ENVIRONMENTAL CONSEQUENCES in rocky mountain coniferous ...

Table 1.--Factors affecting soils or tree growth that are based on specific micro-
organisms.
Microbial action Effect
Nitrogen fixation (symbiotic and non-symbiotic)
Nitrogen input
Nitrification Nitrogen 1 oss
Ectotqycorrhizal symbiosis
decay (non-pathogenic)
Decay (pathogenic)
MICROORGANISMS AND SOIL QUALITY
Nutrient availability
Water availabil ity
Pathogen resistance
Nutrient flux
Production of organic base
Nitrogen jnput
Nutrient flux
Production of organic base
Nitrogen input
Genetic turnover of host
Vegetation changes
As demonstrated in this symposium (Larsen and others 1980; Jurgensen and others
1980; Harvey and others 1980; Fell in l98O), microbial activities are integral to both
positive and negative inputs on soil productfvi ty. Decay organisms convert above-
ground biomass into biologically active soil materials and, in the process, recycle
bound nutrients and support fixation of atmospheric N. Various components of the soil
continue, throughout their lifespan, to support both N-fixing and ectomycarrhizal
activities. The ectomycorrhizal association is necessary to the survival of conifers
in infertile, natural soils (frappe and Fogel IgV), as is an adequate supply of N.
Conversely, activities of certain soil -borne microbial pathogens, particularly root
decsy organisms, may 1 imi t productivity to non-suscepti bl e vegetation (Fell in 1980).
ORGANIC MATTER AND SOIL QUALITY
All soil microbe activities are supported by the organic fraction of a soil . In
terms of wood decay, non-symbiotic N-fixation and ectomycorrhizae, this re1 ationship
is usually positive, i .e., the more organic materials the greater the soil produc-
tivity. In a developing forest soil, productivity increases with accumulation of
organic matter, at least within certain limits (Harvey and others 1980). Therefore,
if these organic accumulations are not lost during harvesting and site preparation,