The influence of pH on the competitive interactions of ectomycorrhizal mycobionts under field conditions
The effects of H2SO4 watering on the competitive interactions of outplanted mycobionts was studied in a jack pine plantation in Quebec. Ectomycorrhizal jack pine seedlings produced in growth pouches and inoculated with either Pisolithustinctorius (Pers.) Coker and Couch or Laccariabicolor (Maire) Orton as well as noninoculated seedlings were exposed weekly to H2SO4 solutions adjusted to pH 5.6, 4.0, 3.2, or 2.5 for 14 weeks. Soil pH was significantly reduced in those plots where the pH was adjusted to 2.5. Seedling growth parameters were not affected by acid treatment. Indigenous colonization was not affected by acid treatment but was suppressed by inoculation, prior to outplanting, with either L. bicolor or P. tinctorius. Acid treatment significantly influenced the persistence of the inoculated mycobiont, P. tinctorius being more sensitive than L. bicolor to acid treatment. A competition index, used to evaluate postplanting competitivity, was higher for P. tinctorius in those plots where the watering solution was adjusted to pH 5.6 while in all other plots L. bicolor was more competitive with the indigenous mycota.