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The Woodland Education Centre
The Heathland Restoration Project
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Ecological Surveys 1996 - 1998

Species similarity between Sections

In 1997, all the sections were quite dissimilar in terms of the species present in them. This is a reflection of the extremely varied seed bank regenerating on the site. By 1998, the sections had many more species in common (although the amount of each species in a particular section varied considerably).

The increasing species similarity between sections resulted from the disappearance of species not suited to current conditions on the site, and the spread of those favoured by current conditions. Current conditions are the result of both prevailing weather conditions and the management regime. 
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Views of strips 6, 7 and 8 on the Heathland Restoration site.

The degree of similarity between the vegetation of different sections can be examined by a comparison of indices of similarity, calculated for paired sections (table below).
1998   
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1997
Indices of similarity for paired sections in 1997 and 1998.
(Paired sections with the highest species similarity are indicated by the indices in bold type.)

 

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.

 

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Ecological Surveys 96 - 98
Contents