What I do know is that the Shannon index is between 0, 5 and 4.5. This value characterizes the balanced ecosystems or assemblies, such as the equatorial forest, with an elevated evenness index (close to 1).
When you are in a desertified areas, thus degraded, after the rain, the annual species (therophytes) appear. Richness "S", the Shannon index (H ') and evenness increase.
Can we also talk about balanced community?
I associate the state of equilibrium at the climax stages.
Can we also talk about balance when the above mentioned parameters increase only in the spring?
You might find your answer in Tilman, D. 1996. Biodiversity: population versus ecosystem stability. Ecology 77(2): 350–363: "species diversity has a clear and significant effect on resistance to disturbance, but an equivocal one on the recovery rate from a disturbance. Possibly, the diversity index can be a good indicator of primary successions, but not of secondary successions. Owing to this, biodiversity indicators would not be adequate to define stability of a system. Neither would they be satisfactory for assessing ecological successions."
For semiarid environments you can also read Karlin, M; Bachmeier, O; Dalmasso, A.; Sayago, J. M. y R. Sereno. 2011. Environmental dynamics in Salinas Grandes, Catamarca (Argentina). Arid Land Research and Management 25(4): 328-350; or 10. Karlin, M. S.; Galán, R.; Contreras, A. M.; Zapata, R. M.; Coirini, R. O. y E. J. Ruiz Posse. 2013. Exergetic model of secondary successions for plant communities in Arid Chaco (Argentina). ISRN Biodiversity.
I quote an extract from Karlin et al. 2011: "According to several authors (Odum, 1972; Patten, 1959; Margalef, 1956), if biodiversity is high, the system gains stability. Therefore, when a community moves toward a climax (or more correctly, steady state), its diversity increases. However, the facts show that this does not always occur. A clear example is what happens after forest fires, where the system experiences the invasion of opportunist species (r) (Begon et al., 2006; Odum, 1972), temporarily increasing its biodiversity. Such species are later replaced by species with higher interspecific competition capacity (K). It is possible that after a fire disturbance, diversity fluctuates despite the system’s recovery (Shafi & Yarranton, 1973), and such diversity depends on the interspecific competition capacity. Thus, abundance and plant cover of some populations take higher values than those of the maximum carrying capacity calculated for quasi-natural conditions, increasing the Euclidean distance from the steady state."
Hi,
I tried to see the plant community settled in different plantations: Olea sp, Opuntia sp and Pinus sp (natural ecosystem).
opposite the pine forest, H 'recorded values around 3, 82 with E = 0.92.
I would like to know is that this balance between species "Strategist R" is just temporary and that appeared just after the rain species share the same resources only for X time?
Or, would it be fair to think that we can not talk about balance in the community when it is mostly composed of ephemeral species even if the indicators of high biodiversity.
Thank you.
Souad.
Shannon index for herbs vary with the season, but for mature tree species remain same and not affected much by rain.
Ok, in this case can we speak of an assembly or a balanced environment only during one season ?
If the spring, the richness and the number of herbaceous increase, Shannon Index and Eveness increase
How to interpret this balance?
Its always better to carry out sampling for herbs in all the seasons, instead of particular one season to quantify the actual Shannon and Evenness index. After that aggregating all the data of each season for the quantification of Shannon and Evenness index can give more accurate result to interpret.
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