Pattern of vegetation turnover during the end-Triassic mass extinction: Trends of fern communities from South China with global context

Ning Zhou,Xingliang Zhang,Yongdong Wang,Liqin Li,Ning Lu,Mihai Emilian Popa,Wolfram Michael Kürschner,Pengcheng An,Yuanyuan Xu

doi:10.1016/j.gloplacha.2021.103585

Abstract

The end-Triassic mass extinction (ETME) is considered to be one of the five most severe extinction events in Earth history and caused the disappearance of ca. 80% of all species. The terrestrial ecosystems were also greatly affected by this extinction, but the severity of the land plant diversity loss is not well understood. Ferns are once a principal component of the terrestrial ecosystem from the late Paleozoic/early Mesozoic era and colonizers taxa commonly found in disturbed environments. In this study, we investigated the diversity and ecology of fern during the Triassic-Jurassic (Tr–J) transition in the Sichuan Basin of South China and focused for the first time on the impact of the end-Triassic mass extinction event on the fern communities. We assembled fern fossil records in 16 localities from the Rhaetian Xujiahe (XJH) Formation to the lowermost Jurassic Zhenzhuchong (ZZC) Formation. Our results indicate that no obvious mass extinctions of macro-microflora of ferns but a clear species turnover was recorded at ETME in the Sichuan Basin, reflected an appropriate response of plants in places far away from CAMP volcanism. The paleoecological analysis based on macroflora and microflora in the Sichuan Basin shows a warm and humid condition of tropical-subtropical climate during Rhaetian followed by an increase of specific dry-resistant taxa, indicating a dryer environment at the Earliest Jurassic. Additionally, multivariate statistical approaches (principal coordinates analysis, cluster analysis, network analysis) for fern macro-remains and spores data in the southeastern Sichuan Basin infer that the members of XJH and ZZC Formation cluster in three groups, corresponding to their environmental conditions, determined by humidity and temperature.

Highlights

Five mass extinction events have been recognized in the Phanerozoic over the past 600 million years (Stanley and Yang, 1994; Olsen, 1999; Finney et al, 1999; Jin et al, 2000; Ward et al, 2001; Whiteside et al, 2010)
The end-Triassic mass extinction (ETME) at ~201 Ma has been linked to the extreme greenhouse warming and ocean anoxia, triggered by Central Atlantic Magmatic Province (CAMP) flood basalt volcanism (McElwain et al, 1999; Van de Schootbrugge et al, 2009; Whiteside et al, 2010; Ruhl and Kürschner, 2011; Ruhl et al, 2011, 2020; Blackburn et al, 2013; Li et al, 2017; Heimdal et al, 2020)
Most studies on terrestrial vegetation at ETME focus on the micro flora while only a few documented the vegetation history based on macroflora

Summary

Introduction

Five mass extinction events have been recognized in the Phanerozoic over the past 600 million years (Stanley and Yang, 1994; Olsen, 1999; Finney et al, 1999; Jin et al, 2000; Ward et al, 2001; Whiteside et al, 2010). The end-Triassic mass extinction (ETME) at ~201 Ma has been linked to the extreme greenhouse warming and ocean anoxia, triggered by Central Atlantic Magmatic Province (CAMP) flood basalt volcanism (McElwain et al, 1999; Van de Schootbrugge et al, 2009; Whiteside et al, 2010; Ruhl and Kürschner, 2011; Ruhl et al., 2011, 2020; Blackburn et al, 2013; Li et al, 2017; Heimdal et al, 2020) This event is characterized by the disappearance of almost 300 families of marine invertebrates and vertebrates and major extinctions among insects in the terrestrial ecosystem (Benton, 1995; Pienkowski et al, 2014). Palynoflora and macroflora appear to show inconsistent trends of diversity loss at ETME

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