Mycoecology of Willow and Cottonwood Lowland Communities in Southern Wisconsin. II. Soil Microfungi in the Sandbar Willow Stands

Abstract

The sandbar willow (Salix interior), a 1-4 m high stoloniferous shrub, colonizes extensively and is the principal plant species found on newly exposed or deposited sand in and along major Wisconsin rivers. Stabilization of these pioneer areas produces conditions which favor the replacement of this shrub community by black willow (S. nigra) and cottonwood (Populus deltoides) trees; ultimately succession leads to the wet-mesic forests (7). The alluvial soils which support the development of S. interior are commonly coarse-grained sands exhibiting only a trace of organic material, minerals, and nitrogen, a slightly acid condition, and a low water-holding capacity. The water table is usually within 0.5-1.5 m of the surface. Litter deposited each autumn is swept away by the spring floods before much of it can be incorporated into the soil. In the summer months, conditions in these areas often simulate those found in deserts with surface temperatures reaching 40-60° C and the sands appearing dry. However, proximity to the river, high water tables, partial canopies, heavy dew, and/or moderate precipitation probably produce humid soil atmospheres during part of the time. The present investigation examines the soil microfungi in 5 sandbar willow stands thought to represent pioneer stages in a plant succession leading to the willow-cottonwood forests. In an earlier paper, the mycoecology of the latter community has been described (11).