[R-sig-eco] How to classify the scales of dbMEMs/PCNMs?

[trichter at uni-bremen.de]

Dear list,

I am working with dbMEMs/PCNMs as spatial covariates in RDA with  
species composition data.
I want to give my covariates some meaning, and as many research papers  
suggest, the way to do it is to divide them into scales ("broad",  
"medium","fine"). However, i cant remember reading about how this  
classification is made, especially when one works in a comparably  
regular grid. So, do you have any advise on this classification?

Thanks a lot, Tim