Biogenic structures and poorly preserved plant materials elucidate Permian to Triassic changes in plant productivity, hydrology, and climate at polar latitudes. In situ stumps within the Buckley Formation (Beardmore Glacier area) reflect forests extant < 1 m.y. before the end of the Permian. Trees were tall, tree density and basal area/ha comparable to those of modern forests, and productivity high. Glossopteris leaves accumulated in abundant ponds in the Permian, but plants are absent from the Triassic. Triassic fluvial channel-fill sandstones contain three trace fossils, including Skolithos. that were all made by one animal, probably an immature insect. The same trace fossils occur in Permian floodplain deposits, but not in Permian channel-fill sandstones. The difference in trace facies-distribution in Permian vs. Triassic deposits reflects differences in hydrologic regime. Extended periods of low flow during the Triassic allowed immature insects to colonize, whereas constant water flow in Permian channels precluded settlement.