Hi Denis Efimov, 

Thank you for the references I have gone through these questions but my question has some other important points which need to be explained/elaborated in detail. 

Dear Arshad

The indices you mention - Shannon and Simpson - suffer from many scientific and mathematical problems. I suggest you to use Fisher Alpha, which is not perfect of course but better than the two others.

Good Luck

Selection of index greatly depends on your objective and there is lot of argumentative literature regarding the topic. Mostly richness is determined by Margalef’s index, diversity by Shannon–Weaver index  and dominance by Simpson index. These indices account for whole vegetation structure of sampled site while IVI taking into account each and every sampled individual. All these can be applied simultaneously. I must say again that whatever indices you use are dependent directly on your objectives.

Hope it works

Regards

Dear Arshad,

I think that Huma has addressed it pretty well.  Each Index has certain biases, and each depends on which mathematical version that you chhose (Do you use log 10 or ln for Shannon-weiner).  It also depends on what question you're asking.  You might think about using simillarity indices if your goal is to compare structure and diversity among sites.

For diversity index: Lots of tools available which contains many indices of diversity. Such software like ESTIMATES has quite complete indices for diversity, richness, fisher, chao etc. With this tool we can compare each indices that we gain from the field and we can calculate the biases of each indices. Then you decide which one will you use.

For IVI: IVI is an index which summarizes the "importance" of one species to other, when compare in terms of its Relative frequency, relative dominance and relative density. 

Do you tried with Hill numbers:

Jost, L. 2006. Entropy and diversity. Oikos 113:363–375.

Jost, L. 2007. Partitioning diversity into independent alpha and beta components. Ecology 88:2427–2439.

shannon-Weiner index is universally accepted index for diversity as it accounts for entropy in an ecosystem or in representative samples. When you calculate Shannon-Weiner index, you will notice that it accounts for both species richness and its evenness or equtability. Therefore, in order to estimate diversity, Shannon-Weiner Index is used.

Simpson index is used to estimate dominance of the species as it does not account for species richness.  If you plot a curve between Shannon-Weiner Index and Simpson Index, you will get a negative regression line indicating that with increasing diversity, dominance decreases which is highly logical.

You can use the two indices for forest, shrub land and also in grassland.

As for Importance value index (IVI) is concerned, it give the importance or dominance of a species in a sample as evident from its formula.

You can best understand the concepts of diversity index, dominance index or IVI if you

refer the two books - 1. Fundamentals of Ecology by E.P.Odum  and 2. Field Biology and Ecology by Smith

Dear Dr. V. K. Srivastava

May I get pdf of book "Fundamentals of Ecology by E. P. Odum"?

Thanks in anticipation

Huma

I had the same problem while doing my study. Previously there was a software called SPECDIVE which was being used for such purposes. But since it was DOS based, the software didn't last long. Hence, I started using ESTIMATE S for he same reason. You are asking about which diversity index is better, that totally depends on your objective but Shannon Wiener and Simpson's index are not considered to be robust indices. However, you could always use Chao indices. Also, for IVI, you need to know the GBH (girth to breast height) of the species to know their dominance in the area. It is calculated by adding relative density, relative frequency and relative dominance. I am giving you link to a similar paper that I wrote.

Article VEGETATION STRUCTURE AND COMPOSITION IN CORE AREA OF SARISKA...

@ Zaara Kidwai Thank you for sharing your experience about this issue and for the Paper. 

For IVI of trees its ok to use GBH but what about for shrub and herb species ? I have gone through many published papers each using different methods for IVI of trees, shrubs and herbs. So the confusion is still there.  

Try using ESTMATE S. To compare each indices and it will give description of which indices give better result of your sites.

Dear Mr. Arshad Ali Shedayi,

As for accounting diversity in any number of sites, Shannon-Weiner Index has been considered to be a better index as compared to Simpson's index. In fact Simpson index is considered more as a dominance index as it accounts proportion of species in a sample. Whereas, Shannon-Weiner index is based on randomness present at a site and considers both species richness and equitability in distribution in a sample. 

When comparing diversity or dominance at a given site, the sample size must be the same for each sample. If the study deals with heterogeneous forest, the sample size for each layer i.e. tree, shrub and herbs must be same at each site. It is advised to lay nest quadrat at such sites.

If you relate the diversity index with dominance index, you will get a negative correlation, since with increasing diversity, dominance decreases. The classic example could be that of a plantation crop of single species. If you calculate Shannon-Weiner index in such case, it will come to close to zero and Simpson index will turn out to be one or close to one.

Simpson index (Dominance index) and IVI are two different ecological measures. Simpson index defines only the dominance of a species in a sample whereas, IVI is based on certain phytosociological characteristics viz relative dominance, relative abundance and relative frequency of species in a sample.

Yes, all these measures can be applied to the same data.

Hope, the above details may help you interpreting your phytosociological data.

yes it is challenged question but

Simpson index is considered more as a dominance index as it accounts proportion of species in a sample. Whereas, Shannon-Weiner index is based on randomness present at a site and considers both species richness and equitability in distribution in a sample.

Important Value Index (IVI)

It is useful to compare the ecological significance of species. It combines data from three parameters (relative frequency, relative density, and relative dominance). It often reflects the extent of the dominance, occurrence, and density of a given species over other associated species in an area. I think like this