Gregory G. McGee

STRUCTURAL CHARACTERISTICS OF OLD-GROWTH, MATURING, AND PARTIALLY CUT NORTHERN HARDWOOD FORESTS

Live tree diameter distributions, and abundance and quality of standing and downed coarse woody debris (CWD), were compared among three northern hardwood stand types in the Adirondack Mountains of New York, USA: old growth; partially cut, uneven-aged with 40–50 cm maximum residual diameters; and maturing, even-aged, 90–100 yr old, postfire. Downed CWD (stumps ≤1 m tall and logs) volumes in the old-growth, partially cut, and maturing stands were 139, 69, and 61 m3/ha, respectively. Large (≥50 cm diameter) CWD comprised 17%, 13%, and 4% of the total downed CWD volume in the old-growth, partially cut, and maturing stands respectively. Approximately one-half the large CWD in the partially cut stands was in the form of cut stumps. Standing CWD (stumps >1 m tall and standing dead trees) basal areas averaged 8.6, 1.2, and 4.1 m2/ha in the old-growth, partially cut, and maturing stands, respectively. Basal area of large (≥50 cm diameter) standing CWD averaged 70%, 0%, and 5% of the total in the old-growth, partia...

Understory response to springtime prescribed fire in two New York transition oak forests

Abstract Portions of two south-central New York transition oak stands received 0, 1 or 2 springtime prescribed fires between 1980/1981 and 1984. Observations 8–12 years later showed that forb richness, forb and shrub cover, and the importance values of forbs relative to shrubs increased in areas receiving one or two fires. Fagus grandifolia, Dennstaedtia punctilobula, Gaultheria procumbens and Trientalis borealis exhibited small, but detectable increases in importance values in burned areas. The importance values of Quercus rubra, Kalmia latifolia and Viburnum acerifolium decreased in burned areas. Areas receiving greater intensity fires contained taller tree regeneration and greater shrub cover, but no important changes in community composition could be attributed to fire intensity. An apparent relationship between rhizome depth and post-fire competitiveness of dominant perennial forbs and shrubs suggests the importance of below-ground morphological traits on survival and recovery following fire. Overall, the 12-year, post-burn cover and density of understory vegetation increased in burned areas and in areas receiving greater intensity fires, however, community composition remained largely unaffected by these springtime prescribed fires.

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

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).

Arboreal Mite Communities on Epiphytic Lichens of the Adirondack Mountains of New York

Abstract We describe the mite fauna inhabiting the canopies of remnant old-growth Acer saccharum (sugar maple) trees in northern hardwood stands under different silvicultural treatments in the Adirondack Mountains. We also compare mites on different arboreal substrates, including bare bark, the crustose lichen Pertusaria velata, and three foliose lichens: Flavoparmelia caperata, Parmelia squarrosa, and Punctelia rudecta. A total of 877 individual mites were collected representing 25 oribatid mite species, at least three of which are undescribed, and nine non-oribatid mite families. Mite abundance was sevenfold greater in Punctelia rudecta than on bare bark, and communities differed among bark, crustose lichen, and foliose lichens, but not among the different species of foliose lichens. Trees in old growth and reserve shelterwood stands supported different mite communities.

Effects of two silvicultural regimes with large tree retention on epiphytic macrolichen communities in Adirondack northern hardwoods, New York, USA

We sampled epiphytic lichen communities in nine Adirondack northern hardwood stands: three old growth, three reserve shelterwood, and three single-tree selection systems. Our objectives were to assess the effects of treatment, tree diameter at breast height, and their interaction on lichen communities and to determine whether lichen traits were associated with particular habitats. Lichen community composition was strongly related to tree diameter at breast height and differed between old growth and reserve shelterwoods. Lichen community composition was also related to an interaction between tree size and stand type. Lobaria pulmonaria (L.) Hoffm. was associated with large trees in old growth, whereas Evernia mesomorpha Nyl., Parmelia sulcata Taylor, and Physcia millegrana Degel. characterized those in shelterwood stands. Nitrophilous lichens were most common on small trees and in reserve shelterwoods, whereas small trees in selection systems and old growth supported lichens that were found to be most asso...

Size of Acer saccharum Hosts Does Not Influence Growth of Mature Bryophyte Gametophytes in Adirondack Northern Hardwood Forests

Abstract Several epiphytic bryophyte species (Anomodon attenuatus, Anomodon rugelii, Brachythecium oxycladon, Leucodon brachypus, Neckera pennata, Porella platyphylloidea, and Rauiella scita) have diminished frequencies of occurrence and abundances in second-growth and partially-cut Adirondack northern hardwood forests relative to old-growth forests. The occurrence and abundances of these species, all of which exhibit mesophytic growth forms and two of which (A. attenuatus and A. rugelii) are known calcicoles, are positively correlated with diameters of sugar maple (Acer saccharum) host trees. The mechanisms causing their specificity for large, old sugar maples hosts are not known, but their distributions may reflect interactions of their respective physiological tolerances with changing microenvironmental conditions on sugar maple bark as the host trees age and mature. We tested this “gradient in time” hypothesis by transplanting mature gametophyte mats on sugar maple trees ranging from 20–85 cm diameter at breast height. Furthermore, we tested this hypothesis at two sites, a mesic and a xeric forest stand, in order to assess the influences of meso-scale (stand-level) environmental factors on the micro-scale (individual tree-level) regulation of gametophyte growth. All but two of the 96 transplants remained alive after six years. Following an initial year of overall dieback, average cover increased 23% over the subsequent five year period. Tree diameter had no effect on expansion rates of any transplanted species. Only one species, Neckera pennata, exhibited significantly greater expansion at the mesic site than at the xeric site. Our data suggest that age-related changes in microenvironmental conditions of sugar maple bark do not have an important influence on the distribution of these “large-maple” epiphytes. Rather, factors such as dispersal limitations or establishment requirements of protonemata probably limit their distribution. Additional, well-replicated transplant experiments are required to determine the effects of micro- and meso-scale environmental variation on the establishment, growth, and reproduction of epiphytic bryophytes. We discuss implications of our results for restoration of epiphytic bryophyte communities in heavily disturbed forest landscapes.

Relationships among forest age, composition and elemental dynamics of Adirondack northern hardwood forests1

Abstract We conducted a biogeochemical analysis of four Adirondack northern hardwood forests (two old-growth and two maturing second-growth) to elucidate correlations among stand age, site conditions and several nutrient cycling processes. One each of the old-growth and maturing forests were located on base-rich sites, while the other two were on base-poor sites. At each site we analyzed soil solution chemistry and estimated nutrient flux rates; measured annual litter production, and nutrient and lignin content; measured annual N mineralization and nitrification rates; and characterized herb- and canopy-layer vegetation, and coarse woody debris volumes. Vascular plant communities of the two base-rich sites were dominated by several rich-site indicator species, while such indicators were lacking at the base-poor sites. Tree basal areas and annual litter production did not differ among the study sites, but the old-growth stands contained 3-fold more coarse woody debris than the maturing stands. Foliar litter N concentrations did not differ among the study sites, but foliar litter from the base-rich sites had higher Ca2+ and lower lignin concentrations than the base-poor sites. Differences in foliar litter quality among the sites were due, in part, to intraspecific variation in litter chemistry. There were no consistent differences between the old-growth and maturing stands in soil solution nutrient concentrations or fluxes. Soil solution H+ concentrations were higher and Ca:Al ratios lower at the two base-poor sites. Annual, net N mineralization rates did not differ among the sites, but net nitrification rates in the organic soil horizons at the rich old-growth site were more than twice those at the other sites. High levels of net nitrification and N leaching were observed only in the base-rich old-growth site. Our data suggest that net forest nutrient retention may be a function of interacting mechanisms associated with forest developmental stage, community composition and site conditions.

Comparison of soil nutrient fluxes from tree-fall gap zones of an old-growth northern hardwood forest1

Abstract The objective of this study was to assess nutrient losses, via soil solutes, from discrete zones of recent, single-tree gaps in an old-growth, northern hardwood forest. Growing season flux rates of all solutes did not differ between the “undisturbed” zones (areas 5 m away from gap-making trees) and “crownfall” zones (areas associated with fallen tree crowns) of the twelve tree-fallgaps we studied. Under assumptions of partial root gap formation (50% root mortality), total cation and anion fluxes were 2-fold greater, and DON and total N fluxes were 2- to 3-fold greater in the “proximate” zones (areas 0–2 m from stumps of snapped, gap-making trees) compared to the crownfall and undisturbed zones. The “pit” zones (areas of disturbed soil associated with tipped-up trees) exhibited 3- to 6-fold greater NH4+, NO3−, and total dissolved N fluxes, and 2-fold greater total cation and anion fluxes than the undisturbed and crownfall zones. We estimated that proximate and pit zones associated with both recent and old tree-fall gaps accounted for 12% and 0.3%, respectively, of the total stand area in this old-growth forest. At the stand level, root throw pits contributed < 1% of the estimated NO3−, total dissolved N, total cations and total anions leaching from the system. Under assumptions of partial root gap formation proximate zones contributed 24–27% of the flux of these solutes. We conclude that the pit zones were inconsequential for nutrient loss and, while proximate zones contributed substantially more to nutrient losses from this system, the majority of nutrients leached from this system (∼ 75%) were leached from undisturbed forest zones. Our results indicate that efforts to account for mechanisms of nutrient loss from old-growth forests must consider variation in leaching rates associated with discrete microenvironments within gaps, and focus greater attention on nutrient retention capacity of the live, intact forest matrix.