Transcript Ecology and Conservation

Quadrats
Advanced Higher Biology
A quadrat is a square frame, often 0.5m x 0.5m
(0.25m2) but can be 1m x 1m. Sometimes it
contains a grid of smaller squares.
50cm
50cm
1. Decide on your research question.
2. Select the locations to be surveyed.
3. Select two or more species to include in your surveys (if you are
comparing biodiversity, you will need to include all species)
4. Mark out the area in a grid. The area will depend on the locations
and the time available. The grid can take a long time but not so long
if you cooperate and work together well.
5. Generate random numbers – numbers out of a hat or use the
random number function on your calculators. These numbers
provide your coordinates where you will place your quadrat.
6. Count the numbers of the selected species of plants in each
quadrat. Always count the number of plants, not the flower heads!
7. Process your raw data and compare.
Things to consider . . . .
Select the species being surveyed . . . . Here we will
make an estimate of the number of daisies and
dandelions.
The area where you set up your grid should be
representative of the habitat you are studying
It is important not to trample the area being surveyed
any more than you need to.
You need to decide on the area to be marked out as a
grid . . . . The larger the better but the process can be
time consuming so you need to work within the time
constraints.
Decide how many quadrat samples you are going to
take. Sources will differ but a suggested sample covering
20% of the grid is common.
Random coordinates
6
5
4
3
x
y
5
1
2
6
3
3
3
5
4
3
6
1
Here the area is 6 x
6 metres.
Where do you place
the quadrats?
2
1
1
2
3
4
5
6
Random coordinates
6
5
4
3
x
y
5
1
2
6
3
3
3
5
4
3
6
1
The quadrats are placed
at the nearest corner to
1,1 on the grid as shown.
This may not be the best
distribution but it is how
it worked out when using
a die.
2
1
1
2
3
4
5
6
Results
3,5
For illustrative purposes, in spite of what I
have said, I will count the flowers as I am
not able to sort out the stems with my
fingers. Remember though that some plants
may not be in flower. I have placed the
coordinates where there are no daisies or
dandelions.
5,1
2,6
4,3
3,3
Coordinates Daisies
Dandelions
5,1
6
34
2,6
8
25
3,3
11
18
3,5
11
20
4,3
7
11
6,1
6
19
6,1
Data Processing
Coordinates Daisies
Dandelions
Remember these are estimates!
5,1
6
34
Population Density
2,6
8
25
Population Density
3,3
11
18
Daisies
3,5
11
20
4,3
7
11
=
average per quadrat
area of the quadrat
= 8.17 = 32.68m-2
0.25
Dandelions = 21.17 = 84.68m-2
0.25
Total Population
6,1
Average
6
8.17
19
21.17
Total population = Population density x total area
The total area may extend beyond the grid marked
on the ground.
Cumulative Frequency
The data below is for Ranunculus acris counted within an area of un-grazed meadow
60
1
2
3
4
5
6
7
8
9
10
11
12
Number of
Ranunculus
acris
9
17
12
18
15
8
16
9
10
15
13
10
Mean of the
numbers
counted
9.0
13.0
12.7
14.0
14.2
13.2
13.6
13.0
12.7
12.9
12.9
12.7
Estimate of
Population
-2
density m
36.0
52.0
50.7
56.0
56.8
52.7
54.3
52.0
50.7
51.6
51.6
50.7
50
Estimated Population m-2
Quadrat
number
40
30
20
10
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
Quadrat number
After 10 quadrat samples, any further samples are unlikely to have any significant effect on
the overall estimate, so 10 samples would be considered sufficient. This is an alternative
approach to surveying the suggested area of 20%. We can use an estimate of 51m-2.
In reality an area usually contains more than two
species and we may want to compare the
biodiversity between two areas either to study the
effect of a human activity or as part of a study into
succession (climax communities usually have a
higher biodiversity). This area contains plantain,
buttercups, clovers, various types of grasses and
probably (on close inspection) some mosses.
Biodiversity considers both the number of species
and the eveness in population size. If one species
dominates, the biodiversity is low.
Total number of species found
Cumulative Total Number of Species
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
1
2
3
4
5
6
7
8
9
Quadrat Number
10 11 12
After 8 quadrat samples, the
total number of species found
is 18. Further sampling does
not find any further species.
While we cannot eliminate
the possibility of another rare
species within the survey
area, 8 quadrat sites are
considered to be sufficient to
sample the area. Further
sampling would be a waste of
time.
Determination of the Simpson’s
Diversity Index
Species
Ranunculus acris
Taraxacum officinale
Bellis perennis
Plantago major
Lolium perenne
Trifolium repens
Trifolium pratense
Dactylis glomerata
Phleum pratense
Agrostis capillaris
Anthoxanthum odoratum
Cynosurus cristatus
Centaurea cyanus
Urtica dioica
Onopordum acanthium
Dactylorhiza fuchsii
Lychnis flos-cuculi
Ajuga reptans
N(N-1)
D=
n(n-1)
Quadrat number
1
2
8
3
9
15
10
15
5
6
26
21
15
23
12
16
4
3
12
14
6
4
4
6
1
0
0
0
0
1
8
2
0
0
0
0
0
0
3
9
12
12
4
19
24
5
9
18
3
2
2
2
2
1
0
4
0
4
12
14
14
2
31
21
4
8
17
9
8
0
0
1
0
2
2
0
5
14
12
9
6
14
16
9
2
10
1
0
1
0
0
1
3
2
5
6
5
15
8
1
16
1
19
7
20
7
1
3
1
1
2
0
4
0
7
16
12
16
0
15
9
12
2
4
5
3
2
0
2
0
0
1
2
8
4
13
12
4
26
29
2
2
5
6
4
0
4
1
1
4
0
0
D = Diversity index
N= total number of organisms of all species found
n= number of individuals of a particular species
Total
71
102
96
28
168
138
79
37
100
41
28
9
7
8
15
9
13
7
Determination of the Simpson’s
Diversity Index
Species
Ranunculus acris
Taraxacum officinale
Bellis perennis
Plantago major
Lolium perenne
Trifolium repens
Trifolium pratense
Dactylis glomerata
Phleum pratense
Agrostis capillaris
Anthoxanthum odoratum
Cynosurus cristatus
Centaurea cyanus
Urtica dioica
Onopordum acanthium
Dactylorhiza fuchsii
Lychnis flos-cuculi
Ajuga reptans
# of each
species
71
102
96
28
168
138
79
37
100
41
28
9
7
8
15
9
13
7
N(N-1)=912980
N(N-1)
n(n-1)
4970
10302
9120
756
28056
18906
6162
1332
9900
1640
756
72
42
56
210
72
156
42
n(n-1) =92550
D=
n(n-1)
D = Diversity index
N= total number of organisms of all species found
n= number of individuals of a particular species
912980
D=
= 9.86
92550