Types of community

1. Seminar Presentation
On

2. SYNOPSIS :-
Introduction
Definition
Characteristics of community
Size of a community
Structure of community
Characters used in the study of community structure
Analytical characters
Synthetic characters
Conclusion
References

3. Introduction :-
Environment
Biotic component Abiotic component
 A group of plants that grow in one or more species in
a particular area is called a plant community .
The overall combination of different plant and animal
population sharing a common habitat result in the
development of biotic communities .

4. Definition :-
According to Mobius (1877) -
“ A community is a group of living being in which all
species are affected by conditions and mutually affect
each other and maintain their existence by
reproduction .”
According to Shelford (1913) –
“ The community is a group of integrally classified
plants that are similar in size type.”

5. Characteristics of a community :-
 Respondent communities have their own
properties on the basis of they are indentified .
 Some key qualities found in a community –
1. Species diversity
2. Growth form and structure
3. Dominance
4. Succession
5. Trophic struture

6. Size of community :-
The size of the biotic community can be either small or large.
Small size or fixed area communities – e.g. – Pond , River ,
Meadows , Rocky platetus , etc.
Large size communities – e.g. – Forest , Swamps , Deserts
,Grassland , Lake , etc .
Very small size communities – e.g. – Micro-organism .
POND FOREST MICRO-ORGANISM

7. Structure of community :-
Structure of community
Producer
( e.g. – All green
plants
Consumer Decomposer
Primary
Consumer
(Cow , Rabbit
, etc.)
Secondary
Consumer
( Fox ,
Mouse ,
etc.)
Tertiary
(Duck ,
Snake , etc.)
Quaternary
Consumer
( Eagle ,
lion , etc.)

8. Characters used in the study of community :-
 According to Hanson and Churchill (1965)
Community Characters
Analytical Characters
Quantitative
Characters
 Frequency
 Density
 Abundance
 Cover and
basal
Qualitative
Characters
Physiognomy
Phenology
Stratification
Sociability
Abundance
Vitality
Life-form
Synthetic Characters
Persence and constance
Fidelity
Dominance
IVI
Other characters

9. Analytical characters of plant community :-
According to Hanson (1950) and Braun
Blanquet (1932) , analytical characteristics are
those features of community which can be
observed or measured directly and each stand .
Analytical character include kinds and number of
species , distribution of individual , species vigour ,
form , number of individuals , height of plants ,
area volume , growth are and periodicity , etc.

10. Types of Analytical Characters :-
These are two types :
 Quantitative – Quantitative , which are
expressed in quantitative terms .
These include such characters as frequency, density,
cover basal area and abundance ,etc.
 Qualitative – Qualitative , which can not be
measured , are expressed only in qualitative way.
These include physiognomy, phenology,
stratification, sociability, vitality and vigour , life
form (growth form) etc.

11. 1. Quantitative characters :-
A. Frequency :-
 Frequency refers to the degree of dispersion in terms of
percentage occurrence .
 In the community , the individuals of all the species are not
evenly distributed .
 Individuals of some species are widely spaced while those of
some other species are found in clumps or mats .
 Frequency is the number of sampling unite (as %) in which a
particular species occurs .
 Frequency(%) =
Number of sampling unite which the species occurred
х 100
Total number of sampling unite
 Raunkiaer frequency law (1934) suggested that the
number of species in 5 frequency class are as; A>B>C>=<D<E

13. B. Density :-
 Density represents the numerical strength of a species in relation to a definite
unite space in the community .
The number of individuals of the species in any unit area is its density .
Density gives an idea of degree of competition .
Density is calculated as follow –
Total no. of individuals of the species in all the sampling units
Total no. of sampling units identified
C. Abundance :-
This is the number of individuals of any species per sampling unit of
occurrence .
It is calculate as follows :-
Total no. of individuals of the species in all the sampling units
No. of sampling units in which the species occurred
But, abundance thus obtained in quantitative terms gives little idea of the
distribution of the species .
Abundance

14. D. Cover and Basal area:-
 The cover implies the area covered or occupied by the
leaves, stems and flowers, as viewed from the top .
Basal area refers to the ground actually pent penetrated by
the stems and is readily seen when the leaves and stems are
clipped at the ground surface .
It is one of the chief characteristics to determine
dominance.
In herbaceous species , it is measured either 2.5 cm above
the ground or actually on the ground .
 In forest the basal area is the cross section area of a tree
measured at 4.5 feet above the ground (DBH).
Basal area per tree = Total basal area/ Number of trees.
The area of coverage is used to express the dominance .
The higher the coverage area the greater is the dominance.

16. 2. Qualitative characters:-
Which are described and not measured.
A. Physiognomy :-
 This is this general appearance of vegetation as determined by the growth
form of dominant species .
 Such a characteristic appearance can be express by single term .
 For example, on the basis of appearance of a community having trees and
some shrubs as the dominants , it can be concluded that it is a forest .

17. B. Phenology :-
 Phenology as the science dealing with the appearance of certain events during
the life cycle of an organism in different seasons of the year .
 The term phenology was first used by Shelford (1929) to mark the events
associated with seasonal , succession in natural communities .
 Phenology , thus forms a part of community periodism .
 In other words phenology is the calender of events in the life history of the
plant.
 Environmental factors tend to influence the phenological behaviour of a
species population .
 Phenology also includes periodicity and aspection.
Fig- A phenogram showing 6 different events.

18. C. Stratification:-
Stratification of communities is the way in which plants of different species are
arranged in different vertical layers in order to make full use of the available
physical and physiological requirements.
On the basis of general observation of 5 layers have been distinguished:
 L1 – Ground stratum like mosses, thallophytes , lichens , etc.
L2 – Herbaceous or ground flora,
L3 – Middle layer or shrubby layer ,
L4 – Top layer or canopy layer of tree.
L5- Emergent layer.

19. D. Abundance:-
Plants are not found uniformly distributed in an area.
They are found in number at each place.
Abundance is divided in five arbitrary groups depending upon
the number of plants.
 Very rare,
 Rare,
 Common,
 Frequent,
 Very much frequent.

20. E. Sociability:-
 Sociability or gregariousness express the degree of
association between species.
 It denoted the proximity of plants to one another.
 Braun- Blanquet (1932) classified plants into the
following five sociability groups :
 S1 – Plants found growing singly.
 S2 – Plants growing in small groups or tufts of plant.
 S3 - Plants growing in small scattered patches.
 S4 – Several bigger groups of plants, large patches.
 S5 – A large group occupying larger area.

21. F. Vitality :-
 It is the capacity of normal growth and reproduction
which are important for successful survival of species.
 In plants, stem height, root length area, leaf number,
number and weight of flowers, fruits, seeds, etc. ,
determine the vitality.
 Daubenmire (1968) gave vitality groups :-
 V1 - Plant whose seedling die .
 V2 - Seedling grow, but unable to reproduce
 V3 - Reproduce only vegetatively
 V4 – Reproduce sexually but uncommon
 V5 – Reproduce sexually and growth regularly .

22. G. Life form(Growth form) :-
 A life form is “the sum of the adaptation of the plant to
climate.”
 Christen Raunkiaer’s classification (1934) of
plant life forms .
 On the basis of the position of perennating buds on
plants and the degree of their protection during
adverse conditions , Raunkiaer classified plants into
five broad life form categories which are as follows :
a. Phanerophytes
b. Chamaephytes
c. Hemicryptophytes
d. Cryptophytes or Geophytes
e. Therophytes

23. Fig – Life –form categories

24. Synthetic Characters :-
These are determined after computing the data on
the quantitative and qualitative characters of the
community .
For comparing the vegetation of different areas ,
community comparison needs the calculation of
their synthetic characters .
Synthetic characters are determined in terms of the
following parameters :

25. A. Presence and Constance:-
 It expresses the extent of occurrence of the individuals of a particular species in the
community.
 E.g. – How uniformly a species occurs in a number of stands of the same type a community
 Presence : indicates the presence of a species in a stand.
 Constance : is t he degree of “presence” in a unit area (sample area ) instead of the whole
stand.
 The species on the basis of its percentage frequency may belong to any of following 5 presence
classes that were first proposed by Braun – Blanquet .
a. Rare present – Present in 1 -20% of the sampling units.
b. Seldom present – Present in 21-40% of the sampling units.
c. Often present – Present in 41 -60% of the sampling units.
d. Mostly present – Present in 61-80% of the sampling units.
e. Constantly present – Present in 81-100% of the sampling units .
 Constance is generally determined from frequency and the following 5
constance classes have been recognized.
a. Constance class 1: 1-20% frequency
b. Constance class 2: 21-40% frequency
c. Constance class 3 : 41-60% frequency
d. Constance class 4 : 61-80% frequency
e. Constance class 5 : 81-100% frequency.

26. B. Fidelity :-
 Fidelity or “faithfulness” is the degree with which a species
is restricted in distribution to one kind of community .
 Such species are sometimes known as indicators .
 The species have been grouped into 5 fidelity classes which
were first formulated by Braun Blanquet:
a. Fidelity 1 :- Plants appearing accidentally (strangers)
b. Fidelity 2 :- Indifferent plants may occur in several kinds
of community (Indifferent)
c. Fidelity 3 :- Species which occur in several kinds of
communities but are predominant in one (Preferentials).
d. Fidelity 4 :- Specially present in one community but may
occasionally occur in the other communities as well
(Selectives) .
e. Fidelity 5 :- Occur only in one particular community and
not in others (Exclusives) .

27. C. Dominance :-
 It is used as synthetic as well as analytical characters
(Daubenmire ,1959).
 The number of organism sometimes may not give correct idea of
the species.
 Thus , cover is included as an important character in
dominance.
 On the basis of density, frequency and dominance (cover) value,
there has been proposed the idea of Importance Value Index
(IVI).
 For IVI value, relative density, relative frequency and relative
dominance are obtained.
 For IVI values of RD,RF and RDo are obtained as follows:
 Relative Density = Density of the species
Total density of all the species х 100

28. Relative frequency (RF)
Frequency of the species х 100
Total frequency of the species
Relative Dominance (RD)
Dominance (cover) of the species х 100
Total dominance (cover) of the species
D. Importance value index (IVI) :-
IVI is used to determined the overall importance of each species in the
community structure .
In calculating this index , the percentage value of the relative frequency ,
relative density and relative dominance are summed up together and this
value is designated as IVI .
It provides the idea of the sociological structure of a species in its totality
in the community .
IVI = RD + RF + RDo .

29. E. Other synthetic characters :-
Besides the above mentioned ones, there have also
been proposed some other characters which have been
quite useful in comparative studies on communities .
Such characters include ,
Interspecific association ,
Association index
Index of similarity
Dominance index
Diversity index etc .

30. Conclusion :-
From the above description it is know that –
our environment is very large , in which the study of the
appearance of all is simplified by analytical and synthetic character .
Reference :-
Elements of ecology – Dr. S. A. Nasim , First pulished 2012 . Axis
books Pvt. Ltd. New Delhi 110002 (India) .
A textbook of plant ecology – Dr. S. A. Shukla , Dr. P. S.
Chandel . S. Chand & Company Ltd. Ram nagar New Delhi
110055 .
Ecology – Dr. Mohan P. Arora , First edition 1990.