Johannes Iversen

Johannes Iversen (December 12, 1904 – October 17, 1972) was a Danish palaeoecologist and plant ecologist. He was born in Sønderborg and began studies in botany at the University of Copenhagen in 1923 under professor C.H. Ostenfeld, and with considerable inspiration from prof.em. Christen Raunkiær. At first he worked with macrophyte vegetation of lakes in relation to water pH. The influence from Raunkiær is particularly evident in Iversen‘s doctoral thesis, in which he divided herbaceous plants into hydrotypes based on experiments and morphological studies: xerophytes, mesophytes, hygrophytes, telmatophytes, amphiphytes and limnophytes. In addition, halobio-types (salt tolerance) were described. He brilliantly used modern equivalents in the interpretation of pollen diagrams, e.g. his now classic studies on frost damage to ivy (Hedera) and holly (Ilex) during the severe winters of the early 1940s led to their fossil pollen being used as climate indicators. Iversen demonstrated the steppe and tundra components of the late glacial flora. Iversen conducted a practical experiment with stone axe clear-cutting and slash-and-burn agriculture in a primeval forest to study the forest regeneration. Iversen was state geologist at the Danish Geological Survey and lecturer in pollen analysis at the University of Copenhagen. He was awarded honorary doctorates at Uppsala University and Cambridge University.