BIOME 6000 (v4.2): Vegetation Maps for the Mid-Holocene and Last Glacial Maximum

The Palaeovegetation Mapping Project (generally known as BIOME 6000: Prentice
and Webb, 1998) was inaugurated in 1994 with the aim of providing global maps
describing the vegetation patterns at 6000±500 yr B.P. (on the radiocarbon time
scale) and the last glacial maximum (defined as 18,000±1000 yr B.P. on the
radiocarbon time scale, equivalent to 21,000 yr B.P. on the calendar time
scale) for use by the modelling community.

The BIOME 6000 project has used a standard methodology to map vegetation
patterns using fossil pollen and plant-macrofossil data from individual sites.
The taxa represented in the pollen or plant-macrofossil assemblages are first
allocated to plant functional types (PFTs) on the basis of the life form, leaf
form, phenology and bioclimatic tolerance of the plant species included within
the taxon. Because of the lack of taxonomic resolution in pollen
identification, some taxa can be classified into more than one PFT. Biomes
(i.e. major vegetation types at a regional scale) are defined by combinations
of PFTs, where these combinations usually include both characteristic and
dominant groups. Some PFTs which are known to occur within a given biome are
not included in the biome definition because they occur in too many biomes to
provide discriminatory power. Once the taxon to PFT and PFT to biome
classifications are made, the affinity of pollen or plant-macrofossil
assemblages from individual sites for each biome is calculated. Each assemblage
is allocated to the biome for which it has the highest affinity. In cases where
the assemblage has equal affinity for more than one biome, which can occur when
one biome is defined by a subset of the PFTs that characterise another biome,
the assemblage is allocated to the biome defined by the subset.

The published version of the BIOME 6000 database (Version 3: Prentice et al.,
2000) was based on maps produced on a region by region basis over a number of
years. Here, we have fused the information from the various regions and
standardised the biome names. We recognise 40 biomes, using names that are
broadly consistent with the BIOME4 equilibrium biogeography-biochemistry model
(Kaplan et al., 2003).

Since Version 3 of the BIOME 6000 database was released, there have been three
new palaeovegetation mapping initiatives. Harrison et al. (2001) added a number
of sites from the continental shelf east of China which date to the last
glacial maximum. The Pan-Arctic Initiative (PAIN) extended the site coverage
from the high-northern latitudes at both 6000 yr B.P. and the last glacial
maximum (Bigelow et al., 2003). Pickett et al. (2004) extended the coverage to
the SEAPAC (South East Asia and the Pacific) region at both 6000 yr B.P. and
the last glacial maximum. These data sets are included in the current version
of the BIOME 6000 data set (Version 4.2).

BIOME 6000 Version 4.2 has records for 11166 modern sites, 1794 sites at 6000
yr B.P., and 318 sites at 18,000 yr B.P.

This data set is also available from the Paleoclimate Modelling
Intercomparison project - Phase II:
http://www-lsce.cea.fr/pmip2/synth/vegmaps.shtml

An early version of this data set is available from the WDC/Paleoclimatology
http://www.ncdc.noaa.gov/paleo/biome6000.html