Plant Succession

SUCCESSION
·       The gradual replacement of one type of plant community by the other is referred to as plant succession.
·       The succession is a progressive development of plant communities at the same site over a period of time.

·       A succession is inventively progressive in nature and the ultimate stage (final) is the climax. e.g.
o   PIONEER:
·       The species which is the first to establish in a new area is called pioneer. Such species can grow in adverse conditions.
o   SERE:
·       Sere is the series of plant communities involved in a succession before a climax is reached.
o   CLIMAX:
·       Climax is the ultimate stage of a plant succession.
o   REGRESSION:
·       It is a reversion to some earlier stage of succession.
o   KINDS OF SUCCESSION
·       Two kinds
1.     Primary succession
2.     Secondary succession
1.     PRIMARY SUCCESSION
OR
AUTOGENIC SUCCESSION
OR
PRE-SERE
·       When the succession starts on the extreme bare area on which there was no previous existence of vegetation it is called primary succession or pres-ere.
2.     SECONDARY SUCCESSION
OR
SUB-SERE
                        OR
ALLOGENIC SUCCESSION
·       This succession is one which takes place after the destruction of whole or part of the previous vegetation of a site. Destruction by Fire, Floods, Landslides, Strong winds, Cultivation, Grazing/Browsing etc.
·       The primary and secondary successions may be of the following types.
i.    Hydrosere:       The plant succession which starts in the aquatic environment is called hydrach. A series of changes taking place in the vegetation is called hydrosphere.
ii.   Halosere:       It is a special type of sere which begins on a salty soil or in saline water.
iii. Xerosere:       When the vegetational succession develops in the xeric or dry habitat is called xerarch or xerosere. Xeroseae may be of two types:-
i.    Psammosere:
·       It refers to the vegetational succession that begins on the sandy habitat.
ii.   Lithosere:
·       It refers to the succession that occurs on the rock surface.
o   SERULE
It refers to the miniature succession of micro-organisms, such as bacteria and different types of fungi on the fallen logs of decaying wood, tree bark etc.
o   SUCCESSION OF VEGETATION IN RIVERAIN AREAS
                                                OR
WHAT ARE THE DIFFERENT STAGES OF PLANT SUCCESSION ON FRESH ALLUVIAL SOIL ALONG INDUS RIVER NEAR HYDERABAD AND SUKKUR? (2009)
  • SUCCESSION STAGES
§  As a result of river action, land in the form of fresh alluvial deposit is formed.
§  This land is submerged by annual flood each year until it is raised above the surface of water by successive river deposits.
§  The newly formed land Kacha is first invaded by Tamarix dioca and Tamarix trroupi seedlings through their air and waterborne seeds and establish themselves into a dense crop.
§  Saccharum spontaneum grass appears sometimes along with and mixed.
§  As the land becomes more elevated but is still subject to annual floods Populus eupharatica and Acacia nilotica seedlings soon make their appearance amidst Tamarix and Saccharum, Populus seeds being carried by air, water and cattle.
§  As the Kacha is gradually raised further by subsequent alluvial deposits, Tamarix and Saccharum established. The land is now stable and is locally called Pakka.
§  Poplar and Kikar crops continue to flourish so long as the land is subject to annual inundation of up to 3 meters depth.
§  But the ground becomes elevated and becomes the reach of ordinary floods. First Poplar and then Kikar commence deteriorating.
§  The crops open out and die off even then the sub-soil moisture by percolation from the river is also shut out.
§  Saccharum munja grass penetrates into open crops.
§  In Southern Punjab region often Dalbergia sissoo appears in places. The seed being disseminated by wind and water.
§  Shisham is capable of drawing moisture from comparatively and Kikar and from crops on elevated ground. Shisham is said to the climax species.
§  However Prosopis cineraria is the climax species in the riverain forests, Hyderabad and Sukkar of Sindh province.
§  Ecologically Populus euphratica forests occupy an edaphic seral development stage in the process of plant succession in the riverain forests of Pakistan.
§  The following succession of different plant species occurs in the riverain forests from low lying young alluvial soil to older land on high level ending up in the arid areas in a cycle of 30 to 35 years.
1.     Low land 
Recent deposits   Saccharum spontaneum
High Deposits                  Tamarix dioca
Nearly wet                       Tamarix troupe, Populus euphratica
Drier then above Populus euphratica, Acacia nilotica
                                          Saccharum spp.
2.     High Land
Dry with ample sub-soil moisture
A. Nilotica, D. sissoo, P. cineraria, Cynodon dactylon
Arid
D. sissoo, P. cineraria, Salvadora persica, S. olevoides, Capparis aphylla, Aristida, A. Senegal, Zizyphus, A. Jacquemonti, Numularia, Cymbopogon
o   RIVERAIN SUCCESSION OF HYDERABAD AND SUKKAR, DING FOREST
1.     The first stage on new alliuviupi is Saccharum spontaneum with Erianthus munja.
2.     This is followed by Tamarix dioca T. troupe and Populus euphratica, Acacia nilotica.
3.     Then comes in replacing the Tamarix, Erianthus spp. Persisting.
4.     This stage is finally succeeded by the climatic climax of Prosopis spicigera, Salvadora, Capparis deciduas.
o   CONIFEROUS SUCCESSION
In the temperate mixed coniferous forests, a typical succession on new sites or abandoned clearings is:-
1.     Shrub associations
2.     Pinus wallichiana
3.     Mixed C. Forest of Deodar, Spruce, and Blue pine.
4.     Mix coniferous forests of Spruce, Fir, and Deodar.
o   ESTUARINE SUCCESSION
The following stages are present in the succession on tidal estuarine, mud flats.
1.     Mangrove scrub
2.     Mangrove trees
3.     slow growing saltwater Heritiera
4.     Finer brackish water Heritiera forest.
5.     Freshwater swamp forest without Heritiera.
6.     Evergreen or semi-evergreen forest.
o   LANDSLIPS
The most successful colonist’s light wing seeds, wind-borne seed. E.g. Salix, Populus, Pinus wallichiana.
o   SAND DUNES
The inland shifting sands are invaded by Herbs and shrubs with the same mechanism of dispersal e.g. Calligonum trees appearing much later when the sand has been more or less stabilized.
o   IMPORTANCE OF SUCCESSION
1.     Classification of forests.
2.     Choice of species for planting.
3.     Determining the successional stage of the most economic species.
o   CLIMAX
·       Climax is the ultimate stage of succession. Suements was of the opinion that the most dominant factors in climax attainment were climate, hence he called it  CLIMATIC CLIMAX.
·       Climax Types:-
1.     Climatic climax
2.     Edaphic climax
3.     Pre-climax
4.     Post-climax
5.     Sub-climax or Biotic climax
1.     Climatic climax
§  Climatic climax owes its special characters to climatic factors, where other influences are not very significant. e.g.
i.    Himalayan moist temperate forest/ western mixed coniferous forests.
ii.   The evergreen Oak or deciduous species are the climax.


2.     Edaphic climax
§  This is the climax as a result of special soil conditions or factors. e.g.
i.    Tropical dry deciduous forests. Acacia nilotica.
3.     Pre-climax
§  These are those plant communities which have the permanence or extent of a climax but are not characteristic of the existing climate of the region. e.g.
i.    Chir pine on ridge tops in sub-tropical broad-leaved forests.
4.     Post-climax
§  The plant community more advanced than the climatic climax of the region found under exceptionally favorable locality factors e.g.
Presence of evergreen and semi-evergreen species in the midst of dry deciduous vegetation.
5.     Sub-climax or Biotic climax
§  This is a climax which differs from the climatic climax of a region, due to certain Biotic influences e.g.
i.    Chir pine forest in areas where Oak is climatic climax (in the Himalayas)
ii.   Deodar in moist areas.
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o   SUCCESSION
1.   The concept of disturbance and succession are inextricably linked in plant ecology.
2.   The basic concept of sequential development of vegetation on BARE surface takes place in phases:-
i.    First colonizing phase.
ii.   Followed by immature (seral) phase.
iii. Culminating in a mature and stable “Climax phase”.
3.   An area absolutely devoid of any vegetation.
      After a point in time, a primitive pioneering species will establish itself there with the passage of the vegetation there will change.
      This phenomenon is called succession. e.g.
o   CONCEPT OF SUCCESSION
·       The gradual replacement of one type of plant community by the other is referred to as succession.
·       The succession is a progressive development of plant community at the same time over a period of time.
·       A succession is inevitably progressive in nature and the ultimate stage is the climax.
o   IMPORTANCE OF PLANT SUCCESSION
i.    Classification of Forests.
ii.   Choice of species for planting.
iii.   Determining the successional stage of the most economic species.
o   KINDS OF SUCCESSION
·       Succession may be classified on the two broad bases:-
i.    Based on Moisture conditions.
ii.   Based on the presence or Absence of vegetation.
i.    Based on moisture conditions at a site, succession is grouped into:-
(a) XERACH succession
(b) HYDRACH succession.
(a) XERACH SUCCESSION
·       It begins in very dry conditions such as bare rocks, wind bellow sand, rocky slope etc.
·       The difference between stages of this succession is the XEROSERE. This, in turn, is of two types.
The lithosere is the one which originates on the bare rock, where the psammosere originates on the sand.
(b) HYRACH SUCCESSION
      Hyrdach succession begins in water, swamps, very wetland, lakes, ponds etc.
      The different stages of this kind of succession are the Hydrosphere.
ii.   Based on the presence or absence of vegetation at a site succession may be classified as:-
(a)   Primary Succession
(b)   Secondary Succession



(a)   PRIMARY SUCCESSION
                  OR
      AUTOGENIC SUCCESSION
                  OR
      PRESERE
·       When the succession starts on the extreme Bare area on which there was no previous existence of vegetation it is called primary succession or PRESERE.
(b)  SECONDARY SUCCESSION
                  OR
      ALLOGENIC SUCCESSION
                  OR
      SUBSERE
·       This succession is one which takes place after the destruction of whole or part of the previous vegetation of a site.
Destruction by Fire, Floods, Landslides, Strong Winds, Cultivation, Grazing, Browsing, Felling/Logging etc.
o   CAUSES OF SUCCESSION    
·       Causes of succession are:-
i.    Initial Causes which provide the basis for a succession to occur.
ii.   Secondary or continuing causes are those which help in the development of plant communities:-
(a)   Ecesis or Establishment
(b)   Migration
(c)   Grouping or Aggregation
(d)   Competition
(e)   Reaction
o   INITIAL CAUSES OF PRIMARY SUCCESSION
·       These may be listed are under:-
i.    Erosion
ii.   Physiography
iii. Elevation and subsidence.
      Tectonic forces may result in the elevation and subsidence of land area above or below the ocean level.
o   INITIAL CAUSES OF SECONDARY SUCCESSION
i.    Climate
ii.   Biotic factors
iii. Physiography or Topography.
i.    CLIMATE
      The vegetation of a place may be destroyed by the action of water, wind, snow etc.
ii.   BIOTIC FACTORS
      Activities of Man, Animals. A man may be the cause of the fire, which may ultimately wipe out huge areas overgrazing may take place due to certain Animals, as a result of which vegetation for a certain area.
o   CONTINUING CAUSES
·       The following are the continuing causes:-
(a)   Migration
(b)   Ecesis or Establishment
(c)   Grouping or Aggregation
(d)   Competition
(e)   Reaction
(a) MIGRATION
·       This is the mass movement of plants from one site to another.
·       A new area may be colonized by migration of a plant community from its present area.
·       Such migration usually takes by means of seeds.
·       The degree of mobility of seeds depends upon:-
i.    Size
ii.   Weight
iii. Presence or absence of special dissemination structures.
·       Seed dispersal is generally with the help of wind, water, animals etc.
·       Seeds dispersed by wind are generally light, small, with wings or silky hairs etc.
·       Seeds which are disseminated by water are light, so that may float.
·       Seed dispersal by animals may have hooks on them.
·       An area may be colonized by dispersal with the help of any of the above or a combination of the above agencies.
(b) ECESIS OR ESTABLISHMENT
·       This is the entire process by which a plant establishes in an establishes in an area that is from germination to reproduction.
·       Germination depends upon the following conditions:-
i.    The seed must be viable.
ii.   The time required for germination should be small so that the seed is not destroyed or eaten up by the bird etc.
iii. The seed coat should not be very hard.
iv.  The soil should be thick enough to allow germination.
v.   The species should be a strong light demander, xerophytic, drought-resistant, frost hardy etc. for Barren area.
(c) GROUPING OR AGGREGATION
·       After a species has set up in an area, a grouping of the established scattered colonies takes place.
·       Thus, in due course of time, the colonizers make a closed canopy.
(d) COMPETITION
·       There is a struggle for the available food, moisture, light between different species and individuals in a plant community.
·       As soon as grouping or a closed canopy results there is competition for the supplies of food, light, and moisture.
(e) REACTION.
·       The plant communities influence the site on which they are growing.
·       This has a bearing on the further development of succession in the area.
·       Effect of plant communities can be grouped into two broad groups as follows:-
(a) EFFECT ON CLIMATE FACTORS:-
1.   Altering light conditions.
2.   Decreasing the daylight air temperature.
3.   Reducing in diurnal range of temperature.
4.   Decreasing wind velocity.
5.   Reduction in hazard of Radiation Frost.
6.   Increasing Relative Humidity.
7.   Increasing precipitation.
 (b) EFFECT ON SOIL:-
1.   Improving the soil temperature.
2.   Adding organic matter to the soil.
3.   Improving the water holding.
4.   Improving the nutrient status of the soil.
5.   Improving soil stability, Reduction in hazards of accelerated erosion etc.
6.   Improving the maturity of the soil.
7.   Increasing the depth of the soil.
8.   Aiding in the process of soil formation.
o   SECONDARY SUCCESSION
·       Due to certain unfavorable factors, a primary succession may be delayed.
·       These factors may be climatic, biotic etc.
·       Regression is the reversion to some adverse influences.
·       When the adverse influences are curbed, succession starts again. This is known as secondary succession.
o   CLIMAX
·       Climax is the ultimate stage of succession.
·       CLEMENTS was of the opinion that the most dominant factor in climax attainment was climate, hence he called it a CLIMATIC CLIMAX.
·       PRECLIMAX is a term given to all those plant communities which have the permanence or extent of a climax but are not characteristics of the existing climate.
o   THEORIES OF CLIMAX
1.   CLEMENTS has proposed a mono-climax theory in which he assumes only one climax.
·       This has been challenged by others, and as a result, the POLY-CLIMAX theory has emerged.
  1. AUBREVILLE’S MOSAIC Theory suggests that a climax is not a static equilibrium but is a dynamic community with periodic alteration in its constituent units.
  2. VEGETATIONAL GRADIENT AND CLIMAX THEORY OF WHIT TAKER:
·       According to this theory, there is no absolute climatic climax for an area.
·       It is the sum of climate, site factors, soil, Biotic factors, species factor etc.
o   CLIMAX TYPES
1.   Climatic climax
2.   Edaphic climax
3.   Pre-climax
4.   Post-climax
5.   Sub-climax or biotic climax
1.   CLIMATIC CLIMAX
·       Climatic climax owes its special character to climatic factors, where other influences are not very significant. e.g.
Himalayan moist temperate forests/ Western mixed coniferous forest. The evergreen oak or deciduous species are climaxes.



2.   EDAPHIC CLIMAX
·       This is the climax as a result of special soil conditions or factors. e.g.
Tropical dry deciduous forests, Acacia nilotica.
3.   PRE-CLIMAX
·       These are those plant communities which have the permanence or extent of a climax but are not characteristic of the existing climate of the region. e.g.
Chir pine on ridge tops in sub-tropical broad-leaved forests.
4.   POST-CLIMAX
·       A plant community more advanced than the climatic climax of the region, found under exceptionally favorable locality factors. e.g.
Presence of evergreen and semi-evergreen species in the midst of dry deciduous vegetation.
5.   SUB-CLIMAX OR BIOTIC CLIMAX
·       This is the climax which differs from the climatic climax of a region, due to certain biotic influences. e.g.
Chir pine forests in areas where oak is the climatic climax.
o   MONOCLIMAX AND POLYCLIMAX INTERPRETATION
·       In successional series climax is the final and stable community.
·       It s the perpetuating and is an equilibrium with the habit.
·       The type of climax is determined by the prevailing environmental factors.
·       Two prominent views concerning the climax communities have been advanced by an ecologist. i.e. Monoclimax and polyclimax interpretation.
o   MONOCLIMAX INTERPRETATION
·       Monoclimax interpretation was first postulated by an American Ecologist CLEMENT (1938).
·       He considers that there is only one climax community for any geographic climate. Thus climax is known as CLIMATIC CLIMAX.
·       The following climaxes are given terminologies by CLEMENT (1938):-
1.   Sub-climax
2.   Post-climax and Pre-climax
3.   Dis-Climax
o   DISCLIMAX
·       When disturbances by man and animals is such that true climax becomes modified or largely replaced by new species, the result is called as DISCLIMAX. e.g.  Dalbergia sissoo and Morus alba are growing in plantation forest of Pakistan and Prosopis juliflora is in abundance in disturbed areas of Indus plains.
·       It is the result of disturbance by man or his domestic animals, rather than climatic factors.
·       A Disclimax implies that a particular type of flora and fauna maintain themselves in the area as a result of recurrent disturbance. The agent responsible for such a disturbance prevents the successful establishment of a climatic climax community in the area.
·       The disturbance may be caused by the biotic elements such as
a.   the recurrent browsing and grazing
b.   continual thinning and cutting of timber for the cultivation of fields by man.
      This prevents succession from continuing beyond a certain stage.
·       Abiotic elements such as windstorm, floods, erosion and periodic fires may result in the establishment of a climax.
·       Continuous occurrence of fire also produced disturbed conditions as a result of which fire-resistant communities would develop.
·       Similarly in an area where there is a continuous process of felling and cutting of larger trees species is giving on a time comes when unwanted trees or shrubs species become climax. this also a case of DISCLIMAX.
o   POLYCLIMAX INTERPRETATION
·       The climax that develops due to the factors other than the climate are named after their respective habitat.
·       Various climax communities described by adherents of POLYCLIMAX INTERPRETATION are:-
1.   Climatic climax
2.   Edaphic climax
3.   Physiographic climax
4.   Disclimax
o   PHYSIOGRAPHIC CLIMAX
·       Physiographic climaxes are the product of local environments, associated with peculiarities of topography.
·       At a given elevation under a uniform climate minor topography. Features like hills, cliffs, rivers, valleys or un-drained depression may exert controlling influence over the vegetation because each of these features produces MICROCLIMATE of its own. e.g.
i.    In moist mountains of Pakistan Northern slopes have luxuriant coniferous forests but on the contrary South slopes are usually drier with sparse vegetation and species also different.

ii.   In the hilly region of Southern Sindh and Balochistan Acacia Senegal is present as dominant species but on dry stream beds with good soil texture, the climax is Acacia jacquemonti community.

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