Isotopic Composition of Carbon in Humus Acids of Albic Retisols and Luvic Chernozems

Eurasian Soil Science - Carbon isotope ratios in soil organic matter are often used in paleoecological research for reconstructing climate and plant communities (type of photosynthesis). The...     

Biological activity of alpine mountain-meadow soils in the Teberda Reserve

The intensity of the actual and potential CO₂ emissions, nitrogen fixation, denitrification, and methane production were determined by gas chromatography in alpine mountain-meadow soils under different types of phytocenoses at the Teberda State Reserve. The main factors that control the intensity of these processes in the mountain-meadow soils are moisture and accumulation of biophilous elements related to the position of the soils on the biogeochemical catena. The CO₂ emission and intensity of the nitrogen fixation in the soils under Geranium-Hedysarum meadows that occupy transit-accumulative positions were 2–3 times higher that these parameters in the soils under the alpine heathlands and Festuca meadows. The soils under the carpet-like alpine meadows, accumulating moisture and mineral nitrogen, were characterized by the highest intensity of denitrification and methane production.     

Can P NMR spectroscopy be used to indicate the origins of soil organic phosphates?

The relationship between organic P status of 4 soils, 20 microorganisms isolated from these soils (2 bacteria and 3 fungi for each soil) and 13 dominant plant species of typical natural ecosystems of these soils was evaluated. The soils used were represented by two pairs with different ratios of monoester and diester P, and of DNA and other diester P. A Dystric Podzoluvisol and an alpine Umbric Leptosol were characterized by a relatively high proportion of diester P including much DNA P, while a Calcic Chernozem and subalpine Umbric Leptosol had lower proportion of diesters containing relatively less DNA P. The proportions of P compounds in bacteria and plants were very similar on average, based on the monoester to diester P ratio and on the proportions of different diesters in alkaline extract, whereas fungi contained considerably higher proportions of monoesters and polyphosphates, and a higher proportion of phospholipids in the diester fraction. The results showed that the P_org composition of NaOH extracts from different soils was more similar to the composition of extracts from different groups of microorganisms. There was no clear correspondence between soil and microbial diester P proportion and composition. A high proportion of polyphosphate P including pyrophosphate P in soil extracts indicates a significant contribution of fungal P compounds in the soil while the monoester to diester P ratio, and DNA to non-DNA P ratio should be used with caution to interpret the origins of soil P_org. The relative contributions of microorganisms and plants to monoester and diester P in soils is only partially understood.     

Efficient near-infrared polymer nanocrystal light-emitting diodes

Conjugated polymers and indium arsenide-based nanocrystals were used to create near-infrared plastic light-emitting diodes. Emission was tunable from 1 to 1.3 micrometers--a range that effectively covers the short-wavelength telecommunications band--by means of the quantum confinement effects in the nanocrystals. The external efficiency value (photons out divided by electrons in) is approximately 0.5% (that is, >1% internal) and is mainly limited by device architecture. The near-infrared emission did not overlap the charge-induced absorption bands of the polymer.     

Comparative analysis of baking qualities of grain of winter rye varieties with various short-stem types

A comparative assessment of winter rye varieties with recessive polygenic and dominant monogenic short-stem types was carried out with respect to processing and baking qualities. It is shown that dominant short-stem varieties are significantly inferior to varieties with a recessive type in grain test weight, starch content, volume yield of pan bread, crumb porosity, and staling rate, but are significantly superior to them in water extract viscosity and form ratio of hearth bread. Differences are found in the content of amylose and amylopectin, their effect on the baking properties of rye grain is shown. The importance of creating low-amylose rye varieties with a better baking quality is pointed out.     

The nature and origins of diester phosphates in soils: a 31P-NMR study

Soils of two climosequences in Russia were investigated by ³¹P-NMR spectroscopy. They comprised Dystric Podzoluvisols, Haplic Greyzems, Calcic Chernozems, and Gypsic Kastanozems, which are located along temperature and precipitation gradients of the Russian Plain. Another sequence of soils included forest Humic Cambisols and Umbric Leptosols of subalpine and alpine meadows, which are formed in different climatic conditions along a climosequence of the Mt. Malaya Khatipara (northern Caucasus). The results showed that accumulation of DNA was high in the cold, wet, and acid soils (Dystric Podzoluvisol, alpine Umbric Leptosol), while phospholipids and teichoic acids mainly accumulated in the more microbially active soils. We performed a laboratory incubation experiment to test the relationship between microbial biomass P and P species identified in soil extracts. The proportions of P compounds resonating at 0.5-3.0 ppm in the NaHCO₃ and H₂SO₄ extracts from the incubated Humic Cambisol increased. The amounts of phosphate diesters resonating at 0 ppm in the same extracts and in the subsequent NaOH extracts decreased after incubation. Based on the results of ³¹P-NMR spectroscopy of native soils and of the laboratory incubation experiment we concluded that signals at 0 ppm in spectra of soil alkaline extracts belong to DNA P which is mainly stabilised in soil organic matter outside microbial cells (at least in soils with relatively low microbial activity). Phospholipids-teichoic acids P extracted with 0.5 M NaHCO₃ seems to be derived from soil microbial biomass, and its proportion can reflect the microbial activity in the soil.     

Effect of K2SO4 concentration on extractability and isotope signature (δ13C and δ15N) of soil C and N fractions

Determination of the labile soil carbon (C) and nitrogen (N) fractions and measurement of their isotopic signatures (δ¹³C and δ¹⁵N) has been used widely for characterizing soil C and N transformations. However, methodological questions and comparison of results of different authors have not been fully solved. We studied concentrations and δ¹³C and δ¹⁵N of salt‐extractable organic carbon (SEOC), inorganic (N–NH₄⁺ and N–NO₃^?) and organic nitrogen (SEON) and salt‐extractable microbial C (SEMC) and N (SEMN) in 0.05 and 0.5 m K₂SO₄ extracts from a range of soils in Russia. Despite differences in acidity, organic matter and N content and C and N availability in the studied soils, we found consistent patterns of effects of K₂SO₄ concentration on C and N extractability. Organic C and N were extracted 1.6–5.5 times more effectively with 0.5 m K₂SO₄ than with 0.05 m K₂SO₄. Extra SEOC extractability with greater K₂SO₄ concentrations did not depend on soil properties within a wide range of pH and organic matter concentrations, but the effect was more pronounced in the most acidic and organic‐rich mountain Umbrisols. Extractable microbial C was not affected by K₂SO₄ concentrations, while SEMN was greater when extracted with 0.5 m K₂SO₄. We demonstrate that the δ¹³C and δ¹⁵N values of extractable non‐microbial and microbial C and N are not affected by K₂SO₄ concentrations, but use of a small concentration of extract (0.05 m K₂SO₄) gives more consistent isotopic results than a larger concentration (0.5 m ).     

Combinatorics and Soil Classification

Eurasian Soil Science - Experimental data on 1029 soil profiles examined in the area of the Chashnikovo Experimental and Training Soil-Ecological Center of Moscow State University in Moscow region...