Interactions between tree roots, mycorrhizas, a saprotrophic fungus and the decomposition of organic substrates in a microcosm

A microcosm technique has been used to evaluate the effects of tree seedling root systems, their mycorrhizas and a saprotrophic basidiomycete fungus and their interactions in the decomposition of organic substrates. The component elements were added to the experimental system in a factorially designed experiment of increasing complexity. Roots and mycorrhizas significantly enhance the rate of decomposition of the substrates. The mycorrhizal fungus Suillus luteus was the most active decomposer of all substrates. This root-induced enhancement of decomposition was suppressed in the presence of the saprotroph, Mycena galopus. Plant growth was influenced by the substrate, in that the nitrogen-containing substrates, hide powder and chitin, promoted greater growth than the pure carbohydrate, cotton. Presence of the saprotroph, Mycena galopus significantly enhanced tree growth. The data are discussed in relation to previous studies on the influence of roots and their mycorrhizas on decomposition.