H' and E are the important parameter to understand the diversity in both disturbed and undisturbed ecosystem. As you mentioned in disturbed ecosystem a few species (therophytes) influencing the diversity indices. In such a situation, parameter  like density, basal area and IVI of each species are also important. From the value of these parameter we can easily prepare a list of possible influencing species along with the other species which are contributing to increase or decrease the value of H' and E.

Thank you very much.

I work with land use intensity, so I evaluate differences between natural-conserved systems and human-modified ones. I think that it is very valid to show how in modified systems the H´and E is changing over the time, and explain the mechanism of those changes. Even at more high land use intensity, plant community responds to assembly processes driven by management practices and environmental filters. However, I would be very careful when you interpret the diversity indices, because part of the movie was lost (species composition). I would recommend that you also use other metrics and technique such as indices of dissimilitude, rank abundance curves, anosim and simper analysis. With these tools you can understand not only how the richness and species abundance is changing but also the composition of species and the shifts for dominance among them over the time.

Thank you for your answer.

What I wanted to know is:

In stable ecosystems, H 'can reach 4.5 ( Exp. Tropical forest)

In a disturbed environment but  planted, H ' can reach for example  3.5 and E = 0.80.

Based on these values, the studied community is diverse and balanced.

I think, it is not the same balance as the stable ecosystem, since these values are temporary and are obtained only in spring (Presence of therophytes =ephemeral).

In this case, what can I say from my community? How to describe it?

Thank you very much.

In the mentioned case I feel that the seasonal data should be recorded and placed forth. IVI and species richness should be calculated for each seasonal data. A comparison between the seasonal observations for a continous period of time like 5 years or so could help to derive significant conclusions.

Thank you,

My question is clear: 

With high value of H' and E,  what about my assemblage?

Is it  in equilibrium with its environment (a temporary equilibrium)?

I think looking at just a few indices loses the context of the ecosystem.  One should use as wide a range of indices as possible.  For instance I use the following:species richness, population (or frequency), biomass, rarity/commonness, Simpson's Index and estimated species richness (chao 1&2 bootstrap an jackknife).

Certainly, I also used the other indices mentioned.

My question is: can we describe my community  that is diverse and balanced only in the spring?

Are there any ecological significance? ( seasonal equilibrium).

Souad

Some indices will vary with season (population and biomass for example) and some may be more constant (Simpson's and rarity index).  Obviously it is best to time surveys when the most indices will be applicable.

Please Alan,

I give you an example:

Winter: Richness (S) = 5, Abundance (N) = 50, M '= 1.6, E = 0.6

Spring: Richness = 15,  Abundance (268), H' = 3.68, E = 0.80.

Can you describe the two situations?  

Can I say that my assemblage is diversified and balanced during spring and is not in the winter?

Does this mean that the number of ecological niches increases with the appearance of  therophytes (ephemeral) in spring?

If this balance (share of habitat resources) is only seasonal, ecologically speaking is really a balance?

My English is very bas, sorry.

Thank you for your patience.

I think that ecological conclusions or hypotheses based just in numbers it's simply too risky. The changes in community may be driven by seasonal variations rather than merely to the community itself , if the area is the same and in 2 sampling recording season, let's say in winter species X appear, but doesn't in spring, that's it mean that the species is extincted in Spring? or if present, Does the population of this species be same in two contrasting seasons?, well numbers are just a simple tool, that's why composition, ecology knowledge and biology are more important.

Let me know your opinion

I understand your difficulty and in the UK we have exactly that problem with birds which are migratory.  We have answered this by doing transect bird population surveys each month of the year.  This has worked well and the results accord well with national bird biodiversity results.  This will be the subject of publication in about a year's time .  If you wish I can send a datasheet that shows these results.

I know that  the composition, ecology knowledge and biology are more important.

In this case, when  Shannon index and Equitability have high values, only   during spring  How to describe my community? What can i say in this situation?

Thanks.

The H or E value of the area can be used to show the difference plant community between seasons. i think you can use the CSR s (C: competitive, S: stress tolerant, R: ruderal linked to different stages of succession) plant strategy adaptation by Grime for explanation why your species just survive during spring season not in other season. Some plants can stand for environment stress (disturbance) by specific strategy, other can avoid the stress by dormant strategy.

I hope it will help you, Hari

Ok.

Most plants are ruderal.

Precisely,  can i say that my community knows an equilibrium (on the basis of high value of  H' and E) in the spring?

Ecologically, can we speak of a seasonal equilibrium  even if the majority of plants are ruderal.

Souad.

Hello,

Diversity indices are dangerous to use without a clear understanding of their mathematical properties. They all come from concepts in physics or communication and not from an ecological point of view. So, even if your community is seen as balanced by any envenness index, does it have an ecological meaning?

We know that natural communities are unbalanced, so why do we use indices where the optimal value is obtained for a completly even distribution ? In my opinion you can't speak of any equilibrium with such indices as they bring an inappropriate view on abundance distribution and moreover there is no real equilibrium in living communities.

Stability is a complex idea that cannot be expressed by just a few values. In addition, you chose Shannon's entropy and consequently you have chosen to express a particular point of view on abundance distribution among species: the one where rare and abundant species are equally weighted.

HTH

Nicolas

I agree with Nicolas and personally would not rely on H' and E alone as surrogates for biodiversity and stabilty (whatever you mean by these). As for the structural comparison of the community structure at the two points in time (seasons) you can compute a diversity profile using Hill's numbers. However, when it comes to more functional issues, I would suggest to resort to functional groups and functional diversity analysis.

My approach has always been that no one index can possibly cover the range of characteristics in a biodiversity assessment.  Indeed I use two variations of the E and H measures: one based on numbers of individuals per species and another on the biomass of individuals per species (see Feest et al.  paper in Ecological Indicators).  Interestingly these evenness/dominance indices are the first to show change when change is occurring rather than species richness or population.  Can we get away from discussing individual indices of biodiversity and move on to assessing the balance of characteristics expressed by a range of indices?

From your question I am trying to determine, what exactly are you looking to measure in the plots?   From you question, it sounds like the three planted perennials are exotics, the cactus, pine and olive, and you have some native desert annuals that sprout each year?    Are you looking to see if these plots will revegetate naturally with local native plants?