Thursday , August 18 2022

Researchers use drilling pools to track fires and the last 600,000 years – ScienceDaily



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Van Lake in eastern Turkey is considered a unique climate archive. Years ago, an international team of University-led scientists led Medieval sediment from the bottom of the lake that reflects the last 600,000 years. An interdisciplinary group of soil scientists and paleobotanists from the University of Bonn have now evaluated drilling traits for the remains of early fires – with surprising findings. The fires did not occur mainly during specific periods of dry as it was thought, but in relatively damp and warm periods – because the forests grow particularly vegetable and provide fuel for fires. The results have now been published in the magazine "Quaternary Science Reviews. "

Every summer there are more and more reports on tree fires and forests in the south. But even before the man adapted the vegetation of the ground for its purposes or started fires, large fires occurred regularly. Researchers at the University of Bonn have investigated the frequency and intensity of these stepp, shrubs and forest fires over the last 600,000 years using drilling pools from the bottom of Lake Van in eastern Turkey. During this period, the rain washed the soil and the pollen from the surrounding area to the lake, and became a unique archive.

In 2010, an international team of scientists led by Professor paleobotancer, Professor Dr. Thomas Litt of the Geosciences and Meteorology Foundation has already drilled Van Lake deposits with a mobile platform. "In the 220 meter deep sediment profile, we were able to rebuild the past 600,000 years vegetation using pollen," said Litt. On the basis of the composition of the pollen in the individual layers, paleobotancer decided which plants grew especially during specific periods. Based on the temperature and water requirements of these plant species, scientists were able to draw conclusions about the appropriate climate.

Along with soil scientists from the Institute of Crop and Conservation of Resources (INRES) at the University of Bonn, researchers analyzed the remains of fire in the drilling pools. The partially small fire residue particles are microscopic and are split into the sediments. "We have therefore used a method that works independently of the visibility of the charcoal remains," explains soil scientist Professor Dr. Wulf Amelung or INRES. Polycarboxylic benzene acids were biomarkers for the fire residues, respectively as a biomarker for Black Carbon. The age of the layers in the drilling pools, the pollen contained in it and the content of benzene-polycarboxylic acids make it possible to recreate the largest vegetation and fire incidents.

"Our thesis was that fire activities were higher during dry weather periods," said lead author, Dr. Arne Kappenberg, a Ph.D. student at Professor Amelung. After all, even today, fires often occur in summer in the dry forests and Mediterranean Mediterranean shrub heath, while the cold and humid temperate lines are prohibited in mainly.

Fires were particularly violent between the ice ages

However, the data of the last 600,000 years of Van Lake drilling holes shows the opposite. "Fires in the forest increased during the periods where a remarkable oak forest grew with coniferous trees in a relatively late climate and warmth," summarizes Litt. Therefore, it was not dry brushes as a tire that was determined for the early fires, but the number of plants (biomass) produced was dependent on temperature and precipitation. The biomass was particularly large in the warmer periods between the ice ages. As only a man had more extensive appearance in the Middle East about 11,000 years ago through agriculture and animal breeding, the fires were predominantly natural.

The fires show a special circle: Around every 100,000 years there were special fires. This is probably related to the Milankovic rings known herein. These refer to the regular Ordnance variations of the Earth, which lead to higher irradiation of our planet in this rhythm. "This is considered to be a power for the change between warm and cold times," said Amelung. The researchers suspect that these differences in irradiation lead to a collection of forest fires not only locally, but globally. Japan data indicates that. "This assumption must be tested on the basis of further studies," said Kappenberg.

So far, there have been studies on campe fire and forests dating back to 150,000 years. The drill colors from Lake Van cover the last 600,000 years. The data also allows future outcomes. Litt: "If the tendency of drought in the summer continues to continue in Germany, then the risk of forest fires will rise here too." After all, there are lush forests in Germany – and according to the results of the study, the fire risk increases with the biomass.

The study was carried out at the Cologne and Base Universities and the RWTH Aachen Universities' SFB 806 Cooperative Research Center "Our Way to Europe".

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Materials provided by Bonn University. Note: Content may be edited for style and length.

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