SPECIES: Tsuga canadensis
SPECIES: Tsuga canadensis
AUTHORSHIP AND CITATION : Carey, Jennifer H. 1993. Tsuga canadensis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ .
ABBREVIATION : TSUCAN SYNONYMS : NO-ENTRY SCS PLANT CODE : TSCA COMMON NAMES : eastern hemlock Canada hemlock hemlock spruce TAXONOMY : The currently accepted scientific name for eastern hemlock is Tsuga canadensis (L.) Carr. . Fernald  recognizes a dwarf form, T. canadensis forma parvula Vict. and Rousseau, that grows in mats up to 3 feet (1 m) high in Quebec and New England. LIFE FORM : Tree FEDERAL LEGAL STATUS : No special status OTHER STATUS : NO-ENTRY
SPECIES: Tsuga canadensis
DISTRIBUTION AND OCCURRENCE
GENERAL DISTRIBUTION : In the United States, eastern hemlock occurs throughout New England, the mid-Atlantic states, and the Lake States, and extends south in the Appalachian Mountains to northern Georgia and Alabama and west from the mountains into Indiana, western Ohio, and western Kentucky. At its northern limit, eastern hemlock ranges along the southern border of Canada from southern Ontario to Cape Breton Island, Nova Scotia [20,35]. ECOSYSTEMS : FRES10 White - red - jack pine FRES11 Spruce - fir FRES15 Oak - hickory FRES18 Maple - beech - birch FRES19 Aspen - birch STATES : AL CT DE GA IN KY ME MD MA MI MN NH NJ NY NC OH PA RI SC TN VT VA WV WI NB NS ON PE PQ BLM PHYSIOGRAPHIC REGIONS : NO-ENTRY KUCHLER PLANT ASSOCIATIONS : K093 Great Lakes spruce - fir forest K094 Conifer bog K095 Great Lakes pine forest K096 Northeastern spruce - fir forest K097 Southeastern spruce - fir forest K103 Mixed mesophytic forest K104 Appalachian oak forest K106 Northern hardwoods K107 Northern hardwoods - fir forest K108 Northern hardwoods - spruce forest SAF COVER TYPES : 5 Balsam fir 17 Pin cherry 18 Paper birch 19 Gray birch - red maple 20 White pine - northern red oak - red maple 21 Eastern white pine 22 White pine - hemlock 23 Eastern hemlock 24 Hemlock - yellow birch 25 Sugar maple - beech - yellow birch 26 Sugar maple - basswood 27 Sugar maple 28 Black cherry - maple 30 Red spruce - yellow birch 31 Red spruce - sugar maple - beech 32 Red spruce 33 Red spruce - balsam fir 34 Red spruce - Fraser fir 35 Paper birch - red spruce - balsam fir 37 Northern white-cedar 39 Black ash - American elm - red maple 44 Chestnut oak 52 White oak - black oak - northern red oak 53 White oak 57 Yellow-poplar 58 Yellow-poplar - eastern hemlock 59 Yellow-poplar - white oak - northern red oak 60 Beech - sugar maple 97 Atlantic white-cedar 108 Red maple SRM (RANGELAND) COVER TYPES : NO-ENTRY HABITAT TYPES AND PLANT COMMUNITIES : Eastern hemlock occurs as a dominant or codominant in coniferous and mixed-hardwood forests. It is often the only conifer present in mixed mesophytic forests of the eastern United States . Publications listing eastern hemlock as codominant or dominant are as follows: The natural forests of Maryland: an explanation of the vegetation map of Maryland  A multivariate analysis of forest communities in the western Great Smoky Mountains National Park  The vegetation of Wisconsin  The principal plant associations of the Saint Lawrence Valley  Field guide: forest habitat types of northern Wisconsin  A classification of the deciduous forest of eastern North America  The natural communities of South Carolina  Forest associations in the Harvard Forest  Vegetation of the Great Smoky Mountains 
SPECIES: Tsuga canadensis
WOOD PRODUCTS VALUE : Eastern hemlock wood is of low value because of brittleness and abundant knots . It is used for pulp, light framing, sheathing, roofing, subflooring, and boxes and crates . IMPORTANCE TO LIVESTOCK AND WILDLIFE : Dense stands of eastern hemlock provide excellent wildlife habitat . Cove forests in the southern Appalachian Mountains provide nesting habitat for many species of birds. The black-throated blue warbler, black-throated green warbler, and blackburnian warbler are especially abundant in virgin eastern hemlock cove forests . Large eastern hemlocks can be climbed by small black bear cubs. In northeastern Minnesota, black bear mothers and cubs spent more than 95 percent of the time in April and May within 600 feet (183 m) of either an eastern hemlock or an eastern white pine (Pinus strobus) larger than 20 inches (51 cm) in d.b.h. . Eastern hemlock has high cavity value for wildlife . Large hollow trees are commonly used as dens by black bears . The seeds are eaten by birds and mammals , and in the winter the foliage is browsed by white-tailed deer, moose, and snowshoe hares [2,59]. PALATABILITY : In the winter, eastern hemlock browse is moderately preferred by moose and highly preferred by white-tailed deer [2,10]. In the summer, white-tailed deer prefer hardwood sprouts and seedlings to eastern hemlock . The seeds of eastern hemlock are not as preferred by white-footed mice, red-backed voles, and meadow voles as red pine (Pinus resinosa) and white pine seeds . NUTRITIONAL VALUE : NO-ENTRY COVER VALUE : Eastern hemlock provides cover to ruffed grouse, wild turkey, fishers, and other wildlife [4,20]. It provides excellent thermal protection and snowfall interception for moose and white-tailed deer in the winter [2,17]. VALUE FOR REHABILITATION OF DISTURBED SITES : NO-ENTRY OTHER USES AND VALUES : From 1880 to 1930, eastern hemlock was extensively harvested for its bark which is a source of tannin . Eastern hemlock is planted as an ornamental . OTHER MANAGEMENT CONSIDERATIONS : Multiple removal cuttings are the best method for regenerating eastern hemlock. Suddenly released seedlings often die, and a series of removals releases hemlock more slowly . On moist sites, a two-cut shelterwood system leaving about 50 percent cover may be adequate. On drier sites, a three-cut system is appropriate, initially leaving 70 to 80 percent crown cover and 50 percent after the second cut . If too few residual trees are left, they may die when exposed, and they are subject to windthrow . Scarification of seedbeds and removal of competing hardwoods may be necessary . Eastern hemlock regeneration must be at least sapling size when released if it is to compete successfully with uncontrolled hardwoods . Single tree selection is also an effective method to harvest and regenerate eastern hemlock . Effective reproduction may be absent in areas with high deer populations [3,10]. Regeneration in the Porcupine Mountains in Michigan has declined over the last several decades because of white-tailed deer browsing in the winter . In the Allegheny National Forest in Pennsylvania, the eastern hemlock-northern hardwoods forest type covered 83.4 percent of the land in 1800 and only 15.8 percent in 1986. Extensive harvesting, fire, and overbrowsing are responsible for the decline . Numerous insects attack eastern hemlock, but only a few are of economic importance cause sporadic or local mortality . Mortality usually occurs following complete defoliation by insects [43,62]. Eastern hemlock seedlings are sensitive to damping-off fungi, root rots, and stem and needle rusts . Eastern hemlock appears to be resistant to ozone .
SPECIES: Tsuga canadensis
BOTANICAL AND ECOLOGICAL CHARACTERISTICS
GENERAL BOTANICAL CHARACTERISTICS : Eastern hemlock is a native, evergreen conifer with heavily foliaged and upsweeping branches. At maturity, it is commonly 60 to 70 feet (18-21 m) tall and 24 to 48 inches (61-122 cm) in d.b.h. One of the largest eastern hemlock recorded was 175 feet (53 m) tall and 76 inches (193 cm) in d.b.h. It reaches ages in excess of 800 years. Eastern hemlock roots are shallow and widespreading [20,26]. RAUNKIAER LIFE FORM : Phanerophyte REGENERATION PROCESSES : Trees begin producing seed when they are 20 to 30 years old. Eastern hemlocks older than 450 years still produce large seed crops. This species bears cones every year, and large crops are frequent, usually every 3 to 4 years. The small winged seeds are dispersed by gravity and wind; most fall within one-tree-height distance from the source [20,54]. The seeds are partially dormant and germinate best when stratified for about 10 weeks at or slightly above freezing. Germination occurs at a range of temperatures; seeds from the northern portion of its range germinate at lower temperatures than seeds from the southern portion [20,54]. Seeds do not remain viable if they do not germinate the first spring after seedfall . Seeds germinate best on moist substrates, such as rotten wood, mineral soil, mineral soil mixed with humus, well-decomposed litter, and moss mats [14,62]. The number of seedlings established on rotten logs and stumps increases as the wood decays and the moss cover increases. Seedlings commonly establish on "tip-up mounds" formed by fallen trees . Seedlings grow slowly and cannot tolerate full sunlight until fully established, usually when they are 3 to 5 feet (0.9-1.5 m) tall . Eastern hemlock regeneration appears to be periodic and is influenced by fire, windthrow, drought, and stand conditions. A young dense stand may exclude regeneration for many years because of severe root competition in the upper soil layers, dense low shade, and dry acidic litter [27,56]. Hemlock regeneration is present in the understory of stands with a parent overstory density of up to 140 square feet per acre (32 sq m/ha) but is most abundant when eastern hemlock comprises 80 to 100 square feet per acre (18-23 sq m/ha) of the overstory . Eastern hemlock does not sprout and layers only rarely . SITE CHARACTERISTICS : At its western and southern limits, eastern hemlock is confined to moist cool valleys, moist flats, northern and eastern slopes, coves, benches, and ravines. In the northern part of its range, it tolerates drier and warmer sites. Eastern hemlock also occurs at swamp borders provided peat and muck soils are shallow [14,20,40,65]. Favorable eastern hemlock sites are moist to very moist with good drainage. Eastern hemlock grows in a wide variety of acidic soils; textures include sandy loams, loamy sands, and silty loams with gravel of glacial origin in the upper profile [14,20]. While generally considered a moisture-demanding species, eastern hemlock grows on dry sites protected from fire, such as rocky ledges . Two types of eastern hemlock have been described: one grows in mesophytic habitats and one on subxeric slopes . The types cannot be termed ecotypes, however, because of incomplete habitat differentiation. Eastern hemlock growing on "subxeric" slopes may actually be receiving moisture from seeps . In the northeastern United States, eastern hemlock grows at elevations ranging from sea level to 2,400 feet (730 m). In the southern Appalachian Mountains it grows from 2,000 to 5,000 feet (610-1,520 m). In the Allegheny Plateau region of New York, Pennsylvania, and Ohio, it grows from 1,000 to 3,000 feet (300-910 m) [13,20,34]. Understory associates are scarce because of acidic infertile humus, low light, and cool conditions [14,34]. Shrub and small tree associates that occur in canopy gaps include sweet birch (Betula lenta), striped maple (Acer pensylvanicum), mountain maple (A. spicatum), hobblebush (Viburnum alnifolium), mapleleaf viburnum (V. acerifolium), mountain winterberry (Ilex montana), rhododendron (Rhododendron spp.), mountain-laurel (Kalmia latifolia), and witch hazel (Hamamelis virginiana). Herbs can include Canada mayflower (Maianthemum canadense), star flower (Trientalis borealis), common woodsorrel (Oxalis montana), and goldthread (Coptis groenlandica). Other associated species include clubmosses (Lycopodium spp.), bracken (Pteridium aquilinum), woodfern (Dryopteris spp.), and sedges (Carex spp.). Common mosses include Dicranium spp. and Polytrichum spp. [14,20,32,45,65]. SUCCESSIONAL STATUS : Obligate Climax Species Eastern hemlock is very shade tolerant . Seedlings survive in as little as 5 percent of full light . Individuals are able to survive several hundred years of suppression, and many show numerous growth releases and suppressions . Saplings less than 2 inches (5 cm) in d.b.h. may be more than 100 years old . Seedlings are able to establish under the canopy of mature individuals. Eastern hemlock establishes under dense sugar maple canopies and can replace that species . Eastern hemlock uniquely modifies semipermanent soil properties, such as acidity, which favors its reproduction. Opportunities to establish in a mature forest increase over time as nurse logs and tip-up mounds accumulate . The general desgination of eastern hemlock as a climax species has been questioned [22,41]. In some old-growth eastern hemlock stands, the smaller size classes of hemlock are being replaced by American beech (Fagus grandifolia) and sugar maple . Because of this lack of regeneration, Hemond and others  suggest that eastern hemlock requires disturbance to perpetuate itself. In contrast, other authors suggest that disturbance is responsible for the lack of regeneration in mature hemlock forests [3,6,51]. White-tailed deer populations have increased since presettlement times because logging of virgin forests opened up habitat, predators declined, and the deer were protected. Deer often consume all eastern hemlock seedlings and saplings in the winter. Where deer populations are low, eastern hemlock appears to be able to reproduce in its own shade and become a component of a self-perpetuating homogenous climax forest . Eastern hemlock requires partial shade for establishment and is a late colonizer of disturbed sites . In the Pisgah Forest in southwestern New Hampshire, 80 percent of old-growth eastern hemlock established within 37 years of disturbance. Hardwoods grew rapidly into the canopy while eastern hemlock grew slowly as shade-tolerant saplings. Eastern hemlock extended into the canopy following subsequent disturbance . The understory population of eastern hemlock readily takes advantage of canopy gaps. Eastern hemlock increased in importance as American chestnut (Castanea dentata) declined from chestnut blight . It is currently replacing American beech where that species is succumbing to beech bark disease . Eastern hemlock is not successful in regenerating in canopy gaps in areas such as the New York Botanical Forest, where the occasional light arson fire, trampling, and other urban stresses kill seedlings. In addition, the removal of fallen logs in the forest decreases the amount of adequate substrate for germination . The slow invasion of oak-dominated sites by eastern hemlock appears to be related to heavy leaf litter and the absence of favorable seedbed conditions . SEASONAL DEVELOPMENT : Eastern hemlock male strobili open and pollen is dispersed in late April to early June, depending on locality. This is usually 2 weeks after the leaf buds open. Fertilization is complete in about 6 weeks, and cones reach full size in late August or early September. The cones open in mid-October, but seed dispersal may extend into the winter . Cones close in wet weather and open again in subsequent dry weather, prolonging seed dispersal. Germination occurs in the spring .
SPECIES: Tsuga canadensis
FIRE ECOLOGY OR ADAPTATIONS : Eastern hemlock is very susceptible to fire because of its thin bark, shallow roots, low-branching habit, and heavy litter deposits [20,51]. It is possibly the most fire-sensitive mesophytic tree species in its range . Eastern hemlock usually escapes fire because it occurs in moist habitats and is often associated with hardwoods which do not readily burn. If a fire starts in a cutover area, a windfall area, or an area with dead standing timber, it may carry into a northern hardwoods forest if there is strong wind . In Michigan, the average return time for severe crown fires in the hemlock-white pine-northern hardwoods type is estimated to be about 1,400 years . In northeastern Maine, the average return interval for fire in spruce-fir forests in which eastern hemlock is a minor component is about 800 years . Vogl  considers eastern hemlock a fire-initiated species rather than a fire-independent species because it benefits from fire-prepared seedbeds. However, suggestions that fire promotes regeneration of eastern hemlock are not well documented. Given the difficulties in accurate age estimates because of heart rot, Rogers  suggests that even-aged eastern hemlock forests that regenerated after fire may actually be uneven-aged. POSTFIRE REGENERATION STRATEGY : Tree without adventitious-bud root crown Secondary colonizer - off-site seed
DISCUSSION AND QUALIFICATION OF PLANT RESPONSE :
SPECIES: Tsuga canadensis
IMMEDIATE FIRE EFFECT ON PLANT : Low-severity fire readily kills seedlings and saplings of eastern hemlock, and may also kill larger trees. A low-severity ground fire in a northern hardwoods community in south-central New York killed 93 percent of the eastern hemlock saplings. Sixty percent of the mature eastern hemlock died or were badly injured as a result of the fire . The presence of fire scars indicates that larger trees have thick enough bark to survive low-severity surface fires [18,36]. DISCUSSION AND QUALIFICATION OF FIRE EFFECT : NO-ENTRY PLANT RESPONSE TO FIRE : Eastern hemlock appears to invade burned sites over time. In the Pisgah Forest in southwestern New Hampshire, 80 percent of old-growth hemlock germinated within the first 37 years after a major fire in 1665 .
FIRE MANAGEMENT CONSIDERATIONS : NO-ENTRY
SPECIES: Tsuga canadensis
REFERENCES : 1. Abbott, Herschel G. 1962. Tree seed preferences of mice and voles in the Northeast. Journal of Forestry. 60: 97-99.  2. Allen, Arthur W.; Jordan, Peter A.; Terrell, James W. 1987. Habitat suitability index models: moose, Lake Superior region. Biol. Rep. 82 (10.155). Washington, DC: U.S. Department of the Interior, Fish and Wildlife Service. 47 p.  3. Anderson, Roger C.; Loucks, Orie L. 1979. White-tail deer (Odocoileus virginianus) influence on structure and composition of Tsuga canadensis forests. Journal of Applied Ecology. 16: 855-861.  4. Arthur, Stephen M.; Krohn, William B.; Gilbert, James R. 1989. Habitat use and diet of fishers. Journal of Wildlife Management. 53(3): 680-688.  5. Baker, Frederick S. 1949. A revised tolerance table. Journal of Forestry. 47: 179-181.  6. Brown, James H., Jr.; Castaneda, Cesar A.; Hindle, Robinson J. 1982. Floristic relationships anddynamics of hemlock (Tsuga canadensis) communities in Rhode Island. Bulletin of the Torrey Botanical Club. 109(3): 385-391.  7. Brush, Grace S.; Lenk, Cecilia; Smith, Joanne. 1980. The natural forests of Maryland: an explanation of the vegetation map of Maryland. Ecological Monographs. 50(1): 77-92.  8. Busing, Richard T. 1989. A half century of change in a Great Smoky Mountains cove forest. Bulletin of the Torrey Botanical Club. 116(3): 283-288.  9. Callaway, Ragan M.; Clebsch, Edward E. C.; White, Peter S. 1987. A multivariate analysis of forest communities in the western Great Smoky Mountains National Park. American Midland Naturalist. 118(1): 107-120.  10. Curtis, John T. 1959. The vegetation of Wisconsin. Madison, WI: The University of Wisconsin Press. 657 p.  11. Dansereau, Pierre. 1959. The principal plant associations of the Saint Lawrence Valley. No. 75. Montreal, Canada: Contrib. Inst. Bot. Univ. Montreal. 147 p.  12. DeGraaf, Richard M; Shigo, Alex L. 1985. Managing cavity trees for wildlife in the Northeast. Gen. Tech. Rep. NE-101. Broomall, PA: U.S. Department of Agriculture, Forest Service, Northeastern Forest Experiment Station. 21 p.  13. Duncan, Wilbur H.; Duncan, Marion B. 1988. Trees of the southeastern United States. Athens, GA: The University of Georgia Press. 322 p.  14. Eyre, F. H., ed. 1980. Forest cover types of the United States and Canada. Washington, DC: Society of American Foresters. 148 p.  15. Fernald, Merritt Lyndon. 1950. Gray's manual of botany. [Corrections supplied by R. C. Rollins]. Portland, OR: Dioscorides Press. 1632 p. (Dudley, Theodore R., gen. ed.; Biosystematics, Floristic & Phylogeny Series; vol. 2).  16. Foster, David R. 1988. Disturbance history, community organization and vegetation dynamics of the old-growth Pisgah Forest, south-western New Hampshire, U.S.A. Journal of Ecology. 76: 105-134.  17. Frelich, Lee E.; Lorimer, Craig G. 1985. Current and predicted long-term effects of deer browsing in hemlock forests in Michigan, USA. Biological Conservation. 34: 99-120.  18. Frelich, Lee E.; Lorimer, Craig G. 1991. Natural disturbance regimes in hemlock-hardwood forests of the upper Great Lakes region. Ecological Monographs. 61(2): 145-164.  19. Garrison, George A.; Bjugstad, Ardell J.; Duncan, Don A.; [and others]. 1977. Vegetation and environmental features of forest and range ecosystems. Agric. Handb. 475. Washington, DC: U.S. Department of Agriculture, Forest Service. 68 p.  20. Godman, R. M.; Lancaster, Kenneth. 1990. Tsuga canadensis (L.) Carr. eastern hemlock. In: Burns, Russell M.; Honkala, Barbara H., technical coordinators. Silvics of North America. Volume 1. Conifers. Agric. Handb. 654. Washington, DC: U.S. Department of Agriculture, Forest Service: 604-612.  21. Hacker, David; Renfro, James. 1992. Great Smoky Mountain plants studied for ozone sensitivity. Park Science. 12(1): 6-7.  22. Hemond, Harold F.; Niering, William A.; Goodwin, Richard H. 1983. Two decades of vegetation change in the Connecticut Arboretum Natural Area. Bulletin of the Torrey Botanical Club. 110(2): 184-194.  23. Henry, J. D.; Swan, J. M. A. 1974. Reconstructing forest history from live and dead plant material- an approach to the study of forest succession in southwest New Hampshire. Ecology. 55: 772-783.  24. Hibbs, D. E. 1983. Forty years of forest succession in central New England. Ecology. 64(6): 1394-1401.  25. Hooper, Robert G. 1978. Cove forests: bird communities and management options. In: DeGraaf, Richard M, technical coordinator. Proceedings of the Workshop Management of Southern Forests for Nongame Birds; 1978 January 24 - January 26; Atlanta, GA. Gen. Tech. Rep. SE-14. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southeastern Forest Experiment Station: 90-97.  26. Hosie, R. C. 1969. Native trees of Canada. 7th ed. Ottawa, ON: Canadian Forestry Service, Department of Fisheries and Forestry. 380 p.  27. Hough, A. F.; Forbes, R. D. 1943. The ecology and silvics of forests in the high plateaus of Pennsylvania. Ecological Monographs. 13(3): 299-320.  28. Kelty, Matthew J. 1987. Shelterwood cutting as an even-aged reproduction method. In: Nyland, Ralph D., editor. Managing northern hardwoods: Proceedings of a silvicultural symposium; 1986 June 23-25; Syracuse, NY. Faculty of Forestry Miscellaneous Publication No. 13 (ESF 87-002); Society of American Foresters Publication No. 87-03. Syracuse, NY: State University of New York, College of Environmental Science and Forestry: 128-142.  29. Kelty, Matthew J. 1988. Sources of hardwood regeneration and factors that influence these sources. In: Smith, H. Clay; Perkey, Arlyn W.; Kidd, William E., Jr., eds. Guidelines for regenerating Appalachian hardwood stands: Workshop proceedings; 1988 May 24-26; Morgantown, WV. SAF Publ. 88-03. Morgantown, WV: West Virginia University Books: 17-30.  30. Kessell, S. R. 1978. Adaptations and dimorphism in eastern hemlock, Tsuga canadensis (L.)Carr. American Naturalist. 113(3): 333-350.  31. Kittredge, David B.; Ashton, P. Mark S. 1990. Natural regeneration patterns in even-aged mixed stands in southern New England. Northern Journal of Applied Forestry. 7: 163-168.  32. Kotar, John; Kovach, Joseph A.; Locey, Craig T. 1988. Field guide to forest habitat types of northern Wisconsin. Madison, WI: University of Wisconsin, Department of Forestry; Wisconsin Department of Natural Resources. 217 p.  33. Kuchler, A. W. 1964. Manual to accompany the map of potential vegetation of the conterminous United States. Special Publication No. 36. New York: American Geographical Society. 77 p.  34. Kudish, Michael. 1992. Adirondack upland flora: an ecological perspective. Saranac, NY: The Chauncy Press. 320 p.  35. Little, Elbert L., Jr. 1979. Checklist of United States trees (native and naturalized). Agric. Handb. 541. Washington, DC: U.S. Department of Agriculture, Forest Service. 375 p.  36. Martin, S. Clark. 1980. Mesquite. In: Eyre, F. H., ed. Forest cover types of the United States and Canada. Washington, DC: Society of American Foresters: 118.  37. Lorimer, Craig G. 1977. The presettlement forest and natural disturbance cycle of northeastern Maine. Ecology. 58: 139-148.  38. Marquis, David A. 1975. Seed storage and germination under northern hardwood forests. Canadian Journal of Forestry Resources. 5: 478-484.  39. Martin, N. D. 1959. An anaylsis of forest succession in Algonquin Park, Ontario. Ecological Monographs. 29(3): 187-218.  40. Martin, William H. 1992. Characteristics of old-growth mesophytic forests. Natural Areas Journal. 12(3): 127-135.  41. McIntosh, Robert P. 1972. Forests of the Catskill Mountains, New York. Ecological Monographs. 42: 143-161.  42. Monk, Carl D.; Imm, Donald W.; Potter, Robert L.; Parker, Geoffrey G. 1989. A classification of the deciduous forest of eastern North America. Vegetatio. 80: 167-181.  43. Jones, Steven M. 1989. Application of landscape ecosystem classification in identifying productive potential of pine-hardwood stands. In: Waldrop, Thomas A., ed. Proceedings of pine-hardwood mixtures: a symposium on management and ecology of the type; 1989 April 18-19; Atlanta, GA. Gen. Tech. Rep. SE-58. Asheville, SC: U.S. Department of Agriculture, Forest Service, Southeastern Forest Experiment Station: 64-69.  44. Moore, William H.; Johnson, Frank M. 1967. Nature of deer browsing on hardwood seedlings and sprouts. Journal of Wildlife Management. 31(2): 351-353.  45. Nelson, John B. 1986. The natural communities of South Carolina. Columbia, SC: South Carolina Wildlife & Marine Resources Department. 54 p.  46. Palik, Brian J.; Pregitzer, Kurt S. 1992. A comparison of presettlement and present-day forests on two bigtooth aspen-dominated landscapes in northern lower Michigan. American Midland Naturalist. 127(2): 327-338.  47. Raunkiaer, C. 1934. The life forms of plants and statistical plant geography. Oxford: Clarendon Press. 632 p.  48. Raynal, D. J.; Roman, J. R.; Eichenlaub, W. M. 1982. Response of tree seedlings to acid precipitation. I. Effect of substrate acidity on seed germination. Environmental and Experimental Botany. 22(3): 377-383.  49. Rogers, Lynn L.; Allen, Arthur W. 1987. Habitat suitability index models: Black bear, upper Great Lakes region. Biol. Rep. 82 (10.144). Washingtion D. C.: U.S. Department of the Interior, Fish and Wildlife Service. 54 p.  50. Rogers, Lynn L.; Wilker, Gregory A.; Scott, Sally S. 1990. Managing natural populations of black bears in wilderness. In: Lime, David W., ed. Managing America's enduring wilderness resource: Proceedings of the conference; 1989 September 11-17; Minneapolis, MN. St. Paul, MN: University of Minnesota, Minnesota Extension Service; Minnesota Agricultural Experiment Station: 363-366.  51. Rogers, R. S. 1978. Forests dominated by hemlock (Tsuga canadensis): distribution as related to site and postsettlement history. Canadian Journal of Botany. 56: 843-854.  52. Rudnicky, James L.; McDonnell, Mark J. 1989. Forty-eight years of canopy change in a hardwood-hemlock forest in New York City. Bulletin of the Torrey Botanical Club. 116(1): 52-64.  53. Runkle, James R. 1990. Eight years change in an old Tsuga canadensis woods affected by beech bark disease. Bulletin of the Torrey Botanical Club. 117(4): 409-419.  54. Ruth, Robert H. 1974. Tsuga (Endl.) Carr. hemlock. In: Schopmeyer, C. S., ed. Seeds of woody plants in the United States. Agric. Handb. 450. Washington, DC: U.S. Department of Agriculture, Forest Service: 819-827.  55. Spurr, Stephen H. 1956. Forest associations in the Harvard Forest. Ecological Monographs. 26(3): 245-262.  56. Stearns, Forest. 1951. The composition of the sugar maple-hemlock-yellow birch association in northern Wisconsin. Ecology. 32(2): 245-265.  57. Stickney, Peter F. 1989. Seral origin of species originating in northern Rocky Mountain forests. Unpublished draft on file at: U.S. Department of Agriculture, Forest Service, Intermountain Research Station, Fire Sciences Laboratory, Missoula, MT; RWU 4403 files. 7 p.  58. Swan, Frederick R., Jr. 1970. Post-fire response of four plant communities in south-central New York state. Ecology. 51(6): 1074-1082.  59. Telfer, Edmund S. 1972. Browse selection by deer and hares. Journal of Wildlife Management. 36(4): 1344-1349.  60. U.S. Department of Agriculture, Soil Conservation Service. 1982. National list of scientific plant names. Vol. 1. List of plant names. SCS-TP-159. Washington, DC. 416 p.  61. Vogl, Richard J. 1977. Fire: a destructive menace or a natural process?. In: Cairns, J., Jr.; Dickson, K. L.; Herricks, E. E., eds. Recovery and restoration of damaged ecosystems: Proceedings of the international symposium; 1975 March 23-25; Blacksburg, VA. Charlottesvile, VA: University Press of Virginia: 261-289.  62. Wendel, G. W.; Della, Bianca, Lino; Russell, James; Lancaster, Kenneth F. 1983. Eastern white pine including eastern hemlock. In: Burns, Russell M., tech. comp. Silvicultural systems for the major forest types of the United States. Agric. Handb. 445. Washington, DC: U.S. Department of Agriculture, Forest Service: 131-134.  63. Whitney, Gordon G. 1986. Relation of Michigan's presettlement pine forests to substrate and disturbance history. Ecology. 67(6): 1548-1559.  64. Whitney, G. G. 1990. The history and status of the hemlock-hardwood forests of the Allegheny Plateau. Journal of Ecology. 78: 443-458.  65. Eriksson, Gosta; Jonsson, Alena; Dormling, Ingegerd; [and others]. 1993. Retrospective early tests of Pinus sylvestris L. seedlings grown under five nutrient regimes. Forest Science. 39(1): 95-117.