Stand-level effects on the role of decaying logs as vascular plant habitat in Adirondack northern hardwood forests1

Abstract

GREGORY G. MCGEE (State University of New York-College of Environmental Science and Forestry, 1 Forestry Drive, Syracuse, NY 13210). Stand-level effects on the role of decaying logs as vascular plant habitat in Adirondack northern hardwood forests. J. Torrey Bot. Soc. 128:370-380. 2001.-The objectives of this study were to determine (1) if decaying logs provide critical habitat for any vascular plants in Adirondack northern hardwood forests; and (2) whether environmental factors that vary at the stand-scale influence the role of decaying logs as vascular plant habitat. Herbaceous ramet densities and woody seedling/sapling basal area were characterized on well-decayed logs and adjacent forest floor microsites in three northern hardwood stand types: old-growth, partially-cut, and 15to 29-year-old shelterwoods. No common herbaceous species were restricted to the log microsites, although Dryopteris intermedia had greater densities on logs. Betula alleghaniensis, Tsuga canadensis and Abies balsamea all attained greater basal areas (stems --15.0 cm diameter at the root collar) on decaying logs, while Acer pensylvanicum, Acer saccharum, Fagus grandifolia and Viburnum alnifolium had greater basal areas on forest floor microsites. Average (+ 1 SD) total basal area of woody stems was greatest in the shelterwoods (1775 + 615 mm2 m-2), compared to the partially-cut (714 + 266 mm2 m-2) and old-growth (503 + 657 mm2 m-2) stands. Betual alleghaniensis accounted for a substantial proportion of the basal area in the shelterwoods. In these shelterwood stands B. alleghaniensis basal areas were not statistically discernible between the forest floor and log microsites (P = 0.07). However, in partially-cut stands, B. alleghaniensis basal area was greater on the decaying log microsites (P = 0.05). In the old-growth stands, no B. alleghaniensis stems > 2 cm diameter were sampled. This study indicates that decaying logs provide early establishment sites for some tree species and the fern, D. intermedia, in northern hardwood forests. While B. alleghaniensis favored logs as establishment sites in the partially-cut stands, this species was capable of widespread establishment throughout the shelterwood stands. Even though B. alleghaniensis readily germinated on decaying logs, its recruitment into larger sapling size classes appeared to be consistently limited by factors varying at the stand level (e.g., light levels).