The effect of competition on the distribution of marram grass.

Authors Avatar

The effect of competition on the distribution of marram grass

A transect was measured out at a 90˚ angle to the shoreline. Along this transect 2 sites were chosen a mobile and fixed dune. At each zone a sampling area of 20m x 20m was measured out using measuring tape. The measuring tapes were then used as references (x/y axis) so that co-ordinates from a table of random numbers were easily found.

A random number table is a list of numbers, the first number lower than 20 in the first column on the table is the x-axis co-ordinate, and the second number lower than 20 will be the y-axis co-ordinate. This was the best way to select an unbiased sample so every species had an equal probability of being selected.

At the fist 5 co-ordinates an optimum quadrat size was calculated. A range of quadrat sizes e.g. 10cm x 10cm, 20cm x 20cm, 30cm x 30cm, 40cm x 40cm, 50cm x 50cm and 1m x 1m, were used at each co-ordinate and the numbers of species were counted. The average species count for each quadrat was then calculated.

  Sum of plant species

Amount of samples taken = Average species count

This data was then used to make a graph in which species number was on the y-axis and the quadrat size on the x-axis. This meant the smallest quadrat that gives a representative sample was chosen.

After the optimum size was calculated 10 of these quadrats were dropped in each area at their co-ordinates. At each co-ordinate species abundance was measured by % cover of each species. The quadrat had gridlines so it was easier to judge what % each species of plant covers.    

Abiotic factors were also recorded at 5 co-ordinates in each area. Abiotic factors have to be measured as they may significantly affect the results.

The pH of the soil was determined, by obtaining a sample of soil just below the surface using a soil corer (Top soil is affected too much by other variables). The distance below the surface the soil was taken was kept constant as this may have affected the pH result. 1cm of the soil sample was placed at one end of the sample tube (both ends open). Distilled water was then added up to the blue mark, solid barium sulphate was then added until it was level with the second mark. An equal amount of universal indicator was added last, the tube was then shaken and the colour of the waster compared against a colour chart, the result was then recorded onto a table.

Join now!

Temperature was simply measured using an alcohol thermometer or temperature probe. The reading should be taken only about 15cm from the ground as this the temperature where the plants grow. The number was then either read off the gauge on the thermometer or simply recorded from the screen on the temperature probe.

Infiltration rate was also recorded. This calculated the rate at which water filters through various soil types. A 250cm3 measuring cylinder was pushed into the ground so that the 20cm3 line was level with the ground. The cylinder was filled with water and a stopwatch was started as ...

This is a preview of the whole essay