Résumé
During the Permian, the warming of the global climate from icehouse to hothouse conditions allowed forests to gradually colonize higher latitudes and to extend well beyond the polar circle. Antarctica (then part of the supercontinent Gondwana) was located at approximately the same latitudes than today and sediments document a rapid arrival of plants as the climate warmed. I will present ongoing work on polar forests from the Transantarctic Mountains that were growing at 75°–85°S during the Late Permian. These forests were largely dominated by one extinct group of trees, the Glossopteridales, with an understory of mosses, ferns, lycophytes and sphenophytes (horsetails). Growth ring analysis indicate that the trees were growing much faster than those of boreal forests today, with a productivity more comparable to that found in extant temperate forests. They also had the ability to regenerate their crown by producing adventitious branches, and had a very unique root system. Antarctic fossils also provide information on various types of interactions in these polar ecosystems, with evidence of fungal wood decay, mycorrhizal associations, arthropod activity, and plant-plant facilitation. Together, all this information provides a better of understanding of Late Permian forests in general and raises questions about plant adaptation to high latitude environments on a warmer planet.