Field performance of black spruce and jack pine inoculated with selected species of ectomycorrhizal fungi

Seedlings of black spruce (Picea mariana (Mill.) B.S.P.) and jack pine (Pinus banksiana Lamb.) were inoculated with fragmented hyphae of one of five species of ectomycorrhizal fungi and outplanted on reforestation sites after 14 weeks of growth in the nursery. Black spruce were planted on a peatland site and a stony loam site; jack pine were planted on the same stony loam site and on a sandy site. Inoculation of both species with Laccaria proxima (Boud.) Maire resulted in significantly better shoot growth compared with uninoculated seedlings over a 2-year period on all sites. Hebeloma cylindrosporum Romagn. improved the height growth of black spruce on the peatland site and of jack pine on the stony loam site after 2 years. Laccaria bicolor (Maire) Orton also improved the height growth of jack pine on the stony loam after 2 years. Black spruce inoculated with L. bicolor were significantly smaller than uninoculated seedlings. Size differences present in black spruce at outplanting persisted for two growing seasons, whereas initial size did not predict the field performance of jack pine. Inoculation of black spruce with L. proxima resulted in higher foliar concentrations of K and Zn compared with uninoculated seedlings on the peatland site. Foliar concentrations of N, P, K, and Zn in jack pine inoculated with L. proxima were significantly higher than those of uninoculated seedlings at the stony loam site. All inoculated fungi (except Pisolithus tinctorius (Pers.) Coker & Couch, which did not form mycorrhizae) remained on the root systems for two growing seasons, but their presence declined sharply in the 2nd year. Laccaria bicolor was the most persistent mycobiont on root systems of both tree species. Colonization of black spruce by indigenous ectomycorrhizal fungi was faster on the stony loam site than on the peatland site. The diversity of wild ectomycorrhizae on the planted seedlings was higher on both the peatland and sand sites than on the stony loam site.