Japanese Soils Research Articles

Comparative Analysis of Japanese Soils: Exploring Power Generation Capability in Relation to Bacterial Communities

Comparative Analysis of Japanese Soils: Exploring Power Generation Capability in Relation to Bacterial Communities

Evaluation of Soil Suppressiveness of Various Japanese Soils against the Soybean Cyst Nematode Heterodera glycines and Its Relation with the Soil Chemical and Biological Properties

This study aimed to evaluate the suppressive potential of different soils on soybean cyst nematodes (SCN) and to estimate the suppressive mechanism. Fifteen soils (designated as soil A to O) from different agricultural fields with varying organic inputs were added with SCN-infested soil and grown with a green soybean variety. The SCN density in the soil at 6 weeks of soybean growth was markedly different depending on the soils used, indicating a different level of disease suppressiveness. No significant correlation was observed between the SCN density and any of the soil physicochemical and biological characteristics tested. Then, to estimate a suppression mechanism, F-soil that showed the lowest density of SCN was added to the SCN-infested soil with or without streptomycin to kill bacteria and grown with soybean. SCN density was not increased by the addition of streptomycin, indicating that soil bacteria may not be involved in the suppressiveness of F-soil. In total, 128 fungal strains were isolated from the rhizosphere of F-soil and inoculated in a combination or singly in the SCN-infested soil. After repeated screenings, five strains were selected since the SCN density was consistently decreased by them. Sequence analysis showed that they were closest to Clonostachys rosea, Aspergillus niger, Aspergillus fumigatus, Fusarium oxysporum, and Cylindrodendrum alicantinum. All five strains significantly reduced the mobility of second-stage juveniles (J2). Further, C. rosea a2, A. niger a8, and F. oxysporum a25 significantly decreased hatching. Overall, the present study demonstrated that soil fungi played an important role in SCN suppression in F-soil.

Development of Standard Operation Procedures for Receiving International Emergency Medical Teams. Cooperation Between the United States National Disaster Medical System (NDMS) Disaster Medical Assistant Team (DMAT) and Japan DMAT

Introduction:Japan DMAT and US DMAT have been conducting several tabletop exercises to prepare for major earthquake disasters in Japan. Japan is predicting overwhelming disasters on Japanese soil soon, which needs efficient and optimum use of resources in medical assistance, including additional support from the US. The Japanese government established a large-scale Earthquake/Tsunami Disaster Emergency Response protocol in 2020. However, this protocol does not include any standard operation procedure (SOP) to receive an international medical team. The purpose of this study is to establish the SOP of receiving medical assistance from US-DMAT based on the WHO International Emergency Team (EMT) initiative through tabletop exercises.Method:Collaborated with the Office of the Administration for Strategic Preparedness and Response (ASPR) of the United States Health and Human Services, tabletop exercises assuming that a large-scale earthquake occurred during the hosting of the 2025 Osaka Expo was conducted utilizing an online meeting system.Results:A provisional SOP was composed. Even though Japan had several disaster medical assistance collaborations with US DMAT and is well-familiarized with the Classification and Minimum Standards for Emergency Medical Teams", many issues need to be prepared to accept US DMAT.Conclusion:Numerous procedures need to be conducted to receive US DMAT assistance during a large-scale earthquake in Japan. With this SOP, receiving US medical team assistance will be conducted promptly, eventually saving many lives. This SOP can be modified for other international teams' acceptance in Japan. It could reference other countries seeking to have SOP for receiving international medical team assistance shortly.

Distribution of strontium-90 in soils affected by Fukushima dai-ichi nuclear power station accident in the context of cesium-137 contamination

90Sr and 137Cs activity concentrations were determined by radiometric methods in 76 soil samples (soil, litter, rain gutter deposit, and roadside sediment samples) affected by the Fukushima Dai-ichi Nuclear Power Station (FDNPS) accident and collected from the Fukushima exclusion zone. The 90Sr and 137Cs activity concentrations were in the range of 3 to 1050 Bq kg−1 (median 82 Bq·kg−1) and 0.7 to 6770 kBq·kg−1 (median 890 kBq·kg−1), respectively (decay correction date: March 15, 2011). A strong positive correlation was found between 90Sr and 137Cs activity concentration and higher mobility of 90Sr was confirmed in Japanese soil samples. The activity ratio of 90Sr/137Cs in 85% of all samples was in the range of 5.0 × 10−5 to 5.0 × 10−4 with a median of 1.2 × 10−4. From the activity ratio values it was concluded that the 90Sr released to the atmosphere was only around 0.0003–0.02 PBq which is negligible compared to the Chernobyl accident (∼10 PBq) or other nuclear accident contaminations. From the standpoints of radioecology and radiation safety, 137Cs remains the primary pollutant of the FDNPS accident.

Investigation of the Receiving United States National Disaster Medical System (NDMS) Disaster Medical Assistant Team (DMAT) in Japan: Development of Standard Operation Procedures for Receiving International Medical Teams

Background/Introduction:Japan DMAT and US DMAT have been collaborating in the past to prepare for expected and unexpected disasters in Japan. Japan is predicting overwhelming disasters on Japanese soil soon, which needs efficient and optimum use of resources in medical assistance, including additional support from overseas, particularly from the US. The Japanese government established a large-scale Earthquake/Tsunami Disaster Emergency Response protocol in 2020. However, this protocol does not include any standard operation procedure (SOP) to receive an international medical team.Objectives:Establishing the SOP of receiving medical assistance from US-DMAT based on the WHO International Emergency Team (EMT) initiative.Method/Description:Collaborated with the Office of the Assistant Secretary for Preparedness and Response (ASPR) of the United States Health and Human Services, tabletop exercises assuming that a large-scale earthquake occurred during hosting the 2025 Osaka Expo was conducted online meeting system.Results/Outcomes:Provisional SOP was formed by the Japan research team and ASPR representatives. Even though Japan had several disaster medical assistance collaborations with US DMAT and is well-familiarized with the Classification and Minimum Standards for Emergency Medical Teams, many issues need to be prepared to accept US DMAT.Conclusion:Numerous procedures need to be conducted to receive US DMAT assistance during a large-scale earthquake in Japan. With this SOP, receiving US medical team assistance will be conducted promptly, eventually saving many lives. This SOP can be modified for other international teams’ acceptance in Japan. It could reference other countries seeking to have SOPs for receiving international medical team assistance in the near future.

Application development and practice model for radiation education

Application development and practice model for radiation education

Microplastic Extraction from Agricultural Soils Using Canola Oil and Unsaturated Sodium Chloride Solution and Evaluation by Incineration Method

Environmental pollution by microplastics (MPs) has become a global problem, but little is known about MPs in soils. This is because MP extraction methods from soils have not yet been standardized. In this study, we tried to establish a simple and economical method to extract soil MPs using the buoyancy of canola oil and the density separation process using sodium chloride (NaCl). In addition, the incineration method was adapted to evaluate the effectiveness of extraction methods precisely. First, the ability and suitability of seven different oils to extract MP from soil were investigated and canola oil was selected. Then, the spiking and recovery test was performed with canola oil and NaCl solution for low-density polyethylene (LDPE), polypropylene (PP), and polyvinylchloride (PVC) as follows: (1) soil and MP mixtures were prepared, (2) 5 g L−1 NaCl and canola oil were added and shaken thoroughly, (3) the oil phase containing MPs were separated after sedimentation, (4) the extracted MPs were rinsed with 99.5% ethanol, and (5) the organic adherents to the extracted MPs were digested with hydrogen peroxide. After drying and incineration, the substantial recovery rates were calculated. In the spiking and recovery test for MP particles (<1 mm) from five typical Japanese agricultural soils, the recoveries of LDPE, PP, and PVC were 95.2–98.3%, 95.2–98.7%, and 76.0–80.5%, respectively, higher than those obtained by the density separation using saturated NaCl solution. In conclusion, the method is effective for extracting MPs, especially LDPE and PP, from soils and is less sensitive to soil type, texture, and physicochemical properties.

Phylogeographic analysis of Ligidium japonicum (Isopoda: Ligiidae) and its allied species reveals high biodiversity and genetic differentiation in the Kanto region, Japan

AbstractResearch of the diversity and evolutionary history of Japanese soil invertebrates is scarce. Molecular data analysis can help to elucidate species classifications and evolutionary processes. We analyzed the mitochondrial cytochrome oxidase subunit I (COI) and nuclear 28S rDNA genes and the morphology of the male pleopod 2 endopod of Ligidium japonicum and its allied species from 67 sites in Hokkaido, Honshu and Shikoku, where only L. japonicum is thought to occur. We found males of the L. japonicum complex with a pleopod 2 endopod morphology matching that of the L. japonicum syntype specimens, except for the number of denticles at the inner margin. There were also more than five species that differed morphologically from the L. japonicum complex, and most of these species had allopatric distributions despite the absence of obvious barriers. A time‐calibrated molecular phylogeny implied that the L. japonicum complex of the Kanto region first differentiated allopatrically in the mountains; this was followed by independent dispersal of three lineages to the Kanto Plain and Boso Peninsula, where secondary contact occurred. Two of the three sympatrically distributed L. japonicum complex lineages had a significant difference in the number of denticles at the inner margin of male pleopod 2 endopods. This variation implies the presence of cryptic species within the L. japonicum complex.

Assessment of Acaricidal Efficacy of Ivermectin Against Ectoparasitic Skin Lesions in Goats

We have conducted a research experiment to investigate the efficacy of commercial Ivermectin preparations (Ivertin®, Invet®, and A-Mectin®) against skin lesions in goats. The generic Ivermectin is, in fact, a naturally-derived dihydro derivative of avermectin originating exclusively from a single microorganism isolated from Japanese soil, displaying an extensive range of antiparasitic efficacy against internal and external parasites of human and domestic animals. The ectoparasites such as ticks, lice, and mites cause heavy economic losses to the livestock industry due to their blood-sucking habit, which adversely affects economic production. Ectoparasites have been recognized as the notorious threat due to severe irritation, formation of crust, wrinkled, thickened, and or loss of hair, allergy, and toxicosis and eventually brought about financial havoc in goat farming. Presently, this is the best-known drug available for combating ectoparasitic diseases in livestock. After being bound, the drug disrupts parasitic neuro-muscular transmission, causing hyperpolarization of the neuronal membrane, inducing paralysis of somatic muscles, particularly the pharyngeal pump, killing the parasites. To investigate the comparative efficacy of commercially available different ivermectin preparations in the local market against skin lesions in goats, the research work was conducted on 12 goats of both sexes having skin lesions from July to August 2017. Subcutaneous injection of Ivertin® of Chemist Laboratories Ltd, Invet® of Popular Pharmaceuticals Ltd, and A-Mectin® of The Acme Pharmaceuticals Ltd, Bangladesh @ l ml per 50 Kg bwt where each ml contains 10mg of generic Ivermectin on the first day followed by the second dose at 7thday and the third dose at 14th day of experimentation. Our results revealed within 28 days of treatment with these preparations of Ivermectin, both smaller and larger skin lesions in goats of all experimental groups were almost cured at a rate of 99%. No adverse effect was observed following ivermectin therapy. The animals were seen with increased vigor, better growth, and improved coat color. Although the precise mode of action and interactions of Ivermectin is yet to be revealed fully, the drug certainly had a tremendously positive effect in alleviating ectoparasitic diseases from goats.

Soil priorities in Japan

This paper shows soil-related research and its contribution to the policy in Japan. Japanese soil is characterized by fresh volcanic tephra in parent materials and the erosion and deposition processes in steep topography. Main soil types in Japan are Brown forest soils, Andosols and Fluvic soils. However, agricultural land is mainly covered by Fluvic soils and Andosols due to its development in flat area. About 7000 soil data are provided as open data with geocodes. Soil survey data were also used to identify and remove contaminations of cadmium or radiocesium. Fertilization guides have been constructed based on those soil data. However, the amount of nitrogen fertilizer applied is one of the top three in the world. In 2021, Japan formulated “Strategy for Sustainable Food Systems” to promote innovations in improving food productivities and reducing environmental burdens.

Comparison of soil characteristics related to C and N processes in Eastern Hungarian and Central Japanese soils under different land use and nutrient supply

ABSTRACT This comparative investigation aimed to evaluate controlling factors for the changes of chemical and microbial properties in soils taken from chemical fertilizer experiments carried out mainly in Chernozem and Andosol in Hungary and Japan, respectively. The plant available nutrient content of the soil, the stock of C and N and the soil microbial parameters of the carbon and nitrogen cycles were examined under different land-use and vegetation. In the Japanese soils, there was about 2–3 times higher organic C content than in Hungarian soils. The average CO2-production was about 1.5 times higher in Hungary soils than Japanese soils, and significantly increased (9–37%) in the fertilized treatments compared to control in all Hungarian long-term experiments. Regarding the Hungarian soils, the NPK-fertilization especially increased the nitrate and phosphorus content of soils, among the microbial parameters of the CO2-production, MBC, MBN, net nitrification, saccharase and urease activities – in most cases significantly increased – among the six microbial examined parameters. With reference to Japanese soils, the nitrogen fertilization especially increased the nitrate and phosphorus content of soils and had the highest effect on the microbiological parameters in the forest soil, where the MBC, MBN, net nitrification, saccharase and urease activities increased significantly. Only the net nitrification increased significantly in the fertilized treatments in the all Numata experiments, and generally 10–100 times higher values were found in the Japanese soils than in the Hungarian ones. The microbial activity decreased according to land use in the following order: maize>forest>grassland in Hungary soils, and forest>grassland>apple orchards in Japanese soils. These results confirm that climate conditions and human activity have important impacts on the C and N cycles of the soil–plant–atmosphere system. Based on our results, it appears that land-use and chemical fertilization resulted in a larger change in the stock of organic matter and soil microbiological processes in the Hungarian long-term experiments compared to the Japanese experiments.

Distribution of heavy metals and related health risks through soil ingestion in rural areas of western Japan

The distribution of heavy metal concentrations and related human health risks were investigated for Shimabara City, Nagasaki Prefecture. The purpose was to clarify the potential for heavy metal contamination in an area already known to be affected by nitrate pollution. A total of 188 soil samples was collected at 47 sites. The heavy metal content of the soil was measured in laboratory using an X-ray analyzer. The highest contents of heavy metals exceeded common background concentration in Japanese soils. The highest concentrations of Cu and Zn appear to be related to application of livestock waste in agriculture. Principal component and cluster analyses were performed to classify the sampling sites based on soil content of heavy metals. Three principal components (PCs) were extracted with the first PC explaining crustal constituents, the second explaining application of livestock waste, and the third explaining other types of anthropogenic pollutants. The cluster analysis resulted in 5 groups regarding the sampling locations. In total, 44% of sampling locations belonged to Group 1 and 46% to Group 2, distributed over the agricultural land in the northern part of the city and the urban area in the southern part of the city, respectively. There is a potential temporal health risk for the Pb content at specific locations in the area.

Quantification of Phytophthora infestans population densities and their changes in potato field soil using real-time PCR

Tuber infection of Phytophthora infestans often occurs at harvest. However, it is difficult to accurately estimate the population densities of P. infestans in soil, especially Japanese soil. In the present study, P. infestans DNA was extracted from soil samples using a modified CTAB-bead method and quantified using real-time PCR to accurately, rapidly and easily estimate the P. infestans population densities in upland soils in Japan. P. infestans was well quantified in eleven types of soil samples, including nine types of upland soils in Japan, that were artificially inoculated with a zoosporangia suspension. The amounts of P. infestans DNA estimated by the real-time PCR were proportional to the inoculum densities. In the non-controlled experimental potato field, P. infestans population densities in soil corresponded to the development of symptoms and were correlated with the number of lesions on the potato foliage. These results imply that the proposed real-time PCR assay is suitable for the estimation or monitoring of P. infestans population densities in upland soils in Japan. The population densities at the ridge bottoms were larger than those at any other location in commercial potato fields. These results were similar to those of a previous report using a bioassay. Moreover, a correlation between DNA quantity and inoculum potential was observed. In conclusion, the real-time PCR assay developed in this study is suitable for indirect estimation of the inoculum potential of P. infestans.

Characterization of metal concentration, heavy metal elution, and desalination behavior of municipal solid waste incineration bottom and grate sifting deposition ash based on particle size

Resource and environmental safety protocols of incineration residues were evaluated by analyzing the metal concentration, heavy metal elution, desalination behavior, and chlorine removal ratio owing to particle size differences between bottom ash (BA) and grate sifting deposition ash (GA). In the total content test, Cl, Zn, and Cr in the incinerator BA exceeded the cement acceptance standard (Cl: 1000 mg/kg; Zn: 1700 mg/kg, and Cr: 170 mg/kg) at almost all of the particle sizes, while Au, Ag, Pd, and Zn had high contents in the GA. When using BA as a construction material, heavy metal elution values and contents are restricted as per the product quality standards based on the Japanese soil pollution control law. Lead within the BA and GA exceeded the standard values for most particle sizes. We predicted that there would be a limit on the elution of K by only washing with water. The removal ratio of total chlorine by particle size was approximately 20–70%, where the effect of the particle size on the removal ratio was small, suggesting that the elution of chlorine was complete in approximately 6 hours. These results contribute to information on the recycling of BA and GA.

Zainichi Koreans Invited to Home Base: Building Ethnic Identity and Its Impact on the Development of Korean Baseball (1956–70)

Zainichi Koreans are a unique political product of the Korean Peninsula. They were taken to Japan under the Japanese occupation (1910–45) of Korea and stayed there without becoming naturalized Japanese citizens. Baseball was a mechanism for the children of Zainichi Koreans, who were oppressed on Japanese soil, to overcome the discrimination they were experiencing in their daily lives and assimilate into Japanese society. From 1956 to 1970, South Korean newspapers invited Zainichi Korean children playing baseball to their home country for regular national baseball exchanges. This event provided nourishment for the growth of Korean baseball and served as the only cultural bridge for Zainichi Korean children to experience and understand their motherland, which they had previously only imagined.

Impact of farmland reclamation on soil distribution in Japan: the case of Andosols in Nagano Prefecture

In modern times, farmlands in Japan have been reconstructed at a large-scale through the cutting and filling of soils. In principle, such reconstruction should be carried out with a minimum amount of soil transportation to decrease environmental impacts and cost, and the soil distribution and properties should be determined by the subsequent reclamation process. To assess this issue, we attempted to evaluate the impacts of farmland reclamation on soil distributions in Japan. Farmland soil in the reconstructed area was surveyed from a pedological perspective using geographic information system (GIS) data. To enable a simple comparison of topsoil thickness and soil distribution before and after farmland reclamation, we selected survey soils classified as “High-humic Cumulic Allophanic Andosols” under the Japanese soil classification system, which are more than 50 cm in thickness in the Melanic horizon. Changes in the thickness of the topsoil were evaluated by direct measurement at 30 field survey positions. The extent of farmland affected by large-scale reclamation was calculated from a GIS-based comparison of topography before and after reclamation based on a digital elevation model (DEM). The reclamation process decreased the thickness of topsoils from more than 50 cm to an average of 26.9 cm over the 30 surveyed positions. The minimum topsoil thickness of 15 cm observed in this study corresponds to the recommended topsoil conservation level under Japanese guidelines for the reclamation of paddies. There was no significant difference in the topsoil thicknesses obtained through soil filling and cutting reclamation processes. These results indicate that the original soil distributions potentially lost the “High-humic Cumulic” feature. Although the topsoils were conserved during farmland reclamation processes carried out in accordance with the Japanese guidelines, the results of this study revealed the influence of the reclamation process on soil properties and, as a result, their classification, through a decrease in topsoil thickness and mixing with subsurface horizons. We confirm the importance of taking topsoil conservation into account in determining the influence of agricultural reclamation on soil distribution in Japan. In reclaimed upland fields, most managed topsoils have sufficient thickness to fill the diagnostic surface horizon. An exception is managed topsoil in reclaimed paddies, which can have insufficient to thickness to meet the corresponding diagnostic surface horizon. We suggest that some soils in modern reclaimed farmlands do not currently fulfill the criterion of diagnostic surface horizon regardless of their reclamation magnitude.

Studies on the sorption behavior and plant uptake of pesticides in Japanese soils.

To estimate pesticide residue levels in succeeding crops based on those in soils, the relationship between pesticide concentrations in komatsuna (Brassica rapa var. perviridis) and the concentrations extracted sequentially from soils using water and acetone was investigated. The concentrations of many pesticides in komatsuna shoots showed higher positive correlation with water-extractable concentrations (CW) than total-extractable concentrations in soils, so that the CW was available for evaluating the phytoavailability of pesticides in the soil. As a result of examining the dissipation behavior of the CW, the dissipation of the CW was able to be predicted by considering time-dependent soil sorption, which could be estimated using the sorption coefficients (Kd) measured by a standard batch method. Furthermore, the present study showed that the properties of soil organic carbon such as black carbon content and the molecular structure of pesticides were important for estimating the Kd values more accurately.

Classification of volcanic soils in the Soil Classification System of Japan and verification based on forest soils

ABSTRACT In 2017, the Japanese Society of Pedology (the Fifth Committee for Soil Classification and Nomenclature) established the Japanese soil classification system. In the classification system, all the soils derived from volcanic ejecta (volcanic ash, pumice, scoria, etc.) are classified into the Great Group of Andosols, excluding Man-made and Organic soils, although some volcanic soils were classified into other soil groups, such as the Podozols and Brown forest soils in the previous classification systems. The aim of the present study was to verify and propose revision for the new system based on physicochemical data collected from forest soils across the Japan archipelago. Approximately 20% of the forest soils have andic properties and were classified into the Andosols in the Soil Classification System of Japan, which is consistent with the Andisols in Soil taxonomy and Andosols in World Reference Base for Soil Resources, excluding a few soils with low andic horizon thickness. Many other forest soils that were not classified into Andosols possessed some of the regosolic andic properties, and it was challenging to classify them into Regosolic Andosols or Brown forest soils. Therefore, additional diagnostic activities on the volcanic ejecta and glass are required to classify such soils appropriately. In the new classification system, the Fulvic Andosols soil group was abolished and substituted with the Humic and Brown-humic subgroups under the Non-allophanic and Allophanic Andosols, respectively. The revision was consistent with the traditional forest soil classification system. In conclusion, the classification of volcanic soils in the Soil Classification System of Japan was verified using forest soil data in Japan. Abbreviations CFSJ: Classification of Forest Soils in Japan (1975); CSCSJ: Comprehensive Soil Classification System of Japan, 1st approximation (2011); SCSJ: Soil Classification System of Japan (2017); ST: Keys to Soil taxonomy, Twelfth Edition (2014); USCSJ: Unified Soil Classification System of Japan, 2nd Approximation (2002); WRB: World Reference Base for Soil Resources (2014, 2015 updated)

Effects of temperature on the dissipation of total- and water-extractable pesticides in Japanese soils.

We investigated the dissipation of 27 pesticides in five Japanese soils at three temperatures and the variability of activation energies (Ea). The dissipation of total pesticides extracted sequentially using water and acetone was fitted to a single first-order (SFO) model. The Ea values calculated from the dissipation rate constants of the SFO model showed a normal distribution with a median of 61.1 kJ mol−1. The dissipation of water-extractable pesticides (i.e., phytoavailable pesticides) was fitted to a double first-order in parallel model with two dissipation rate constants: k1 and k2. The Ea values calculated from k1 and k2 showed normal or lognormal distribution, and the medians of the normal distribution calculated from k1 and k2 were 62.8 and 45.2 kJ mol−1, respectively. Furthermore, the method for estimating the biphasic dissipation of phytoavailable pesticides at different temperatures by using the median Ea values of the laboratory experiment was demonstrated in a field experiment.

The mineralization rate of black soil carbon in the deep layers of Japanese volcanic ash soil may be easily accelerated by labile carbon supply

ABSTRACT The stability of black soil carbon in the deep layers of Japanese volcanic ash soil (i.e., buried A horizons) is often explained by its unique chemical (molecular structure) and physical (associated with short-range-order minerals) recalcitrance. However, the stability of black soil C in buried A horizons may be changed by labile C supply for soil microbes. Here, we hypothesized that the mineralization of black soil C in buried A horizons of Japanese volcanic ash soil could be easily accelerated by a supply of labile C (i.e., a priming effect; PE). To test our hypothesis, we investigated the direction and magnitude of the PE with a buried A horizon in Japan using 13C-labeled glucose (2.188 atom %) in a short-term (21 days) incubation study. We also investigated the effect of mineral nitrogen (N), which could contribute to microbial activity in this incubation study. We found that a positive PE occurred by glucose supply with (182%) or without (181%) mineral N input over the 21-day incubation, and its values were very similar to the PE ratios previously reported in other deep soils. The estimated mean residence time (MRT) of black soil C considering PE was clearly accelerated by glucose supply, regardless of mineral N input, compared with the initial soil MRT. These results strongly support our hypothesis that the mineralization rate of black soil C in buried A horizons is easily accelerated by a labile C supply, and it also demonstrates important implications for the effects of global warming on buried A horizons (e.g., increased root exudation, fine root biomass supply, and N deposition) in Japanese volcanic ash soils.