How and where did temperate trees survive during the Last Glacial Maximum (LGM)? Whether temperate trees survived only in the glacial refugia of Southern Europe or also in isolated pockets of refugia (i.e., microrefugia) in Central Europe has long been debated in ecology and conservation biology. The Swiss National Science Foundation project ECO-ICE aims to answer this question through a multidisciplinary approach involving pollen analysis, sedimentary DNA, lipid biomarkers, and chironomids to reconstruct climate and vegetation in potential microrefugias across Central and Southern Europe. Lakes in potential microrefugias will be cored to retrieve sediments spanning the length of the LGM.

The Organic Geochemistry Group at Basel will focus on lipids, such as brGDGTs and plant waxes, often called ‘molecular fossils’, preserved in the lake sediments, to reconstruct the climatic and vegetation landscape of those environments. To quantify lake and air temperatures during the LGM, we will use branched glycerol dialkyl glycerol tetraethers (brGDGTs), membrane-spanning lipids produced by bacteria. The relative abundance of the different brGDGTs in the sediments can be used to reconstruct temperatures. Furthermore, the hydrogen isotopic ratio of precipitation,δ²H_pre, will be isolated from the δ²H values of plant wax n-alkanes and fatty acids, which will give us an insight into climatic variability in temperature, sources of precipitation and vegetation changes during the LGM. Combining information from the various proxies will help us determine whether these supposed temperate tree microrefugia existed during the LGM, particularly north of 45°N, and the climatic and environmental conditions that supported them.