Vegetation Reconstruction From Siberia and the Tibetan Plateau Using Modern Analogue Technique–Comparing Sedimentary (Ancient) DNA and Pollen Data

To reconstruct past vegetation from pollen or, more recently, lake sedimentary DNA (sedDNA) data is a common goal in palaeoecology. To overcome the bias of a researcher’s subjective assessment and to assign past assemblages to modern vegetation types quantitatively, the modern analogue technique (MAT) is often used for vegetation reconstruction. However, a rigorous comparison of MAT-derived pollen-based and sedDNA-based vegetation reconstruction is lacking. Here, we assess the dissimilarity between modern taxa assemblages from lake surface-sediments and fossil taxa assemblages from four lake sediment cores from the south-eastern Tibetan Plateau and northern Siberia using receiver operating characteristic (ROC) curves, ordination methods, and Procrustes analyses. Modern sedDNA samples from 190 lakes and pollen samples from 136 lakes were collected from a variety of vegetation types. Our results show that more modern analogues are found with sedDNA than pollen when applying similarly derived thresholds. In particular, there are few modern pollen analogues for open vegetation such as alpine or arctic tundra, limiting the ability of treeline shifts to be clearly reconstructed. In contrast, the shifts in the main vegetation communities are well captured by sedimentary ancient DNA (sedaDNA). For example, pronounced shifts from late-glacial alpine meadow/steppe to early–mid-Holocene coniferous forests to late Holocene Tibetan shrubland vegetation types are reconstructed for Lake Naleng on the south-eastern Tibetan Plateau. Procrustes and PROTEST analyses reveal that intertaxa relationships inferred from modern sedaDNA datasets align with past relationships generally, while intertaxa relationships derived from modern pollen spectra are mostly significantly different from fossil pollen relationships. Overall, we conclude that a quantitative sedaDNA-based vegetation reconstruction using MAT is more reliable than a pollen-based reconstruction, probably because of the more straightforward taphonomy that can relate sedDNA assemblages to the vegetation surrounding the lake.

Pollen-based paleoclimate reconstructions of North-Еastern Bulgaria during the last 7000 years using modern analog technique (MAT)

The aim of the present study is to reconstruct the palaeoclimate variables in North-Eastern Bulgaria during the last 7000 years, based on the pollen analysis from 2 lacustrine cores and using modern analogue technique (MAT). Pollen data were used for the reconstruction of four parameters: the average annual temperature, the average temperature of the warm and cold half-year and the average annual precipitation.

Late Quaternary salinity variation in the Lake of Siebleben (Thuringia, Central Germany) – Methods of palaeoenvironmental analysis using Ostracoda and pollen

We test several methods of ostracod-based palaeoenvironmental reconstruction using indicator species approach, mutual ecological/climatic range methods, transfer functions, modern analogue technique and morphological variation within Cyprideis torosa in reconstructing the site evolution of a late Quaternary small lake basin in Thuringia, Central Germany. Sediment sections containing a diverse ostracod fauna were studied and compared with those from modern water bodies of Thuringia. Palynological investigations were executed to reconstruct the environmental conditions in the catchment area and for a obtaining a biostratigraphical framework. The brackish water ostracod Cyprideis torosa as well as the foraminifer Haplophragmoides indicate phases of saline groundwater influence, fed by salt bearing sediments of the Triassic basement. The accompanying freshwater ostracod fauna, however, reflects only low variations of salinity and temperature. Environmental changes in salinity, temperature and ecological stability indicated by microfossils and pollen are caused by an interplay of climatic shifts and the local geological and hydrological setting.