PLEISTOCENE AND HOLOCENE FLORAS OF NEW ENGLAND AS A FRAMEWORK FOR INTERPRETING ASPECTS OF PLANT RARITY

The times of arrival from southern sources and the rates and directions of migration are now known for many species of forest trees in New England. This information has made possible the reconstruction of generalized vegetation types for the period 14,000 to 9000 yr. B.P., as has been done recently by R. Davis and G. Jacobson for Vermont, New Hampshire, and Maine. The regional pattern, which has been based mainly on studies of fossil pollen from wind-pollinated trees, includes a diverse and biogeographically interesting flora of bryophytes, herbs, and shrubs that only recently is becoming defined through studies of plant macrofossils. The most thoroughly investigated sites, Tom Swamp (Massachu setts), Columbia Bridge (Vermont), and Upper South Branch Pond (Maine) have produced late-glacial floras with numerous calcicoles, some of which are rare or lacking in the present New England flora. Fossils of arctic-alpine species are also present at these sites, which are all at low elevations. A prominent calcicole element exists in the late-glacial fossil record regardless of whether the extant flora near a site contains such plants. This pattern is evident for both seed plants and bryo phytes. For areas with acidic soils, the loss of calcicoles is correlated with the late Pleistocene arrival of spruce (as documented by increases in macrofossils) at 12,800 yr. B.P. in southern New England, and some 2300 radiocarbon years later in north-central Maine. Leaching, humus or litter accumulation, and other aspects of soil genesis may have been responsible for the loss, but what caused the pattern is poorly understood. As viewed on a continental scale and over thousands of years, the elimination of calcicoles has left fragmented ranges and rare occurrences in eastern North America of boreal or northern plants that otherwise are today widespread to the west.

[1]  J. G. Packer,et al.  Atlas of the North European Vascular Plants North of the Tropic of Cancer. , 1988 .

[2]  N. G. Miller,et al.  History of late- and post-glacial vegetation and disturbance around Upper South Branch Pond, northern Maine , 1986 .

[3]  B. Tiffney,et al.  Holocene fruit, seed and leaf flora from riverine sediments near New Haven, Connecticut , 1986 .

[4]  G. Jacobson,et al.  Late Glacial and Early Holocene Landscapes in Northern New England and Adjacent Areas of Canada , 1985, Quaternary Research.

[5]  M. Tolonen,et al.  Late-glacial vegetational succession at four coastal sites in Northeastern New England: ecological and phytogeographical aspects , 1984 .

[6]  B. Mishler,et al.  Distributional studies of Massachusetts bryophytes , 1983 .

[7]  G. Crow,et al.  RARE AND ENDANGERED VASCULAR PLANT-SPECIES IN NEW-ENGLAND , 1981 .

[8]  H. H. Birks.  Plant macrofossils in Quaternary lake sediments , 1980 .

[9]  J. Terasmae,et al.  Late Wisconsin white spruce (Picea glauca (Moench) Voss) at Brampton, Ontario , 1980 .

[10]  Gary G. Thompson,et al.  Boreal and Western North American Plants in the Late Pleistocene of Vermont , 1979, Journal of the Arnold Arboretum..

[11]  H. Iltis.  THE GENUS GENTIANOPSIS (GENTIANACEAE): TRANSFERS AND PHYTOGEOGRAPHIC COMMENTS , 1965 .

[12]  G. Argus,et al.  Macrofossils from a late-glacial deposit at Cambridge, Massachusetts , 1962 .

[13]  M. Davis.  Three pollen diagrams from central Massachusetts , 1958 .

[14]  Merritt Lyndon Fernald,et al.  Gray's Manual of Botany. , 1951 .

[15]  E. T. Wherry.  SOIL TESTS OF ERICACEAE AND OTHER REACTION-SENSITIVE FAMILIES IN NORTHERN VERMONT AND NEW HAMPSHIRE , 1920 .

[16]  E. W. Hilgard.  The Soil-preferences of Certain Alpine and Subalpine Plants , 1908 .