Monday 16 April 2012

Experiment in the forest – By Vicky and Maggie.

Sampling Plant Biodiversity

Maggie and I chose to investigate the plant biodiversity in different areas of the forest. We hypothesised that plant biodiversity would be higher in the locations exposed to the sun due to the plants photosynthesising and not having to compete for sunlight. We decided we would examine three areas of the forest using two variables the first was elevation and the second looked at the level of light. If you follow the path through the forest you will notice that the incline increases the further into the forest you go. We followed the path to the outside perimeter of the forest and therefore the highest point we could reach. Once we had selected a sampling location we randomly threw a 10x10 grid into an area in the shade, then an area in the sunlight and measured the plant diversity in the grid. The results were recorded in a table along with the light measurement in (lx) and the elevation of the sampling site. This process was repeated in a sampling area of low, medium and high elevation and random samples were taken from areas in shade and sunlight. We analysed the data using two different methods, the basic biodiversity Index and the Simpson Index of Diversity. When comparing the data, we found that the basic biodiversity index and the Simpson index of diversity showed that plant biodiversity was highest on medium ground elevation in the light, but this is probably due to the woodlands being far less dense then the lower and higher ground where we found that one species appeared to be more dominant then another. We were however, surprised to find that a greater number of species was found in all the sampling areas in the shade. There were flaws in our experiment however, so if we were to repeat the experiment again we would make sure that we were able to ascertain that the areas we sampled in the shade were under a canopy and in the shade at all times.




The raw data and calculations collected from our investigation are shown in the tables below.


 West lower ground
Species
Percentage covered %
Sunlight or shade
Light (lx)
B
85
Sunlight
258 x 100
C
3
Sunlight
258 x 100
E
1
Sunlight
258 x 100
D
5
Shade
38 x 100 (378 x 10)
B
83
Shade
38 x 100 (378 x 10)
A
11
Shade
38 x 100 (378 x 10)





South path medium ground
Species
Percentage covered %
Sunlight or shade
Light (lx)
B
100
Shade
190 x 100
A
10
Shade
190 x 100
F
4
Shade
190 x 100
G
6
Shade
190 x 100
F
6
Sunlight
223 x 100
A
19
Sunlight
223  x 100
B
2
Sunlight
223 x 100




North higher ground
Species
Percentage covered %
Sunlight or shade
Light (lx)
A
1
Sunlight
215 x 100
A
1
Shade
21 x 100
B
70
Sunlight
215 x 100
B
100
Shade
21 x 100
C
1
Shade
21 x 100
D
1
Shade
21 x 100

 



Using the raw data collected we calculated a Biodiversity score, using 2 different methods.
Method 1 - a Basic Biodiversity Index and method 2 - Simpson Index of Diversity.



Method 1 – Basic Biodiversity Index

Lower ground:
Sunlight or shade
Number of species
Total number of individuals
Basic Biodiversity Index
Light
3
89
0.0337
Shade
3
99
0.0303

Medium ground:
Sunlight or shade
Number of species
Total number of individuals
Basic Biodiversity Index
Light
3
27
0.1111
Shade
4
120
0.0333

Higher ground:
Sunlight or shade
Number of species
Total number of individuals
Basic Biodiversity Index
Light
2
71
0.0281
Shade
4
103
0.0388



Method 2 - Simpson Index of Diversity

Lower ground light:
Species
n (number of individuals)
n(n-1)
B
85
7140
C
3
6
E
1
0



Total N
89

Total n(n-1)

7146
                                                               
                                                                 D = 1 - (7146/7832) = 0.087
Lower ground shade:
Species
n (number of individuals)
n(n-1)
A
11
110
B
83
6806
D
5
20



Total N
99

Total n(n-1)

6936

                                                                 D = 1 – (6936/9702) = 0.286
Medium ground light:
Species
n (number of individuals)
n(n-1)
A
19
342
B
2
2
F
6
30



Total N
27

Total n(n-1)

374

                                                                    D = 1 – (374/702) = 0.467

Medium ground shade:
Species
n (number of individuals)
n(n-1)
A
10
90
B
100
9900
F
4
12
G
6
30



Total N
120

Total n(n-1)

10032

                                                                   D = 1 – (10032/14280) = 0.297
Higher ground light:
Species
n (number of individuals)
n(n-1)
A
1
0
B
70
4830



Total N
71

Total n(n-1)

4830

                                                                                D = 1 – (4830/4970) = 0.281

Higher ground shade:
Species
n (number of individuals)
n(n-1)
A
1
0
B
100
9900
C
1
0
D
1
0



Total N
103

Total n(n-1)

9900

                                                                                D = 1 – (9900/10506) = 0.057