Hi,
   There are three explantation matrixs(topography, soil and  PCNMs variation matrixs) and one response matrix.  And I want to know the contribution of each explantation matrix to the response matrix using the function of varpart which is contained in vegan package. But there are  two questions as follows:
    1) Should insignificant variations of each explantation matrix be excluded prior to partitioning using forward selection or other selection methods?
    2) PCNM method could provide spectral decomposition of the spatial relationships among the sampling sites. The significant PCNM variations could be divided into several submodels according to scales, however, how can I achieve this process of dividing in R?
   Thanks for all your attention!
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