Assistant Professor Katayama and her research group have revealed changes in soil microbiota due to soil erosion occurring in the Kyushu Mountains.

2023.10.21 Environment & Sustainability

＊The following sentences are translated by the automatic translation function.

POINT

Comprehensive analysis of soil microbial community composition revealed that soil erosion in the Kyushu Mountains is changing the soil microbiota.
The changes in the soil microbiota due to soil erosion have been directed toward making it difficult for plants to establish themselves, and the environment is likely to undergo further erosion in the future.
The results of this study promote understanding of the ecological mechanisms of soil erosion in forests where understory vegetation has disappeared, and provide basic knowledge for future forest management and mountain land conservation.

SUMMARY

A research team led by Dr. Fu-Chia Chen, a doctoral student in the Department of Natural Resources and Environmental Science, Graduate School of Agricultural Engineering, University of Miyazaki, and Assistant Professor Ayumi Katayama, Faculty of Agriculture, Kyushu University, has revealed that soil erosion in the Kyushu spine mountains, which straddle Miyazaki and Kumamoto prefectures, is changing the soil microbiota in the forest.
In the Kyushu spine, areas of soil erosion are often observed where deer and other predators eat plants in the forest understory, causing soil erosion that washes away soil from the ground surface. The soil microbiota plays an important role in the material cycle of forest ecosystems by decomposing organic matter in the soil and transferring nutrients to plants. However, the effects of soil erosion on soil microbiota and ecosystems in forests have been unknown.
A joint research team from Miyazaki University and Kyushu University has revealed that soil erosion in the Kyushu spine mountains, which straddle Miyazaki and Kumamoto prefectures, is changing the soil microbiota in the forest. In the Kyushu Seiriwa Mountains, deer and other predators have caused the loss of understory vegetation and fallen leaves in some forests. The loss of understory vegetation and fallen leaves has led to soil erosion, in which the surface soil is exposed to raindrops and freezes and thaws, causing the soil to flow downslope. This soil erosion is known to cause a decrease in the amount of organic matter in the soil and an increase in soil density, but it was not known how the soil microbiota changes during the process or what role it plays.
The research team conducted a comprehensive analysis of soil microbiota at three sites in the Kyushu Mountains, and found that soil erosion has caused similar changes in the microbiota at the three forest sites. The team analyzed the community composition of microorganisms related to the changes and their function in the environment, and found that the relative abundance of ectomycorrhizal fungi (*1), which have a symbiotic relationship with plants, decreased, while the relative abundance of phytopathogenic and rotifers (*2) increased. In terms of prokaryotes, the proportion of taxa that can grow in oligotrophic environments and taxa that are dominant in deep soils increased. These results indicate that the microflora in areas where soil erosion has occurred are becoming more difficult for plants to establish, suggesting that the inability to establish may lead to a negative spiral that causes further soil erosion.
These research results promote understanding of the changes in forest environments caused by feeding damage by deer and other predators, which is increasing throughout Japan, and the soil ecosystem mechanisms related to subsequent soil erosion and forest degradation, and provide basic knowledge for future forest management and mountain land conservation.
The research results were published in the Journal of Forest Research on October 10, 2023. Based on the findings, the research team is continuing its research on conservation of forest soil ecosystems and mountain land conservation.

Figure 1: Overview of the three areas surveyed (top row). The lower row shows areas where roots are badly exposed due to soil erosion.

Research-related inquiries

Ayumi Katayama,Assistant Professor
Faculty of Agriculture,Department of Bioresource Sciences

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