Natural Reestablishment of Mycorrhizae in Disturbed Alpine Ecosystems

Abstract

Vesicular-arbuscular mycorrhizal fungi were surveyed in several successional areas of the Beartooth Mountains in Montana. Roots were examined for percentage of mycorrhizal infection, and spores were counted in rhizosphere soils from undisturbed, - 25-yr-old seral, and 3- and 7-yr-old revegetated areas in 1983 and 1984. The three most abundant grasses of early seral areas, Deschampsia caespitosa, Agropyron trachycaulum, and Poa alpina, showed similar patterns: spore counts and percent infection of these species were generally higher in undisturbed than seral and revegetated areas in 1983, but in 1984 the spore numbers and infection were similar because the values dropped in undisturbed areas and increased in the other areas. Patterns of mycorrhizal infection varied for the other species, and Geum rossii, a late seral dominant, was heavily colonized by an unidentified nonendogonaceous fungus. Plant colonization is slow in the alpine, but once plants are established, mycorrhizal fungi apparently colonize quickly. Even the 3-yr-old revegetated area had infection equal to some of the undisturbed areas. However, only a single mycorrhizal fungal species was obtained from the revegetated areas, in contrast to more than 11 species from older areas.