Mullaghmore Sand Dune Fieldwork

Mullaghmore is situated in County Sligo and Bunduff Strand. Just to the south is Bunduff Lough and to the west is coniferous woodland. Mullaghmore is a peninsula with two beaches, a rocky headland which has a castle on the top, a marsh with sand bottomed freshwater lake. There is extensive low lying flat grassland influenced by sand blown in from the beach, which in the summer has an abundance of orchids and a very large area of wooded dunes. Large areas have a Special Area of Conservation protection. However in the 1990’s, the farming practices approached this area and illegally flattened the land to make it easier for farming. The spreading of slurry has affected the natural flora and fauna, trees have been removed and the dunes. The dunes are also coming under attack from tourism development and other activities. Coastal sand dunes in Ireland and Britain may date back to as long ago as the last glaciations. If sand that forms the dunes contains shells of marine organisms the dunes are alkaline. If there are few or no shells in the sand then the dunes become acidic. The conditions needed are a large dry reservoir of sand and a large tidal range to expose the sand, allowing it to dry sufficiently to become available for transport, and strong prevailing onshore winds. The sand must be dry and fine and lots of it is needed for the formation of sand dunes. At least 4.5metres/second of wind are needed to be blowing onshore to provide the dunes with enough sand. The vegetation present helps to stabilise the sand and to trap more sand.

The formation of sand dunes –

Tides form and storms deposit piles of seaweed and detritus. Amongst this are seeds and colonising plants. These seeds germinate and grow quickly, trapping sand that has been blown from lower down the beach. Over time these mounds of sand are colonised by Couch Grass giving a series of isolated embryo dunes along the top of the beach. As this is happening, a new drift line appears in front of these embryo dunes and this is colonised by pioneer species. The embryo dunes gradually join to give a continuous ridge. As the embryo dunes grow and get larger they are inhabited by Marram Grass which is a very vigorous plant and is very efficient at trapping the sand and the rate of growth of the dune slowly increases. The constant formation of new drift lines, embryo and yellow dunes, gives a series of dunes and hollows. The older dunes continue to get taller until they are no longer receiving new sand. The harsh conditions have been made more favourable. The Marram Grass is still dominant but diversity has increased. The vegetation increases due to the presence of more humus and organic matter, which increases water retention and nutrient availability. At Mullaghmore, the grazing of the cows prevents tall species becoming dominant and maintains high species diversity. Due to blowouts, whole dunes can disappear leaving wet and dry slacks behind the main dunes. The slacks are wet because sand is blown away until the water table is reached. Plants inhabit these areas, but they may have to tolerate water logging for up to 6 months a year. The plants stabilise the sand and allows the succession to start again. If given enough time, tree species such as birch, alder and eventually oak would give rise to dune woodland, which is the climax community.

Sand dune succession –

Sand dune succession is the progressive change in vegetation from the initial colonisation of bare ground through to stable climax vegetation. Succession is a sequence of events described as different plant communities. Each sere contains species adapted to the conditions but which change their environment sufficiently to allow the next set of plants to replace them. Later seral stages tend to be diverse, more stable and have greater ground cover reflecting the improvement in the environment, which allows the process to take place. There is primary succession (from bare ground where there was no ...

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Sand dune succession –

Hypothesis –

Before carrying out our study, we put forward a number of different hypotheses to try and predict what our results would show.

The pH level will decrease as you go further inland.
Salinity will decrease as you go further inland.
Moisture content will increase the further you go inland.
The beach will get higher as more sand builds up.

Method –

Before carrying out the investigation, an equipment list should be checked to ensure that everything that is needed is present.

Ranging poles
Clinometer
Tape measure
Anemometer
Point frame quadrat
Thermometer/Hygrometer
Soil sample pots
Trowel
pH meter
Salinity meter
Plant species key.

When having carried out the experiment, some further work is to be done at the field centre. There is a separate equipment list for this work.

Oven
Electronic scales
Distilled water
Beakers
Mixing spatulas
Crucibles
Baking trays

Working within a group of three students enables you to work efficiently and each have a specific role within the group. Working along a transect across the sand dunes, two ranging poles must be places 10 metres apart. Using a clinometer, from the first ranging pole, line up a point on the second ranging pole and read off the gradient which will be either positive or negative. If the slope is upwards, the gradient will be negative, if it is downwards, the gradient will be positive. At this same point, the wind speed must be measured using an Anemometer. Hold it at the same height at each reading that you take and ensure that you are holding it in the direction of the wind. Keep it steady for 10 seconds at least to make sure that it is an accurate reading. A thermometer with a built in hygrometer must be placed on the ground at the point of the first ranging pole. Remember to reset the hygrometer before each reading. This will record the ground temperature and the humidity. At every point along the transect that you take recordings, a soil sample must also be collected. Using a trowel, dig approximately 5cm below the ground and fill up the collecting pot with soil, label it with the transect number. Remove the first ranging pole from the ground and place it 10 metres past the second. Then take all these same recordings at the point of the second ranging pole. There are four different types of sand dune, and at each one, we took a vegetation count. We made a grid at each sand dune using two tape measures and used a random sampling technique. Getting numbers from a phone book and using them as the coordinates. When having found your coordinate, place your point frame quadrat firmly on the ground. At each point, record what species of plant you have discovered, including bare ground. Take these readings at an embryo dune, a yellow dune, a grey dune and a dune slack. Two recordings from each type of dune must be collected.

Having collected all of the data, you will carry out further research at the field centre in relation to the soil samples that you have collected.

Weigh the empty crucible [W1]
Weigh the crucible filled with wet soil (using distilled water) [W2]
Work out the weight of the wet soil [W3 = W2 – W1]
Weigh crucible with dry soil [W4]
Work out weight of dry soil [W5 = W4 – W1]
Work out weight of water [W6 = W3 – W5]
Work out the percentage of water [{W6/W5} x 100]
Using a salinity meter, measure the soils TDS
Using a pH meter, measure the pH of each soil sample.
Collect all the data together and place in a suitable table of results.

Results –

Spearman’s rank to show the relationship between the percentage of water in the soil and the distance from the sea.

r = 1 – 6 x Σd²

n³ - n

r = 0.435

Spearman’s Rank – 95% = 0.4294

CHI SQUARED INFO GOES HERE>>>>>>>>>>>>>>>>>

Null Hypothesis – there is no association between the 3 species and the 3 types of dune.

REJECT NULL HYPOTHESIS

Hypothesis – there is an association between the 3 species and the 3 types of dune.

Analysis –

The Spearman’s rank coefficient correlation results show that there is a relationship between the soil moisture and the distance from the sea. By working out the results, we can see that there is a 95% positive correlation, and that it almost definitely hasn’t occurred by chance. The soil nearest the sea is moist because the when there is high tide, that area may get covered by the sea. The soil furthest from the sea, in the dune slack, is also very moist because there is stagnant water in the dune slack from where it hasn’t evaporated or been soaked up properly by the soil.

The Chi squared results show us that there is a relationship between the 3 species and the 3 types of dune. The grey dune had the most vegetation present, with the dune slack the least. Given enough time, near the dune slack, tree species such as birch and eventually oak would give rise to dune woodlands, the climax community.

The sand dune profile that was drawn, shows clearly where the different dunes are located. Between 10 and 20 metres along the beach, is where the yellow dune is present. The land then evens out slightly until 70 metres along the transect when it rises peaking at 120 metres, this is the grey dune. After the grey dune, the slope decreases and settles into the dune slack.

The scatter graph showing the relationship between soil surface pH and distance from the sea is very irregular. It doesn’t, however, vary below 8.6 or higher than 9.5. This shows that the overall pH is alkaline. It starts off high at a distance of 10 metres from the sea, and fluctuates, until it reaches 40 metres from the sea when it decreases in the space of 20 metres from 9.2 to 8.7, which then remains constant for 20 metres. Increasing again after the constant brings it back up to the starting pH of 9.4 which soon drops again to 9.6 when it reaches 110 metres. Within 10 metres it then increases to its peak of 9.5 where it then fluctuates until we reach the end of the transect and it rests at 8.6 which is verging on a neutral pH.

The temperature and wind speed scatter graphs were drawn on the same axis, to see if there was any relation between them as well as distance from the sea. The wind speed roughly follows the same pattern as the sand dune profile. Where there is an increase in the gradient, there is also an increase in the wind speed. In the dune slack the wind speed is at its highest, peaking at 3.8m/k. the temperature generally follows the same pattern, except for at a distance of 2 metres from the sea, the temperature is at its lowest, whereas the sand dune profile shows that this is where the yellow dune is present.

The amount of moisture in the soil varies from, 1.9% to 23.2%. this is a huge range, with the lowest being at point 14 along the transect, which according to the sand dune profile, is at a point of decline into the dune slack. The highest percentage of water was at point 7 along the transect which is the upslope towards the grey dune. Why these are located here will be explained in the conclusion.

Conclusion –

The sand dune profile is no surprise as to what it looked like. It follows the usual shape of starting with a smaller yellow dune, a larger grey dune at the back and a dune slack behind. There were a number of embryo dunes in front of the yellow dune, but they exceeded our area of collecting data. We can accept our hypothesis because it stated that as more sand is being blown onto the beach, the beach will get higher. This is true because the sand has been caught in the vegetation on the sand dunes, causing them to over time, build up.

In relation to the spearman’s rank correlation, the results were very accurate. 95% chance that it wasn’t a coincidence. The water that was present near the dune slack is from the water table, which often is present above land in the dune slack. While the water that was present in the soil nearer the sea is from where the sea has washed up and the soil soaked it up for nutrients.

The results that we accumulated from the Chi-squared data were also accurate; it showed that we had a diverse plant species, which is what we expected because the conditions on each type of sand dune are different.

In our hypothesis we predicted that as you go further inland away from the beach, the pH would decrease. We can accept this because the pH that we took from the first sample was 9.4 and the pH from the last sample was 8.6. There were no real anomalies in this data to prove our hypothesis wrong.

We predicted that the moisture content will increase as you go inland. From the results that we collected, and the analysis of them, we can see that this is true. There was one anomaly at 140metres inland which gave a reading of 1.9 which is beyond even the first reading.

Evaluation –

There are a number of limitations that could have caused error in our recordings. The first being human error. This is going to come into account for every experiment that is ever carried out. Limitations that could have affected our results were:

The land was undulating and the grass and weeds were in the way which prevented us from laying the tape measure down flat which meant that it wasn’t exactly 10 metres apart. This could have had a huge impact on our results in the case of the tape measure missing a large mound/dune. To improve this we could have used a trundle wheel which would have given us much more accurate data.
It was extremely difficult to tell if you were travelling in a straight line along the transect, a way of preventing this would be to use 3 ranging poles and leaving one in the ground at the very end so there is a point to aim for. This has its disadvantages though. If there are lots of sand dunes, when you are just ahead of one, you may not be able to see the end ranging pole. You could also have used a compass to specify what direction we were travelling in.
Identifying all the different plant species was difficult and would have been easier if we had a key which would aid us in what to look for in each of the species that we found.
The wind speed was not always accurate because it was taking at different heights due to the different heights of the students working in each group. A way of solving this would be to allocate a mark on the ranging pole so that everyone was to hold the meter at the same height.
The ground was very tough and it was hard to stick the ranging poles in the ground. The ranging poles were also not stuck in the same amount of depth. Having a mark near the bottom of the ranging pole approximately 5cm up would aid confusion.
When taking collecting our data we came across a dune ridge that was unstable which meant that we weren’t able to collect any data there. We did however carry on to the next point which caused confusion with the sand dune profile because it wasn’t shown.
It was difficult to locate the plants that the point-frame quadrat was on, and guess work was sometime used.
We only took 3 vegetation readings, if we had taken more we might have been able to see the transaction from each species to the next.