Automatically generated tables etc
Methods of Vegetational Survey ........................................................................................ 2
1. Quadrate method for vegetational survey ................................................................... 2
Survey can be done by laying out fixed sized quadrate as: ........................................ 2
Determining size of quadrate ...................................................................................... 3
Determining Number of Quadrates ............................................................................. 4
Assessing Diversity and Density of Forest. ........................................................................ 5
A. For dominance of species, IVI has to be calculated ................................................... 6
Interpretation: .................................................................................................................. 8
Table 1 Observation recorded during vegetational survey in each quadrate ...................... 5
Table 2 Clubbing of quadrates data to determine Relative Density, Dominance and
frequency............................................................................................................................. 6
Figure 1 ............................................................................................................................... 3
Figure 2 ............................................................................................................................... 4
Equation 1 Frequency** = Number of quadrate in which species occurred ...................... 7
Equation 2 Relative dominance (RD) = Total basal area of species............................... 7
Equation 3
Relative density = Number of individuals of the species ........................ 7
Equation 4
Relative frequency (RF) .............................................................................. 7
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Vegetational Survey
Part I
As a planner and the manager of forest, we like to know the information on status:
 Biodiversity and dominance of species in the forest.
This information helps us to apply suitable techniques to protect biodiversity or help
certain species of interest to develop or regenerate. To get these information the
following vegetational survey is carried out:
Methods of Vegetational Survey
1. Quadrate method
2. Line transect method
1. Quadrate method for vegetational survey
Quadrate is a square of varying size, laid out in the forest to make observation on
vegetational survey.
Need of quadrate-as the forest area is very big we cannot cover all the area. So we
survey in small area (quadrate) uniformly distributed all over the area. The result from
this survey will reflect the condition of forest (the total area of forest surveyed)
Number of quadrate and their size is important to get good estimate of the forest. There
are two schools for determining the number and size of the quadrate as follows:
Survey can be done by laying out fixed sized quadrate as:
a. 1x1m for grasses
b. 5x5 m for shrubs
c. 10x 10m for trees
According to Singhal 1996
d. 16x16 m for trees (>2m height)
e. 5x5 m for shrubs (1-2 m height)
f. 2x2m for ground flora (< 1m height)
These methods are convenient for implementation but it poses difficulty in
conditions where diversity is too high or too low.
The number of the quadrate will depend on the decision of sample size to be
surveyed.
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Determining size of quadrate
To determine the quadrate size for the particular site, quadrate size of 1x1m is laid out
and recorded the number and species. Then the quadrate size is increased to 2x2m
and again recorded the number and species. We can further increased to 4x4m,
6x6m… and record the information as done for the above two.
6m
4m
2m
1m
1m
Figure 1
2m
4m
6m
Determining size of Quadrate
The number of species obtained per quadrate is plotted against the size of quadrate as
follows. This curve is known as species-area curve.
It is seen that number of species recorded in 2x2m quadrate is same with 4x4m and
also with 6x6m quadrate.
The species recorded in 1x1m quadrate is less than 2x2m. This indicate that the
optimum size for the survey is 2x2m quadrate, which will be economical as well.
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1m
Figure 2
2m
4m
6m
Species-area curve
Determining Number of Quadrates







Number of quadrate will depend on the accuracy of the survey
Where it has to depend on the resource availability and the intensity of sampling
Higher the intensity higher will be the accuracy but the expense will be also
higher.
In general, the intensity is restricted to 10-15% of the total area for the survey.
The number can be determined, by laying out 30-50 quadrates and species
occurring in each quadrate are noted.
The data is plotted with number of quadrates on x-axis and number species on yaxis.
The point at which the curve flattens will indicate the minimum number of
quadrates needed to under take the survey adequately.
Example:


If intensity of survey to be done in 10 ha. Is 12 %, and recommended quadrate
size is 4x4m.
The number of quadrate will be then
o 12% of 1ha = (12/100) x 10000= 1200 m2
o Therefore to cover 1200m2 by 4x4m quadrate= 1200/4x4 = 75 quadrates
o For 10 ha. = 75x10= 750 quadrates
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Assessing Diversity and Density of Forest.


Once number and size of quadrate is fixed, the quadrates are randomly distributed
in the forest.
In a quadrate number of species, corresponding number of individuals and
diameter of individuals is taken.
Example:
In a forest, 5 quadrates were laid out. The data obtained in each quadrate is arranged as
shown in the following table:
Table 1 Observation recorded during vegetational survey in each quadrate
Quadrate
No.
1
Species
Eragrotis curvula
Heteropogon contortus
Rubus ellipticus
Rumax hystatus
Ricinus communis
Dodonia viscose
Shorea robusta
Terminalia tomentosa
No. of Individual Diameter (cm)
Average
20
0.5
10
0.3
8
0.9
5
1.2
7
1.1
3
1.4
9
23.5
6
21.2
2
Heteropogon contortus
Rumax hystatus
Shorea robusta
Terminalia tomentosa
25
4
8
3
0.7
1.0
24.8
20.3
3
Toona ciliata
Shorea robusta
Cynodon dactylon
Berberis lycium
Rubus ellipticus
2
4
23
4
6
19.7
28.3
0.3
1.2
0.8
4
Shorea robusta
Terminalia tomentosa
Berberis lycium
Lantana camara
Bidens pilosa
Parthenium sp
9
4
3
6
30
22
26.2
21.5
1.4
1.2
0.5
0.3
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5
Terminalia tomentosa
Shorea robusta
Toona ciliata
Bidens pilosa
Parthenium sp
5
8
4
25
18
21.1
27.5
23.1
0.5
0.8
Following are indices which depicts diversity, dominance, similarity, dissimilarity
etc. of forest:
A. For dominance of species, IVI has to be calculated
IVI = importance value index = relative density +Relative frequency +Relative
dominance. (Phillips, 1959)
Arrange the data of table:1 in a manner of the following table:2 by clubbing the 5
quadrates together:
Table 2 Clubbing of quadrates data to determine Relative Density, Dominance and frequency.
Species
Eragrotis curvula
Heteropogon
contortus
Rubus ellipticus
Rumax hystatus
Ricinus communis
Dodonia viscose
Shorea robusta
Terminalia
tomentosa
Toona ciliata
Cynodon dactylon
Berberis lycium
Lantana camara
Bidens pilosa
Parthenium sp
Total
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No.of
Individual
Basal
area*
cm2
Frequency**
Relative
density
R.D
R.F
IVI
20
3.93
20
7.12
0.014
3.57
10.70
35
10.33
40
12.46
0.036
7.14
19.63
14
8.11
40
4.98
0.028
7.14
12.15
9
8.80
40
3.20
0.031
7.14
10.38
7
6.65
20
2.49
0.023
3.57
6.09
3
4.62
20
1.07
0.016
3.57
4.66
38
19887.92
100
13.52
69.673
17.86
101.05
18
6289.44
80
6.41
22.034
14.29
42.73
6
2286.00
40
2.14
8.008
7.14
17.29
23
1.63
20
8.19
0.006
3.57
11.76
7
9.1420
40
2.49
0.032
7.14
9.67
6
6.79
20
2.14
0.024
3.57
5.73
55
10.7992
40
19.57
0.038
7.14
26.75
40
10.60
40
14.23
0.037
7.14
21.41
281
28544.74
560
100.00
100.000
100.00
300.00
6
R.D = Relative dominance, R.F = Relative Frequency; * = Basal area = πr2 where r is
radius (diameter/2)
Basal area for Eragrotis curcula = πr2 =3.1415 x (0.5/2)2 = 0.196 cm2, and for 20
individuals the basal area= .196x20= 3.9269 cm2
Similarly, the basal area for Heteropogon contortus in quadrate one will be 0.7 cm2 and in
quadrate two is 9.6 m2, thus the total basal area = 0.7+9.6= 10.3 cm2
Equation 1 Frequency** = Number of quadrate in which species occurred
Total number of quadrate studied
X 100
Eragrotis curcula occurred in one quadrate out of five quadrates, so its frequency is
1/5 x100 = 20, similarly Heteropogon contortus occurred in one and two so the
frequency will be then 2/5 x100 = 40.
Equation 2
Relative dominance (RD) = Total basal area of species
Equation 3
Relative density = Number of individuals of the species
Equation 4
Relative frequency (RF)
RF =
Total basal area of all the species X 100
X 100
Total number of individuals of all the species
Number of occurrence of species (frequency**)
Number of occurrence of all species (sum of frequency**)
X 100
Example:
For Shorea robusta ---Relative dominance =
19887.92
X 100  69.67 (error in chart)
28544.74
38
X 100  13.52
281
100
X 100  18.51
--- Relative frequency =
540
--- Relative density =
Therefore, the IVI of Shorea robusta = 69.67+13.52+18.51= 101.7
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Interpretation:



The species having maximum IVI is the dominant species for that assessed stand
(forest)
For this present example Shorea robusta is dominant with 101.7 IVI and the
next/second dominant species is Terminalia tomentosa with 43.25 IVI.
For cross checking the calculation mistakes, the total IVI should add up to 300, as
we have added up three variables- R-density, R-frequency and R-dominance
where each of them cannot exceed 100.
Adapted from: Handbook of PRACTICAL FORESTRY, by Pankaj Panwar and S.D.
Bhardwaj
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