The mycorrhizal status, root anatomy, and phenology of plants in a sugar maple forest

The phenology, root anatomy, and mycorrhizal colonization of vascular plant species occurring in a hardwood forest site were studied. Sugar maple (Acer saccharum), the dominant tree, ash (Fraxinus americana), another important tree, and the most abundant herbaceous plants were examined periodically. Most of the herbaceous species present were highly colonized by vesicular–arbuscular mycorrhizae (VAM), but some consistently had low levels of VAM, or were nonmycorrhizal, and several had orchid mycorrhizae. Most trees were associated with VAM, although several ectomycorrhizal species occurred in low numbers. Herbaceous plants could be divided into four phenological categories of shoot activity, spring, spring–summer, summer, and fall, but many species had periods of root growth that did not parallel their aboveground activity. Almost all species that produced new roots in summer were well colonized by VAM, while those active mainly in late fall or early spring tended to be nonmycorrhizal. Roots of the woodland plants typically had a well-developed exodermis and also tended to be long-lived and coarse. Possible relationships among these root system characteristics, phenological categories, and levels of mycorrhizal colonization of woodland plants are discussed.