It's the pore that counts: Spatial distribution of pores helps determine where carbon is stored in the soil

The soil stores more carbon than the vegetation on the Earth. There are still many unanswered questions about which processes favor soil growth. A team of soil scientists have developed a new method to show where and under what conditions carbon is stored in the soil. The network of soil pores controls the distribution of carbon.

The importance of soil is often overlooked in the public debate on climate protection. soils store more carbon than forests or the atmosphere. The long-term storage of carbon can be very complex. On one hand, it depends on how much carbon enters the soil through root growth, and on the other hand, it depends on how much dissolved organic compounds are in the soil. On the other hand, it depends on whether the existing carbon in the soil can be stable or degraded. The structure of the soil is the most important factor in determining which process is more efficient.

The lead author of the study says that the carbon stored in plant residues and humus is not degraded if thebacteria and hyphae are larger than the pores in the soil where it is stored. If the pores are permanently filled with water and there is no oxygen supply, it is more difficult to use the carbon. The distribution pattern of the organic carbon within the millimeter and micrometer sized pores was not previously studied.

The scientists at the UFZ have been able to do this. They can precisely locate the carbon in the soil with their new method. It is based on the staining of the organic compounds with osmium tetroxide, which is then visualized using X-ray computed tomography. The researchers can infer the distribution of the carbon from the differences in the images by scanning the soil sample before and after staining. This was only possible with the help of elaborate synchrotronCT methods. Access is limited because there are only two particle accelerators in Germany. In Germany, X-rayCT is more widespread.

The new approach facilitates research. The head of the Department of Soil System Science says that this innovation allows them to draw conclusions about where and how much carbon is enriched in the soil. This gives important information about the processes in the soil and how they affect the stabilization and decomposition of carbon in the soil.

The soil scientists tested their methodology at three different sites with different soil types and different weather regimes. In the immediate vicinity of the pores, the concentration of carbon is lower than in the rest of the soil. Increasing distance from the pores decreases the activity of the microbes.

The pattern has been seen at all three sites. SchlFC;ter says that the proximity to the pore system favors the decomposition of organic matter, and the distance to these pores promotes the stabilization of carbon in the topsoil, which is particularly important for agriculture. There are differences in the carbon content of organic material. The carbon decreases with distance to the plant. The plant's leaves are attached to the bacterium and fungi so they can easily get at the carbon. The products accumulate around the plant. The opposite was true in the Gleysol. The scientists did not find any enrichment of products around the plant. Schl says that dissolved decomposition products are more easily transported over longer distances under the wet conditions.

The carbon is distributed in the subsoil by the deeper soil layers, which is an interesting research perspective that has been opened up by the new methodological approach. There is only circumstantial evidence that the distribution patterns of carbon in the subsoil are different from those in the top of the hill. The latter is not influenced by tillage and is not so intensely mixed by burrowing animals. Carbon can only reach deeper layers through the distribution of dissolved organic substances.

It would be great to find out more about these processes. Plants are increasingly lacking water because of climate change. The importance of subsoil for plant growth is increasing. The researchers hope to better understand the processes of carbon storage in deeper layers as well as the causes of the differences in the carbon balance between different forms of land management.

More information: Microscale carbon distribution around pores and particulate organic matter varies with soil moisture regime, Nature Communications (2022). DOI: 10.1038/s41467-022-29605-w Journal information: Nature Communications Citation: It's the pore that counts: Spatial distribution of pores helps determine where carbon is stored in the soil (2022, April 21) retrieved 21 April 2022 from https://phys.org/news/2022-04-pore-spatial-pores-carbon-soil.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.