To investigate the effects of abiotic factors specifically pH on the abundance of marram grass.

• The digital thermometer and anemometer have a sharp point, when carrying these apparatus they should be held vertically
• Similarly the 3 ranging poles are also dangerous as they are big and have a sharp point. Again they should be held vertically when carried
• Also when walking through the dune. There may be wild animals and the terrain may be extreme so suitable footwear and extra caution should be taken.

Analysis

Table 1

A results table to show the effect of abiotic factors on the abundance of marram grass

Table 1

Table 1 shows the results that were collected. It shows the value of different abiotic factors at different sites, the profile of the land and also the percentage abundance of marram grass present. I will use this data and spearmen’s rank to create a table, which allows me to clearly see whether there is a correlation between the abiotic factors and the % abundance of marram grass.

A results table to show the spearmen’s rank value of abiotic factors measured.

Table 2

The spearmen’s rank value allows me to conclude whether my null hypothesis was correct or not and to what degree I can accept or reject it. Table 2 shows that my I have accepted my null hypothesis for Infiltration, wind speed and moisture. This is again is indicated on the graphs 1 2 and 3 where we can see clearly that there is little or no correlation between these abiotic factors and the percentage abundance of marram grass.

Graph 3

Graph1

Graph 2

The spearmen’s rank value for pH and temperature shows that was a relationship between these two factors and the percentage abundance of marram grass. The graphs 4and 5 also indicate that there was a positive correlation between the pH level and % abundance of marram grass and the temperature and % abundance of marram grass.

Graph 5

Graph 4

A results table to show the relationship between pH and % abundance of marram grass

Table 3

From Table 3 you can see that there is a positive relationship between the % abundance of marram grass and pH. This means that as the pH level increases the % abundance of marram grass also increases however I can see that there is one anomalous point (circled).

As marram grass is not adapted to survive in acidic conditions, it prefers more neutral conditions. This can be seen from Table 3, at a pH of 4.0 there is no marram grass (A.arenaria) but as the pH increases to 6.0 we can see the percentage abundance of marram grass increases to 33.3% and as we keep increasing to a pH of 6.5 the percentage abundance almost trebles to 94.0%. this again highlights the positive relationship between the pH level and the % abundance of marram grass. At low pH levels marram grass will die this is because the increase in H+ ions will interfere with the hydrogen bonds, which hold the enzymes active site in its specific position. These bonds will break distorting the enzymes active site making it unable to form an enzyme substrate complex and therefore the enzyme will be denatured. If the enzyme becomes denatured, some metabolic processes will happen at a very slow rate and others may completely come to a halt. Without the correct metabolic processes occurring the plant will eventually die.

Pioneer species such as Marram grass, often have many adaptations that allow them to colonise in an environment that many other organisms couldn’t. As marram grass colonises in a psammosere it has many xeromorphic adaptations. Marram grass is a R-selected species. This means that in it’s short lifetime it will reproduce a lot. The plant is able to stabilise the sand and as it decomposes, it is able to provide nutrients to sand making the sand habitable for other plant species. The ability of a pioneer species such as marram grass to germinate grow and reproduce is called an Ecesis.

Some of these xeromorphic adaptations are:

Long thin leaves – these leaves roll up in dry conditions. This means that the stomata are hidden into the underside of the leaf. The stomata are away from the strong sea breeze. Moist air is trapped within the leaves, which lengthens the diffusion pathway as the water evaporates into the inner area of the leaf and not into the atmosphere, this creates a local humidity and so transpiration occurs more slowly.

Hair on leaves (trichores) – the hair on leaves reduces the air current around the stomata making it more humid, this therefore reduces the rate of transpiration. On this picture >          

you can see the small hairs which maintain the humidity of the plant.

Undersides of leaves are smooth and glossy – the smooth and glossy nature of the leaves allows it to reduce the transpiration rate. As the leaves roll up, the underside of the leaves are more exposed to the harsh conditions of the psammosere. The underside is bluish coloured, which helps the plant reflect extreme sunlight

Ridges along leaves – the ridges along the leaves again the stomata to be sunken deeply. The ridges also help break up the flow of the wind current reducing transpiration.

Extensive root system – the long roots allow marram grass to search deep below the sand for sources of fresh water. As there are a lot of roots the surface area of absorption is also increased.

The error bars show the range of the range of results above and below the point, which has been plotted. The point that has been plotted is the mean. The smaller the error bars the more accurate my results and therefore the more reliable my experiment.

Evaluation

I feel that overall my method was suitable as it allowed me to obtain a sufficient number of reliable results. I had one anomalous result and this could have occurred because of a number of minor errors and limitations to the experiment.]

Limitations

Lack of time – the lack of time meant that the experiment could not be repeated reducing the reliability of my method greatly.

No repeats - the fact that the experiment was not repeated means that the results that were gained could not be compared against anything. This means that if there were a small anomaly it would not have been easy to spot.

Weather – the week before the experiment was carried on it had rained heavily. This could have affected a number of abiotic factors such as moisture level. We may have obtained a moisture level higher then expected.

 

The error bars show the range of results above and below the point, which has been plotted. The point that has been plotted is the mean. The smaller the error bars the more accurate my results and therefore the more reliable my experiment. As you can see from the graph, error bars of four points cross the trend line. This means that these points were very accurate and reliable. The point at a pH of 7.0 is close to the trend line showing that result could be considered accurate and may have been distorted a bit because of an error with apparatus.

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