing
humus content of the soil favor the arrival of
more trees and vegetation finally becomes
mesophytic. Thus, there develop finally forest
community.

24. • Thank You