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BIOLOGY INTERNAL ASSESSMENT
TOPIC 5 – ECOLOGY
RESEARCH QUESTION: The effect of grazing on the biodiversity of perennial angiosperms as measured
by Simpsons Index
PERSONAL ENGAGEMENT
Overgrazing is linked to many issues, such as water pollution, eutrophication, scarcity of water resources or
degeneration of coral reefs (Conserve Energy Future, 2012).
Many ecosystems have suffered irreversible damage done by overgrazing and biodiversity is negatively impacted.
Overgrazing is also linked to phosphorus and nitrogen contamination in the South China Sea (Conserve Energy
Future, 2012).
Malham Tarn is one of 8 alkaline lakes in Europe, located in Yorkshire Dales. Conservation grazing is said to be
used in Malham Tarn, which is sometimes essential for management of wildlife habitats. Even though overgrazing
has many restrains, conservation grazing control more aggressive animals, maintaining species–rich habitats and
by preventing scrub encroachment (Polskasites.com, 2017). Cattle is often used to avoid damage, as it only grazed
on the top part on the plant, therefore grazing by cattle is often selected to support sustainability. Personally, I
believe that maintaining mediocracy when taking advantage of land and nature is essential when staying
sustainable.
In order to establish whether sustainability is maintained and biodiversity is conserved, by employing conservation
grazing, I decided to investigate whether biodiversity is different in frequently and infrequently grazed area. Hence,
the research question generated is as follows: “The effect of grazing on the biodiversity of perennial angiosperms
as measured by Simpsons Index?”
BACKGROUND
Grazing livestock has an advantage as they convert resources which would be wasted into useful products. Three
main types of livestock used to graze grasslands are sheep, cattle and horses. Sometimes goats are also used.
(Polskasites.com, 2017).
Grazing can have a negative impact on biodiversity and bring damage to many ecosystems. For example, the
continued trampling of animals speeds up the death of vegetation as animals graze on the slightest shoots of new
growth (Conserve Energy Future, 2009), which means they consume recently planted vegetation before it fully
develops. The animals will eventually leave the soil bare, by eating all the plants in the (Articles.extension.org,
2011) and thus, the soil is exposed to harsh weather such as direct sunlight, heavy rain or high temperatures. This
disintegrated the rocks and carried the top soil away, which causes soil erosion (Conserve Energy Future, 2009).
Compaction and erosion caused by overgrazing can cause land degradation, and sometimes can lead to complete
desertification, as denying an area of vegetation is also depriving it of water, which leads to the soil being unable
to hold the water or the nutrients needed for plants to grow (Conserve Energy Future, 2009). The natural water
cycle is also affected by overgrazing, results in pollution such as animal waste or farming chemicals. These
pollutants can contaminate the local drinking water and oceans alike (Articles.extension.org, 2011). Additionally,
overgrazing significantly affects the naturally occurring abundance of species and their ability to regenerate
(Conserve Energy Future, 2009). Crops are originally made up of herbs with nutritional value and pastures of hight
quality, however, grazing by animals leads to damage of roots of plants which contain food reserves. The crops
are replaced by highly adaptive weeds and unpalatable plants, which have less nutritional value (Conserve Energy
Future, 2009).
Aside from biodiversity, grazing is also said to affect height of plants. Plants growing on grazed areas have to
tolerant to soil compaction and its effects on soil conditions, as plants are constantly being trampled (Field-studiescouncil.org, 2018). Trampling often results in different heights of vegetation, so competition for light may be a
factor (Field-studies-council.org, 2018). Additionally, plant growth is limited by reduced food production.
Chloroplasts are plant organelles containing chlorophyll, which is a green pigment that traps light energy needed
for photosynthesis to occur. Because most of the chloroplasts contained in a plant are located in the leaves, when
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leaves are trampled and destroyed by livestock, the number of chloroplasts enclosed in a plant is reduced. Since
the number of chloroplasts is directly proportional to the amount of photosynthesis occurring in a plant, the less
chloroplasts are present the less photosynthesis occurs, meaning less energy and food is produced. This limits the
plant growth, resulting in shorter plants (University et al., 2007). Moreover, seed production is prevented as the
growing point is destroyed (Deeprootsmag.org, 2017).
In order to establish which factors may impact plant life and biodiversity, a number of abiotic measurements will
be taken. These include soil temperature, moisture, organic matter, pH and depth. Soil temperature varies with
depth and time and the optimal soil temperature is between 6 and 24°C (Alberta.ca, 2019). It has an indirect effect
on plant growth, as it impacts root growth, as well as water and nutrient uptake (Alberta.ca, 2014).
Optimal soil moisture for clay soil is between 20-35%. Saturated soil is not advantageous for healthy plant growth
as the conditions in saturated soil are anaerobic (Help Desk, 2015).
Because Malham Tarn is an alkaline lake, the pH of the soil is slightly higher than typically expected. Soil pH
affects availability of nutrients, which are most available in the optimum 5.5 to 7.0 range
(Archive.naplesnews.com, 2019). Additionally, the structure of the soil is affected by the pH, especially in clay
soils. In high or low pH, the soil is hard to cultivate and tends to become sticky, whereas in the optimum range it
is granular (Archive.naplesnews.com, 2011).
The types of plants that are able to grow is deeply influenced by soil depth, as deeper soils tend to provide more
nutrients and water, as well as mechanical support (Sciencedirect.com, 2017).
The depth of the soil is likely to have an effect on height of plants, as deeper soils are able to grow plants with
larger roots.
Organic matter affects biological properties of the soil in chemical, biological and physical ways. Because of
livestock manure, I hypothesize that soil organic matter will be higher in the frequently grazed area. Manure is
an important source of carbon, which is an important source of energy that makes nutrients available to plants
(Garden and Garden, 2011).
The type of grazing animal has a large impact on the biodiversity. In Malham Tarn, cattle is employed. Due to
the structure of it’s mouth, cattle is only able to consume the shoot of the plant, leaving most of the stem and the
root untouched (U.S. Food and Drug Administration, 2019). This allows the more sensitive species to survive,
maintaining biodiversity.
In this experiment, frequently (12 month a year) and infrequently (1 month a year) grazed grasslands will be
investigated. Compared to usual soil conditions around the world, the soil in both of these areas tends to be more
alkaline. As shown above, moderate grazing can have positive impact on biodiversity. Based on this, species
diversity should not be much different in two areas as conservation grazing is done in Malham Tarn. However, it
can be predicted that height of plants and length of leaves is significantly different in two areas.
Null hypothesis: There is no significant difference between species diversity in frequently and infrequently grazed
grassland.
Alternative Hypothesis: There is a significant difference between species diversity in woodland and infrequently
grazed grassland.
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PROCEDURE
Variables:
In order to ensure that the results of the investigation are reliable, multiple
throughout the investigation.
TABLE 1: Control variables
CONTROL VARIABLE
REASONS FOR CONTROLLING THE
VARIABLE
Measuring equipment
Different measuring equipment has different
accuracy levels
Person carrying out the Minimizes researcher bias
investigation
Sampling technique
Ensures data sets are comparable
factors had to be kept constant
HOW
THE
VARIABLE
CONTROLLED
Use the same equipment
IS
Have the same person carry out the
investigation
Use the same sampling technique
Number of trials
Needed to make the investigation a fair test and
make the data comparable
Carry out 10 trials in each location
Time of the year
During different times of the year abiotic
factors vary, affecting the number of plants
growing
During different times of the day abiotic factors
vary
Carry out the experiment during the same
day
Time of the day
Height above sea level
Ensures that the height above sea level does not
affect the number and type of plants growing
Carry out the experiment as quickly as
possible and move on to the second
location as soon as 10 trials have been
carried out in the first
Choose locations so that both are at the
same height above sea level
Abundance of limestone
Limestone is alkaline and can therefore affect Choose locations that are equally far from
the growth of plants
the same alkaline lake
Distance from a body of water The number and type of plants growing is Choose locations so that both are equally
impacted by the pH of the soil, which is far from the lake
affected by the pH of the body of water
TABLE 2: independent, dependent and monitored variables
INDEPENDENT VARIABLE
DEPENDENT VARIABLE
MONITORED VARIABLES
Type of land
Infrequently grazed grassland (1
month a year)
Frequently grazed grassland (12
months a year)
Species diversity
Depth of soil
Height of the tallest plant
Length of the longest leaf
Soil depth
Soil temperature
Soil moisture
Soil organic matter content
pH of soil
Apparatus
Open quadrat (x1)
Soil sampling cups (x20)
Ruler (x1) ±0.1mm
Distilled water (400ml)
Oven (x2) ±1C
Garden shovel (x1)
pH meter (x1) ±0.01pH
Tape measure (x2) ±1cm
Soil pin (x1)
Crucible (x20)
Weighing scale (x1) ±0.01g
Calculator (x1)
Grass rod (x1)
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Method:
1. Using 2 tape measures, set up a 10x10 grid in infrequently grazed area
2. Using a calculator, generate 2 random number and use them as coordinates on the grid.
3. Place the bottom left corner of the quadrat on the point where the coordinates meet.
4. Take a soil sample from the middle of the quadrat using a small garden shovel. Place it in a sampling cup.
5. Measure the soil temperature by placing the soil thermometer halfway into the soil in the centre of the quadrat.
6. Stick the soil pin in the middle of the quadrat until it reaches rock.
7. Take out the soil pin and use a ruler to measure how far it went into the soil.
8. Measure the length of the longest leaf in the quadrat using a ruler.
9. Measure the height of the tallest plant in the quadrat using a ruler.
10. Identify different species of plants present in the quadrat and letter them.
11. Record the number of each species in the quadrat
12. Repeat steps 2-11 nine times
13. Repeat steps 1-12 in frequently grazed area.
Soil samples analysis:
1. Place 20g of soil into a measuring cylinder
2. Add 20ml of water
3. Mix well using a glass rod to form slush
4. Using a pH meter, record the pH of the slush
5. Repeat steps 1-4 with all other soil samples
6. Record the weight of the crucible
7. Record the weight of the crucible with the soil
8. Repeats steps 6-18 with other soil samples
9. Place 20 crucibles onto a tray and place the tray into an oven
Preliminary investigation
In order to establish where data samples would be taken from, a preliminary investigation was carried out. As
some of the infrequently grazed grassland was trampled by people, I chose to use the area that was not used for
walking, in order to eliminate extraneous variables. This is because height of plants would be negatively affected
by trampling, affecting my conclusions. Regarding the frequently grazed grassland, I chose an area roughly the
same height above the lake as in infrequently grazed grassland, in attempt to minimize the effect of different pH
levels in two areas.
Having collected data on height of plants, soil moisture and soil organic matter, I noticed a great difference in
measurements between the two areas, which I decided to prove using statistical tests.
Sampling technique and data processing
Due to the uniform nature of two areas, random sampling technique was employed. Using data collected,
Simpson’s diversity index will be calculated for every quadrat, in order to fairly compare which area maintains
richer biodiversity. To determine whether the difference in species diversity is statistically significant, a T-test
will be carried out. In addition, a T-test will be used to establish whether there is a significant difference in other
biotic factors, such as plant height and leaf length, as well as other abiotic factors.
Risk assessment
Ethical considerations: No major ethical considerations need to be taken into account in the experiment as no
animals were involved.
Environmental considerations: It is best to walk over plants as little as possible to minimize the disturbance done
to plants and animals.
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Safety considerations
TABLE 3: Risk assessment
1 – low, 2 – medium, 3- high
HAZARD
RISK
Stones,
slippery Falling or tripping over
slopes
Cold weather
Hypothermia
Species
Grazing animals
Getting attacked
Insects
Bites, infections
Spiky plants
Scratches, injuries
CONTROLS
Walk slowly and carefully
Likelihood
2
Severity
2
Wear warm clothes
1
3
Stay calm, don’t be loud, don’t walk
near the animals
Avoid contact with insects
2
3
3
2
Avoid contact with plants, wear
clothes that cover skin
3
2
RAW DATA
TABLE 4: Number of plants of each species in every quadrat in frequently grazed area
Q1
Q2
Q3
Q4
Q5
Q6
Q7
Q8
Spring sandwort
Marsh Helleborine
Blue moor -grass
Field Gentians
Dandelion
Alpine Pennycress
Milkwort
21
3
1
11
32
0
0
12
0
3
12
28
1
1
28
0
2
10
25
3
0
13
2
1
15
30
4
0
11
0
0
20
24
2
0
29
2
2
13
23
2
1
15
0
0
17
25
2
0
16
0
1
14
26
4
1
Q9
Q10
17
1
0
15
27
2
2
28
0
0
18
26
3
1
TABLE 5: abiotic and biotic factor measurements in frequently grazed area
Abiotic
factor
Soil
temperature
(°C) ±0.1
Q1
Q2
Q3
Q4
Q5
Q6
Q7
Q8
Q9
Q10
Mean
13.30
12.80
15.20
15.10
14.50
14.50
13.50
14.70
13.10
15.20
12.74
Standard
deviation
0.86
Soil
depth
(mm) ±1
Soil pH ±0.1
Soil moisture
(%) ±0.03
Soil organic
matter (%)
±0.04
Biotic factor
Height
of
tallest plant
(cm)
Length of leaf
(cm)
194.0
191.0
155.0
174.0
127.0
250.0
144.0
193.0
166.0
181.0
170.64
32.07
8.53
11.89
8.20
10.82
7.58
9.16
7.55
6.77
7.39
12.38
7.60
10.54
8.20
11.73
8.50
7.89
7.90
9.34
8.10
8.55
7.96
9.92
0.39
1.77
15.62
9.10
14.57
12.02
8.65
10.87
16.27
13.51
16.94
13.33
13.01
2.75
10.1
4.6
6.6
7.2
12.2
8.6
9.7
9.4
6.2
13.7
8.43
2.34
4.5
3.6
4.1
4.1
5.1
3.6
4.2
5.2
4.2
3.8
4.17
0.48
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TABLE 6: Number of plants of each species in every quadrat in infrequently grazed area
Species
Q1
Q2
Q3
Q4
Q5
Q6
Q7
Spring Sandwort
19
20
13
24
13
47
18
Milkwort
5
0
0
2
9
0
1
Lady’s Mantle
5
0
48
2
30
5
4
Marsh Helleborine
3
3
1
4
0
4
9
Rock Rose
4
5
0
3
0
4
0
Grass-of-Parnassus
4
4
1
5
0
3
2
Alpine Penny-Cress
2
7
4
0
4
5
2
Scurvy Grass
22
5
2
8
0
8
7
Melancholy Thistle
3
3
1
1
1
6
2
Flat Sedge
8
9
12
10
13
3
6
Field Gentians
8
4
0
11
3
18
1
Blue moor-grass
0
0
7
0
7
0
0
TABLE 7: abiotic and biotic factor measurements in frequently grazed area
Abiotic factor Q1
Q2
Q3
Q4
Q5
Q6
Q7
Q8
Soil
temperature
(°C) ±0.1
Soil
depth
(mm) ±1
Soil pH ±0.1
Soil moisture
(%) ±0.03
Soil organic
matter (%)
±0.04
Biotic factor
Height
of
tallest
plant(cm)
Length of leaf
(cm)
Q8
3
3
4
0
11
8
0
2
4
7
11
3
Q9
31
0
32
2
0
0
4
4
4
0
7
5
Q10
0
4
35
0
0
0
1
0
3
23
5
6
Q9
Q10
Mean
12.2
15.2
12.2
13.3
12.2
13.0
14.6
14.2
13.3
13.3
13.35
Standar
d
deviatio
n
1.04
64.00
172.00
201.00
329.00
145.00
132.00
420.00
199.00
225.00
110.00
190.90
118.46
7.79
35.05
7.88
44.32
7.62
33.67
7.56
32.90
7.62
35.26
7.54
37.98
7.50
41.09
7.49
36.38
7.56
41.36
7.43
42.24
7.60
38.03
0.14
3.98
12.63
14.10
11.47
13.62
8.57
9.67
14.85
8.97
10.02
10.56
11.45
2.24
35.90
38.00
51.00
42.20
41.00
42.50
46.70
48.50
34.20
55.00
43.50
6.38
13.20
14.70
15.20
11.80
11.00
12.30
12.50
13.00
18.20
8.00
12.9
2.57
PROCESSED DATA
Calculation of average abiotic and biotic factors:
Soil temperature – frequently grazed area
(13.30 + 12.80 + 15.20 + 15.10 + 14.50 + 14.40 + 13.50 + 14.70 + 13.10 + 15.20) / 10 = 12.74
Calculation of species diversity
𝐷=
𝑁(𝑁 − 1)
∑ 𝑛(𝑛 − 1)
D = Diversity / N = Total organism number - all species / n = Total organism number - each species
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Infrequently grazed Quadrat 1:
N = 19 + 5 + 5 + 3 + 4 + 4 + 2 + 22 + 3 + 8 + 8 = 83 / N–1 = 79 – 1 = 82 / N(N–1) = 6806
∑n(n-1) = (19×18) + (5×4) + (5×4) + (3×2) … = 994
𝐷=
N(N-1)
6806
9945
= 6.85
TABLE 8: species diversity in infrequently grazed grassland
Q1
Q2
Q3
Q4
Q5
6806.00
7140.00 6320.00 2652.00 7832.00
Q6
1260.00
Q7
756.00
Q8
1806.00
Q9
3080.00
Q10
3192.00
∑n(n-1)
994.00
2588.00
1314.00
468.00
2022.00
264.00
338.00
524.00
976.00
1024.00
Infrequently
grazed
diversity
6.85
2.76
4.81
5.67
3.87
4.77
2.24
3.45
3.16
3.12
TABLE 9: species diversity in frequently grazed grassland
Q1
Q2
Q3
Q4
Q5
Frequently
grazed
diversity
2.98
3.11
3.13
3.33
3.06
Frequently grazed grassland
Q6
Q7
Q8
Q9
Q10
3.45
3.16
3.49
3.39
3.32
Infrequently grazed grassland
Graph 1: Spread of species diversity as measured by Simpson’s Diversity Index in frequently and infrequently
grazed grassland. It can be seen that the average species diversity in frequently grazed grassland is higher than in
infrequently grazed grassland.
Calculation of T test for species diversity
𝑡=
𝑋1 = mean1
𝑋2 = mean2
𝑆1 = standard deviation1
𝑆2 = standard deviation2
|𝑋1 − 𝑋2 |
𝑆
𝑆
√𝑛1 + 𝑛2
2
1
𝑛1 = number of values1
𝑛2 = number of values2
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𝑡=
|3.24 − 3.74|
√0.17 + 0.96
10
10
= 1.49
Degrees of Freedom = (𝑛1 –1) + (𝑛2 –1) = 9 + 9 = 18 / Critical Value = 2.1
The calculated value of 1.49 is lower than the critical value 2.1 for 18 degrees of freedom at a significance level
of 0.05. This means that there is more than 5% probability that the results are due to chance. Thus, I can accept
the null hypothesis:
There is no significant difference between species diversity in frequently and infrequently grazed grassland.
Calculation of T-test for height of plants
𝑡=
|8.43 − 43.5|
√2.34 + 6.38
10
10
= 37.6
Degrees of Freedom = (𝑛1 –1) + (𝑛2 –1) = 9 + 9 = 18 / Critical Value = 2.1
The calculated value of 37.6 is higher than the critical value 2.1 for 18 degrees of freedom at a significance level
of 0.05. This means that there is less than 5% probability that the results are due to chance. Thus, I can accept the
alternative hypothesis:
There is a significant difference between height of plants in frequently and infrequently grazed grassland.
Calculation of Pearson’s Correlation Coefficient for soil moisture and soil organic matter vs. height of plants
As height was greater in infrequently grazed grassland than frequently grazed grassland, abiotic factor
measurements were taken into consideration in order to establish whether there is a significant correlation in the
average values of the same factor in the two grasslands. A Pearson’s Correlation Coefficient calculation was
carried out for soil moisture and soil organic matter, as a significant difference was noticed. Simpson’s diversity
index in each quadrat is compared with both abiotic factors. Pearson’s Correlation Coefficient is used to establish
strength of a relationship between two factors. If the value of the correlation coefficient is close to ±0.01, a strong
relationship can be assumed. The sign determines whether the relationship is negative or positive. It can be used
to provide explanation for the difference in height of plants between two grassland due to difference in soil
moisture and soil organic matter.
𝑟=
∑𝑋𝑌 −
√(∑𝑋 2 −
(∑𝑋)(∑𝑌)
𝑛
(∑𝑋)2
(∑𝑌)2
2
𝑛𝑥 ) (∑𝑌 − 𝑛𝑦 )
∑𝑋 = sum of X values / ∑𝑌 = sum of Y values / n = number of ‘pairs’ of data
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Graph 2: Height of plants is compared against Soil Moisture Levels in each quadrat. An overall positive correlation
can be seen in the graph – as % soil moisture levels increase, height of plants increases. Seeing as height can be
considered an indicator of growth, higher soil moisture levels allow for greater growth, therefore more flowering.
This results in greater number of seeds, leading to more plants.
TABLE 10: Pearson’s Correlation Coefficient Values for species diversity vs. soil moisture
X =Height of plants X2
Y = Moisture %
Y2
XY
10.10
102.01
35.05
1228.50
354.01
4.60
21.16
44.32
1964.26
203.87
6.60
43.56
33.67
1133.67
222.22
7.20
51.84
32.90
1082.41
236.88
12.20
148.84
35.26
1243.27
430.17
8.60
73.96
37.98
1442.48
326.63
9.70
94.09
41.09
1688.39
398.57
9.40
88.36
36.38
1323.50
341.97
6.20
38.44
41.36
1710.65
256.43
13.70
187.69
42.24
1784.21
578.69
35.90
1288.81
11.89
141.37
426.85
38.00
1444.00
10.82
117.07
411.16
51.00
2601.00
9.16
83.91
467.16
42.20
1780.84
6.77
45.83
285.69
41.00
1681.00
12.38
153.26
507.58
42.50
1806.25
10.54
111.09
447.95
46.70
2180.89
11.73
137.59
547.79
48.50
2352.25
7.89
62.25
382.67
34.20
1169.64
9.34
87.24
319.43
55.00
3025.00
8.55
73.10
470.25
∑𝑋 = 520
∑𝑋 2= 20179.63
∑𝑌 = 479.32
∑𝑌2=15614.07
∑XY = 7615.97
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𝑟=
1737.56 −
(520)(479.32)
10
(520)2
(479.32)2
√(20179.63 −
)
10 ) (15614.07 −
10
= 0.9414
Degrees of Freedom = (𝑛𝑥 –1) + (𝑛𝑦 –1) = 9 + 9 = 18 / Critical Value = 0.562
The absolute value of the calculated value of 0.9414 is higher than the critical value 0.562 for 18 degrees of
freedom at a significance level of 0.01. This means that there is less than 1% probability that the results are due to
chance. Thus, I can reject the null hypothesis and accept the alternative hypothesis:
There is a significant correlation between soil moisture levels and height of plants, and the positive correlation
seen in the data is most likely due to chance.
For soil organic matter:
𝑟=
−221.181
√(134.082)(4126.69)
= −0.2973
Degrees of Freedom = (𝑛𝑥 –1) + (𝑛𝑦 –1) = 9 + 9 = 18 / Critical Value = 0.562
The absolute value of the calculated value of -0.2973 is lower than the critical value 0.562 for 18 degrees of
freedom at a significance level of 0.01. This means that there is more than 1% probability that the results are due
to chance. Thus, I can accept the null hypothesis:
There is no significant correlation between soil organic matter and height of plants, and any correlation seen in
the data is most likely due to chance.
CONCLUSION
The aim of this investigation was to establish whether there is a significant difference in species diversity between
frequently and infrequently grazed grasslands, to see if conservation grazing in employed in Malham Tarn and
biodiversity is conserved.
As can be seen in the graph 1, and supported by the T-test, there is no statistical significant difference in species
biodiversity between frequently and infrequently grazed grassland (mean of 3.24 vs. 3.74 species diversity index
respectively). These findings do not support my original hypothesis but can be explained by the fact that
conservation grazing is employed in Malham Tarn, which maintains biodiversity. As described above, grazing is
usually thought to reduce diversity of plants as animals eat all the plants in the grassland, leaving the soil bare.
However, in this experiment the diversity of plants in frequently and infrequently grazed grasslands were found to
be really close. This can be explained by the fact that conservation grazing was employed in Malham Tarn, which
seemed to maintain biodiversity. Firstly, livestock allows allows the less competitive plants, for example
wildflowers, to grow alongside more competitive plants by eating and removing vegetation (South Manchester
Nutrition, 2009). This also encourages germination as the build-up of dead material is removed, which is necessary
as all grass and wildflower seeds need to be in direct contact with ground to establish a root system and germinate
(South Manchester Nutrition, 2009).
As mentioned previously, the area is grazed by cattle. Due to the structure of their mouth and fewer teeth, they
are only able to consume the top part of plant, leaving the rest untouched. This allows more sensitive species to
survive in frequently grazed grassland, maintaining biodiversity (U.S. Food and Drug Administration, 2019).
Furthermore, biodiversity is improved by dispersal of seeds by animals’ hooves during grazing and reduced
competition between the same species of plant as the seeds are more likely to be found further away from their
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parent. Livestock also break up the crust by trampling the soil, stimulating the growth of grass (Fao.org, 2019).
This ensures a variety of species continues to flourish (Polskasites.com, 2019).
As can be seen in graph 2, and further supported by the T-test, there is a significant statistical difference in height
of plants in frequently and infrequently grazed grassland (mean of 8.43cm and 43.50cm respectively). A reason
for higher plants in infrequently grazed area could be soil moisture levels. Frequently grazed grassland had an
average of 9.92%, whilst infrequently grazed grassland had an average of 38.03% water. Neither of the areas had
an optimal soil moisture percentage. In infrequently grazed area the soil is oversaturated, whilst in frequently
grazed area it is too dry. When clay soils are dry, they become difficult for the roots to dig in and when they are
over-saturated, they deprive the plant of oxygen (Soils, 2017).
However, soil moisture levels in infrequently grazed grassland are more optimal for plant growth (optimal levels:
20-35%) than in frequently grazed grassland, which could be the reason for increased plant height in infrequently
grazed grassland (Spruce, 2019). To further support this, a Pearson’s Correlation Coefficient was calculated, which
stated that there is a significant positive correlation between height of plants and soil moisture levels: as soil
moisture levels increased from 6.77% up to 42.24%, height of plants increased form 4.6cm to 55cm.
All the other abiotic factors that were measured do not vary much between the two areas, hence it can be assumed
that they do not make a big difference for plant life. For example, soil temperature was 12.74˚C in frequently
grazed area and 13.35 ˚C in infrequently grazed area. Because measurements were not taken simultaneously, it
can be assumed that time of the day has affected these results. Soil depth differed by 20cm between the two areas
(170.64cm in frequently grazed and 190.9cm in infrequently grazed), however since both of these measurements
are above the minimum soil depth required for plants to grow (45cm), it can be assumed that soil depth did not
affect biotic measurements. Even though the average soil organic matter is higher in frequently grazed are than in
infrequently grazed area (13.01% compared to 11.45%), no correlation was found in the Pearson’s Correlation
Coefficient between soil organic matter and height of plants.
In conclusion, conservation grazing is employed in Malham Tarn, which maintains diversity of plants, even though
heights of plants and plant leaves are affected.
EVALUATION
One of the strengths of the investigation includes that a number of abiotic and biotic factors were taken into
consideration, and after carrying out a correlation test, an effect of certain abiotic factors could be determined on
biotic factors. For example, height of plants was found to be significantly affected by % soil moisture.
Trying to examine the reliability of collected data, it is usually compared to previous measurements. However,
there are no abiotic factor data collected before in these locations. From the processed data, we can tell that the
standard deviation is relatively low for most of the measurements, suggesting the data points are close together,
implying reliability of results. However, considering every quadrat was only measured once, the results can be
assumed to be unreliable. No uncertainties are implicated as measuring tools were not used, which could also
impact reliability of results.
Abiotic measurements were found to have low standard deviation, implying that the data points are not spread out,
suggesting that data is reliable, however, lack of repeats in each quadrat questions the reliability of data.
No anomalies can be identified due to lack of previous research done in this area, leading to lack of expected
results. In attempt to minimize the effect of natural variations on the abiotic factor measurements in different
quadrats, 10 samples were taken.
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TABLE 8: limitations and modifications of the investigation
PROBLEM
CORRECTION
Research bias when
More repeats.
collecting data
One person collecting all the data.
Difficult to count
More repeats.
small plants
Difficult to
More repeats.
distinguish between
Track every plant down its root.
different plants
Measuring height of
More repeats. Use a ruler with a smaller
plants
scale. Take measurements from the same
point at the root.
Measuring length of
leaves
Measuring soil depth
Trampling reduces
flowering of plants
Measure all longer leaves.
Stretch out all leaves.
More repeats.
Measure in multiple points in the quadrat
and take the average.
More repeats. Carry out an investigation
in a wider area.
Establish species of plants by their leaves
rather than by their flowers
EFFECT ON RESULTS
Species may be omitted or unnoticed depending on
the researcher.
Many plants in both, frequently and infrequently
grazed areas, were very small and hard to identify.
Many plants had many leaves, which covered the
roots and vegetation was thick. This made it
difficult to tell the number of plants in a quadrat.
If the starting point of the measurement is different
for each plant, different heights are recorded,
affecting the conclusions drawn from investigation.
Because some leaves were not stretched out, they
could have appeared shorter than they are and were
therefore not measured.
The depth in the center of the quadrat was not
representative of the depth of soil in the quadrat as
it varied in different points.
In frequently grazed area, plants’ ability to flower is
reduced, therefore they can be more difficult to
distinguish, making it easier for the researcher to
misclassify plants and hence identify less species.
Suggestions for further research
As species diversity was not found to be statistically significant, it can be assumed that the plants that grow in
frequently grazed grassland have different structure to those that grow in infrequently grazed grassland, thus a
research question can be generated, “How does the root type vary between frequently and infrequently grazed
land?”
As the aim of this research was to establish whether sustainability is maintained in conservation grazing, it would
be interesting to investigate whether deforestation has an impact on biodiversity – “Is there a significant difference
in biodiversity between grassland and woodland?”
As cattle is primarily employed in Malham Tarn, further investigation can be done to research “How does the type
of grazing animal affect biodiversity/height of plants?”
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