Vegetation of Eurasia from the last glacial maximum to present: key biogeographic patternsстатья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 24 мая 2017 г.
Аннотация:Broad-scale estimates of vegetation cover over past millennia reflect the response of plant species to climate change. They inform the assessment of changes in vegetation cover and land-surface properties and of biogeographic trends, and they can help assess the effectiveness of simulations of climate change using forward and inverse modelling approaches. With the advent of transient and contiguous time-slice palaeoclimate simulations, vegetation datasets with similar temporal qualities are desirable. We collated fossil pollen records for the period 21,000-0 yr BP (ka BP; calibrated ages) for Europe and Asia north of 40°N, using extant databases and new data; we filtered records for adequate dating and sorted the nomenclature to conform to a consistent taxon list. From this database we extracted pollen spectra representing each time-slice from 21 ka BP to present and used the biomization approach to define the most likely vegetation biome represented. Biomes were mapped for the 22 time slices, and key PFTs (plant functional types, the constituents of the biomes) were tracked though time. An error matrix and index of topographic complexity clearly showed that the accuracy of pollen-based biome assignments (when compared with modern vegetation) was negatively correlated with topographic complexity, but modern vegetation was nevertheless effectively mapped by the pollen, despite moderate levels of misclassification for most biomes. The pattern at 21 ka is of herb-dominated biomes across the whole region. From the onset of deglaciation (17-18 ka BP), some sites in Europe record forest biomes, particularly the south, and the proportion of forest biomes gradually increases with time through 14 ka BP. During the same period, forest biomes and steppe or tundra biomes are also intermixed across the central Asian mountains, and forest biomes occur in coastal Pacific areas. Occasional sites recording forest biomes, combined with plant macrofossil data, indicate that some tree populations existed in southern and Eastern Europe and central Eurasia. PFT composition of the herbaceous biomes emphasises the significant contribution of diverse forbs to treeless biomes. An increase in moisture ca. 14 ka BP is suggested by increasing numbers of sites, a shift to woody biomes and expansion of wetlands, particularly in the European portion of the region. Deforestation of Western Europe, presumably related to agricultural expansion, is clearly visible in the most recent two millennia.