2.4 The British Isles
The following video presents information about how oaks colonised the British Isles after the last ice age using data from scientific papers (Birks, 1989; Clark et al., 2012; Lowe et al., 2005). You will use the information in the video to calculate how quickly they spread. You will also look at how references to sources of information are presented and what each part of one means, so that you can see when it was published and be able to find the source again easily.
While watching the video, record the following information to use in the questions that follow:
- the year of the first record of oaks in the British Isles
- the year the most northerly record was reached
- the details of the publication that the map with the coloured arrows came from.
How long ago did oaks first arrive in the British Isles? Give you answer to the nearest 500 years.
Figure 2 is a repeat of one of the figures in the video but here one route of oak dispersal in the British Isles is picked out in red.
Using Figure 2, estimate the distance that the dark red line represents.
Approximately how many years are represented by the line in Figure 2 that traces this particular oak dispersal route?
Now you know the distance and the timescale involved, you can calculate the rate at which oaks spread through the British Isles.
How fast did the oak spread along the dark red line in Figure 2? Don’t forget to give your answer to the correct number of significant figures.
Does this rate seem reasonable? If you think about an oak dispersing acorns, what does this number mean? Write some notes on the interpretation of what the rate means and how realistic the rate might be. (Your answer should be between 100 and 200 words.)
To achieve a rate of 220 m year, an acorn could be dispersed 220 metres from the parent plant and then grow and produce another acorn that is spread 220 metres in the following year. However across 3300 years, some acorns are likely to be dispersed long distances and others short distances, so the rate calculated represents an average across the years, so there may have been periods of faster and slower spread.
In addition, oaks do not produce acorns until they are mature trees, so the scenario described at the beginning of this paragraph would be impossible as oaks can’t produce acorns within a year. This means that the distance they are dispersed must be much further than 220 metres to account for the time lag in producing new acorns. That is, if an acorn germinated and it took some years to produce acorns, then you would need to multiply that number of years by the 220 m to determine a more realistic dispersal distance.
If you have watched the oak tree level video, you will know oaks begin producing acorns at about 40 years. Instead of thinking of how far oaks spread acorns in one year, you could think about how far an oak must disperse its acorn in 40 years in order to account for the time lag in production and distribution. So, 220 m y−1 × 40 y = 8800 m or 8.8 km.
This seems a long way for acorns to be dispersed. From these calculations, you might speculate that animals, perhaps squirrels and jays, play an important role in the colonisation of oaks across the British Isles.
The data in Figure 2 stem from a combination of diagrams from published scientific papers. The details of the papers were provided in the video, where this figure also appeared.
The map with the dated pollen cores came from the reference below and, in order, this reference shows: the author, year of publication, article title, journal, journal volume and the starting and finishing page numbers of the original article.
Birks, H.J. (1989), ‘Holocene isochrone maps and patterns of tree-spreading in the British Isles’, Journal of Biogeography, vol. 16, pp. 503–40.
Another paper reported the DNA of extant oaks. It is important that you can identify the source of information and know how to interpret a reference. When viewing the video you were asked to jot down the details of the paper that identified the various routes of oak distribution. Use your notes to complete the following statements by selecting the correct options from the drop-down lists.
Various organisations and publications use different ways to cite and give references, and it is useful for you to be able to understand and interpret these different styles.
The video collated information from published research papers, and with some additional measurements and calculations you worked out how far and how fast oaks spread. You were also able to interpret the references to identify the first author, the year it was published and in which journal – information that could help you search for the original papers in the library, or prepare your own reference list.
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