Numerical Analyses - Raasay
Frequency of Occurrence
Thirteen species are known from all 98 recording units on Raasay:
| Anthoxanthum odoratum | Oxalis acetosella |
| Blechnum spicant | Potentilla erecta |
| Calluna vulgaris | Prunella vulgaris |
| Erica cinerea | Sagina procumbens |
| Galium saxatile | Succisa pratensis |
| Juncus effusus | Viola riviniana |
| Luzula campestris |
The following chart shows the frequency of taxa in bands of recording units e.g. 59 taxa are known from at least 90 recording units. There are 616 taxa in the dataset.
The large number of species known from fewer than 10 recording units reflects the introduced taxa and weeds found in the limited area under cultivation, as well as the rarer native species.
The full list of plants with frequencies is available from the author.
The Richest Recording Units
|
Number of Taxa |
Recording Units |
|
>300 |
1 |
|
250-299 |
3 |
|
200-249 |
22 |
|
150-199 |
38 |
|
100-149 |
31 |
|
<100 |
3 |
|
Total |
98 |
The recording unit that includes Inverarish and West Suisnish is by some way the richest with 362 taxa at 7 May 2009. Next is the square containing Raasay House with 295. This confirms the importance of human influence, though a significant part of this biodiversity results from introductions.
The other major sources of high taxa counts are habitat diversity and geology with the influence of the east coast lime being apparent in the diagram below.
Only three recording units fall below 100 taxa: Holoman Island which is very small but falls into its own 1 km square, the northwest part of Eilean Tigh which again is small and is extremely exposed, and one square in the middle of the moor which is just dull. Holoman Island is the only recording unit where dandelion has not been recorded.