Ectomycorrhiza formation and root development patterns of conifer seedlings on a high-elevation mine site

Three conifer species, Pinuscontorta Dougl., Pinusflexilis James, and Piceaengelmannii Parry ex Engelm. were inoculated with the ectomycorrhizal fungi Pisolithustinctorius (Pers.) Coker & Couch, Suillusgranulatus (L. ex Fr.) Kuntze, and Cenococcumgeophilum Fr. These, plus noninoculated seedlings were planted under two fertilization treatments and grown for 5 years on a high-elevation (3200 m) mine site. One-year-old P. contorta and P. engelmannii seedlings inoculated with the ectomycorrhizal fungi P. tinctorius and S. granulatus were planted under two fertilization and three water conservation treatments, and grown on a high-elevation mine site for 1 year. After one growing season, mycorrhizae formed by P. tinctorius and S. granulatus were still visible on P. contorta seedlings root systems. However, after five growing seasons, P. tinctorius and C. geophilum were not visible on the roots of P. contorta and P. flexilis seedlings, although mycorrhizae formed by S. granulatus appeared to be present. Few mycorrhizae were observed on the root systems of 1- or 5-year-old P. engelmannii seedlings. Root system development of 1- and 5-year-old P. contorta and P. engelmannii seedlings was dramatically reduced by the sewage sludge and wood-chips fertilization treatment, but fertilization treatments had no apparent effects on root system development of 5-year-old P. flexilis.