Plant growth and ectomycorrhiza formation by transplants on deglaciated land near Exit Glacier, Alaska

Ectomycorrhiza (EM) formation on plant roots in successional communities ma y vary with plant species, plant age, and age of vegetation after disturban ce. To evaluate differences in mycorrhizal fungus communities on roots of s ame-aged seedlings across a deglaciated chronosequence, indoor-grown bioass ay plants of four dominant species Epilobium latifolium L. (dwarf fireweed) , Populus balsamifera ssp. trichocarpn (Torr.&Gray) Hult. (black cottonwood ), Alnus sinuata (Regel) Rydb. (Sitka alder), and Picea sitchensis (Bong,) Carr. (Sitka spruce) were transplanted into five successional stages (Barre n, Isolated Plant, Patchy, Alder, and Cottonwood) following deglaciation ne ar Exit Glacier, Alaska. The species were selected for their successional s tatus and mycorrhiza formation potential [EM or arbuscular mycorrhiza (AM) or both]. Seedlings were transplanted in June 1992, and half were harvested at the ends of the two subsequent growing seasons. The EM communities on P . balsamifera differed across the chronosequence while those of the other s pecies did not. Morphotype B dominated the EM on P. balsamifera after the B arren stage, and the greatest EM colonization was in the Isolated Plant and Patchy stages. No AM were found. The EM observed on even-aged seedlings in this study were a subset of the EM found on naturally occurring plants (se edlings to mature trees) in a prior study, and some were common to multiple plane species. Most plant growth responses were not significant across sta ges or were inconsistent among plant species.