Table 3 Frequency of Frankia clades occurring in clones derived from Alnus tenuifolia rhizosphere soils in mid succession (densePopulus balsamifera forests) that were either unfertilized, fertilized with N (NH4NO3), or fertilized with P (P2O5). P-values in bottom rows were derived from Fisher’s exact test conducted for pairwise comparisons of a priori interest.