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Heterogeneous occurrence of EBLFs in East Asia during the Cenozoic. The earliest occurrence occurred in southern China during the Middle Eocene (A), followed by southwestern China during the Late Eocene to Early Oligocene (B, C), Japan during the Early Oligocene (C), and finally central-eastern China during the Miocene (D). Precipitation above 600 mm during the wettest period (PWetQ) may play an important role in the occurrence of EBLFs (grey contours). Courtesy of Jiagang Zhao and Shufeng Li
Evergreen broadleaf forests (EBLFs) are the most characterized biome in East Asia. They play a fundamental role in the biodiversity function and ecosystem services of the East Asian plant kingdom. Therefore, understanding the historical dynamics of EBLFs and their underlying factors is of great importance for conserving EBLF diversity in this region.
However, the occurrence of EBLFs remains a topic of debate in various fields. Some recent paleobotanical studies have shown that EBLFs likely formed during the Middle Eocene in southeastern China and the Late Eocene to Early Oligocene in southwestern China, which may be earlier than molecular dating studies. Furthermore, the plant fossil record provides more direct and reliable evidence, and the high-quality geochronology and unique fossilization allow for spatiotemporal investigations into the occurrence of EBLFs.
In a study published in the journal Plant Diversity, a team of researchers from the Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences (CAS) examined plant fossils to investigate where in East Asia the EBLF originated.
“Modern EBLFs are mainly characterized by families such as Fagaceae, Lauraceae, Magnoliaceae and Theaceae,” explains Zhekun Zhou, first and co-corresponding author of the study. This biome typically occurs under a monsoon climate, with hot and humid summers and fairly cold winters. Therefore, the paleoclimate and paleovegetation of fossil assemblages mainly serve as key indicators for identifying the occurrence of EBLFs.”
The researchers compiled a dataset of Cenozoic paleobotanical records from four regions in East Asia (southwest China, southern China, central-eastern China, and Japan), reconstructed the fossil history of the dominant genera in the EBLF, calculated paleoclimates, and determined the extant vegetation that is most similar to each fossil assemblage.
“Our results show that most plant fossil assemblages in East Asia have taken the form of EBLFs throughout geological time. Combining the peak periods of the appearance of dominant genera with the locations of fossil excavation sites, we infer that the occurrence of EBLFs has distinct spatiotemporal patterns,” Zhou added.
In addition, the study involved paleoclimate simulations based on the Hadley Centre Coupled Model version 3 (HadCM3) in collaboration with Professor Paul J. Valdes and Dr. Alex Farnsworth of the University of Bristol, UK.
By comparing the quantitative reconstruction and simulation results, it was inferred that a wettest season precipitation amount (PWetQ) exceeding 600 mm was a key factor in the occurrence of EBLFs. Combined with the latest research on the Asian monsoon, this study suggested that the multi-stage evolution of the Asian monsoon led to the diverse occurrence of EBLFs in East Asia.
“Contrary to previous popular views, our findings highlight that EBLFs in East Asia emerged in different temporal and spatial patterns,” Zhou concludes.
Further information: Jiagang Zhao et al. “Heterogenous evergreen broadleaf forests in East Asia: evidence from plant fossils.” Plant Diversity (2024). DOI: 10.1016/j.pld.2024.07.004
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Source: Plant fossils in East Asia reveal heterogeneous occurrence of evergreen broad-leaved forests (August 20, 2024) Retrieved August 20, 2024 from https://phys.org/news/2024-08-heterogeneous-occurrence-evergreen-broad-forests.html
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