How can I analyse % cover data?
The Shannon-Weiner Index can be used with % cover data when you want to compare sites which have all been sampled in the same way. Care must be taken not to compare the diversity measures calculated with those generated from full quantitative data. A site with cover values 4,1,1,1,1 will have a higher Shannon diversity than a site with 5,1,1,1,1 because the former is more equitable. A site with 5,5,5,5,5 will have a higher diversity still. This is all quite reasonable and works as one would expect. You should note that the Shannon-Weiner value calculated for percentage cover data will tend to just reflect the species number. This is because the values can only range from 1-5 rather than from 0-infinity thus the resolution of differences in equitability between sites is much reduced. The question is, do you really need to use the Shannon index? Perhaps you might be better using species richness. From your vegetation surveys you could use one of the recently developed total species richn
