Nitrogen cycling in an Antarctic ecosystem. 1. Biological nitrogen fixation in the vicinity of Syowa Station

As part of the studies of the nitrogen flows in the Antarctic terrestrial ecosystems, nitrogen-fixing activities of moss communities, algae and lichens, collected in various ice-free areas near Syowa Station, East Antarctica, were measured by the acetylene reduction method. Moss communities which grew on the sand at dry habitats had dense cover of cyanobacteria and showed high nitrogen-fixing activities, while those at wet habitats near streams showed weak or no activity. Folious colonies of Nostoc sp. Showed significant activities. Some colonies of Chlorophyceae Prasiola crispa had weak activities which were probably due to associating cyanobacteria. No activity was detected for lichen species tested. The results suggest that nitrogen fixation by cyanobacteria, especially those epiphytic on mosses, plays an important role in the nitrogen budgets of terrestrial ecosystems developed in dry ice-free areas near Syowa Station

Synthesis of Guaiacylglycerol-β-Coniferyl and β-Coniferyl Aldehyde Ethers

この論文は国立情報学研究所の学術雑誌公開支援事業により電子化されました。A new synthetic method for the preparation of guaiacylglycerol-β-coniferyl and β-coniferyl aldehyde ethers, representing the most important lignin substructure are described as one in a series of synthetic studies of lignin model compounds

セルロースの還元性未端基の反応性 I : フェニルセルロシドの調製

As the first step in a project to synthesize cellulose derivatives with highly regioselelective functionality, we planned to introduce a specific functional group into only the reducing-end group of a cellulose derivative. Glycosylation reactions, which are specific for the hemiacetal hydroxyl group, were carried out using cellulose triacetate (CTA) as the starting material and phenol, a simple and easily identifiable compound, as the aglycon. CTA was reacted with phenol in the presence of boron trifluoride etherate to obtain phenyl peracetyl celluloside (PPAC), which contains the phenyl group in only the reducing-end group, in high yield. Based on the molecular weight of the product, calculated both from viscosity and from the absorbance at 274 nm, it was concluded that under these reaction conditions a certain degree of depolymerization also occurs. However, it is clear that a phenyl group was introduced into each new reducing-end group formed by the cleavage of a glycosidic bond. Thus, the reaction proceeding under these conditions is a sort of henolysis of CTA. The present method offers one means to introduce a specific functional group into only the reducing-end group of CTAセルロースの高位置選抗的置換誘導体の合成研究の一環として, まずセルロースの還元性未端基のみにある特定の官能基を導入することを計画した。出発物質としてセルローストリアセテー卜 (CTA), アグリコンとして最も簡単で, 同定しやすいフェノールを用いて, ヘミアセタール性水酸基に特異的であるグリコシル化反応を試みた。三フッ化ホウ素エーテル錯塩の存在下, CTAとフェノールを反応させたところ, フェノールがCTAの還元性未端基のみに導入されたフェニルパーアセチルセルロシド (PPAC) が高収率で得られた。生成物の溶液粘度および274nmの吸光度から求めた分子量から, この反応条件下ではある程度の解重合が進行するが, グリコシド結合が切断した後に新たに生成した還元性未端基には必らずフェノールが導入されることが判明した。すなわち, この反応は一種のCTAのフェノール分解であり, 本法はCTAの還元性未端基のみにある特定の官能基を導入するための一つの手段を提供するものと考えられる

Relationships between vegetation types and soil properties along a topographical gradient on the northern coast of the Brgger Peninsula, Svalbard

Vegetation patterns in the high Arctic vary not only with proglacial chronosequence but also with a topographical gradient on older deglaciated areas which are covered by mature vegetation. A preliminary survey of local scale vegetation patterns along a topographical gradient with special reference to soil properties was conducted on the northern coast of the Brgger Peninsula, Svalbard in the high Arctic. Three community types of vascular plants were distinguished by common dominants: Cardamine type, Salix type and Oxyria/Luzula type. Each community type was comprised of different habitat types. The Cardamine type was restricted to near the bottom of depressions, where there was high soil water content. The Oxyria/Luzula type was characterized by habitats belonging to upper slopes to ridges, having high gravel content soils. On the other hand, the habitat preference of the Salix type, which had higher vegetation cover and biomass of vascular plants compared to the other two types, was not clear. The core habitat of fertile/undisturbed area, as described by the centrifugal community organization model, might be dominated by Salix polaris in this area. The other species had a refugium from interspecific competition in their preferred peripheral habitats such as exposed ridge or wetland

Estimating SPAD value, chlorophyll and mineral components using hyperspectral data of maize leaves

Background: Visible-infrared hyperspectral data have been widely used recently in remote sensing for nondestructive crop-quality estimation in the field. The authors applied hyperspectral remote sensing to the field of feed maize to investigate the estimation of feed contents of the whole maize plant (including leaves, stems, and grains) from the hyperspectral data of maize community. Methods: In this study, as a preliminary step to the estimation of feed contents, we attempted to estimate the SPAD value, chlorophyll (a, b and a+b), and mineral components (T-N, T-P, and T-K) contained in leaves from the hyperspectral data (390-983 nm, 60 bands) of maize leaves. Results and discussions: Regarding the estimation method, we compared the estimation accuracy of two kinds of partial least squares regression (PLSR) using either all bands (60 bands) or only selected ones as explanatory variables. When all bands were used as explanatory variables, estimation was possible with accuracy that is sufficient for practical use for all parameters except chlorophyll b, phosphorus (T-P) and potassium (T-K) (R2 = 0.82-0.90, El = 19.7-24.5, El Rank= B). When waveband selection was conducted, it was judged that all parameters except phosphorus (T-P) and potassium (T-K) can be estimated with accuracy that is sufficient for practical use (R2 = 0.78-0.91, El = 19.6-21.7, El Rank= B). Based on the relation between measured values and estimated ones in verification, it was judged that actual estimation was possible for three parameters: the SPAD value, chlorophyll a+b and nitrogen (T-N). Conclusion: The results described above demonstrate that the SPAD value related to the greenness (depth of green color) of the leaf blade, chlorophyll a+b and nitrogen (T-N) can be estimated by applying PLSR, or PLSR with band selection, to hyperspectral data of maize leaves

Deciphering Japanese Early Childhood Education and Care from the Viewpoint of the Reggio Emilia Approach: Focusing on Young Children’s Subjectivity and Teachers’ Involvement

The purpose of this study is to decipher the characteristics of Japanese Early Childhood Education and Care (ECEC) from the viewpoint of Reggio Emilia in terms of young children’s subjectivity and teachers’ involvement. Specifically, I will discuss the characteristics of Japanese ECEC and the Reggio Emilia Approach relative to the children’s subjectivity and teachers’ involvement and examine their similarities. In doing this, I aim to decipher the characteristics of Japanese ECEC from the viewpoint of the Reggio Emilia Approach. As the results of this study made clear, the Reggio Emilia Approach and Japanese ECEC have similarities, in terms of how the curricula support children’s subjectivity and the suppression of teachers’ interventions. In addition, it was clear that Japanese ECEC emphasizes not only positive emotional experiences but also the negative emotional experiences of children

The methane flux along topographical gradients on a glacier foreland in the High Arctic, Ny-Alesund, Svalbard

In order to examine the relationship between the methane (CH_4) flux and soil factors and vegetation in High Arctic tundra, we investigated the CH_4 flux along topographical gradients on a glacier foreland in Ny-Alesund, Svalbard (79°N, 12°E). The CH4 flux rates varied widely among sites even within the same vegetation type, ranging from positive (emission) to negative (absorption) values. High CH_4 emission rates were detected on ridges and in sites with a low soil water content, but there was no significant relationship between CH_4 flux rates and soil factors including soil moisture, pH, soil carbon and nitrogen content. Mean values of CH_4 emission and CH_4 absorption were 0.30±0.33 mg m^(-2) h^(-1) (n=12) and 0.11±0.06 mg m^(-2) h^(-1) (n=11), respectively. These findings suggest that the study area is a small source of CH_4 with a mean flux of 0.11 mg CH_4 m^(-2) h^(-1) (0.083 mg C m^(-2) h^(-1)). It was concluded that carbon flux derived from CH_4 accounts for an extremely small proportion of the total carbon flux from soil in this area

Characterization of soil microflora on a successional glacier foreland in the high Arctic on Ellesmere Island, Nunavut, Canada using phospholipid fatty acid analysis

We investigated soil microbial biomass and community structure along a primary successional gradient after deglaciation in the high Arctic, at Ellesmere Island, Nunavut, Canada(80°50\u27N, 82°45\u27W). Soil samples were collected from five glacial moraines(M1 to M5) with different developmental periods. Time since the recession of glaciers at M1, M3, and M5 was estimated to be 300, 9000, and over 17000 years, respectively. Soil samples from five points in each moraine were subjected to phospholipid fatty acid(PLFA) analysis. Total PLFA content(an index of microbial biomass) in M1 was significantly lower than those in older moraines(M2-M5), whereas the content remained at an almost constant level from M2 to M5. Significant differences in PLFA composition(an index of microbial community structure) were also observed between M1 and older moraines(M2-M5); the proportion of straight chain saturated fatty acids in M1 was higher than those in older moraines(M2-M5), whereas those of branched fatty acids and unsaturated fatty acids in M1 were lower than those in older moraines(M2-M5). These results suggest that changes of microflora occurred in the early phase of succession after deglaciation and became stable thereafter. Microbial biomass had a positive correlation with soil carbon and nitrogen contents over the successional chronosequence, suggesting that development of soil microflora was affected in part by organic matter accumulation