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Catastrophic events transport tree forests thousands of miles to a burial at sea



  Catastrophic events transport tree forests thousands of miles to a burial at sea.
Trees as high as the mountains can be transported thousands of miles downriver to the Bay of Bengal as part of an ancient cycle that seems to be triggered by monsoons and other catastrophic events. Picture credits: Christian France-Lanord, University of Lorraine

Flooding caused by heavy rains caused by hurricanes and monsoon towers, as well as other catastrophic events, has resulted in huge amounts of fresh wood being brought deep into a watery grave deep beneath the ocean, according to earth scientists.

Their research, published in the Proceedings of the National Academy of Sciences on October 21

, shows for the first time that trees can travel thousands of miles away from their mountain homes to settle in the vast sediments From the mouth of the river, the sea extends.

Wood from ancient trees found in the deep sea.

An international team of researchers led by Sarah Feakins, Professor of Earth Sciences at the USC Dornsife College of Letters, Arts and Sciences, studied the core samples taken from the seabed more than a thousand miles off the coast of Bangladesh in the Bay of Bengal ,

The US-operated research vessel R / V Joides Resolution, part of the International Ocean Discovery Program, extended a drilling mechanism more than three kilometers from the sea surface to the seabed and drilled more than half a mile into the sediments.

They then returned the samples to the lab where they were re-examined. The search team scoured the resulting core samples. They discovered wood chips in the 19 million year old sand layers.

Their analysis showed that most layers of wood were from lowland sources, but one layer was wood from trees high in the mountains.

"We found flawless softwood pieces," said Feakins. "These trees grow two miles above sea level in the Himalayas."

The trees were probably uprooted during the last ice age due to a massive release of water from the rupture of a natural dam, which was caused by a glacier, landslide or similar landfall. In a rush of water, the trees rode thousands of kilometers from Nepal via Bangladesh to the Bengal Fan, the largest underwater sediment collection in the world.

The scientists studied other layers in the core sample, also found wood from the plains. These woodchips were probably carried into the sea by heavy rains and floods during monsoons or hurricanes, which occurred frequently over a period of 19 million years.

River Export Trees

As well as revealing the astonishing distance, trees can be transported by rivers into the sea. Due to natural phenomena in the ocean, the study found that this tree wood is an important part of the carbon cycle.

  Catastrophic events transport forest trees thousands of miles to a funeral in the sea.
Scientists studying sediments in the Bay of Bengal have found 19 million-year-old wood sediments that seem to have come from trees high in the mountains – a sign that wood migrates thousands of miles into the deep sea. Here is an aerial view of a section of the river route. Credit: Christian France-Leonard, University of Lorraine

Most of the planet's carbon is in the rock, but the remainder flows in various forms between land, air and ocean, migrating through plants, animals and microbes.

In the air, carbon can be Part of carbon dioxide, methane or other greenhouse gases that can store heat in the atmosphere and cause the greenhouse effect.

On the other hand, the plant-bound carbon remains bound from the atmosphere until it is released into the metabolism, decay or combustion, usually shortly after death. However, rapid transport events by rivers bypass the decomposition that normally follows a fall of trees and instead provide fresh wood that can be trapped in sediments on the seabed.

The findings point to a previously unrecognized way in which carbon can be locked away and effectively removed from the seabed carbon cycle for millions of years. The abundance of wood suggests that earlier estimates of carbon export through the modern Ganges-Brahmaputra rivers were small.

Considering wood, the amount of exported and buried carbon could now be 50% higher than previously thought.

Since we were trying to calculate the amount of carbon in all parts of the carbon cycle, we did not know anything about this forest of fragmented trees buried in the seabed, "Feakins said." Now we have to add it to the equation. "

Carbon Degradation

Feakins added that the findings underscore the importance of free flowing carbon sequestration fluxes.

Temperatures have dropped significantly, "Feakins said, as did the atmospheric CO2 content.

This was due to natural processes such as the weathering of rocks (including the Himalayas) and the burial of off-shore plant carbon that removes carbon from the atmosphere. This study points to the need to inventory millions of years of carbon sequestration in these elusive wood sediment layers, without which greenhouse gases would have kept temperatures high.

Furthermore, the 50-million-year cooling trend has reversed rapidly in recent decades

Feakins notes that understanding carbon sequestration services that provide natural ecosystems and rivers, in parallel with emission reductions, influence decisions on forest management and dams can address elimination and other problems in terms of their potential to control the carbon cycle.


Is the theory about the Earth's climate wrong in the last 15 million years?


Further information:
Hyejung Lee el al., "Sustainable Wooding in the Bengal Fan for the Last 19 Years", PNAS (2019). www.pnas.org/cgi/doi/10.1073/pnas.1913714116

Provided by
University of Southern California




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Catastrophic events bring tree forests thousands of miles to a funeral at sea (2019, October 21)
retrieved on 21 October 2019
from https://phys.org/news/2019-10-catastrophic-events-forests-trees-thousands.html

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