The mean relative humidity is 46.7% in coppiced woodland whereas in ancient woodland the relative humidity is 60.25%, which is greater than in coppiced woodland. The average air temperature is 27.4°C in coppiced woodland, whereas it is 20.1°C in ancient woodland. The mean relative humidity and the air temperature both affect the rate of transpiration. Transpiration is the loss of water vapour, by diffusion down a water potential gradient, from a plant to its environment. The cells in the mesophyll layers are not tightly packed and have many spaces around them filled with air. The walls of the mesophyll cells are wet and some of this water evaporates into the air spaces, so that the air inside the leaf is saturated with water vapour. The air in the internal spaces has direct contact with the air outside the leaf through the stomata. When there is water potential gradient between air inside the leaf and outside the leaf the water vapour will move down a water potential gradient out of the leaf. In the coppiced woodland we found it has a lower mean relative humidity than found in ancient woodland. A low humidity increases the rate of transpiration as it steepens the water potential gradient between the air inside the leaf and the air outside the leaf so the water vapour moves down a water potential gradient out of the leaf more quickly. This is the case in the coppiced woodland. Further the rate of transpiration is increased by a higher temperature. Higher temperatures are found in the coppiced woodland of 27.4°C. This increased temperature steepens the water potential the water vapour will diffuse down. As a result water vapour diffuses down the water potential gradient between the air inside the leaf and outside the leaf more quickly, increasing the rate of transpiration. Grasses and xerophytes are adapted to dry conditions: they can close their stomata and allow their leaves to wilt to reduce the rate of transpiration from their leaves. (1, 5)
The mean % of humus in the soil is 13.72% in coppiced woodland and 15.56% in ancient woodland. We found out that the coppiced woodland contains higher species diversity by using the species diversity index. As containing a greater variety of species we would have expected the coppiced woodland to contain a higher mean % of humus in the soil as the plants die, they decay to produce humus and improve the quality of the soil. Some areas will be shallower than others due to compaction of soil by humans and grazing animals. (4)
The soil quality will also be enhanced due to the presence of rabbits and other animals grazing on the land. Those animals add nitrate to the soil as they excrete faeces, which decomposes to form ammonium in the soil. Further the process of nitrogen fixation by lightning, rhizobium or free living bacteria in the soil converts nitrogen in the air to organic nitrogen in the soil which decomposes to ammonium which is then nitrified further by nitrobacter and nitrosomonas in the soil forming nitrates which are then taken up by the plants. Grazing prevents the process of plant succession which will reduce the species diversity of an area. This could be one of the reasons for the low species diversity in ancient woodland. Compaction reduces the amount of air available in the soil and oxygen is needed for oxidative phosphorylation in respiration to accept the electrons from the oxidised hydrogen in the electron transport chain. The oxygen is reduced to give water. The transfer of electrons down the ETC makes energy available to convert ADP and inorganic phosphate to ATP. (1, 4, 6)
When using the species diversity index the result was that the coppiced woodland has greater species diversity with the value of 4.83 (to 3 s.f.). Whereas the ancient woodland has a species diversity index of 2.87 (to 3 s.f.). The higher species diversity index found in the coppiced woodland suggests a well-established, stable community with many successful species. The lower species diversity index found in the ancient woodland assumes a less well-established, less stable community often dominated by just a few species. The ancient woodland only had 5 species when carrying out the fieldwork: Dog’s mercury, Ground ivy, nettle, Bluebell and grasses, sedges and moss. Out of those five species three are indicator species: Dog’s mercury, Ground Ivy and Bluebell for ancient woodland. On the other hand in coppiced woodland the variety of species was much greater with ten different species.
The average % of water in soil in coppiced woodland is 60.23%, whereas in ancient woodland it is 52.80%. In ancient woodlands some species have long taproots which grow towards the water table, where they will be greater availability of water. As a result the soil is drier near the surface. We took our soil samples from near the surface. Whereas in coppiced woodlands the species have their roots near the surface to reach the water and the soil has a higher average % of water in the soil. Flowering plants have root hairs, which are very thin extensions of the cells that make up the outer layer of a root. Each soil particle is coated with a thin layer of water and it is this water the root hairs make contact with and absorb it by osmosis. The water moves down a water potential gradient as there is a lower potential inside the root hair cells diffusing into the root hair cell.
The mean soil pH is 5.7 in both ancient and coppiced woodland. When carrying out the soil pH test the mean result for coppiced woodland was a pH of 7.8, whereas in ancient woodland the mean test result was found to be 6.2 which is a slightly lower value than found in the coppiced woodland. Enzyme activity is further affected by the pH of the soil. As each enzyme has its optimum temperature, each enzyme has its optimum pH where its activity is at a maximum. Most enzymes have their greatest activity at fairly neutral conditions. pH is a measure of the concentration of hydrogen ions in a solution. The lower the pH, the higher the hydrogen ion concentration. Hydrogen ions can interact with the R groups of amino acids, affecting the way in which they bond with each other and therefore affect their 3D arrangement. A pH which is very different from the optimum pH can cause denaturation of an enzyme. The mean soil pH is for both types of woodland the same; this could assume that it is the optimum pH for enzyme reactions to occur. (1)
The bar chart showing the average air temperature in coppiced and ancient woodland shows clearly that the average air temperature in coppiced woodland is greater than in ancient. In ancient woodland it is an average temperature of 20.1°C and in coppiced woodland it is 27.4°C- a difference of 7.3°C between both woodlands. The bar chart demonstrating the % of humus in the soil shows that in ancient woodland there is a higher % of humus in the soil of 15.56%, whereas in coppiced woodland the % of humus in the soil is 13.72%- a relatively small difference of 1.86% between ancient and coppiced woodland. The following bar chart outlining the average pH demonstrates that both woodlands have the same average pH of 5.7. The bar chart illustrating the average light intensity in coppiced and ancient woodland shows that in coppiced woodland the average light intensity is 1411 lux more than twice the amount found in ancient woodland where the average light intensity is 674 lux. The bar chart screening the average relative humidity shows that the ancient woodland has a higher mean relative humidity of 60.3%, whereas in coppiced woodland the mean relative humidity counts for 46.7%. As the air temperature the soil temperature is greater in coppiced woodland than in ancient woodland- in coppiced woodland it is 15.1°C and in ancient woodland it is 13.7°C. The bar chart demonstrating the average % of water in soil shows that the coppiced soil samples had a greater % of water in the soil than the ancient soil samples. The % in coppiced woodland is 60.23% and in ancient woodland the % of water in the soil is 52.80%. The last bar chart illustrates the average results of the soil pH test using ancient and coppiced woodland soil samples. The outcome shows that average pH in the soil samples in coppiced woodland is 7.8 whereas in ancient woodland soil samples it is 6.2 which is slightly more acidic than the more neutral soil samples in the coppiced woodland.
Chi-squared (4, 7):
Stage 1:
Null hypothesis: There is no difference in species abundance and species diversity between coppiced and ancient woodland.
Alternative hypothesis: There are differences in the species abundance and diversity between the two woodlands- ancient and coppiced.
Stage 2:
Stage 3:
Expected frequencies:
∑O=130
For k1 (all values rounded to the nearest whole number):
- (∑k1*∑r1)/∑0=14.53846…=15
- (∑k1*∑r2)/∑0=12.461538…=12
- (∑k1*∑r3)/∑0=1.661538…=2
- (∑k1*∑r4)/∑0=0.4153846…=0
- (∑k1*∑r5)/∑0=1.66153846…=2
- (∑k1*∑r6)/∑0=3.323076…=3
- (∑k1*∑r7)/∑0=13.292307…=13
- (∑k1*∑r8)/∑0=2.4923076…=2
- (∑k1*∑r9)/∑0=0.4153846…=0
- (∑k1*∑r10)/∑0=1.2461538…=1
- (∑k1*∑r11)/∑0=2.076923…=2
- (∑k1*∑r12)/∑0=0.4153846…=0
For k2 (all values rounded to the nearest whole number):
- (∑k2*∑r1)/∑0=20.461538…=20
- (∑k2*∑r2)/∑0=17.53846…=18
- (∑k2*∑r3)/∑0=2.3384615…=2
- (∑k2*∑r4)/∑0=0.5846153…=1
- (∑k2*∑r5)/∑0=2.3384615…=2
- (∑k2*∑r6)/∑0=4.676923…=5
- (∑k2*∑r7)/∑0=18.707692…=19
- (∑k2*∑r8)/∑0=3.5076923…=4
- (∑k2*∑r9)/∑0=0.58461538…=1
- (∑k2*∑r10)/∑0=1.75384615…=2
- (∑k2*∑r11)/∑0=2.9230769…=3
- (∑k2*∑r12)/∑0=0.58461538…=1
Stage 4:
Chi-squared for coppiced woodland:
- (O-E)/E=225/15=15
- (O-E)/E=81/12=6.75
- (O-E)/E=1/2=0.5
- (O-E)/E=0/0=0
- (O-E)/E=4/2=2
- (O-E)/E=25/3=8.33333…
- (O-E)/E=81/13=6.23076923…
- (O-E)/E=16/2=8
- (O-E)/E=1/0=∞
- (O-E)/E=4/1=4
- (O-E)/E=9/2=4.5
- (O-E)/E=1/0=∞
Add 1-12 up: 55.314069…=55.3 (to 1 d.p.)=X2
Chi-squared for ancient woodland:
- (O-E)/E=225/20=11.25
- (O-E)/E=81/18=4.5
- (O-E)/E=1/2=0.5
- (O-E)/E=0/1=0
- (O-E)/E=4/2=2
- (O-E)/E=25/5=5
- (O-E)/E=81/19=4.2631578…
- (O-E)/E=16/4=4
- (O-E)/E=1/1=1
- (O-E)/E=4/2=2
- (O-E)/E=9/3=3
- (O-E)/E=1/1=1
Add 1-12 up: 38.5131578…=38.5 (to 1 d.p.)= X2
Stage 5:
Calculate degrees of freedom:
Df=(r-1)*(k-1)
Degrees of freedom for coppiced and ancient woodland:
Df=(r-1)*(k-1) = (12-1)*(2-1) =11
Stage 6:
Both chi-squared values for the ancient and coppiced woodland are less than 0.05, which means the results of 38.5 (to 1 d.p.) for ancient and 55.3 (to 1 d.p.) for coppiced woodland are both highly significant and not due to chance. Therefore the number of species we observed in each category is significantly different from what would be expected. Both values of chi-squared are smaller than the conventionally accepted significance level of 0.05. As a result we can reject our null hypothesis that there is a difference in species abundance and species diversity between coppiced and ancient woodland. We have to accept the alternative hypothesis that there are differences in species abundance and diversity between the ancient and coppiced woodland.
Species diversity index (4):
N=the total number of all the organism in the community
n=the number of organisms of a particular species
D= (N*(N-1))/ (∑n*(n-1))
Area coppiced woodland:
- N=3+1+4+8+22+6+1+3+5+1=54
- (N-1)=53
- N*(N-1)=54*53=2862
- Dog’s mercury=n*(n-1)=0
- Ground ivy= n*(n-1)=3*2=6
- Nettle= n*(n-1)=1*0=0
- Bluebell= n*(n-1)=0
- St john’s wart= n*(n-1)=4*3=12
- Spear thistle= n*(n-1)=8*7=56
- Grass, moss and sedges= n*(n-1)=22*21=462
- Hawthorn= n*(n-1)=6*5=30
- Primrose= n*(n-1)=1*0=0
- Dock leaf= n*(n-1)=3*2=6
- Bramble= n*(n-1)=5*4=20
- Forget-me-not= n*(n-1)=1*0=0
- ∑n*(n-1)=6+12+56+462+30+6+20=592
- D=2862/592=4.83445945…=4.83 (to 3 s.f.)
Area ancient woodland:
- N=35+27+3+1+10=76
- (N-1)=75
- N*(N-1)=76*75=5700
- Dog’s mercury=n*(n-1)=35*34=1190
- Ground ivy= n*(n-1)=27*26=702
- Nettle= n*(n-1)=3*2=6
- Bluebell= n*(n-1)=1*0=0
- St john’s wart= n*(n-1)=0
- Spear thistle= n*(n-1)=0
- Grass, moss and sedges= n*(n-1)=10*9=90
- Hawthorn= n*(n-1)=0
- Primrose= n*(n-1)=0
- Dock leaf= n*(n-1)=0
- Bramble= n*(n-1)=0
- Forget-me-not= n*(n-1)=0
- ∑n*(n-1)=1190+702+6+90=1988
- D=5700/1988=2.8672032…=2.87 (to 3 s.f.)
Evaluation:
The investigation went well but there are still some anomalies as the experiment was carried out in nature and not everything can be as accurate as when carried out in a school lab. Anomalies could be as a result of not carrying out enough repeats when measuring the abiotic factors or not handling the measuring apparatus correctly causing inaccurate results leasing to wrong assumptions. When taking soil samples from both woodlands, they were not used until one week after collecting them. By this time water from the soil samples could have evaporated, reducing moisture content of the soil, causing inaccuracy in the data obtained.
Comment on main error:
The main error was carrying the investigation out in the summer only and not taking into account all other three times of the year as different plants have different seasons of growing. This limitation may have caused the greatest inaccuracy and as a result our results are inaccurate and we have reduced species diversity. An improvement would be to consider all times of the year when carrying out another investigation in nature this would assure us more accurate outcomes. As we were a school class we didn’t have the time to consider all seasons throughout the year as this would have taken too much time into account.
Comment on species diversity index:
Due to other limitations, e.g. not considering all times of the year, the species diversity index is not as accurate as it could be. As expected the coppiced woodland has greater species diversity than the ancient woodland. The coppiced woodland has a species diversity index of 4.83 (to 3 s.f.) and the ancient woodland has a species diversity index of 2.87 (to 3 s.f.) which is roughly two units less than in the coppiced woodland. On the whole the species diversity index was easy to calculate.
Comment on chi-squared:
Our chi-squared values are accurate but not as accurate as they could be due to other limitations. As expected we rejected our null hypothesis and had to accept our alternative hypothesis. Due to grazing and not taking into account the plant growth during the whole year our chi-squared values are not as accurate as they could be. On the whole the chi-squared values were easy to calculate.
Comment on standard deviation:
Overall the standard deviations vary between coppiced and ancient woodland. All standard deviations, except the standard deviation for soil pH, are greater in coppiced woodland than in the ancient woodland. The highest standard deviation is for the light intensity in coppiced woodland with ±424.95 (to 2 d.p.), which means my results are very unreliable. The smallest standard deviation of ±0.16 for soil temperature in ancient woodland is very reliable and accurate.
Accuracy (8):
-
Accuracy of 10cm3 syringe: ±0.5cm3
The % Error is: (0.5/10)*100=5%
The % accuracy is 95%.
- Accuracy of stop clock: ±1 sec
- Accuracy of top pan balance: ±0.005g
The % Error is: (0.005/6.61)*100=0.0756429…= 0.076% (to 2 s.f.)
The % accuracy is 99.92% (to 2 d.p.).
The % Error is: ± 8%.
The % accuracy is 92%.
- Air and soil temperature:
The % Error is: ±1%
The % accuracy is 99%.
The % Error is: ±4%
The % accuracy is 96%.
The % Error is: ±0.1%
The % accuracy is 99.9%.
Comment on accuracy:
The calculated accuracies are not significant as the percentages are very low. The greatest percentage error has the data logger when testing the % relative humidity with an inaccuracy of 8.6 (to 2 s.f.), followed by the 10cm3 syringe with an inaccuracy of 5%. The stop clock is very accurate with an accuracy of ±1 sec. The most accurate apparatus we used was the top pan balance with a percentage error of 0.076 (to 2 s.f.). The experiment is not as accurate as it could be due to limitations and inaccuracy.
A table to show some possible effects of limitations on the method
Bibliography:
- Advanced Sciences : Biology 1, page 42-49, page 92-100, page 135-139
- Advanced Sciences : Biology 2, page 28-44 and page 17-24
- Advanced Biology by Michael Kent
- Class notes
- A2 level Biology by Phil Bradfield, John Dodds, Judy Dodds and Norma Taylor, pages 31-45
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Internet:
-
: Internet
-
: Internet
References are marked as numbers in brackets, for example (4) which means number 4 in the bibliography.