Quantitative evaluation of carbon dioxide emissions from the subsoils of volcanic and non-volcanic ash soils in temperate forest ecosystems

Abe, Yukiko; Nakayama, Masataka*; Atarashi-Andoh, Mariko; Tange, Takeshi*; Sawada, Haruo*; Liang, N.*; Koarashi, Jun

Geoderma, 455, p.117221_1 - 117221_11, 2025/03

https://doi.org/10.1016/j.geoderma.2025.117221

Subsoils (typically below a depth of 30 cm) contain more than half of global soil carbon (C) as soil organic C (SOC). However, the extent to which subsoil SOC contributes to the global C cycle and the factors that control it are unclear because quantitative evaluation of carbon dioxide (CO) emission from subsoils through direct observations is limited. This study aimed to quantify CO emission from subsoils and determine factors that control CO emission, focusing on the decomposability of soil organic matter (SOM) and the characteristics of the mineral-SOM association in soils. Therefore, a laboratory incubation experiment was conducted using surface soils (0-10 cm and 10-25 cm depth) and subsoils (30-45 cm and 45-60 cm depth) collected from four Japanese forest sites with two different soil types (volcanic ash and non-volcanic ash soils). The CO emission from the subsoils was found to be responsible for 6%-23% of total CO emission from the upper 60-cm mineral soil across all sites. Radiocarbon signatures of CO released from the subsoils indicated the decomposition of decades-old SOM in the subsoils. The correlations between CO emission rate and soil factors across both soil types suggested that the CO emission from the subsoils is mainly controlled by the amounts of SOC easily available to soil microbes and microbial biomass C, not by the amounts of reactive minerals. Given the potential active participation of subsoils in terrestrial C cycling, most of the current soil C models that ignore subsoil C cycling are likely to underestimate the response of soil C to future climate change. The quantitative and mechanistic understanding of C cycling through a huge subsoil C pool is critical to accurately evaluating the role of soil C in the global C balance.

Quantitative importance of subsoil nitrogen cycling processes in Andosols and Cambisols under temperate forests

Nakayama, Masataka; Abe, Yukiko; Atarashi-Andoh, Mariko; Tange, Takeshi*; Sawada, Haruo*; Liang, N.*; Koarashi, Jun

Applied Soil Ecology, 201, p.105485_1 - 105485_12, 2024/09

https://doi.org/10.1016/j.apsoil.2024.105485

Nitrogen often limits plant growth in forest ecosystems. Plants, including trees, change vertical root distribution when nutrient competition is strong within surface soil layer and take up nitrogen even from subsurface soil layers in addition to the surface soil. However, there is still limited knowledge about nitrogen cycles within deeper soil layers. In this study, we investigated the vertical profiles (0-60 cm) of the net nitrogen mineralization and nitrification rates at four Japanese forest sites with two different soil types (Andosols and Cambisols). The partial least square path modeling (PLS-PM) was used to determine factors affecting nitrogen-cycling processes. The net nitrogen mineralization and nitrification rates per unit soil weight were considerably higher in surface soil layer than in deeper soil layers in Andosols but not in Cambisols. PLS-PM analysis showed that microbial biomass and soil organic matter quantities were the main factors influencing the net nitrogen mineralization and nitrification rates, indicating that a similar mechanism creating the spatial variations of nitrogen-cycling processes in surface soil layer predominantly regulates the processes in subsoil layers. Moreover, it was estimated that the net nitrogen mineralization rate could be comparable at all soil types and depths when the rate was expressed per unit soil volume. Therefore, our results suggest that subsoil layers are a quantitatively important nitrogen source for plant nutrients in Andosols and Cambisols, supporting high forest productivity.

Individual exposure dose assessment of residents for lifting of evacuation orders (Contract research)

Sato, Rina; Sanada, Yukihisa; Yoshimura, Kazuya; Nakayama, Mariko*

JAEA-Review 2022-055, 42 Pages, 2023/01

JAEA-Review-2022-055.pdf:1.31MB

The evacuation order zones established after the accident at the Tokyo Electric Power Company's Fukushima Daiichi Nuclear Power Station have been reorganized according to the decrease in ambient dose equivalent rates and the decontamination progress. It has been decided to decontaminate the difficult-to-return zones and lift the evacuation order depending on the evacuee's intention of returning to the areas over the course of the 2020s. In order to consider the future of individual exposure dose assessment for residents for lifting of the evacuation orders, the methods and characteristics of the assessment that have been conducted after the accident using personal dosimeter measurements and simulations were systematically reviewed. This report summarized the results of the review.

Soil microbial community responding to moderately elevated nitrogen deposition in a Japanese cool temperate forest surrounded by fertilized grasslands

Nagano, Hirohiko; Nakayama, Masataka*; Katata, Genki*; Fukushima, Keitaro*; Yamaguchi, Takashi*; Watanabe, Makoto*; Kondo, Toshiaki*; Atarashi-Andoh, Mariko; Kubota, Tomohiro*; Tateno, Ryunosuke*; et al.

Soil Science and Plant Nutrition, 67(5), p.606 - 616, 2021/10

https://doi.org/10.1080/00380768.2021.1974799

We analyzed the relationships between nitrogen deposition (deposition of nitrate and ammonium ions) and soil microbial properties in a cool temperate forest surrounded by normally fertilized pasture grasslands in northern Japan. The aim of the present study was to gain the primary information on soil microbial response to moderately elevated nitrogen deposition ( 10 kg N ha y). We established three experimental plots in the forest edge adjacent to grasslands and other three plots in the forest interior at least 700 m away from the grasslands. During May to November 2018, nitrogen deposition in each plot was measured. In August 2018, litter and soil (0-5 cm depth) samples were collected from all plots to measure net nitrogen mineralization and nitrification rates as indicators of microbial activity, and microbial biomass carbon and nitrogen and various gene abundances (i.e. bacterial 16S rRNA, fungal ITS, bacterial amoA, and archaeal amoA genes) as indicators of microbial abundance and structure. Nitrogen deposition in the forest edge was 1.4-fold greater than that in the forest interior, even while the maximum deposition was 3.7 kg N ha. Nitrogen deposition was significantly correlated to the net nitrogen mineralization and nitrification rates and the 16S rRNA and bacterial amoA gene abundances. Microbial community structures were different between litter and soil samples but were similar between the forest edge and interior. Significant correlations of nitrogen deposition to the soil carbon to nitrogen ratio, and the nitrate and ammonium contents were also observed. Thus, our results show that moderately elevated nitrogen deposition in nitrogen-limited forest edges can stimulate microbial activities and abundances in soils.

Collection of measurement data from in-situ experiment for performance confirmation of engineered barrier system at Horonobe Underground Research Laboratory (FY2015)

Nakayama, Masashi; Ono, Hirokazu; Nakayama, Mariko*; Kobayashi, Masato*

JAEA-Data/Code 2016-005, 55 Pages, 2016/07

JAEA-Data-Code-2016-005.pdf:11.32MB
JAEA-Data-Code-2016-005-appendix(CD-ROM).zip:32.68MB

The Horonobe URL Project has being pursued by JAEA to enhance the reliability of relevant disposal technologies through investigations of the deep geological environment within the host sedimentary formation at Horonobe, northern Hokkaido. The Project consists of two major research areas, "Geoscientific Research" and "Research and Development on Geological Disposal Technologies", and proceeds in three overlapping phases, "Phase I: Surface-based investigations", "Phase II: Investigations during tunnel excavation" and "Phase III: Investigations in the underground facilities". Phase III investigation was started in 2010 fiscal year. The in-situ experiment for performance confirmation of engineered barrier system (EBS experiment) had been prepared from 2013 to 2014 fiscal year at GL-350m gallery, and heating by electric heater in simulated overpack had started in January, 2015. One of objectives of the experiment is acquiring data concerned with Thermal-Hydrological-Mechanical-Chemical (THMC) coupled behavior. These data will be used in order to confirm the performance of engineered barrier system. This report summarizes the measurement data acquired from the EBS experiment from December, 2014 to March, 2016.

Unraveling the pathogenic species in the plastisphere in aquatic ecosystems

Battulga, B.*; Nakayama, Masataka*; Atarashi-Andoh, Mariko; Koarashi, Jun

no journal, , 

Soil CO release increase and microbial community sift under dry-wet cycles; Comparison of surface soils and buried humus layers

Suzuki, Yuri*; Nagano, Hirohiko*; Suzuki, Kazuki*; Hiradate, Shuntaro*; Koarashi, Jun; Atarashi-Andoh, Mariko; Abe, Yukiko; Nakayama, Masataka*

no journal, , 

Study on long-term integrity assessment for engineered barriers; Overview of testing plan in under-ground research laboratory

Nakayama, Mariko*; Kobayashi, Masato*; Kawakubo, Masahiro*; Suzuki, Kei*; Eto, Jiro*; Nakayama, Masashi; Ono, Hirokazu; Asano, Hidekazu*

no journal, , 

no abstracts in English

Estimating the source of carbon for increase in soil CO release due to dry-wet cycles using surface and buried soils

Suzuki, Yuri*; Hiradate, Shuntaro*; Koarashi, Jun; Atarashi-Andoh, Mariko; Nakayama, Masataka*; Suzuki, Kazuki*; Abe, Yukiko; Nagano, Hirohiko*

no journal, , 

no abstracts in English

Increase in soil CO emission and change in soil microbial community structure due to drying and wetting cycles

Suzuki, Yuri*; Nagano, Hirohiko*; Suzuki, Kazuki*; Hiradate, Shuntaro*; Koarashi, Jun; Atarashi-Andoh, Mariko; Abe, Yukiko; Nakayama, Masataka*

no journal, , 

no abstracts in English