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Earth & Life (http://www.geofinds.com), 2006-10-1, Vol.1. , No.1: 12-15.
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Cold climate after the end-Permian crisis as implied by the aftermath vegetation*
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Abstract The flora after the end-Permian mass extinction is characterized by the presence of conifers and lycopod, e.g., Pleuromeia. It resembles modern boreal forest in community structure and may represent similar climatic conditions. The needle-shaped leaves of the Pleuromeia and its companion by conifer indicate it is adapted to cold climate, instead of hot dry climate. The replacement of the flourishing tropical-subtropical floras of the Latest Permian by the aftermath flora like modern boreal forest should be caused by a substantial climate cooling. The universal distribution of this flora indicates that there was no climate zonation after the mass extinction and the whole Earth was a “cooling ball”. Keywords: end-Permian, mass extinction, flora, climate, boreal forest
1 The aftermath flora and its paleoecologyDuring the Late Permian Changhsingian Stage, the terrestrial plants were very flourishing. They differentiated into 4 floral kingdoms: the Angara kingdom, Atlantic kingdom, Cathaysian kingdom and Gondwana Kingdom (Dobruskina, 1987), representing North Temperate mid-latitude climates, palaeo-equator and lower latitude climate, paleo-equator and low latitude climate, and South Temperate to Cold high latitude climate, respectively. The crisis at the close of the Permian totally destroyed the four floras, leaving only a few refugees including a few conifers, some Glossopteris, and some lycopods. The aftermath flora of the early Griesbachian was very monotonous in composition. It contained some conifers, such as Voltzia, some seed fern, such as Glossopteris, and some lycopods, such as Pleuromeia. Though its simple composition, this flora had worldwide distribution (Meyen, 1973; Dobruskina, 1987). The conifer Voltzia and seed fern Dicriodium occurred at almost all paleo-latitudes (Dobruskina, 1987; Veevers et al., 1994; Retallack, 1995) and Pleuromeia was encountered in virtually all coastal habitats (Wang, 1996). It accommodated only a few large animals, but with abundant insects. Mainly adapted to cool to cold climates, modern conifers are mainly distributed in the frigid zone, temperate zone, variable zone, as well as the high mountains in the torrid zone. The conifer of the aftermath flora such as Voltzia should be adapted to similar climatic conditions. Modern lycopods are distributed to every parts of the Earth, including the torrid zone, subtropics, temperate zone, variable zone, as well as frigid zone, indicating they are climatically eurytopic. The needle-shaped leaves of Pleuromeia have been regarded to be adapted to arid climate. But knowledge from modern botany tells us that needle-shaped leaves can be an adaptation to cold climate, an adaptation to the physiological drought resultant from cold climate (Wu et al., 1983). Since they were associated with conifers, the needle-shaped leaves of Pleuromeia were adapted to cold climate, instead of hot dry conditions. As a whole, the aftermath flora characterized by conifers and lycopods was adapted to cold climate. |
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*Supported by National Natural Scientific Foundation of China (No. 40472015) and the State Key Laboratory of Modern Paleontology and Stratigraphy (No. 053102), as well as the Key Laboratory for Minerals and Resources, Chinese Academy of Sciences. Wu Y.S.: Currently Associate Professor of Chinese Academy of Sciences, with PhD from Chinese Academy of Sciences. His studies focus on reefs, diagenesis, P-T boundary, PTB conodonts. |
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