Percentages of mycorrhizal seedlings (A) and mycorrhizal colonization index (B) on P. halepensis inoculated with three ectomycorrhizal fungi under different N fertilization sources (ammonium nitrate-NH₄NO₃, ammonium-(NH₄)₂SO₄, nitrate-HNO₃). For each inoculation treatment, different letters indicate significant differences (Contingency tables for percentage of mycorrhizal seedlings, Duncan’s test, p ≤ 0.05 for mycorrhizal colonization).