In my research, I would like to find the abundance of plants along water point in my region. In the literature, it is possible to find the abundance using the Braum Blanquet for example. There is : Using Vegetation To Assess Environmental Conditions in Wetlands; which defends this method.
After finding the abundance, calculate the Shannon index and other botanical index. how could I do it if I don't count plant individually to compute the Shannon index but I use the cover class?
Shannon index : -∑PilnPi, and Pi, it is found from number of a specie/ total number of species.
My Shannon index will then be compare to other Shannon indexes.
Thank you for you view.
Evans, E.
By cover classes data or abundance through Braun Blanquet method Shannon index cannot be determined. By calculating abundance/density/basal area through quantitative methods (counting number of individuals in quadrates) one can determine shannon index for a plant community.
Dear Evans, it seems to me, that was efforts in previous SU to elaborate approach that give possibility to use it for higher than species level (may be Riabov et al.) I will see if will have time. Serious investigator of all connected with using of this index is prof. Emelianov from Zoological Institute of Ukraine (several books and Dr. sci. diss). But for me enough enigmatic is what for in your investigation is necessity, if practical using of separate index is enough hard, as it is based on two arguments – amount of species, and equitability.
Anyway, quantity is necessary
Of course, diversity indices can also be calculated from cover data. Many examples can be found in the literature and the pros and cons were amply discussed over decades. there is no difference between the proportion of the cover of a species of the total cover from the proportion of individuals of a species from the total abundance. However, cover must be estimated in a cardinal scale. The Braun-Blanquet scale is only ordinal, thus any algebraic operation is forbidden. Cover should be estimated using the Londo scale (which is quasi-metric) or percent. Frequency data also be used. The question is: for what purpose do I want to know the Shannon diversity? Comparison? Assessment? Theory formation? In vegetation Shannon indices are weakly linked to other interesting properties.
I agree with Dr. G. Wiegleb. Unless there is clear purpose, merely arriving at some number / index will not be advisable because it varies according to plot size and intensity of sampling. Hence, it cannot be compared with other studies.
If you have estimated cover and mean height of plants, these two measures still could give you an index of dominance provided you have not used the B-B scale.
Best,
Gopal Rawat
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