Pollen, deposited in the lake sediments, are the most established tool for paleovegetation reconstruction. The signal can, however, be biased from long distance transport and erosion of fossil pollen from soils. The latter must be regarded as a possible source for ELSA-20-Stack-Pollen, which all come from lakes with fluvial inflow. Accordingly, single pollen grains, which do not fit the general picture, must be treated carefully before interpretation. We regard all pollen records to be reliable environmental indicators, if the pollen profile show those patterns, which are consistently reproduced at different maar sites. Such pattern is established for the Holocene and becomes now apparent also for the early MIS3 (GI17-14), when spruce dominates the pollen profile with more than 60%. The pollen profile from Dehner Maar has documented for the first time a MIS3 profile for the Eifel (Sirocko 2009; Sirocko et al. 2016), a pattern which is now reproduced for 5 other records.
Most pollen records from MIS3 reveal grass, birch, and pine, with abundance being higher during interstadials. Some stadial sediments are, however, free of pollen. This could represent a landscape free of vegetation, e.g., during the Heinrich 4 event, or the pollen have been dissolved. Pollen are extremely hard and cannot be dissolved by any acid, but they deteriorate as soon as they are exposed to oxygen. This must have been the case in the sediments of the stadials and the LGM, when temperatures were below 4 °C even in the summer nights, which cause surface water to sink to the lake basin because of its high density. It is thus most likely the glacial and stadial perennial deep water formation, which dissolved the pollen. Accordingly, absence of pollen hints towards cold summer nights.