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Tropical soil degradation can be hidden source of CO2



  Tropical soil degradation can be hidden source of CO2
Tropical areas such as Congo experience extensive deforestation and land use conversion for agriculture. Credit: Rob Spencer

Thousand-year-old tropical land upgraded by accelerating deforestation and agricultural land use can release carbon dioxide into the atmosphere, according to a recent study by researchers at Florida State University.

In a survey of 1

9 sites in the eastern Democratic Republic of Congo, researchers discovered that heavily refined areas are leaking organic carbon that is significantly older and more biodegradable than the organic carbon removed from urban areas.

Starting from deeper soil horizons and leaching from rain to watercourses, the older, chemically unstable organic carbon is finally consumed by current-bearing microbes that consume the rich compounds and respect carbon dioxide back into the atmosphere. It's a process that can compromise local ecosystems and further burn the greenhouse effect, researchers said.

"In many ways, it is similar to what happened in the Mississippi River Basin 100 years ago, and recently in the Amazon," said studying author Rob Spencer, associate professor of the FSU Department of Earth, Ocean and Atmospheric Sciences. "Congo is now facing the conversion of pristine soils for agriculture. We want to know what that can mean for the carbon dioxide."

Although the broader effects of deforestation on the carbonic acid cycle are well known, scientists said that the findings published today in the journal Nature Geoscience it is proposed that there is an additional path or leakage of coal in rivers from soil which is hugged by deforestation and land conversion.

"At this time, it is difficult to know the extent of this flux and thus the relative importance of this process compared to other anthropogenic sources of carbon dioxide, but it is likely to grow with further deforestation and land use conversion," said the former FSU. Postdoctoral researcher Travis Drake, the main author of the study. "We hope this document stimulates more research into the relative importance of this process."

To better distinguish the various fields in their study, the researchers analyzed the dissolved organic carbon released from study places to outflows and rivers. Using ultra-high resolution mass spectrometry data generated by advanced tools at the National High Magnetic Field Laboratory's FSU headquarters, the team found that the older dissolved organic substances released from deforested areas were more energy-rich and chemically different from those of better-preserved forests [19659010] Tropical soil degradation can be hidden source of CO2 ” title=”Tropical areas like the Congo are experiencing widespread deforestation and land-use conversion for agriculture. Credit: Florida State University”/>

Tropical areas such as Congo experience extensive deforestation and land use conversion for agriculture. Credit: Florida State University

Overall, forest areas were released considerably more loosely organic carbon than deforested areas. However, the dissolved organic substances that departed from the deforested and land-converted regions were exceptionally bio-labile or suited to microbial consumption.

"The composition was the dissolved organic matter from deforested land full of the things that microbes prefer to eat-easier and readily available compounds with a lot of nitrogen," said Drake, who is now conducting research at the Swiss Federal Technical Institute in Zurich. "We believe that the microbial consumption of these old organic substances coming from soils can partly explain the higher concentrations of carbon dioxide we observed in the separated area streams."

When developing tropical areas such as Congo, deforestation-related soil degradation has the potential to dramatically increase the leaching of organic carbon through rain. The loss of organic matter could compromise the soil fertility and reduce downstream transport of critical nutrients that support aquatic and coastal ecosystems.

More generally, this process means that coal that was certainly sequestered in the earth over the millennia could now enter the modern carbon dioxide cycle. If scientists positively release the carbon dioxide in the atmosphere as carbon dioxide, it can contribute to the greenhouse effect.

Scientists said these findings underscore how urgent it is to identify the second and third order effects of deforestation, soil transformation and uncontrolled disturbance of deep, nutritious soils in the tropics. While widespread and systematic forest saving is the best antidote, the paper suggests that less disturbing farming methods could compensate for some of the destabilization.

"This research focuses on Congo, as the tropics really are at the forefront of agricultural-driven land-use conversion," Spencer says.

"Ultimately, it is due to the conservation of forests that maintain and store coal in the ground over longer time frames," Drake added. "When land-use conversion occurs, better methods such as terraces, use of buffer strips and application of organic residues can improve some of the observed organic carbon lacquers."


Ancient permafrost is rapidly converted to carbon dioxide upon thawing


More information:
Mobilization of aging and biolabile charcoal through tropical deforestation, Nature Geoscience (2019). DOI: 10,1038 / s41561-019-0384-9, https://www.nature.com/articles/s41561-019-0384-9

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Florida State University




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Tropical soil degradation can be hidden source of CO2 (2019, June 24)
June 25, 2019
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