BIOME 6000 - Version 4.2: 18 ka BP

Vegetation map for the late Last Glacial Maximum period around 18 ka BP. 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.
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