Spatiotemporal colonization of Scots pine roots by introduced and indigenous ectomycorrhizal fungi in forest humus and nursery Sphagnum peat microcosms

Mycorrhizal and non-mycorrhizal Scots pine (Pinus sylvestris L.) seedling c ombinations were grown in two-dimensional Perspex microcosms containing for est humus or nursery Sphagnum peat, without additional fertilization. Spati al and temporal patterns of mycorrhizal fungal colonization of roots were a ssessed over a 3-month period, through visual morphotyping and polymerase c hain reaction assisted rDNA fingerprinting of developed mycorrhizas. Six di stinct morphotypes of mycorrhiza developed on non-mycorrhizal seedlings gro wn in forest humus. Three of the morphotypes (white1-, black-, and brown-ty pe) were, respectively, associated with the fungi Suillus bovinus (L. ex Fr .) O. Kuntze, Cenococcum geophilum Fr., and Thelephora terrestris Ehrh.:Fr. (= Tomentella radiosa (P. Karst.) Rick). A fourth pink-type morphotype dis played features indicating root colonization by Tomentellopsis submollis (S vrcek) Hjortstam, but this could not be confirmed because of a lack of sour ce restriction fragment length polymorphism (RFLP) data. Brown-type mycorrh iza were the first to appear after seedling transplantation and black-type mycorrhizas showed local and dispersed root colonization dynamics. Mycorrhi za development in the unfertilized nursery peat substrate was restricted to a single unidentifiable brown-type morphotype, which appeared after 44 day s. Rapid colonization of adjacent non-mycorrhizal seedlings by Tomentellops is submollis, but not S. bovinus, was detected following the introduction o f preinoculated seedlings into the humus or peat microcosms. The biomass of seedlings grown in nursery peat, regardless of mycorrhizal status, was sig nificantly lower than that of mycorrhizal seedlings grown in humus. These f indings support and extend previous bait seedling studies, as they provide a primary in situ characterization of distinct root colonization strategies of mycorrhizal species in forest humus and nursery peat.