Effects of high soil moisture on formation of ectomycorrhizas and growth of karri (Eucalyptus diversicolor) seedlings inoculated with Descolea maculata, Pisolithus tinctorius and Laccaria laccata.

Seedlings of Eucalyptus diversicolor P. Muell. I noculated with the ectomycorrhizal fungi Descolea maculata Bougher (two isolates), Pisolithus tinctorius (Pers.) Coker & Couch and Laccaria laccata (Scop, ex Fr.) Berk. & Br. were raised under glasshouse conditions in a yellow sand at a gradient of four soil moisture levels ranging from above field capacity to near waterlogged. All fungi enhanced growth of seedlings above that of uninoculated seedlings, but in soils near saturation there was no response to inoculation. Reduced mycorrhizal formation in relation to increasing soil moisture occurred to various degrees for all fungi. This was particularly marked with Pisolithus tinctorius. In contrast, Laccaria laccata maintained a relatively high number of mycorrhizal roots at all moisture levels applied, except at the wettest soil treatment. An isolate of D. maculata from a swamp environment did not produce a greater number of mycorrhizal roots at high soil moisture than an isolate of this species from a forest environment.