Abstract:
Basidiospores of Rhizopogon viriicolor Smith and R. colossus
Smith were inoculated onto container-grown Douglas-fir (Pseudotsuga
menziesii (Mirb.) Franco) seedlings and grown under two levels of
soluble fertilizer and one level of slow-release fertilizer. Both
fungi formed abundant (54%) ectomycorrhizae under the soluble
fertilizer regimes. Slow-release fertilizer greatly reduced percent
ectomycorrhizae for both fungi. Stern height was significantly
increased under low fertility with all basidiospore application
rates of R. colossus and the three lowest application rates of
H. vinicolor. High fertility significantly increased
ectomycorrhizae at all application rates of R. colossus. The HIGH
fertility regime produced plantable Douglas-fir seedlings with
abundant ectomycorrhizae of R. colossus and H. vinicolor. Five different conifers grown in a bareroot nursery were
inoculated with three basidiospore rates of seven hypogeous
ectomycorrhizal fungi. Two Douglas-fir seed sources were
successfully inoculated with both R. vinicolor and R. colossus. For
seedlings inoculated with B. vinicolor the HIGH basidiospore rate
produced the most ectomycorrhizae on the greatest number of
seedlings. For seedlings inoculated with R. colossus the HIGH
basidiospore rate (seed source 062) or the MEDIUM rate (seed source
252) produced the most ectomycorrhizae on the greatest number of
seedlings. No significant differences in stem heights or diameters
could be detected between treatments.
Bareroot nursery grown Douglas-fir noninoculated or inoculated
with basidiospores of B. vinicolor were outplanted on a routine
reforestation site formerly occupied by alder in southwestern
Oregon. After two years, inoculated seedlings had significantly
increased survival, stem height, stem diameter, and seedling biomass
(PVI). Although new feeder roots of noninoculated and inoculated
seedlings were colonized by indigenous fungi, B. vinicolor persisted
on the old root system and colonized new feeder roots on inoculated
seedlings.
