Null models have frequently been used to test whether the observed beta-diversity patterns are related to changes in alpha- or gamma- diversity or to actual changes in underlying mechanisms across different context (e.g. tropical vs temperate forests as in Myers et al. 2013 - Ecology Letters). These null models are usually applied to presence-absence data (as in Chase et al. 2011 - Ecosphere) or when individuals are counted (as in Kraft et al. 2011 -Science, or DeCaceres et al 2012 - GEB).

In plant ecology, abundance is usually estimated using percentage cover or other ordinal scales (e.g. Braun-Blanquet's). Is there any null model that could be applied to such data?

I have a site x species matrix, with species abundances being represented by their % cover (transformation of Braun-Blanquet scale).

I need a null model to create permuted communities which retain:

1. Site richness and overall gamma diversity (number of species in the species pool)

2. Site total abundances

and possibly

3. the probability of occurrence of each species (rare species should be less represented than common species in the permuted communities)

4. the usual abundance of a species (e.g. a tree should be given on average a higher cover than a herb species)

Does anybody know whether such a model, or something similar, has already been developed? Was it implemented in R?