Similarity between project sections.

The index of similarity between two sections was calculated using the following formula:

Index of Similarity = 2C
(A + B)

Where A = the number of species in section A

B = the number of species in section B

C = the number of species common to both sections

The closer the index of similarity is to 1, the more similar the sections are.

1996 data was not analysed because many of the species present in 1996 were only identified to genus level. The results would thus not be truly comparable to those obtained in 1997 and 1998.

Species numbers obtained from the random data were used to calculate the indices for 1997 and 1998 (Table above). This was done because the belt transect data routinely underestimates the number of species present due to the smaller number of samples taken and the narrow band actually sampled (more here).

Comparisons of the indices of similarity for paired sections reveals a number of general insights.

Sections adjacent to each other tended to be the most similar. This is fairly obvious, because species will be able to spread and colonize neighbouring sections more readily. Also, environmental conditions are likely to be similar in adjacent sections.

The vegetation of the sections became more similar in terms of the species present between 1997 and 1998. However, because the relative abundance of the individual species varied considerably, the sections still looked markedly different.

Sections 2 and 4 became much more similar to each other in the period 1997- 1998. Both sections were also highly similar to section 7. This is likely to be related to the fact that they are all cut in the spring.

The section with the highest similarity to the unmanaged control section in 1998 was section 7.

Sections 1 and 9 had a high similarity to each other in 1998. This was presumably related to the position of these sections. Although they are at opposite ends of the project site, both are bordered by woodland on one side.