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The central question of this paper is what kind of view Dōgen had about Mazu. At first glance, this may seem completely irrelevant to the theme of this issue. In fact, however, Dōgen’s view points to a subtle relationship between Buddhism and Hinduism in an interesting way. Dōgen seems to regard Mazu as an ambiguous figure, standing on the borderline between Buddhism and Hinduism. However, Dōgen’s intention was to save Mazu and keep him on the side of Buddhism. So how can Mazu be saved? To answer this question is to trace the fundamental boundary between Buddhism and Hinduism according to the outstanding Zen master. In this study we adopt the usual method of textual analysis. Our discussion proceeds in the following order. (The steps do not correspond exactly to the section breaks.) (1) First, the argument of a person called Senni is presented from Dōgen’s Bendōwa, where Dōgen severely criticizes him as a non-Buddhist heresy. At this step we will confirm that Senni is a Sāṅkhya theorist (hence, a Hinduist). (2) We take up a parallel to the above passage from Dōgen’s Shōbōgenzō, Chapter “Sokushinzebutsu”. It becomes clear that the true target of Dōgen’s criticism was Mazu, the great Chinese Chan master. (3) The above operation shows that Dōgen was trying to position Mazu as someone on the borderline between Hinduism and Buddhism. (4) We try to reconstruct from the text what in Senni angered Dōgen, or, in other words, from what he wanted to save Mazu. As a result, the borderline as seen by Dōgen will be visible to us. The main findings of this paper are as follows: (1) The mark that distinguishes Buddhism from Hinduism, according to Dōgen, is the presence of the never-ending Bodhi-mind. This is in fact what TSUNODA Tairyū suggested in his 1985 article. Dōgen implemented this idea as an endless loop of Bodhi-mind, which makes the goal unreachable. (2) The implicit object of Dōgen’s criticism is not the Japanese Tendai or the Darumashū, but Mazu, as HE Yansheng indicated in his 2000 book. The so-called Critical Buddhism movement began on the basis of a misunderstanding. The large amount of secondary literature that has resulted is also indirectly based on this error.

Shrinking pupal cocoons of Rhyacophila lezeyi were often found during summer in Shibukuro Stream, a highly acidic mountain stream in northern Japan (pH = 2.82 on average). We performed both field surveys and laboratory rearing experiments to clarify the mechanisms of R. lezeyi cocoon shrinkage. The R. lezeyi cocoon shrinkage proportion increased in years with high stream water temperatures and was related to water temperatures before and after pupation at the study site. Approximately 90% of the prepupae and pupae inside the shrinking cocoons died during the rearing experiment, implying that cocoon shrinkage caused by high water temperature strongly influenced R. lezeyi pupal survival. Laboratory experiments showed that R. lezeyi ’s pupal cocoon membranes were semi-permeable and that the cocoon fluids were always hyperosmotic, indicating that water molecules can continuously enter the cocoon fluids from the stream water until the turgor of the cocoon wall is reached. However, the shrinking cocoons showed lower fluid volume and higher osmolarity than the normal turgescent cocoons. The reduction of osmotic gradient across the membrane during decreased stream flow due to less precipitation and/or the damage to the cocoon membrane and pupal body from high and fluctuating water temperatures and low pH are possible mechanisms for R. lezeyi pupal cocoon shrinkage.

Isotopomer ratios of N2O (bulk nitrogen and oxygen isotope ratios, δ15Nbulk and δ18O, and intramolecular 15N site preference, SP) are useful parameters that characterize sources of this greenhouse gas and also provide insight into production and consumption mechanisms. We measured isotopomer ratios of N2O emitted from typical Japanese agricultural soils (Fluvisols and Andisols) planted with rice, wheat, soybean, and vegetables, and treated with synthetic (urea or ammonium) and organic (poultry manure) fertilizers. The results were analyzed using a previously reported isotopomeric N2O signature produced by nitrifying/denitrifying bacteria and a characteristic relationship between δ15Nbulk and SP during N2O reduction by denitrifying bacteria. Relative contributions from nitrification (hydroxylamine oxidation) and denitrification (nitrite reduction) to gross N2O production deduced from the analysis depended on soil type and fertilizer. The contribution from nitrification was relatively high (40%–70%) in Andisols amended with synthetic ammonium fertilizer, while denitrification was dominant (50%–90%) in the same soils amended with poultry manure during the period when N2O production occurred in the surface layer. This information on production processes is in accordance with that obtained from flux/concentration analysis of N2O and soil inorganic nitrogen. However, isotopomer analysis further revealed that partial reduction of N2O was pronounced in high‐bulk density, alluvial soil (Fluvisol) compared to low‐bulk density, volcanic ash soil (Andisol), and that the observed difference in N2O flux between normal and pelleted manure could have resulted from a similar mechanism with different rates of gross production and gross consumption. The isotopomeric analysis is based on data from pure culture bacteria and would be improved by further studies on in situ biological processes in soils including those by fungi. When flux/concentration‐weighted average isotopomer ratios of N2O from various fertilized soils were examined, linear correlations were found between δ15Nbulk and δ18O, and between SP and δ15Nbulk. These relationships would be useful to parameterize isotopomer ratios of soil‐emitted N2O for the modeling of the global N2O isotopomer budget. The results obtained in this study and those from previous firn/ice core studies confirm that the principal source of anthropogenic N2O is fertilized soils.

Sulfur-based denitrification may be a key biogeochemical nitrate (NO 3 − ) removal process in sulfide-rich regions, but it is still poorly understood in natural terrestrial ecosystems. We examined sulfur-driven NO 3 − reduction using streambank soils in a headwater catchment underlain by marine sedimentary rock in Akita, Japan. In a catchment exhibiting higher sulfide content in streambed sediment, we sampled two adjacent streambank soils of streambank I (two layers) and of streambank II (eight layers). Anaerobic long-term incubation experiments (40 days, using soils of streambank I) and short-term incubation experiments (5 days, using soils of streambank II) were conducted to evaluate variations of N solutes (NO 3 − , NO 2 − , and NH 4 + ), N gases (NO, N 2 O), and the bacterial flora. In both experiments, two treatment solutions containing NO 3 − (N treatment), and NO 3 − and S 2 O 3 2− (N + S treatment) were prepared. In the N + S treatment of the long-term experiment, NO 3 − concentrations gradually decreased by 98%, with increases in the SO 4 2− , NO 2 − , NO, and N 2 O concentrations and with not increase in the NH 4 + , indicating denitrification had occurred with a high probability. Temporal accumulation of NO 2 − was observed in the N + S treatment. The stoichiometric ratio of SO 4 2− production and NO 3 − depletion rates indicated that denitrification using reduced sulfur occurred even without additional S, indicating inherent S also served as an electron donor for denitrification. In the short-term incubation experiment, S addition was significantly decreased NO 3 − concentrations and increased NO 2 − , NO, and N 2 O concentrations, especially in some subsoils with higher sulfide contents. Many denitrifying sulfur-oxidizing bacteria ( Thiobacillus denitrificans and Sulfuricella denitrificans ) were detected in both streambank I and II, which dominated up to 5% of the entire microbial population, suggesting that these bacteria are widespread in sulfide-rich soil layers in the catchment. We concluded that the catchment with abundant sulfides in the subsoil possessed the potential for sulfur-driven NO 3 − reduction, which could widely influence N cycling in and NO 3 − export from the headwater catchment.

Succinate is a core biochemical building block; optimizing succinate production from biomass by microbial fermentation is a focus of basic and applied biotechnology research. Lowering pH in anaerobic succinate fermentation culture is a cost-effective and environmentally friendly approach to reducing the use of sub-raw materials such as alkali, which are needed for neutralization. To evaluate the potential of bacteria-based succinate fermentation under weak acidic (pH <6.2) and anaerobic conditions, we characterized the anaerobic metabolism of Enterobacter aerogenes AJ110637, which rapidly assimilates glucose at pH 5.0. Based on the profile of anaerobic products, we constructed single-gene knockout mutants to eliminate the main anaerobic metabolic pathways involved in NADH re-oxidation. These single-gene knockout studies showed that the ethanol synthesis pathway serves as the dominant NADH re-oxidation pathway in this organism. To generate a metabolically engineered strain for succinate production, we eliminated ethanol formation and introduced a heterogeneous carboxylation enzyme, yielding E. aerogenes strain ΔadhE/PCK. The strain produced succinate from glucose with a 60.5 % yield (grams of succinate produced per gram of glucose consumed) at pH <6.2 and anaerobic conditions. Thus, we showed the potential of bacteria-based succinate fermentation under weak acidic conditions.

This data paper provides some biogeochemical nitrogen (N) properties and related chemical properties of forest soils from 39 sites throughout the Japanese archipelago. The data set was collected and analyzed under the GRENE (Green Network of Excellence) environmental information project and the ReSIN (Regional and comparative Soil Incubation study on Nitrogen dynamics in forest ecosystems) project. The sites cover 44°20′N to 26°50′N and the climate ranges from cool-temperate zone to subtropical zone. At each site, litter on forest floor and soil samples (three or four layers to 50 cm depth) were collected between August and November in 2010–2013 from five soil profiles. From the litter layer samples, the stocks and concentrations of total carbon (C) and N were measured. From the mineral soil samples, bulk density, pH (H 2 O), total C and N concentrations, net and gross rates of N mineralization, nitrification and concentrations of water-soluble substances were measured. The measurements are relevant for other biogeochemical N studies in forest ecosystems and the data set provides basic information on the N pool and fluxes with related chemical properties of forest soils across the Japanese archipelago. The average rates of net and gross N transformation at 20 °C across the sites were 0.26 ± 0.47 mgN kg −1 soil d −1 for net N mineralization, 0.25 ± 0.45 mgN kg −1 soil d −1 for net nitrification, 4.06 ± 0.47 mgN kg −1 soil d −1 for gross N mineralization, and 1.03 ± 1.29 mgN kg −1 soil d −1 for gross nitrification (average ± SD).

The spatial variability of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) fluxes from forest soil with high nitrogen (N) deposition was investigated at a rolling hill region in Japan. Gas fluxes were measured on July 25th and December 5th, 2008 at 100 points within a 100 × 100 m grid. Slope direction and position influenced soil characteristics and site-specific emissions were found. The CO2 flux showed no topological difference in July, but was significantly lower in December for north-slope with coniferous trees. Spatial dependency of CH4 fluxes was stronger than that of CO2 or N2O and showed a significantly higher uptake in hill top, and emissions in the valley indicating strong influence of water status. N2O fluxes showed no spatial dependency and exhibited high hot spots at different topology in July and December. The high N deposition led to high N2O fluxes and emphasized the spatial variability.

The 2011 Tohoku tsunami had a serious impact, such as an increase in harmful substances and salinity over a large area. Herein, we evaluated transitions in bacterial communities in agricultural fields in the four years after the 2011 Tohoku tsunami. Bacterial communities were compared across four different types of soil—unflooded field (UF) soil, soil flooded for a short term (ST), soil flooded for the long term (LT), soil flooded long term and cultivated fields (LTC), and marine environmental materials (bay sediment, sea sand and sea water), using a polymerase chain reaction (PCR) and pyrosequencing of 16S ribosomal RNA genes. In the soil bacterial communities that were flooded by the 2011 Tohoku tsunami, these effects were not seen after 2013. Although the difference in bacterial communities between LT and UF became smaller during the four years, the bacterial communities in LT were different from those in UF in several ways, such as a higher tendency frequency of sulfur-oxidizing bacteria (SOB) and the presence of halotolerant SOB. Therefore, it is thought that the Tohoku tsunami affected the microbial communities in the soil for more than four years. Especially genus Halothiobacillus, which is Halotolerant SOB in flooded soils, was detected neither in unflooded soil nor in the marine environment. Therefore, it is thought that inundation by a tsunami produces a unique environment with bacterial communities to form in soil. Further, SOB structure, especially halotolerant, might serve as a good indicators of the impacts of inundation on bacterial communities in agricultural fields over the long term.

It is difficult to investigate the factors that control the riverine nitrate-nitrogen (NO 3 − -N) export in a watershed which gains or losses groundwater. To control the NO 3 − -N contamination in these watersheds, it is necessary to investigate the factors that are related to the export of NO 3 − -N that is only produced by the watershed itself. This study was conducted in the Shibetsu watershed located in eastern Hokkaido, Japan, which gains external groundwater contribution (EXT) and 34 % of the annual NO 3 − -N loading occurs through EXT. The riverine NO 3 − -N exports from 1980 to 2009 were simulated by the SWAT model, and the factors controlling the temporal and spatial patterns of NO 3 − -N exports were investigated without considering the EXT. The results show that hydrological events control NO 3 − -N export at the seasonal scale, while the hydrological and biogeochemical processes are likely to control NO 3 − -N export at the annual scale. There was an integrated effect among the land use, topography, and soil type related to denitrification process, that regulated the spatial patterns of NO 3 − -N export. The spatial distribution of NO 3 − -N export from hydrologic response units (HRUs) identified the agricultural areas with surplus N that are vulnerable to nitrate contamination. A new standard for the N fertilizer application rate including manure application should be given to control riverine NO 3 − -N export. This study demonstrates that applying the SWAT model is an appropriate method to determine the temporal and spatial patterns of NO 3 − -N export from the watershed which includes EXT and to identify the crucial pollution areas within a watershed in which the management practices can be improved to more effectively control NO 3 − -N export to water bodies.