ENVIRONMENTAL CONSEQUENCES in rocky mountain coniferous ...

ECOLOGY OF ECTOMYCORRHIZAE IN NORTHERN ROCKY MOUNTAIN FORESTS
A1 an E. Harvey, Research Plant Pathologist
USDA Forest Service, Intermountain Forest
and Range Experiment Station
Mi chael J. Larsen , Research Mycologist
Center for Forest Mycology Research
USDA Forest Service, Forest Products Laboratory
Martin F. Jurgensen, Professor of Forest Soils
Department of Forestry
Mi chi gan Technological University
ABSTRACT
Activity of ectomycorrhizal symbionts depends on the nature of the
soil and vegetation, as controlled by climate and natural or man-
caused disturbances over time. Organic materials in the form of
litter, humus, decayed wood or charcoal that occur in layers or mixed
in the mineral soil are key factors governing ectomycorrhizal activities
in forest soil s. Importance of these organic fractions to ectomy-
corrhizal activity can be predicted, based on their quantity and
distribution in the forest floor, the season, and the relative
position of the site along a temperature-moisture gradient. Organic
materials are most important in the harshest soils. This appears to
result directly from their ability to buffer wide variations of pH,
moisture and temperature. Because the ectomycorrhi zal association
depends on host trees, manipulations of the stand also provides
direct control of ectomycorrhizal activity.
KEYWORDS : harvesting, residues, fire, biological impact, soil
qual i ty, ectomycorrhizae.
INTRODUCTION
The strong positive effect of soil organic layers or organic amendments on
abundance of ectomycorrhizae (Mikola 1973; G6bl 1967; Rayner 1936) and the
dependence of conifers on this symbiotic association (Trappe and Fogel 1977)
suggests a relationship between organic materials and soil qual i ty. The ability
of decayed wood to support ectomycorrhizae (Harvey and others 1976; Zak 1971 ;