Table 2 Frequency of Frankia sub-clades occurring in clones derived from Alnus tenuifolia rhizosphere soils in early (denseAlnus tenuifolia stands) or late succession (mature Picea glauca forests), or in areas lacking A. tenuifolia in late succession forests. P-values in bottom rows were derived from Fisher’s exact test conducted for pairwise comparisons of a priori interest.