CHỈ SỐ SHANNON-WIENER The Shannon-

CHỈ SỐ SHANNON-WIENER
The Shannon-Weaver index H measures overall
biodiversity. H is maximized when all species have
the same number of individuas. For example, it is
biggest when the forest has 4 tigers, 4 antelope, and 4
aardvarks. H is smaller when the forrest has 1 tiger, 2
aardvarks, and 5 antelopes. Note that both forests have
8 inhabitants.
The formula is: H = (-1)*(the sum from i to s)of(n_i/N *
ln(n_i/N))
for i = 1, 2, ... s
where 1 represents species 1, 2 represents species 2,
etc..., and N is the total number of "animals," and n_i (n
sub i) is the number of animals of the ith species
CÁC CHỈ SỐ ĐDSH THÔNG DỤNG VÀ Ý
NGHĨA
The value of the Shannon-Wiener Index usually lies
between 1.5 and 3.5 for ecological data and rarely
exceeds 4.0. May (1975) notes that if species follow
a log normal abundance distribution the sample
must hold 100,000 species for H to be greater than
5.0. By itself, this index often gives little more
insight than Species number .
Ý NGHĨA CỦA SIMPSONS D (SIMPSONS INDEX)
As species richness and evenness increase, so diversity increases.
Simpson's Diversity Index is a measure of diversity which takes into
account both richness and evenness.
The Simpson's index D is the chance that second animals selected
from the forrest are of the same species. 0 is infinite diversity and 1
is no diversity(all the same species).
"Simpson's Index is heavily weighted towards the most abundant species
in the sample, while being less sensitive to species richness."
The formula is: D = (the sum from i to s)of(n_i/N)^2
the n_i's and N are the same as before.
For example, in a forrest with one tiger and 9 aardvarks, D = 1/100 +
9^2/100 = 82/100 = .82.
In a forrest with 4 aardvarks, 4, antelopes, and 2 tigers, D = 4^2/100 +
4^2/100 + 2^2/100 = 36/100 = .36.
Since .36 is closer to zero than .82, the second forest is more diverse.
Source(s):
Wikipedia.org has a great section on this
Ý NGHĨA CỦA MARGALEF D
I
Margalef
= (S - 1) / ln(N)
Strictly speaking, these are not measures of
diversity, as they do not include any component of
evenness. They are attempts to estimate species
richness independently of the sample size.
The index will be independent of the number of
individuals in the sample only if the relationship
between S (or S - 1) and ln(N) or √N is linear.
Ý NGHĨA CỦA MCINTOSH D
McIntosh Diversity Index
It was suggested by McIntosh in 1967. The values
are between 0 – 1. When the value is getting closer
to 1, it means that the organisms in a community
are homogeneously distributed (McIntosh 1967).
Mc = [ N - (∑ni2) ] / [ N - N ]
Mc : McIntosh Diversity Index
ni : Number of individuals belonging to i species
N : Total number of individuals