The structure and diversity of the animal communities in a broadland reedswamp



The fauna of a Phragmites reedswamp at Alderfen Broad, Norfolk, is described in terms of structure and diversity. Three transects were laid parallel to the water's edge at 1 m (T1), 10 m (T2) and 25 m (T3) from the reedswamp/open water interface. Twenty samples were taken randomly along each transect in July and all the macroinvertebrates in the samples were collected. The pH at each site was measured. The pH fell from 8–4 at T1 to 6–4 at T3.

The fauna of the three transects was analysed by recurrent groups and by plotting the log abundance against the frequency for each species and dividing the resulting graph into units in terms of abundance and frequency. Both methods gave very similar results but the recurrent groups analysis only gave information on the most frequent species. The recurrent groups of the three transects had no common elements. The abundance/frequency analysis is simple to perform and could be of considerable use in evaluating sites for conservation purposes.

Transect T2 had the greatest species diversity, equitability and evenness, T3 the least. Reasons for this are discussed.