COMMUNITY COEFFICIENTS
Community is a
group of different population component.
It is vast group of species, and as the number of species increased, the
complexity of community is also increased.
So, for the determination of the complexity in community, some indices
are used. These indices are based upon
some coefficients, which are known as community coefficients.
For determining
the continuum and discontinuity, similarity or dissimilarity in the community
is studied as well as the degree of association is also important. On the basis of degree of similarity, species
are places in same community or different communities. For finding the similarities in the
community, coefficient of similarity is calculated. It is the main criteria for community
classification. It shows that greater
the number of species is common in the communities, then greater affinity in
the community is seen. Some important
coefficients are following which indicate the species structure in the
community.
Index of Dominance (C)0
C
= ∑(n/N)2
Where n, is the
importance value for each species (number of individual, biomass, production,
and so forth).
N is the total of importance
values.
Index of
similarity (S) between two Samples
S = 2 C / (A+B)
Where
A is the number of species in
sample A
B
is the number of species in sample B
C is the
number of species common to both the samples.
Note: Index of dissimilarity = 1-S
Indices of
Species Diversity
1. 3 species richness or variety indices d
d1 = S-1/log N
d2 = S / /n
d3 = S per 1000 individuals
Where S is the number of species,
N
is the number of individuals, etc.
2. Evenness index e:-
__
e = H/log S
Where,
__
H is the Shannon index
S is the number of species
3. Shannon index of general diversity H
__
H =
- ∑ (n/N) log (n1/N)
= ∑ Pi log Pi
Where
(--) n, is the importance values for each species
N
is the total of importance values
P1
is the importance probability for each species (n1 / N)
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