Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Sato, Yuhi*; Ishizuka, Shigehiro*; Hiradate, Shuntaro*; Atarashi-Andoh, Mariko; Nagano, Hirohiko*; Koarashi, Jun
Environmental Research, 239(Part 1), p.117224_1 - 117224_9, 2023/12
Times Cited Count：0 Percentile：0(Environmental Sciences)The stability of soil organic matter (SOM) is important for improving our understanding of the global carbon cycle and ongoing climate change. This study examined the applicability of loss-on-ignition of soil with a stepwise increase in temperature (SIT-LOI) to evaluate the stability of the SOM using soil samples from Japan having different organic matter (OM) and mineral contents and different mean residence times (MRTs), estimated from radiocarbon analysis, for SOM. As the result of this examination, SIT-LOI data was strongly correlated with MRTs. This clearly suggests that SIT-LOI can be an indicator evaluating the stability of SOM in actual environments.
Katata, Genki*; Yamaguchi, Takashi*; Watanabe, Makoto*; Fukushima, Keitaro*; Nakayama, Masataka*; Nagano, Hirohiko*; Koarashi, Jun; Tateno, Ryunosuke*; Kubota, Tomohiro
Atmospheric Environment, 298, p.119640_1 - 119640_12, 2023/04
Times Cited Count：1 Percentile：58.15(Environmental Sciences)Nagano, Hirohiko*; Atarashi-Andoh, Mariko; Tanaka, Sota*; Yomogida, Takumi; Kozai, Naofumi; Koarashi, Jun
Frontiers in Forests and Global Change (Internet), 6, p.1228053_1 - 1228053_9, 2023/00
Times Cited Count：0 Percentile：0.01(Ecology)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
Times Cited Count：2 Percentile：19.73(Plant Sciences)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.
Unc, A.*; Altdorff, D.*; Abakumov, E.*; Adl, S.*; Baldursson, S.*; Bechtold, M.*; Cattani, D. J.*; Firbank, L. G.*; Grand, S.*; Gudjonsdottir, M.*; et al.
Frontiers in Sustainable Food Systems (Internet), 5, p.663448_1 - 663448_11, 2021/07
Times Cited Count：33 Percentile：94.29(Food Science & Technology)Agriculture in the boreal and Arctic regions is perceived as marginal, low intensity and inadequate to satisfy the needs of local communities, but another perspective is that northern agriculture has untapped potential to increase the local supply of food and even contribute to the global food system. Policies across northern jurisdictions target the expansion and intensification of agriculture, contextualized for the diverse social settings and market foci in the north. However, the rapid pace of climate change means that traditional methods of adapting cropping systems and developing infrastructure and regulations for this region cannot keep up with climate change impacts. Moreover, the anticipated conversion of northern cold-climate natural lands to agriculture risks a loss of up to 76% of the carbon stored in vegetation and soils, leading to further environmental impacts. The sustainable development of northern agriculture requires local solutions supported by locally relevant policies. There is an obvious need for the rapid development of a transdisciplinary, cross-jurisdictional, long-term knowledge development, and dissemination program to best serve food needs and an agricultural economy in the boreal and Arctic regions while minimizing the risks to global climate, northern ecosystems and communities.
Koarashi, Jun; Atarashi-Andoh, Mariko; Nagano, Hirohiko*; Sugiharto, U.*; Saengkorakot, C.*; Suzuki, Takashi; Kokubu, Yoko; Fujita, Natsuko; Kinoshita, Naoki; Nagai, Haruyasu; et al.
JAEA-Technology 2020-012, 53 Pages, 2020/10
JAEA-Technology-2020-012.pdf:3.71MB
There is growing concern that recent rapid changes in climate and environment could have a significant influence on carbon cycling in terrestrial ecosystems (especially forest ecosystems) and could consequently lead to a positive feedback for global warming. The magnitude and timing of this feedback remain highly uncertain largely due to a lack of quantitative understanding of the dynamics of organic carbon stored in soils and its responses to changes in climate and environment. The tracing of radiocarbon (natural and bomb-derived 
C) and stable carbon (
C) isotopes through terrestrial ecosystems can be a powerful tool for studying soil organic carbon (SOC) dynamics. The primary aim of this guide is to promote the use of isotope-based approaches to improve our understanding of the carbon cycling in soils, particularly in the Asian region. The guide covers practical methods of soil sampling; treatment and fractionation of soil samples; preparation of soil samples for C (and stable nitrogen isotope, 
N) and C analyses; and C, N, and C measurements by the use of isotope ratio mass spectrometry and accelerator mass spectrometry (AMS). The guide briefly introduces ways to report C data, which are frequently used for soil carbon cycling studies. The guide also reports results of a case study conducted in a Japanese forest ecosystem, as a practical application of the use of isotope-based approaches. This guide is mainly intended for researchers who are interested but are not experienced in this research field. The guide will hopefully encourage readers to participate in soil carbon cycling studies, including field works, laboratory experiments, isotope analyses, and discussions with great interest.
Nagano, Hirohiko; Atarashi-Andoh, Mariko; Koarashi, Jun
Soil Science and Plant Nutrition, 65(5), p.525 - 533, 2019/10
Times Cited Count：3 Percentile：17.68(Plant Sciences)In the present study, two volcanic ash soils (soil A and B) from a temperate broad-leaved forest in eastern Japan were incubated under repeated dry-wet cycles and continuously constant moisture conditions. The primary aims were to quantify the potential for enhancement of carbon dioxide (CO
) release owing to increased water fluctuation and to examine differences in the responses of volcanic ash soils with different physicochemical properties. Soil B, rather than soil A, was a typical Andosol. During incubation at 20 
C for 120 days with five dry-wet cycles, the CO release rate was measured periodically. Abundance of the stable carbon isotope in CO (
C-CO) was measured to capture changes in the origin of decomposed soil organic matter (SOM) owing to the dry-wet cycles. The CO release rate under the dry-wet cycles was up to 49% higher than the values predicted from a parabolic relationship between CO release and water content during incubation under the continuously constant moisture condition. The magnitude of CO release enhancement was 2.7-fold higher in soil B relative to that in soil A. The C-CO value in the dry-wet cycles was enriched by 0.3-2.3%
compared to that during incubation under the continuously constant moisture conditions, suggesting that the decomposition of old and/or well-metabolized SOM was enhanced by the dry-wet cycles. Thus, the present study suggests that Andosols, which have been believed to have a strong SOM stabilization ability, are vulnerable to dry-wet cycles. Then, increased water fluctuation in a future warmer world would have significant potential to stimulate CO release from soils.
Ueyama, Masahito*; Iwata, Hiroki*; Nagano, Hirohiko; Tahara, Narumi*; Iwama, Chie*; Harazono, Yoshinobu*
Agricultural and Forest Meteorology, 275, p.196 - 207, 2019/09
Times Cited Count：26 Percentile：90.21(Agronomy)Fire is the major disturbance in North American boreal forests, and is thought to be the most important process that determines the carbon balance in North American boreal forests. This study conducted four years of tower flux measurements in a burned ecosystem from one to four years after a fire, and nine years of measurements in a young regeneration from five to 13 years after a fire in interior Alaska. The fire scar acted as a source of 248 g C m
yr one year after the fire, and the annual CO emissions continuously decreased until seven years after the fire. At the final year of the study period, 13 years after the fire, the older forest became a CO sink. During the 13 years after the fires, the total post-fire emissions were 767 g C m across both sites. Gross primary productivity (GPP) and ecosystem respiration (RE) recovered to those of mature black spruce forests 10 years after the fire. The successional recovery of GPP was mostly explained by the recovery of the leaf area index (LAI). Anomalous weather, such as a cold spring, hot summer, and high summer rainfall, increased the CO emissions rather than the uptake. In interior Alaska, the post-fire CO emissions (35-48 Tg C) were estimated to be approximately one third to fourth of the direct CO emissions (156 Tg C) by combustions from 1998 to 2017, which indicates that post-fire emissions are important to the regional CO balance. The forest successional trajectory at young age still contains large uncertainties due to lack of data, and thus adding new data improves our understanding of the post-fire CO balance.
Nagano, Hirohiko; Kim, Y.*; Lee, B.-Y.*; Shigeta, Haruka*; Inubushi, Kazuyuki*
Soil Science and Plant Nutrition, 64(6), p.793 - 802, 2018/12
Times Cited Count：5 Percentile：26.98(Plant Sciences)In this study, we conducted an incubation experiment on a frozen soil core collected from a black spruce forest in Interior Alaska, in order to investigate potential changes in greenhouse gaseous (GHG) and microbial dynamics during thawing of frozen soil. The soil thawing is an important environmental process determining the annual GHG balance in the northern high-latitude ecosystem. A core spanning the ground surface to upper permafrost with a depth of 90 cm was vertically grouped into three layers (top, middle, and bottom layers). Then, 12 soil samples from 3 layers (i.e., 4 soil samples per layer) were incubated for 3 weeks, and net carbon dioxide (Co) and methane (CH
) release/uptake rates were estimated. During the incubation, temperature was changed weekly from 0 to 5, then 10C. The net amounts of CO released by six of the eight soil samples from the top and middle layers were 1.5 to 19.2-fold greater at 5C than at 0C, while the release at 10C was reduced in the cases of three of these six soil samples. Net CH release was the greatest in bottom-layer soil samples incubated at 0C. Then, low but apparent CH release was observed in top and middle-layer soil samples incubated at 0C. At 5 and 10C, net CH release from bottom-layer soil samples was decreased. Then, net CH uptake was observed in the top and the middle-layer soil samples. Both net uptake and release of CH were reduced upon the addition of a chemical inhibitor (i.e., 2-bromoethane sulfonate) of anaerobic methanotrophic and methanogenic activity. The bacterial and archaeal community structures based on 16S rRNA amplicon analysis were changed along the depth, while they were less changed during thawing. Thus, it was found that soil GHG dynamics responded sensitively and variously to thawing, while there was less change in 16S rRNA-based microbial community structures during the thawing prog
Kobayashi, Hideki*; Suzuki, Rikie*; Yang, W.*; Ikawa, Hiroki*; Inoue, Tomoharu*; Nagano, Hirohiko; Kim, Y.*
Polar Data Journal (Internet), 2, p.14 - 29, 2018/11
The Arctic and boreal regions have been experiencing a rapid warming in the 21st century. It is important to understand the dynamics of boreal forest at the continental scale under the climate and environmental changes. While the role of understory vegetation in boreal forest ecosystems on carbon and nutrient cycling cannot be ignored, they are still one of least understood components in boreal ecosystems. Spectroscopic measurements of vegetation are useful to identify species and their biochemical characteristics. In this data paper, we present spectral reflectances of 44 typical understory formations and five 30-m long transects. The spectral reflectance covers the spectral region of visible, near infrared and shortwave infrared (350-2500 nm). For the transect measurements, we decided the length of transect at 30 m, similar to the scale of one pixel of a Landsat type satellite imagery. The photographs at all positions, where spectral reflectances were obtained, are included to understand the structure and status of each sample. The data set contains six dwarf shrubs (blueberry (
), cowberry (
), feltleaf willow (
), young birch (
), young aspen (
), and young black spruce (
)), two herbaceous (cottongrass (
) and marsh Labrador tea (
)), three mosses (Sphagnum moss, splendid feather moss (
), and polytrichum moss (
)), and reindeer lichen (
). Spectral reflectances from several non-vegetative such as snow, litter, and soil are also included. This spectral and photographic data set can be used for understanding the spectral characteristics of understory formations, designing newly planned spectral observations, and developing and validating the remote sensing methodology of large scale understory monitoring.
Saito, Kazuyuki*; Iwahana, Go*; Ikawa, Hiroki*; Nagano, Hirohiko; Busey, R. C.*
Geoscientific Instrumentation, Methods and Data Systems, 7(3), p.223 - 234, 2018/07
Times Cited Count：2 Percentile：8.86(Geosciences, Multidisciplinary)A fibre-optic DTS (distributed temperature sensing) system using Raman-scattering optical time domain reflectometry was deployed to monitor a boreal forest research site in the interior of Alaska. Surface temperatures range between -40C in winter and 30C in summer at this site. In parallel experiments, a fibre-optic cable sensor system (multi-mode, GI50/125, dual core; 3.4mm), monitored at high resolution, (0.5m intervals at every 30min) ground surface temperatures across the landscape. In addition, a high-resolution vertical profile was acquired at one-metre height above the upper subsurface. The total cable ran 2.7km with about 2.0km monitoring a horizontal surface path. Sections of the cable sensor were deployed in vertical coil configurations (1.2m high) to measure temperature profiles from the ground up at 5mm intervals. Measurements were made continuously over a 2-year interval from October 2012 to October 2014. Vegetation at the site (Poker Flat Research Range) consists primarily of black spruce underlain by permafrost. Land cover types within the study area were classified into six descriptive categories: relict thermokarst lake, open moss, shrub, deciduous forest, sparse conifer forest, and dense conifer forest. The horizontal temperature data exhibited spatial and temporal changes within the observed diurnal and seasonal variations. Differences in snow pack evolution and insulation effects co-varied with the land cover types. The apparatus used to monitor vertical temperature profiles generated high-resolution (ca. 5mm) data for air column, snow cover, and ground surface. This research also identified several technical challenges in deploying and maintaining a DTS system under subarctic environments.
Kobayashi, Hideki*; Nagai, Shin*; Kim, Y.*; Yan, W.*; Ikeda, Kyoko*; Ikawa, Hiroki*; Nagano, Hirohiko; Suzuki, Rikie*
Remote Sensing, 10(7), p.1071_1 - 1071_19, 2018/07
Times Cited Count：13 Percentile：51.57(Environmental Sciences)Plant phenology timings, such as spring green-up and autumn senescence, are essential state information characterizing biological responses and terrestrial carbon cycles. Current efforts for the in situ reflectance measurements are not enough to obtain the exact interpretation of how seasonal spectral signature responds to phenological stages in boreal evergreen needleleaf forests. This study shows the first in situ continuous measurements of canopy scale (overstory + understory) and understory spectral reflectance and vegetation index in an open boreal forest in interior Alaska. Two visible and near infrared spectroradiometer systems were installed at the top of the observation tower and the forest understory, and spectral reflectance measurements were performed in 10 min intervals from early spring to late autumn. We found that canopy scale normalized difference vegetation index (NDVI) varied with the solar zenith angle. On the other hand, NDVI of understory plants was less sensitive to the solar zenith angle. Due to the influence of the solar geometry, the annual maximum canopy NDVI observed in the morning satellite overpass time (10-11 am) shifted to the spring direction compared with the standardized NDVI by the fixed solar zenith angle range (60-70 degree). We also found that the in situ NDVI time-series had a month-long high NDVI plateau in autumn, which was completely out of photosynthetically active periods when compared with eddy covariance net ecosystem exchange measurements. The result suggests that the onset of an autumn high NDVI plateau is likely to be the end of the growing season. In this way, our spectral measurements can serve as baseline information for the development and validation of satellite-based phenology algorithms in the northern high latitudes.
Kobayashi, Hideki*; Nagai, Shin*; Kim, Y.*; Nagano, Hirohiko; Ikeda, Kyoko*; Ikawa, Hiroki*
no journal, ,
In the Arctic and sub-Arctic regions, including Alaska, warming trends have been accelerating. It is particular important how the carbon uptake by terrestrial vegetation changes due to the phenological change under climate change. The spectral reflectance of black spruce, the dominant tree in interior Alaska, is relatively stable throughout the growing season, while satellite phenology metrics is likely influenced by understory plant phenology. However, how the spectral signatures are influenced by the forest overstory status, understory plant phenology and other factors is poorly investigated in Alaska. In this study, we investigated the overstory and understory seasonality in spectral reflectance observed in an black spruce forest in Interior Alaska from 2015 to 2017 to understand how the seasonality in spectral reflectances are related with changes in the surface conditions. We also examined the relationship between seasonality of overstory and understory and carbon and water fluxes.
Nagano, Hirohiko; Koarashi, Jun; Atarashi-Andoh, Mariko
no journal, ,
It is important to examine the relationship between the size of soil aggregates and the density and property of soil organic matter associating with aggregates, in order to understand the process of soil carbon stabilization. However, the relationship between aggregate size and soil organic matter characteristics varies depending on soils. Then, it is difficult to estimate the relationship without the aggregate fractionation. In this study, we investigated the relationship between aggregate size and carbon (C) and nitrogen (N) concentrations of aggregates for several soils collected from Japanese forests. In a soil collected from a forest of Miyazaki (phosphoric acid absorption coefficient was 14 g PO
/kg), both C and N concentrations were similar among different sizes of aggregates. In a soil from a forest of Hiroshima (phosphoric acid absorption coefficient 4 g PO/kg), C and N concentrations in micro-aggregates were two-hold higher than those in macro-aggregate. Although further evaluation using more forest soils is necessary, the dependence of the organic matter concentration on the aggregate size could be estimated from the phosphoric acid absorption coefficient.
Ueyama, Masahito*; Iwata, Hiroki*; Nagano, Hirohiko; Tahara, Narumi*; Harazono, Yoshinobu*
no journal, ,
no abstracts in English
Harazono, Yoshinobu*; Futakuchi, Yusuke*; Yoshikawa, Kota*; Iwata, Hiroki*; Ueyama, Masahito*; Nagano, Hirohiko; Sakabe, Ayaka*; Kosugi, Yoshiko*
no journal, ,
no abstracts in English
release from volcanic ash soilsNagano, Hirohiko; Atarashi-Andoh, Mariko; Koarashi, Jun
no journal, ,
no abstracts in English
Nagano, Hirohiko; Atarashi-Andoh, Mariko; Fukushima, Keitaro*; Nakayama, Masataka*; Katata, Genki*; Yamaguchi, Takashi*; Watanabe, Makoto*; Kondo, Toshiaki*; Tateno, Ryunosuke*; Koarashi, Jun
no journal, ,
no abstracts in English
Koarashi, Jun; Atarashi-Andoh, Mariko; Takagi, Kentaro*; Kondo, Toshiaki*; Teramoto, Munemasa*; Nagano, Hirohiko; Kokubu, Yoko; Takagi, Masahiro*; Ishida, Sachinobu*; Hiradate, Shuntaro*; et al.
no journal, ,
no abstracts in English
Atarashi-Andoh, Mariko; Koarashi, Jun; Takagi, Kentaro*; Kondo, Toshiaki*; Teramoto, Munemasa*; Nagano, Hirohiko; Kokubu, Yoko; Takagi, Masahiro*; Ishida, Sachinobu*; Liang, N.*
no journal, ,
no abstracts in English
