Late Quaternary North American Vegetation Dynamics Data ----------------------------------------------------------------------- World Data Center for Paleoclimatology, Boulder and NOAA Paleoclimatology Program ----------------------------------------------------------------------- NOTE: PLEASE CITE CONTRIBUTORS WHEN USING THIS DATA!!!!! NAME OF DATA SET: Late Quaternary North American Vegetation Dynamics Data LAST UPDATE: 2/2010 (update to this documentation file) 7/2007 (upates to *.din documentation files) CONTRIBUTOR: Jack Williams, Limnological Research Center, University of Minnesota IGBP PAGES/WDCA CONTRIBUTION SERIES NUMBER: 2003-089 SUGGESTED DATA CITATION: Williams, J.W., et al., 2003, Late Quaternary North American Vegetation Dynamics Data, IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series # 2003-089. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA. ORIGINAL REFERENCE: Williams, J.W., B.N. Shuman, T. Webb III, P.J. Bartlein, and P.L. Leduc, 2004, Late Quaternary vegetation dynamics in North America: scaling from taxa to biomes Ecological Monographs, Vol. 74, No. 2, pp. 309–334, May 2004. GEOGRAPHIC REGION: North America PERIOD OF RECORD: 21 KYrBP - present LIST OF FILES: readme_na_grided.txt (this file), plus gridded data files and associated *.din contents description for each: t17_02.dat, t17_02.din t17_115.dat, t17_115.din t17_36.dat, t17_36.din t17_621.dat, t17_621.din t17_710.dat, t17_710.din FUNDING SOURCES: This research was supported by the National Center for Ecological Analysis and Synthesis, a center funded by NSF (Grant #DEB-94-21535), the University of California Santa Barbara, the California Resources Agency, and the California Environmental Protection Agency and grants from the Earth System History Program at NSF (ATM-9910638, ATM-0317736). DESCRIPTION: Vegetation changes in North America over the last 21,000 years derived from fossil pollen preserved in lake and bog sediments. Data set consists of gridded pollen data and derived vegetation cover at 250 year intervals. Gridded data files are interpolations to a 50-km grid, based on data from approximately 500 North American pollen cores. A majority of the source raw pollen data is available from the Global Pollen Database: http://www.ngdc.noaa.gov/paleo/pollen.html The derived vegetation cover is presented in image form at: http://www.ngdc.noaa.gov/paleo/pubs/williams2004/williams2004.html The projection used is Albers Equal Area, with standard parallels at 33.33N and 66.66N, with the center set at 70N, 100W. A 'unit sphere' was used for the Albers projection, meaning that the radius of the 'earth' was set to 1.0. To convert the Albers X/Y distances (expressed as distances from center) to km, multiply these values by the radius of the earth (6371km). Gridded pollen percentage data are recorded in 5 data files, totaling 50 MB, each including data for a specific interval of 2,000 - 5,000 years. The files are formatted for use with the mapping program PSColor created by Pat Bartlein at the University of Oregon. The format and variables for each data file (*.dat) are described in an associated *.din information file with matching filename. Each *.din information file contains variable list and descriptive info as follows: *.din File Format: -A header or title that describes the data (1 line) -The number of variables in the data file (1 line) -Information about the variables (1 line per variable, space delimited) -A variable name (max eight characters) -Variable number -Minimum & maximum values (These do not have to correspond to actual min/max -- but PSColor will not map values outside range.) -Missing data flag -Comments (any length) -The number of observations in the file (1 line) -A Fortran format statement or comment (1 line) -The number of observations to omit (1 line) -Observations to omit (1 or more lines, space delimited) This study was made possible by the generous contributions by many palynologists of their data to the North American Pollen Database and by the efforts of E. Grimm, J. Keltner, and others at the National Geophysical Data Center and National Climatic Data Center. Additional data was supplied from the Base de Données Polliniques et Macrofossiles du Québec by P. Richard and the PALE-PARCS program by P. Anderson. ABSTRACT: This paper integrates the mapping of late-Quaternary biomes with palynological evidence for individualistic species responses to environmental change. We document vegetation history in boreal and eastern North America for the past 21,000 calendar years (21 ka), reconstructing past vegetation from fossil pollen evidence at ecological resolutions ranging from individual plant taxa to biomes. At these scales, climatic control of vegetation change is exerted at the level of individual species, from which higher-order properties of the vegetation emerge. Vegetation distribution and composition were relatively stable during full-glacial times (21-17 ka) and the mid- to late Holocene (7-0.5 ka), but changed rapidly during the late glacial and early Holocene (16-8 ka) and after 0.5 ka. Most plant distributions shifted northward, but taxa also moved east or west as, for example, the area of high abundances for spruce, pine, and other cold-tolerants expanded from eastern North America into central and western Canada. Modern associations such as beech-hemlock and spruce-alder-birch date to the early Holocene, whereas other associations common to the late-glacial (e.g. spruce- sedge-ash-hornbeam) no longer exist. Biomes are dynamic entities that have changed in distribution, composition, and structure since the last ice age and before. Distinct suites of biomes grew during the late Pleistocene and Holocene. The pollen-based biome reconstructions are able to capture the major features of late-Quaternary vegetation but downplay the magnitude and variety of vegetational responses to climate change by 1) limiting apparent land-cover change to ecotones, 2) masking internal variations in biome composition, and 3) obscuring the migrations and changes in abundance among individual taxa. The compositional differences between full-glacial and recent biomes of the same type are similar to or greater than the spatial heterogeneity in the composition of present-day biomes, both for individual plant taxa and for plant life forms (conifers, broad-leaved trees, and herbs). The spatial and temporal heterogeneity in biome composition allows maps of biomes to accommodate individualistic changes among taxa but masks climatically important variations in taxonomic composition as well as significant variations in vegetation structure.