Reason for choosing Guincho
Location and features
The reason for choosing Guincho is because it has an extensive and dynamic dune system, accessible (close to school), safe. North-west facing beach, on Atlantic coast, thus wind speeds are higher and wave action is higher, so dune system id more dynamic, about 10 km west of Cascais. Part of Sintra natural Park. It is one of the best well kept (or relatively well kept beaches for sand dunes. ()
Sintra natural Park
The Sintra-Cascais Natural Park is one of the 13 . While only established in 1994 as a Natural Park by the Portuguese Government, it has been protected since 1981. Its area is approximately 145km². It includes the Mountain Range but extends all the way to the coast and Cabo da Roca, continental Europe's . Within 25km of Lisbon, it is an extremely popular tourism area containing many different individual historical and natural sites and attractions.
Methods of data collection:
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For this field work a systematic and quadrat method was used for sampling. The reasons a systematic and quadrat method was used for sampling was because:
- The quadrates help see clearly the vegetation cover in each site.
- And a systematic method was helpful because it was easier to see whether there was any correlation with the distance from the HTM and the vegetation cover.
- Also, because of the systematic method it was easier to organise results properly as there is a set distance, it help especially with our wind speed results.
A transect line was selected and that line was kept by using a bearing. Measures were taken every 5m, this was done to get a sample of the whole system and also time was an issue. It would have been more accurate to do this in shorter intervals but it would have taken too much time. We only did 32 survey sites in total; this was mainly due to lack of time.
To calculate the wind speed a simple method was used; by placing a measuring pole upright in the sand on the appropriate site and then placing a small ball of cotton wool on the top of the pole. Then dropping the cotton wool off the pole and measuring the time it takes to get to the ground, with a stopwatch. And measuring the distance it travelled with the measuring pole. However, although it was easy to do, it is the same reason for the problem with this experiment.
Data presentation and processing
Presentation of Results
Kite diagrams
To graph these results I decided to graph the total percentage of vegetation cover along the transect line. I am going to show these results using kite graphs. This is because they are ideal for representing distributional data (i.e. quantity along the transect line).
Spearman’s Rank
Spearman’s rank was used to see if there was any correlation, statistically, between the variables. The result can then be used to see the significance of the results. This was used for seeing if there was a correlation between the distance from the HTM and the percentage of vegetation cover. As well as whether there was a correlation between the percentage vegetation cover and the wind speed.
(4) Equipment used
We used a variety of equipment for the field work.
(5) Table showing the Distance from the HTM and the Average Vegetation percentage cover, for Kite diagram (graph).
(6)
Table below is showing the Spearman’s rank, to see the correlation between Wind speed and vegetation cover.
Table below is showing the Spearman’s rank, to see the correlation between the Distance from the HTM and vegetation cover.
(6)
Wind Speed _ Distance from HTM
Calculations for Spearman’s rank Calculations for Spearman’s rank
rs= 1 – (6Σd2) rs= 1 – (6Σd2)
(n3–n) (n3–n)
= 1 – (6 (5603)) = 1 – (6 (3932.5))
(32768–32) (32768–32)
= 1 – (33618) = 1 – (23595)
(32736) (32736)
= 1 – 1.03 = 1 – 0.72
= -0.03 = 0.28
Finding the significance of the result Finding the significance of the result
t = rs √ (n-2) t = rs √ (n-2)
(1 – rs2) (1 – rs2)
= -0.03 √ ( 30 ) = 0.28 √ ( 30 )
(1 – (-0.03)2) (1 – (0.28)2)
= -0.03 √ ( 30 ) = 0.28 √ ( 30 )
(0.9991) (0.9216)
= -0.03 √ (30.03) = 0.28 √ (32.55)
= -0.03 (5.5) = 0.28 (5.7)
= -0.165 = 1.5975
Analysis of results
Kite diagrams
Throughout the graph you can see many high and low parts, however the highest parts seem to be either at the very front of the transect or at the end of it. This is probably due to the fact that the transect line used started on a hill and so it was less prone to stamping, this was the same for the next two samples; hence the graph shows a higher percentage of vegetation cover. However as you go further away from the HTM the percentage cover of vegetation decreased, this was because the land became more flat and so the vegetation had little protection from wind and tramples. Finally near the end of the transect line the land started going downhill, and so the vegetation cover increased. I suspect that this is because the vegetation is being protected by the hill from wind, and since it is on a hill few people walk around there, also as you go further down there is less sand and more soil, this helps the vegetation grow.
Spearman’s Rank
Wind speed – Like the HTM, the wind speed has a low spearman’s rank, however it is much lower, at -0.03; while t then equalled -1.64, making it a very random set of results. Nevertheless, as the HTM, I still believe that even though the results here are completely random, there is still a correlation between wind speed and percentage of vegetation cover, just not on this site. There were also various problems and limitations to the method used to calculate the wind speed, by using such a simple method, the results are harder to understand.
HTM - After doing the spearman’s rank I got the result of 0.28, which is quite a low number, showing little or no correlation. And then when I used it to find out its significance, I discovered that the t answer was 1.6. this is also a very low number, when checking the significance of the result using the t-table, I discovered that I could only be less that 90% certain that there was a correlation, however as it is below 90% I cannot positively say that there was a correlation. However, I believe that although these results do not clearly show the correlation between the distance from the HTM and the vegetation cover, one cannot disregard the fact that although the result was low, one can still say that there is some sort of correlation between the two. And perhaps the area chosen to study might have been my biggest limitation, as not only did I only study one transect but also the location as well as other factors might have influenced the data.
Evaluation and Conclusion
Overall this investigation didn’t show what I guessed, although in the kite diagram it was quite obvious that as one goes further down the transect line the percentage cover of vegetation will increase. This is not show, however, in the results for the spearman’s rank. Instead it says that there might be a correlation with the distance from the HTM and the vegetation cover, however the probability is very low. The increase in the vegetation cover was most probably due to the ups and downs of the land, and not so much the distance which it had from the HTM; thus making my hypothesis mistaken. As for the wind speed, although the results do not show this, if I were to repeat this investigation again, using a larger range of transect lines, and if I were to use an anemometer instead of the method I used, then for certain I would probably have gotten better and more correlating results.
Aerial photo of Guincho, photo was taken from Google earth.
Calculations for Spearman’s rank
Table and graph for Spearman’s rank of Wind speed.
Table and graph for Spearman’s rank of HTM.