Paleovegetation maps of Northern North America, 18 000 to 1 000 BP

Open File 4682

 

Table of Contents:

1.      Description

2.      Recommended Citation

3.      Contacts

4.      Metadata

5.      Attribute descriptions

6.      Legend

 

1. Description:

 

Biomes are climate-controlled vegetation and animal distributions, in equilibrium with climate provided that the climate is not changing too rapidly. They can be reconstructed from paleontological sources with reasonable confidence. Here we present biome maps spanning from the last glacial maximum (18 000 years ago) to modern times. Because the ice sheets during the last glaciation sat in near maximal configurations for a period of about 10 000 years, the vegetation distribution at the last glacial maximum was probably as nearly in equilibrium with its contemporaneous climate as the modern distribution is with the modern climate. Subsequent changes in biome distribution during deglaciation and thereafter reflect the complex interplay of climate forcing and the dynamic constraints that limit plant migration rates. The waning ice sheet configuration was one of the strongest controls of continental climate zones until about 7000 years ago, particularly early in deglaciation. Late deglaciation of the eastern part of the continent delayed attainment of maximum postglacial warmth there. Despite these complexities, regional climate trends through time can be reliably inferred from changing biome distributions. Further analysis of the sensitivity of vegetation to climate change at the biome level would be best facilitated if empirical climate reconstructions for the same time interval based on sources other than vegetation history were available. Nevertheless, because there is evidence of general cooling during the last 3000-5000 years, and longer in places, middle and early Holocene biome distributions and species compositions are reasonable analogues of future equilibrium displacements due to equivalent warming, at least in areas that were long-since deglaciated at these times. Peak postglacial warmth, although not synchronous across the continent, has been estimated elsewhere to have been mainly in the range of 2-4°C above mid 20th century values. Some estimates of immediate future warming exceed that range.

 

2. Recommended Citation:

 

Dyke, A.S., Giroux, D. And Robertson, L.

2003 : Paleovegetation maps of Northern North America,18 000 to 1 000 BP. Geological Survey of Canada, Open File 4682.

 

3. Contact Information:

 

A.S Dyke (adyke@nrcan.gc.ca) and L. Robertson (lorobert@nrcan.gc.ca) Geological Survey of Canada, 601 Booth, St, Ottawa, ON, K1A 0E8.

 

4. Metadata

 

Datasets:          icebioxxk => polygonal dataset of paleo regions where xx indicates k-year BP

macrof => point dataset of carbon 14 dated macrofossil sites

pollen => point dataset of carbon 14 dated pollen sites

mammal\manxxk => point dataset of carbon 14 dated mammal sites where xx indicates k-year BP

 

Projection:

Lambert Conic Conformal

1st standard parallel: 49 0 0 N

2nd standard parallel: 77 0 0 N

Central meridian: 95 0 0 W

Origin of latitude: 49 0 0 N

Spheroid: Clarke 1866

Datum: NAD27

No false easting or northing

 

Scale of  published map compilation:

Base information from 1:7.5million Atlas of Canada Base Maps

 

5. Attribute descriptions

 

Attributes for each paleo regions, time slice are found under the attribute label ECOREGION. Values are:

Herb tundra : A treeless area lacking shrubs other than small, prostrate willows and dominated by bare ground and herbs, typically sedge, grass, and sage with a variety of forbs; includes fellfield.

Alpine tundra : Similar to herb or shrub tundra but occurring at high elevations.

Shrub tundra : A treeless area with a nearly continuous cover of sedge, grass, sage, and forbs along with prostrate and semi-erect willows as well as one or more additional shrubs, chiefly dwarf birch, alder, and juniper, in increasing order of required warmth.

Forest tundra : A zone transitional between shrub tundra and boreal forest. That is, a continuous ground cover of herb and shrub vegetation with open stands of erect trees, typically spruce, larch, and (or) poplar (birch in Iceland).

Boreal forest : Nearly continuous cover of trees dominated by northern conifers (mainly spruce, jackpine, larch, and fir) and northern hardwoods (mainly birch, aspen, poplar), broken by wetlands.

Boreal parkland : Open stands of boreal forest trees growing in ground covers dominated by herb and (or) lichen. Includes the modern aspen parkland at the southern fringe of the western boreal forest in the Prairie Provinces and the lichen woodland (open spruce forest) of the eastern boreal forest, which grades to forest tundra.

Subalpine forest : The conifer-dominated forest in mountainous terrain of the Cordillera. Dominated by subalpine fir, Engelmann spruce, mountain hemlock, lodgepole pine, and whitebark pine in northern reaches; limber pine, bristlecone pine, and juniper farther south.

Interior forest : The conifer-dominated forest of the relatively dry interior of the Cordilleran region, which occurs south of the western boreal forest and experiences cold winters; typically dominated by Douglas fir, lodgepole pine, whitebark pine and Ponderosa pine, with western hemlock, Engelmann spruce, Sitka spruce, and cedar.

Conifer forest : A cover of conifer trees different in composition from modern boreal, subalpine, or interior forests. Typically dominated by lodgepole pine in areas of modern subalpine and interior forests.

Coast forest : The conifer-dominated forest of the wet coastal ranges and lowlands of the Pacific coast, which experience mild winters; typically dominated by western hemlock, western red cedar, and Sitka spruce with Douglas fir, alder, and grand fir.

Mixed forest : Conifer-hardwood associations mainly occupying the transition zone between the boreal forest and the deciduous forest of eastern North America. Dominated by boreal elements (conifers and northern hardwoods [birch, beech, elm]) on the north and temperate elements on the south. Includes a diverse mosaic of associations dominated by white pine, hemlock, white cedar, maple, yellow birch, oak, etc.

Deciduous forest : The broad-leaf, temperate, deciduous forest of eastern North America; typically dominated by oak with beech, birch, maple, basswood, hickory, chestnut, ironwood, hemlock and white pine.

Savannah : A zone transitional between grassland and deciduous forest, with oak typically dominating the trees.

Grassland : Treeless or nearly treeless vegetation dominated by grass, sage, or chenopods, grading to steppe with decreasing moisture; includes long- and short-grass prairie.

Steppe : Treeless or nearly treeless semi-desert vegetation dominated by sagebrush, chenopods, shadscale, and grass, with occasional lodgepole pine, Ponderosa pine, and juniper.

Unknown : Areas of ice, lake or water

 

Attributes for each ice margins, time slice are found under the attribute label SYMB. Values are :

ICE : areas cover with ice

LAND : areas free of ice cover

LAKE : areas of fresh water

WATER : areas of non-fresh water

 

Attributes for the macrofossil sites are defined as follows:

            Site : Geographic site name.

            Reference : The literature source(s) for the radiocarbon date and fossil identification.

            Latitude : Latitude in decimal degrees.

            Longitude : Longitude in decimal degrees.

            Observatio : Observations at this site, namely fossil identification, age in thousands of years, and radiocarbon laboratory code.

            Map_XX_ka : The interpretation of the Observation displayed on the map for xx ka BP.

            Comments : Comments relating to interpretation of this site.

 

Attributes for the pollen sites are defined as follows:

            Site : Geographic site name.

            Reference : The literature source(s) for the pollen analysis.

            Latitude : Latitude in decimal degrees.

            Longitude : Longitude in decimal degrees.

            Descriptio : A description of the pollen assemblage at a particular point in time (XX ka) at this site.

            Biome_xxka : A biome-level interpretation of the pollen assemblage.

            Assoc_xxka : A plant-association level interpretation of the plant assemblage.

            Comments : Comments on the pollen stratigraphic record, such as basal age or chronological problems and adjustments.

 

Attributes for the mammal sites are defined as follows:

            Lab_number : The radiocarbon laboratory code for the dated sample.

            Material_d : Material used in radiocarbon dating (e.g., collagen, bone, plant).

            Map : The time slice map on which the site is plotted; i.e., the time slice that is within 500 years of the fossil age.

            C_14_age:  The age in radiocarbon years of the sample.

            Std_err : The standard error of the radiocarbon age calculation, which for most laboratories is one standard deviation.

            Lat : Latitude in decimal degrees.

            Long : Longitude in decimal degrees.

            Biome : The biome-level interpretation of the fossil.

            Reference : The literature source(s) for the radiocarbon date and fossil identification.

            Year : Publication year of the Reference.

            Taxon_date : The taxonomic identification of the radiocarbon dated mammal remains.

            Taxon_assoc : Mammalian taxa that were found stratigraphically associated with the radiocarbon-dated sample.

            Comments : Comments on the site or the radiocarbon date.

 

6. Legend