Data collection
I joined the group which investigated Plantago major in Bielański Forest. The data which my partner and I had collected is coloured blue.
Data processing
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The mean value (eg: of the number of Plantago Major in one square) will be calculated according to the formula:
Where:
is the mean value;
is the sum of all Plantago Major from all investigated squares;
is the total number of squares.
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The standard deviation will be calculated using the programme Excel 2003 according to the formula:
Note: The error bars represent the standard deviation which values are presented in Table 5.
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To compare two populations of Plantago major the t-test will be used. It will be calculated according to the formula:
Where:
– mean values of the data from the Parc / Forest.
- standard deviation of the data from the Parc / Forest
- number of plantains in the Parc / Forest.
Now, I will calculate the t-test for the data representing each plantian’s feature.
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The average number of Plantago major in the square
Degree of freedom is 22+21-2=41. For this degree of freedom the level of significance is 2.02.
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The number of leaves on Plantago major.
Degree of freedom is 136+159-2=293. For this degree of freedom the level of significance is 1.96.
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The width of a biggest leaf of Plantago major.
Degree of freedom is 136+159-2=293. For this degree of freedom the level of significance is 1.96.
Conclusions
This field laboratory showed that two populations of Plantago major from Sowiński Park and Bielański Forest differ however, in some cases, not significantly.
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The number of Plantago major per square.
Looking at Graph 1 I see that Plantago major from Bielański Forest are more frequent than those in Sowiński Park. It is indicated by the sole fact that 159 plantains were found in 21 squares in Bielański Forest while 136 in Sowiński Park in 20 squares. The average amount of plantains per square in the Park is 6.80 and in the Forest 7.23. The relatively high values of standard deviation (presented in Table 5) to these means indicate that the number of Planatago major varied from square to square sometime very significantly. Moreover, on the Graph 3 it is visible that in 50% of the squares from Sowiński Park 1 to 7 plantains were found while in Bielański Forest in 61.9%. Therefore, I can say that the density of Plantago major in the Forest is higher than in the Park.
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The average number of leaves at Plantago major.
In the Table 5 it is visible that the average number of leaves per a plantain is higher in Bielański Forest than in Sowiński Park (this is also supported by the median value found in Table 6). The values of standard deviation are similar though significant. This means that number of leaves per plantain varied in both populations. When dividing the number of leaves into equal classes it comes out that the majority of plantains from both Park and Forest possess from 3 to 4 leaves. It can be also noticed that in the Sowiński Park the majority of plantains possess less leaves than the majority of Plantago major from the Forest.
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The average width of the biggest leaf of Plantago major.
It is visible that in Bielański Forest the biggest leaf of Plantago major is much wider than of the plantains from Sowiński Park (Graph 1). The higher value of standard deviation for plantains in the Forest indicates that growing there plantains are more diverse. Graph 5 shows us that in Sowiński Park the majority of plantains’ widest leaf can be found in the classes 1-10 mm, 11-20 mm, 21-30 mm, 31-40 mm and 41-50 mm. In fact, no wider leaf than 50mm was found in Sowiński Park. In contrary, in Bielański Forest, the majority of leafs are classified in classes from 31-40 mm to 61-70 mm. It is therefore visible, that plantains in the Forest have much more wider leaves which can reach even 130mm.
- The comparison of two populations.
In order to compare two populations of Plantago major the t-test values should be discussed. It mu be remembered that if obtained value of t-test is lower than this given in the table of t-test values’ significance, then the populations do not vary significantly. This can also mean that taken probes are not representative. If obtained value of t-test is higher than this given in the table of t-test values’ significance, then investigated populations differ. The higher the change in t-test values is the more significant difference between populations.
It is clear that in the case of the number of plantains per square and the number of leaves at Plantago Major two populations overlap because the values of t-test for these variables are lower than those given in the table of t-test significance. However, when moving to the width of the biggest leaf, t is visible that calculated value of t-test is more than 7 times bigger than this suggested by the table. This fact suggests that in the case of the width of leaves the specialization of populations could have take place.
- Why the differences between two populations occurred?
The answer lies in the environment and condition in which plantains grow. The first factor which conditions this change is the air pollution. I deduce that Sowiński Park is much more polluted than Bielański Forest, as it is located in the city center, near noisy and crowded streets. Therefore, plantains in Bielański Forest grow in cleaner environment and thus are better developed (i.e. have wider leaves). Moreover, Sowiński Park is much more frequently visited by people than the Forest what have negative effects on its ecosystem. This fact is indicated by the quantitative data gained in the Park which shows that Plantago major growing there are commonly devastated by humans. Aditionally, the fact that the grass in Sowiński Park is regularly cut down may suggest that Plantago major growing on lawns are also cut down and thus their growth is strictly controlled. In contrary to the Park, Bielański Forest is less frequently visited by people but even if yes, people follow pathways, do not enter the forest freely and therefore, do not step and devastate Plantago major. In the result, plantains are more frequent in the Forest than in the Park.
What is next, the soil in which plantains grow influence their appearance and frequency. However, to my and my group’s disappointment, it came out that the pH of the soil from the Forest and the Park does not vary greatly (only by 0.3 in pH scale – Table 10) and is slightly acidic, nearly neutral (Table 10). Even though Park’s soil is fertilized artificially, its pH is only a little bit more neutral than of Forest’s. Therefore, I cannot state that the pH influences the most the differences in two population of Plantago major.
Moreover, my group and I had also measured the permeability of the soil from the Park and Forest. It came out that the soil from Bielański Forest is much more permeable for the water (and possibly for other liquids and dissolved in it minerals and salts) than in Sowiński Park (Table 11). This fact can explain the differences occurring in two populations in Plantago major in these environments. In Bielański Forest, plantains have greater access to the water, salts and minerals coming within the rain. Therefore, they had better chance to develop wider leaves and the plantains with numerous leaves.
To sum up I can say that these are human actions and pollution what influenced and still affect the most the growth, appearance and the density of Plantago major. It is a well-known fact that humans devastate and affect significantly the plants. Nevertheless, the permeability of the soil can play a significant role in these features of the plantains and their specialization.
Evaluation
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It was not clearly stated what to do with Plantago major which were found on the boundary of used square frames. Next time, it should be said whether to count them or not.
- In many square frames plantains were so numerous that it was difficult to count them precisely. Next time, all plantains should be counted very carefully. Moreover, a method for counting them could be considered, eg. labeling every already counted plantain by putting on in a small piece of coloured paper (and removing it afterwards!).
- The measurement of leaves was problematic and thus may cause some errors. In the future, a special pad for supporting the leaves while the measurement could be used.
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We do not have the sufficient means to judge whether the specification of these two populations occurred. Still, the sole t-test cannot be treated as fully trustworthy. To ameliorate this weakness, other tests and statistical means which would investigate the differences between two populations could be used. Moreover, the long-term observations of Plantago major in Park and Forest would enable us to reach more reliable conclusions.
- The plantains were investigated in one certain part of a Forest. Therefore, it is hard to judge whether the specialization really occurred. In the future, the sample from all over the Forest should be taken.
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The calculated percentage data is difficult to compare as not equal number of squares were investigated (to prove this statement the graph will percentage values was plotted – Graph 3; it can be observed that obtained results cannot be compared reliably and easily) . For the next time, the equal amount of squares should be investigated both in the Park and the Forest. This would make the percentage data be more reliable and possible to compare trustworthy.
- It would be very interesting to measure other factors which can influence the appearance and the density of the plantains, for instance the type of soil or amount of rains in the region of the Park and forest.
Bibliography
Books:
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Pyłka-Gutowska, Ewa; Ekologia z ochroną środowiska (English: Ecology with the environment protection), Wydawnictwo Oświata, Warszawa 1996.
Web pages:
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, cited 27.02.2009
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, cited 03.03.2009
Pyłka-Gutowska, Ewa; Ekologia z ochroną środowiska (English: Ecology with the environment protection), Wydawnicto Oświata, Warszawa 1996, p.91.