Terrestrial Ecosystem Crisis at the Permian-Triassic Boundary

Academic Background

The Permian-Triassic boundary (approximately 252 million years ago) marks one of the most severe mass extinction events in Earth’s history, devastating not only marine ecosystems but also profoundly impacting terrestrial ecosystems. Although scientists generally agree that this event is linked to the massive volcanic activity of the Siberian Traps Large Igneous Province, the specific mechanisms and temporal progression of the terrestrial ecosystem crisis remain highly debated. In particular, whether the terrestrial ecosystem crises occurred synchronously across different regions and how climate change drove these crises are still unresolved questions.

To address these questions, a research team from the China University of Geosciences, the University of Texas at Arlington, the University of Leeds, and Natural Resources Canada conducted an integrated paleontological and geochemical study. Their goal was to reveal the spatiotemporal differences and driving mechanisms of the terrestrial ecosystem crises in North and South China during the Permian-Triassic transition.

Source of the Paper

The paper, titled “Diachronous end-Permian terrestrial crises in North and South China,” was co-authored by Daoliang Chu, Haijun Song, Jacopo Dal Corso, and others. It was published in Geology, Volume 53, Issue 1, in 2024. The manuscript was submitted on August 1, 2024, revised on September 3, 2024, accepted on September 13, 2024, and published online on October 4, 2024. The paper is available under the Gold Open Access model, following the CC-BY license.

Research Process

1. Study Areas and Sample Collection

The research team selected four Permian-Triassic boundary sections in North and South China as study sites: - North China: Dayulin Section (34.48504°N, 112.18245°E) in Henan Province and Shichuanhe Section (35.02917°N, 108.87833°E) in Shaanxi Province, with a paleolatitude of approximately 20°N. - South China: Chinahe Section (26.13077°N, 104.35637°E) in Yunnan Province and Chahe Section (26.72054°N, 103.82125°E) in Guizhou Province, located near the paleoequator.

These sections cover different stratigraphic units during the Permian-Triassic transition, including the Sunjiagou Formation, Liujiagou Formation, Xuanwei Formation, Kayitou Formation, and Dongchuan Formation. The team collected plant macrofossils, palynomorphs, and sediment samples layer by layer, conducting detailed paleontological and geochemical analyses.

2. Experimental Methods

• Plant Fossil and Palynomorph Analysis: Plant macrofossils and palynomorphs were collected layer by layer to analyze vegetation changes. Palynomorph samples were extracted using acid maceration techniques and identified under a microscope.
• Mercury (Hg) Content Measurement: A Lumex RA-915 mercury analyzer coupled with a PYRO-915+ pyrolyzer was used to measure mercury content in sediments, tracking signals of volcanic activity.
• Organic Carbon Isotope (δ13Corg) Analysis: A wavelength-dispersive X-ray fluorescence spectrometer (XRF) was used to measure the organic carbon isotope composition of sediments, revealing changes in the carbon cycle.
• Climate Modeling: The Community Climate System Model (CCSM 3.0) was employed to simulate surface air temperature (SAT) and precipitation changes in the study areas, exploring the impact of climate change on terrestrial ecosystems.

3. Data Analysis

By comparing plant fossils, palynomorphs, mercury content, and organic carbon isotope data from different sections, combined with climate modeling results, the research team revealed the spatiotemporal differences and driving mechanisms of the terrestrial ecosystem crises in North and South China.

Key Findings

1. Terrestrial Ecosystem Crisis in North China

In the Dayulin Section, a plant fossil assemblage dominated by Pseudovoltzia-type and Ullmannia-type conifers was found in the lower part of the Sunjiagou Formation. However, no plant macrofossils were discovered above 25.5 meters. In the Shichuanhe Section, a diverse ichnoassemblage was found in the lower part of the Sunjiagou Formation, but no trace fossils were present above 30 meters. These results indicate that the terrestrial ecosystem crisis in North China began before the negative carbon isotope excursion (NCIE), around 252.21 ± 0.15 million years ago.

2. Terrestrial Ecosystem Crisis in South China

In the Chinahe Section, a rainforest-type Gigantopteris flora was found in the Xuanwei Formation. However, at the base of the Kayitou Formation, the vegetation shifted to a monotonous assemblage dominated by small Peltasperm and lycophyte species. Meanwhile, trilete spores gradually decreased, while non-striate bisaccate pollen significantly increased, indicating a shift from humid to seasonally dry conditions. In the Chahe Section, vegetation diversity also declined sharply, accompanied by a significant increase in charcoal content, suggesting frequent wildfire activity.

3. Climate Modeling Results

CCSM 3.0 simulations showed that in North China, the annual mean temperature increased by 8–10°C during the Permian-Triassic transition, with maximum temperatures exceeding 42°C. Precipitation seasonality also intensified, leading to prolonged droughts. In South China, the annual mean temperature increased by 6–7°C, with maximum temperatures around 38°C, and precipitation seasonality also intensified significantly. These extreme climatic conditions exerted severe pressure on vegetation and animal communities, leading to ecosystem collapse.

Conclusions

The results indicate that the terrestrial ecosystem crisis in North China occurred approximately 300,000 years earlier than in South China. The crisis in North China was primarily driven by extreme heat and drought, while in South China, it was associated with enhanced seasonal precipitation and frequent wildfires. These findings suggest that the terrestrial ecosystem crisis at the Permian-Triassic boundary was not a globally synchronous event but rather a global extinction resulting from the cumulative effects of regional climate changes.

Research Highlights

1. Revealing Spatiotemporal Differences: For the first time, high-resolution geochemical and paleontological data were used to reveal the spatiotemporal differences in the terrestrial ecosystem crises in North and South China during the Permian-Triassic transition.
2. Climate-Driven Mechanisms: By integrating climate modeling and geological records, the study elucidated the lethal effects of extreme heat and enhanced seasonal precipitation on terrestrial ecosystems.
3. Global Implications: The findings support the view that the terrestrial ecosystem crisis at the Permian-Triassic boundary was a global extinction driven by cumulative regional climate changes, providing new perspectives for understanding major extinction events in Earth’s history.

Research Value

This study not only deepens our understanding of the terrestrial ecosystem crisis at the Permian-Triassic boundary but also provides important insights for predicting and addressing the potential impacts of current global climate change on ecosystems. By revealing the lethal effects of extreme climatic conditions on ecosystems, the research offers scientific evidence for formulating strategies to mitigate climate change.