Study of the Microfungal Community of an Andosol

(1) Variations in the composition of the microfungal community of an andosol under a beech forest in northern Spain, both during the course of a year and between the different soil horizons, were studied. Microfungi were recovered by soil dilution, by soil washing and from the surface of leaves. (2) The species-diversity decreased with increasing depth, and was associated with increasing dominance of Aureobasidium pullulans (de Bary) Arnold in the lower soil horizons. Mortierella minutissima van Tieghem was characteristically present in spring isolates, while Trichoderma pseudokoningii Rifai was characteristic of summer isolates. (3) The similarities between microfungal recoveries from the various soil horizons and from different seasons of the year were compared by means of three-dimensional ordinations and dendrograms. (4) Similarity between the different horizons at one particular season was greater than within the same horizon at different seasons, and the floras of subhorizons A1l and A12 were always similar. Winter recoveries differed widely from those of the rest of the year. (5) The microfungal community colonizing the surfaces of fallen leaves in autumn and winter was quite different from the soil community.