北极挪威地区发现雨林树木化石

UK researchers have unearthed¹ ancient fossil forests, thought to be partly responsible for one of the most dramatic shifts in the Earth's climate in the past 400 million years. The fossil forests, with tree stumps² preserved in place, were found in Svalbard, a Norwegian archipelago situated³ in the Arctic Ocean. They were identified and described by Dr Chris Berry of Cardiff University's School of Earth and Ocean Science.

 

Prof John Marshall, of Southampton University, has accurately⁴ dated the forests to 380 million years.

 

The forests grew near the equator during the late Devonian period, and could provide an insight into the cause of a 15-fold reduction in levels of carbon dioxide (CO2) in the atmosphere around that time.

 

Current theories suggest that during the Devonian period (420-360 million years ago) there was a huge drop in the level of CO2 in the atmosphere, thought to be largely caused by a change in vegetation from diminutive⁵ plants to the first large forest trees.

 

Forests pulled CO2 out of the air through photosynthesis⁶ - the process by which plants create food and tissues - and the formation of soils.

 

Although initially⁷ the appearance of large trees absorbed more of the sun's radiation, eventually temperatures on Earth also dropped dramatically to levels very similar to those experienced today because of the reduction in atmospheric⁸ CO2.

 

Because of the high temperatures and large amount of rainfall on the equator, it is likely that equatorial forests contributed most to the drawdown of CO2. Svalbard was located on the equator around this time, before the tectonic plate drifted north by around 80° to its current position in the Arctic Ocean.

 

"These fossil forests shows us what the vegetation and landscape were like on the equator 380 million years ago, as the first trees were beginning to appear on the Earth," said Dr Berry.

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