“The natural and gradual replacement of one plant community by another.” The process may begin on solid rock, soil or water, the end result being generally a forest tolerant (able to grow in the shade) trees. The stages in between may include moss, annual weeds, grasses, brush and intolerant trees (needing full sunlight) and mid-tolerant trees. The stages vary depending on the site and the process may take centuries to complete.
The Ercall – 68 ha OS Map Ref. SJ 640 096 This is an attractive site adjacent to Telford and is part owned by the Shropshire Wildlife Trust and Telford and Wrekin Borough Council. Both the Ercall and The Wrekin are a Site of Special Scientific Interest. The Ercall is mainly composed of Pre-Cambrian acdic igneous rock which was formally quarried to provide road stone for the nearby A5. This was certainly destructive, but it had the exceptionally wonderful effect of laying bare the Earth’s history; revealing rocks from the earliest beginnings of life on this planet. This is a good site for wildlife with a rich variety of plants and springtime flowers, also the favoured stronghold of one of Telford’s speciality butterflies, the dingy skipper. A recent survey of the nature reserve’s invertebrates yielded a staggering 821 species.
Plan This photograph is showing the transect line that I used, going from the outer to the inner of Maddocks Hill Quarry. I used a series of points, 10 metres apart from one another and collected information and samples from each point. This is called systematic sampling. As you can see form the diagram the original workings were in the centre of the quarry becoming more recently worked further out. Sampling Advantages of Sampling
You can either collect information from Primary sources-doing your own field studies-or secondary sources-documents e.g. information other people have collected (books, the internet). It will take much more time than you have available if you want to gather every part of information on a particular topic. “It is often useful to take a sample from the total in order to estimate what is happening. This can save you a lot of time, and if you do it properly the results can be accurate.”
There are different methods of sampling; points, lines (transect) and quadrates. Any of these methods can be arranged in a random, stratified random or systematic way. In this investigation I used a mix of transect and quadratic methods arranged in a systematic way. Transect – eg if you are carrying out a survey of moisture levels by soil, along a series of coastal dunes. Quadrats – find out the proportion of ground covered by a particular plant species eg – woodland or an old abandoned quarry such as the one at Maddocks Hill. Systematic sampling is regularly spaced where there are variables like in the natural environment, it has an advantage of simplicity. It is better than using random sampling because it’s a fairly featureless area (around a town would be best where land marks are used as guides.
As there is less moisture on plots 4 and 8, it looks as if it may have influenced the amount of species that could grow there. Species may have to compete for moisture resulting in fewer plants being able to grow there. An explanation for the lack of moisture in these plots could be, nearby gorse bushes or Ash tress could have a long complex root system, which, especially Ash Tress, can reach up to 60metres in length. As large tress and plants need more moisture and nutrients, these plots could suffer in not being able to produces as many varieties of plants.
Overall, soil moisture does not have a large effect on what grows along this transect as the readings are not hugely variable. Soil moisture is not a limiting factor for this transect, as it is a short distance. If this investigation was done over a long distance eg a mile, testing every 100metres, then soil moisture might effect what grows on each plot. Light intensity There was a definite trend with the results of the light intensity. On each plot where I tested, the light intensity was ‘H’ (High). Like the soil moisture, light wasn’t a limiting factor for these plants.
The apparatus used was definitely limiting as the dial on the kit only pointing to High, Medium or Low. Even by the Ash Tress the reading was still ‘H’ and there was a little shade. To improve the experiment, better equipment could be used to get exact readings. Light intensity could have affected the growth of the plant species on each plot. For example if large bushes or tress shaded an area, different species would grow because they are adapted to the shade.