Hello to all
The relationship between species diversity and ecosystem stability and its maintenance mechanism has been one of the main topic in ecology research.
In the past, diversity indices frequently used for assessing of community stability. in other words, each community that had more diversity, it was more stable. in the last decade, Functional diversity (FD) that defined as the value, range, distribution and relative abundance of the functional characteristics of organisms in a community, was the most popular methods for evaluation of community stability and functioning. While, in the recent years, Functional Redundancy (FR) that defined as some species perform similar roles in communities and ecosystems, and redundant species can therefore be lost with minimal impact on ecosystem processes. In other words, redundant species are considered necessary to ensure ecosystem resilience (resilience and resistance are two concept of stability). The redundancy hypothesis predicts that the species redundancy in a plant community enhances community stability.
Now, my main question is that: Is there another index that measure plant community stability directly?
Best regards
Reza
Please check these researchgate links.
https://www.researchgate.net/publication/236678742_Functional_redundancy_and_stability_in_plant_communities_J_Veg_Sci
https://www.researchgate.net/publication/232129070_Dominance_and_diversity_in_land_plant_communities
Article Functional redundancy and stability in plant communities
Article Dominance and diversity in land plant communities
I would use a selection of plant functional traits to gather information on the community and then use a functional redundancy approach...
But reading your question again, Proff Rod Connolly at Griffith has addressed resilience in very diverse systems....
http://macroecointern.dk/pdf-reprints/P%E9rez-Harguindeguy_AusJBot_2013.pdf
Hello to all
Thank you very much for your guidance. I argue that we can not measure or assess the community stability by Biodiversity indices, Functional diversity or Functional diversity trait, and Functional Redundancy due to changeability of stability across of time.
I accept that all of these methods can effects on community stability, but this effects is relative.
I think, we must used of another methods that consider variation of community attribute across of time. In this regards, Remote Sensing (RS) data could be very useful.
What is your view?
Reza
If you are looking at stability then this would imply that you take repeated measures. Assuming that you are working on plant communities I would raise a few questions:
- What system are you considering? For instance - very arid areas are strongly affected by rainfall, and species become visible very quickly (and briefly) in response to only a few mm of rain.
- What time interval would you consider? You might have some short term variation in plant composition around a certain "central" point.
- What part of the plant community would you look at? In arid areas you can expect more variation in ephemeral plants, but perennial composition may remain consistent. So the perennial plants might be considered stable, while the ephemerals would indicate variation.
I agree that remote sensing might help, that you might look at variation around a "mean", but you would probably need more detailed advice from an RS person considering how responsive the various vegetation indexes are
You could use bi-plots based on (N)MDS to get a visual impact of how plant communities "behave".
As I write I am wondering if one number will actually be able to encompass everything that you are looking at. It might, but then again, the index would have to be sufficiently sensitive to pick up on variations, but not over-sensitive so as to make its interpretation impossible.
My idea is much in the line of ... we use a mean and variance to describe a sample / population, no single number can do both. ... we use species richness, a diversity index and an evenness index to describe different aspects of a plant community - the individual measures have little meaning.
Would you split the vegetation up into ephemerals and perennials and consider them separately?
When you find something, could you post it here as well? I'd really like to see what you come up with.
Regards,
Patrick
Dear Patrick
Thank you very much for your answer. I want consider Stability in plant community (Iranian Rangeland) in relation to gradient of grazing and climate ( form 80 mm to 1200 mm).
In this regard, I want use the variation of vegetation indices (i.e. NDVI, PVI, TVI, TTVI, etc.) time interval of 5, 10, and 20 year as Stability.
Now, I don’t know that use the variation of vegetation indices as stability index is true or not?
Is it necessary that split vegetation up to plant functional groups or different plant type (i.e. ephemeral or perennial)?
Best regards
Reza
Hi Reza,
my remote sensing using NDVI is not solid, so you should definitely get expert opinion on this. Neverthless here are my two cents worth.
If you use only the time intervals you indicate you will only note that something has changed, but not if there is stability. Consider that you may have very high NDVI values in a good rainfall year, but very low values in a dry year. Yet the system as such might still be stable. I would look at the amount of variation that is inherent in the system first. Maybe also look at autocorrelation (in time as well as space) to help you to identify time periods that can will show up changes.
Regarding grazing gradients - keep an eye on the distances from (I assume) water. The grazing intensity changes with a inverse-J relationship (e.g. negative exponential). This depends on the grazing animal and their drinking frequency.
Regards,
Patrick
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