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How did the Permian extinction affect land plants?

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Line graph showing the number of marine animal families from the Precambrian era to the present, with illustrations of key groups such as trilobites, ammonoids, marine reptiles, and diatoms. The graph highlights major extinction events and a rise to 1,900 living families today. — Permian extinction The diversity of marine animal families since late Precambrian time. The data for the curve comprise only those families that are reliably preserved in the fossil record; the 1,900 value for living families also includes those families rarely preserved as fossils. The several pronounced dips in the curve correspond to major mass-extinction events. The most catastrophic extinction took place at the end of the Permian Period.

Land plants were affected by the Permian-Triassic crisis, though they were generally less impacted than animal life, as the decline of late Paleozoic floras had already begun earlier.1

The extinction event was characterized by significant environmental stress. Volcanic activity, specifically the eruption of Siberian flood basalts, likely increased atmospheric carbon dioxide levels and produced volcanic ash clouds. These clouds may have restricted the sunlight necessary for photosynthesis, thereby inhibiting carbon fixation by plants. Additionally, the warming and drying of terrestrial environments throughout the Permian reduced the burial of organic matter, further altering the carbon cycle.2

The transition across the Permian-Triassic boundary saw major shifts in flora. In southern continents, the cool-adapted Glossopteris and Gangamopteris seed fern flora were replaced by Dicroidium, a seed fern better suited to warm, dry conditions. While extensive forests existed in the Triassic, widespread aridity in the Early and Middle Triassic limited their distribution, resulting in generally poor development of floras during that time.1