DOI: 10.5061/dryad.2fqz612mk
title: Data from: Global vegetation patterns of the past 140,000 years

description: Aim Insight into global biome responses to climatic and other
 environmental changes is essential to address key questions about past and
 future impacts of such changes. By simulating global biome patterns 140 ka
 to present we aimed to address important questions about biome changes
 during this interval. Location Global. Taxon  Plantae.
 Methods Using the LPJ-GUESS dynamic global vegetation model, we made 89
 simulations driven using ice-core atmospheric CO2 concentrations, Earth’s
 obliquity, and outputs from a pre-industrial and 88 palaeoclimate
 experiments run using HadCM3. Experiments were run for 81 time slices
 between 1 ka and 140 ka, seven ‘hosing’ experiments also being run, using
 a 1 Sv freshwater flux to the North Atlantic, for time slices
 corresponding to Heinrich Events H0 – H7. Using a rule-based approach,
 based on carbon mass and leaf area index of the LPJ-GUESS plant functional
 types, the biome was inferred for each grid cell. Biomes were mapped, and
 the extent and total vegetation biomass of each biome, and total global
 vegetation biomass, estimated. Results Substantial changes in biome
 extents and locations were found on all vegetated continents. Although the
 largest-magnitude changes were in Eurasia, important changes were seen in
 tropical latitudes and the Southern Hemisphere. Total global extent of
 most biomes varied on multi-millennial (orbital) time scales, although
 some (e.g. Tropical Raingreen Forest) responded principally to the
 ca. 100 kyr glacial–interglacial cycle and others (e.g. Temperate
 Broad-leaved Evergreen Forest) mainly to the ca. 20 kyr precession
 cycle. Many also responded to millennial contrasts between stadial
 (‘hosing’) and interstadial climates, with some (e.g. Tropical Evergreen
 Forest) showing stronger responses than to the multi-millennial changes.
 Main conclusions No two time slices had identical biome patterns. Even
 equivalent Holocene and last interglacial time slices, and the last and
 penultimate glacial maxima, showed important differences. Only a small
 proportion of global land area experienced no biome change since
 140 ka; many places experienced multiple biome changes. These modelling
 experiments provided little evidence for long-term biome stability.
description: he CMass and LAI files are derived from
 outputs produced by LPJ-GUESS simulations.  These simulations were driven
 using palaeoclimates derived from a series of GCM runs, along with the
 associated atmospheric carbon dioxide concentration and orbital
 obliquity.  Full details and relevant citations are given in Allen et al.
 (2020).  The LPJ-GUESS output files were opened (by JRMA) using Microsoft
 Excel, a header line added and, in the case of the CMass files, columns
 added giving the grid cell areas and ice-free land fractions, these being
 copied from the relevant columns of the Ice-free_land_fraction_89_time-slices
 file.  A second worksheet was then added to the CMass files
 and values for grid cell CMass calculated from the LPJ-GUESS CMass per
 unit area values output and the product of the grid cell area and ice-free
 land fraction values. The second worksheet was then saved in
 comma-delimited (.csv) format.   The Biome_assignments_V1.1_89_time-slices.csv file is derived
 from the primary output file generated by the FORTRAN program
 BiomiseLPJ_V1.1.  This program was written by BH and the source code is
 provided in the Supplementary Information to Allen et al. (2020).  The
 program output file was opened (by BH) using Microsoft Excel, a header
 line added, and the resulting worksheet saved in comma-delimited (.csv)
 format.  
 The Biome_extents_V1.1_89_time-slices
 and PFT_CMass_by_biome_V1.1_89_time-slices are also derived from output
 files generated by BiomiseLPJ_V1.1.  Minor editing was performed (by BH)
 using WordPad in order consistently to separate the blocks of data in the
 files and to ensure that all columns had labels in the header rows, thus
 rendering the files easier to open using software such as R.
   The primary data underlying the Ascii
 grid files are the ETOPO1 1-minute topography and bathymetry dataset, and
 the ICE-6G 1-degree ice fraction data files, both datasets being
 downloaded from their respective online locations.  In addition, eustatic
 sea levels prior to 34 ka were estimated using a multiple regression model
 relating eustatic sea levels 0-34 ka to ocean delta-18O values and a
 relative sea-level curve, both of which are available extending back to
 140 ka and beyond.  Fractional ice cover for time slices prior to the Last
 Glacial Maximum (LGM) was taken to be that of the post-LGM time slice with
 the closest matching eustatic sea level.  These various input sources were
 processed using FORTRAN programs written by BH for the purpose to generate
 the 6-minute datasets for land, ocean, ice cover and ice-fraction. 
 Further details are provided in the readme_first.pdf file and in Appendix
 S2 of the Supplementary Information to Allen et al. (2020).
   The data in the
 Ice-free_land_fraction_89_time-slices file was generated from the 1-minute
 ETOPO1 topography and bathymetry dataset and the ICE-6G data using the
 same approach as was used for the 6-minute land and ice-fraction datasets,
 implemented in a FORTRAN program written by BH.  In this case the file
 coverage is only those half-degree grid cells on the current land areas
 and shelf areas exposed at the LGM, whereas the 6-minute files extend over
 the entire global surface.    
description: See Readme_first.pdf.