Comparative Distribution of Ectomycorrhizae in Soils of Three Western Montana Forest Habitat Types

Soil core samples from three western Montana forest sites representing a range of moisture, productivity, and dominant tree species (Douglas-fir, subalpine fir, and hemlock) were analyzed for differences in quantities and types of soil organic matter and the distribution of active (physiologically functioning) ectomycorrhizae in the soil profiles. The lowest levels of soil organic matter and ectomycorrhizal activity occurred in the Douglas-fir and subalpine fir sites. Most of the ectomycorrhizae occurred in the soil organic matter at all three sites, primarily in humus (O2 layer) or in brown cubical decayed wood distributed throughout the soil profiles. In the Douglas-fir site, decayed soil wood was the most frequent substrate for active ectomycorrhizae. In soils of the subalpine fir and hemlock sites, humus was the most frequent substrate for ectomycorrhizae. Consistently high moisture levels in the organic materials, particularly decayed wood, were associated with this phenomenon. Forest Sci. 25:350-358.