Vegetation changeover across the Permian-Triassic Boundary in SouthWest China, survival, recovery and palaeoclimate: What lessons to learn?

Lay summary by David De Vleeschouwer

The Earth’s most devastating extinction event occurred about 252 million years ago, with severe consequences for life in the oceans as well as on land. This specific moment in geologic time is referred to as the Permian-Triassic boundary. Jianxin Yu and colleagues demonstrate that plants, which grew in a swampy environment in present-day Southwest China, experienced a dramatic turnover across the extinction.

The Permian-Triassic extinction has been the subject of numerous geological studies. However, the majority of those studies focuses on the consequences for ocean life. This is because there are simply much more geologic archives that consist of marine sediments, recording environmental changes in the ocean, than there are geologic archives that provide insight in environmental change on land. Moreover, it is often quite difficult to correlate terrestrial archives from around the world, and even more difficult to correlate them with marine archives. These elements make that the cause of the extinction event, hitting life on land and in the ocean at the same time, is still under debate.

The authors contribute to the understanding of the pattern of extinction, survival and recovery of land plants during this critical period of Earth life, by studying plant fossils from five sections in Southwest China (all within a 75 km radius from Xuanwei city). Three are fully terrestrial, and two show the transition of a terrestrial swamp-like environment to a marine near- shore environment. Hence, these well-exposed, continuous sections could be precisely correlated to fully-marine sections about 150 km westwards.

The authors observe 105 different plant species in the late Permian interval, contrary to only 18 in the earliest Triassic. These numbers indicate that the Permian-Triassic boundary in Southwest China is characterized by a turnover from a flora which contained among the most advanced land plants of the Permian to a species-poor assemblage in the early Triassic. Immediately after the extinction event, the authors mark the presence of the vascular plant Annalepis. These were one of the first to initiate the recovery of land plants, right after the extinction event. Therefore, Southwest China may have served as a refuge for plants to survive the disrupting biocrisis, while e.g. North China and Europe were too arid for vegetation to survive.

This study evidences how sensitive land plants are to extreme and fast environmental change. One should therefore consider this paper as a clear warning that human-induced environmental change should be limited, both in speed and amplitude.

Read the Earth-Science Reviews original research article which this summary is based on Vegetation changeover across the Permian–Triassic Boundary in Southwest China: Extinction, survival, recovery and palaeoclimate: A critical review (April 2015).

Visit the profile of the research ambassador, David De Vleeschouwer, who wrote this summary.

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