Marcel-Henri Gaussen (14 July 1891 in Cabrières-d'Aigues (Vaucluse) - 27 July 1981 in Toulouse), was a French botanist and biogeographer. In 1926, he defended his thesis on "the vegetation of the eastern half of the Pyrenees", which laid the foundation for future work on the border between biogeography and vegetation mapping. Gaussen was an early advocate of the ideas of stages and vegetation succession, which are fundamental to phytogeography. His work allowed for the production of a vegetation map of France at a scale of 1/200 000 (completed after his death by the service of the CNRS, but which he had created and directed) and many similar projects in other countries. His work led to many advanced phytogeographic tools such as the xerothermic or Gaussen Index, and the "". As recognition