Mycoecology of willow and cottonwood lowland communities in Southern Wisconsin I. Soil microfungi in the willow-cottonwood forests.

Abstract

A survey of the soil microfungi in 5Salix nigra-Populus deltoides forests in southern Wisconsin was conducted. The dilution plate method was employed to obtain 500 isolates per stand. The species present and their frequencies of occurrence were determined. The dominant forms,Trichoderma viride, Cladosporium cladosporioides, Gliocladium roseum, Mucor hiemalis, Coniothyrium sp. 5154,Mortierella minutissima, andPenicillium thomii, accounted for 41 % of the 2,500 isolates but only 4.5 % of the 154 species. They were followed at a second level of prevalence byPenicillium janthinellum P. multicolor, Mortierella alpina, andPhoma sp. 5157. The distribution of these taxa and others in the willow-cottonwood community was found to be correlated with an organic matter gradient. The Dematiaceae and the Sphaerioidaceae characterized populations obtained from the dry “pioneer” sites; the Mucorales and Moniliaceae became increasingly abundant as the percentage of organic matter increased. The number of fungal propagules ranged from 3,000 to 234,000 per gram of dry soil, the highest numbers occurring in soils with greater organic matter. The willow-cottonwood microfungal population was most similar to one obtained from soils of the closely related southern Wisconsin wet-mesic forests and least similar to ones isolated from the northern Wisconsin bogs and spruce-tamarack swamps.