THE SURVIVAL AND DEVELOPMENT OF INOCULANT ECTOMYCORRHIZAL FUNGI ON ROOTS OF OUTPLANTED EUCALYPTUS-GLOBULUS LABILL

The survival and development of two inoculant ectomycorrhizal fungi (H ebeloma westraliense Bough. Tom. and Mal. and Setchelliogaster sp. nov .) on roots of outplanted Eucalyptus globulus Labill. was examined at two ex-pasture field sites in the south-west of Western Australia. Sit e 1 was a gravelly yellow duplex soil, and Site 2 was a yellow sandy e arth. Plants were grown in steamed or unsteamed soil, in root bags des igned as field containers for young growing trees. Three, 6 and 12 mon ths after outplanting, plants were removed from these bags and assesse d for dry weights of shoots and ectomycorrhizal colonization of roots. The inoculant ectomycorrhizal fungi (identified on the basis of the c olour and morphology of their mycorrhizas) survived on roots of E. glo bulus for at least 12 months after outplanting at both field sites. At Site 1, however, colonization of new fine roots by the inoculant fung i was low (less than 20% of fine root length). Inoculation had no effe ct on the growth of E. globulus at this site. In contrast, at Site 2 t he inoculant ectomycorrhizal fungi colonized up to 30-50% of new fine root length during the first 6 months after outplanting. There was a c orresponding growth response to ectomycorrhizal inoculation at this si te, with a close relationship (r(2) = 0.82*) between plant growth at 12 months and root colonization at 3 months. Plant growth at 12 months was related less closely with root colonization at 6 or 12 months. Ro ot colonization by 'resident' ectomycorrhizal fungi increased with tim e at both field sites. At Site 2, this increase appeared to be at the expense of colonization by the inoculant fungi, which was reduced to l ess than 10% of fine root length at 12 months. Steaming the soil had l ittle effect on colonization by the inoculant ectomycorrhizal fungi at either field site, but decreased colonization by the resident ectomyc orrhizal fungi.