BayCEER Workshop 2023

Quantifying latitudinal dynamics of biomes in Europe by unifying fossil pollen records of the last 12,000 years

O 2.5 in Zooming out: Evolution, biomes, global trends

12.10.2023, 16:30-16:45, H 36

Understanding how the spatial distribution and composition of biomes has developed from past to present is the basis for accurately predicting how plant communities will develop under ongoing anthropogenic climate change in the future. Studies of fossil pollen and genetic information showed that individual plant species dispersed northwards at different rates in Europe after the LGM in response to retreating glaciers and increasing global temperatures. The reconstruction of spatio-temporal distribution of biomes and successional states demonstrated a northward movement of wider ecological units during the Holocene. Biome reconstructions based on present biomes cannot detect former biomes without modern analogues.

Using more than 550 taxonomically standardised fossil pollen time series in Europe encompassing over 230 fossil pollen taxa and the last 12,000 years, I employed unsupervised hierarchical clustering to group fossil pollen assemblages into ecological units conceptually comparable to biomes. Hierarchical clustering is a well-established method to identify biomes in modern macroecological studies but has not been employed on comparable time-scales. I quantified the latitudinal displacement of the identified biomes throughout the Holocene by fitting linear models to the latitude of the spatial centroids, leading and tailing edges of the biomes across 1000-year bins. The formerly demonstrated northward movement of biomes could not be reproduced using extensive pollen assemblage data suggesting that spatio-temporal vegetation patterns are less pronounced when more taxa are considered. The median latitudinal displacement of spatial centroids of biomes ranged form 0.0 to 0.5 latitudinal degrees per 1000 years. New biomes emerged mainly in South and Central Europe. The identified biomes appeared to represent temporally and spatially explicit vegetation communities which were reconfigured with changing abiotic conditions and thus not moving distinctly northward.

Keywords: fossil pollen, biomes, cluster analysis

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