An ecological study of fungi in Calluna-heathland soils

Abstract

The fungal floras of several Calluna-heathland soils distributed over England and Wales were investigated by the soil plate method. Many species of fungi (including Trichoderma viride. Mucor ramannianus, Beauveria bassiana, PeniciIlium adametzi, P. namyslowskii, P. nigricans, Trichobotrys sp., Absidia orchidis, Mortierella isabellina, Pullularia pullulans, and Zygorrhynchus vuilleminii) were found to be of more or less constant occurrence in these soils. Representatives of all major classes of fungi, excepting Oomycetes, were isolated.The numbers of species of fungi decreased with increasing depth, although certain species (Mucor ramannianus, Beauveria bassiana and Trichobotrys sp.) were most commonly isolated from the sub-surface, leached horizons. Evidence suggested that the illuviated horizons checked the downward distribution of spore-producing species.The fungus flora of one small area of heathland soil wasinvestigated in greater detail, on a seasonal basis, byseveral recently described methods of isolation including the immersion tube and a new slide-trap method. The latter two methods, designed to isolate only those fungi actively growing in the soil, yielded closely agreeing results; many of the species of fungi shown to be of constant occurrence by the plating method were isolated also as active mycelia. Many of the species isolated, however, varied according to the method employed.Microscopical examination by the Rossi-Cholodny slide technique revealed the growth habit of many of the species isolated and also the presence of many species which were not isolated - largely humus-inhabiting, dark-coloured hyphomycetes.Whilst no seasonal variation in the occurrence of fungi was demonstrated by the plating method, marked variation was demonstrated by the immersion tube method, In particular the isolation of Trichoderma viride was closely related to the prevailing temperature.The use of several methods of isolation, in conjunction with investigations of specific habitats and microscopical examination, provided a useful means of approach to the problems of soil fungal ecology.