[R-sig-eco] life forms spectrum analysis

[Ludovico Frate]

Dear List,
I would like to analyse the differences  in life form (Raunkiær) composition between two populations. The two populations (plant communities) were sampled randomly and the presence of plant species were recorded. So for each plot I have the frequency of each life form. First, I  thought to a chi square or binomial test. However, I am worried about the applicability because both tests require that the frequency of life forms observed vs expected is grater than 0% (i.e., when a given life form is present in all the plot of both populations - observed = 100% expected = 0%) and less than 100% (better between 20 and 80%).
Pop1, Pop2
present, 70, 56
absent, 0, 0

I have tried also a simple Mann whitney test but it doesn't work well for count data. In addition for uncommon life forms I have a lot of zero counts in my data!


Do you have any ideas about analysing differences in life forms?
Best,
Ludovico



                                                                                                                                
Dott. For. Ludovico
Frate, Ph.D.
University of Molise - Italy
Environmetrics Lab
http://www.distat.unimol.it/STAT/environmetrica/organico/collaboratori/ludovico-frate-1
Department of Biosciences and Territory - DiBT
Università del Molise.
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E-mail ludovico.frate at unimol.it
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