Studies of fungi in a Calluna-heathland soil : II. By the complementary use of several isolation methods

Abstract

The soil plate, immersion tube and slide-trap methods were used in an investigation of the fungus flora of a small area of Calluna -heathland surface soil. A marked seasonal variation in the activity of Trichoderma viride was demonstrated by the two latter (‘direct’) methods. The isolation method and medium, time, position and depth of sampling, and interactions between these factors, differentially affected the results. In general, the soil-plate method favoured the isolation of heavily sporing fungi, particularly Penicillium spp., and the direct methods emphasized the importance, perhaps unduly, of Mortierella spp. and other very rapidly growing fungi. It is suggested that a physical ‘rhizo-sphere’ effect might have been produced by the immersion in soil of solid objects, which stimulated the growth of certain fungi. Competition between species was a major factor in determining the results obtained by all methods. These results were augmented by studies of two specific habitats and by direct observation. An attempt was made to outline certain mycelial space relationships by an analysis combining all methods of study. The direct isolation methods appeared, in part, to be selective for translocating types of mycelia. Even with the use of these several methods, it was apparent that a proportion of the fungus flora, which consisted largely of humus-inhabiting fungi, was unavailable for study.