To compare my DCA analysis with CCA, I would like to downweight the species data also in CCA. Since this option is not available for CCA, how can I do it?
A. In PC-ORD you cannot downweight in CCA in exactly the same way as in DCA. But you can downweight rare species prior to ANY analysis by appropriate adjustment of the data. For example, a simple approach is to delete species that occur in fewer than 5% of the sample units. Other transformations, such as the information function of ubiquity, downweight both very rare and very common species, maximizing the influence of species that occur in half of the sample units.
