Dynamics of 15N natural abundance in wood-decomposing fungi and their ecophysiological implications

Nine species of basidiomycota and one species of ascomycota were grown in an ammonium sulphate media and on beech wood; and the general (15)N dynamic patterns of the hyphae were examined. The fungal body initially became depleted in (15)N in both the types of incubation. However, the underlying mechanisms were quite different, that is, significant fungal (15)N drop on the beech wood is associated with the fungal N reallocation and the uptake of atmospheric ammonia and/or NO(x), in addition to isotope fractionation during assimilation. Although the (15)N values of the wood-decomposing basidiocarps were generally close to the (15)N values of the wood, it does not always indicate that the wood derived N was the sole N source for the fungi throughout the growth periods as shown in our wood-decomposing experiment.     

Investigation of growth responses in saprophytic fungi to charred biomass

We present the results of a study testing the response of two saprophytic white-rot fungi species, Pleurotus pulmonarius and Coriolus versicolor, to charred biomass (charcoal) as a growth substrate. We used a combination of optical microscopy, scanning electron microscopy, elemental abundance measurements, and isotope ratio mass spectrometry (¹³C and ¹⁵N) to investigate fungal colonisation of control and incubated samples of Scots Pine (Pinus sylvestris) wood, and charcoal from the same species produced at 300 °C and 400 °C. Both species of fungi colonise the surface and interior of wood and charcoals over time periods of less than 70 days; however, distinctly different growth forms are evident between the exterior and interior of the charcoal substrate, with hyphal penetration concentrated along lines of structural weakness. Although the fungi were able to degrade and metabolise the pine wood, charcoal does not form a readily available source of fungal nutrients at least for these species under the conditions used in this study.     

Nickel coated on beech wood by electroless nickel coating: effects of complexing agent concentrations on nickel film properties

In order to obtain beech wood substrates with new functions as conductive materials and to develop their utilities in industrial fields, the technique of electroless nickel coating on the beech wood substrate was employed. The influence of complexing agent concentration [Na₂EDTA·2H₂O] on the nickel surface resistivity was studied. The process conditions were Ni(CH₃COO)₂·4H₂O 0.103?mol/L, CH₃CHOCOOH 18.18?mL/L, N₂H₅OH 54.54?mL/L, NaOH 0.193?mol/L, pH value of 9.5, temperature of 75?°C, and the complexing agent concentration varied between 0.012 and 0.061?mol/L. By means of XRD, EDXRF, and SEM, the chemical composition and morphology of the prepared films were investigated. The results showed that when the complexing agent concentration increased from 0.012 to 0.061?mol/L in the electroless nickel coating baths, the gained nickel mass on the beech wood substrate decreased from 17.04 to 9.03?mg/cm², the nickel crystallite sizes reduced from 16.1 to 1.41?nm and the electric measurements demonstrated that the nickel surface resistivity rose from 0.004 to 192.16?kΩ/cm².     

Nitrogen Isotope Ratios in Different Compartments of a Mixed Stand of Spruce,Larch and Beech Trees and of Understorey Vegetation Including Fungi

Abstract

Natural nitrogen isotope ratios were measured in different compartments (needles or leaves and twigs of different age classes and crown positions, roots and soil of different horizons) of spruce (Picea abies), larch (Larix decidua) and beech (Fagus sylvatica) trees in an 11-year-old mixed stand in the Fichtelgebirge, NE Bavaria, Germany. In addition, samples of understorey vegetation (mainly ericaceous shrubs and grass) and of ectomycorrhizal and saprophytic fungi were analyzed. The δ¹⁵N values found for all samples ranged between ?7.5 and + 4.5‰. No significant differences were found for the nitrogen isotope ratios of the three tree species despite of their evergreen versus deciduous foliage and despite of their different rooting depth. Ericaceous shrubs had the most negative and fungi and soil from the mineral horizon the most positive δ¹⁵N values. Positive δ¹⁵N values of the fungi indicate their ability to utilize organic soil nitrogen, but the data do not unequivocally show that plants forming mycorrhizas profit from this organic nitrogen source.     

Effects of surface inactivation, high temperature drying and preservative treatment on surface roughness and colour of alder and beech wood

Although extensive research has been conducted in wood surface quality analysis, a unified approach to surface quality characterisation does not exist. Measurements of the variation in surface roughness and surface colour are used widely for the evaluation of wood surface quality. Colour is a basic visual feature for wood and wood-based products. Colour measurement is one of the quality control tests that should be carried out because the colour deviations are spotted easily by the consumers. On the other hand, a common problem faced by plywood manufacturers is panel delamination, for which a major cause is poor quality glue-bonds resulting from rough veneer. Rotary cut veneers with dimensions of 500 mm × 500 mm × 2 mm manufactured from alder (Alnus glutinosa subsp. barbata) and beech (Fagus orientalis Lipsky) logs were used as materials in this study. Veneer sheets were oven-dried in a veneer dryer at 110 °C (normal drying temperature) and 180 °C (high drying temperature) after peeling process. The surfaces of some veneers were then exposed at indoor laboratory conditions to obtain inactive wood surfaces for glue bonds, and some veneers were treated with borax, boric acid and ammonium acetate solutions. After these treatments, surface roughness and colour measurements were made on veneer surfaces. High temperature drying process caused a darkening on the surfaces of alder and beech veneers. Total colour change value (ΔE^*) increased linear with increasing exposure time. Among the treatment solutions, ammonium acetate caused the biggest colour change while treatment with borax caused the lowest changes in ΔE^* values. Considerable changes in surface roughness after preservative treatment did not occur on veneer surfaces. Generally, no clear changes were obtained or the values mean roughness profile (R_a) decreased slightly in R_a values after the natural inactivation process.     

Natural abundances of 15N and 13C in leaves of some N2-fixing and non-N2-fixing trees and shrubs in Syria

A survey study was conducted on man-made plantations located at two different areas in the arid region of Syria to determine the variations in natural abundances of the ¹⁵N and ¹³C isotopes in leaves of several woody legume and non-legume species, and to better understand the consequence of such variations on nitrogen fixation and carbon assimilation. In the first study area (non-saline soil), the δ¹⁵N values in four legume species (Acacia cyanophylla,?1.73 ‰ Acacia farnesiana,?0.55 ‰ Prosopis juliflora,?1.64 ‰; and Medicago arborea,+1.6 \textperthousand) and one actinorhizal plant (Elaeagnus angustifolia,?0.46 to?2.1 ‰) were found to be close to that of the atmospheric value pointing to a major contribution of N₂ fixing in these species; whereas, δ¹⁵N values of the non-fixing plant species were highly positive. δ¹³C ‰; in leaves of the C3 plants were found to be affected by plant species, ranging from a minimum of?28.67 ‰; to a maximum of?23 ‰. However, they were relatively similar within each plant species although they were grown at different sites. In the second study area (salt affected soil), a higher carbon discrimination value (Δ¹³C ‰) was exhibited by P. juliflora, indicating that the latter is a salt tolerant species; however, its δ¹⁵N was highly positive (+7.03 ‰) suggesting a negligible contribution of the fixed N₂. Hence, it was concluded that the enhancement of N₂ fixation might be achieved by selection of salt-tolerant Rhizobium strains.     

15N natural abundance of non-fixing woody species in the Brazilian dry forest (caatinga)

Foliar δ¹⁵N values are useful to calculate N₂ fixation and N losses from ecosystems. However, a definite pattern among vegetation types is not recognised and few data are available for semi-arid areas. We sampled four sites in the Brazilian caatinga, along a water availability gradient. Sites with lower annual rainfall (700 mm) but more uniform distribution (six months) had δ¹⁵N values of 9.4 and 10.1 ‰, among the highest already reported, and significantly greater than those (6.5 and 6.3 ‰) of sites with higher rainfall (800 mm) but less uniform distribution (three months). There were no significant differences at each site among species or between non-fixing legume and non-legume species, in spite of the higher N content of the first group. Therefore, they constitute ideal reference plants in estimations of legume N₂ fixation. The higher values could result from higher losses of ¹⁵N depleted gases or lower losses of enriched ¹⁵N material.     

Heterogeneous fixation of N2: Investigation of a novel mechanism for formation of NO

Formation of NO initiated by heterogeneous fixation of N₂ during pyrolysis is investigated experimentally and theoretically. The experiments were conducted with beech wood as well as with the pure biomass components cellulose, xylan, and lignin. The NO formation during char oxidation was recorded as function of pyrolysis atmosphere (N₂ or Ar), pyrolysis temperature (700–1050 °C), and oxidizing atmosphere (O₂ in N₂ or Ar). The results confirm earlier reports that biomass char may be enriched in N during pyrolysis at 900 °C and above. The N-uptake involves re-capture of N-volatiles as well as uptake of N₂. During char oxidation, the captured N is partly oxidized to NO, resulting in increased NO formation. The NO yield from oxidation of beech wood char made in N₂ increases with pyrolysis temperature, and is about a factor of two higher at 1050 °C than the corresponding yield from chars made in Ar. The experiments with pure materials show that the lignin char has the strongest ability to form NO from uptake of N₂, while xylan char forms only small amounts of NO from N₂. Density Functional Theory (DFT) calculations on model chars have revealed a number of chemisorption sites for N₂, many of which are weakly bound and therefore expected to have a short half-life at the higher pyrolysis temperatures. However, the chemisorption of N₂ across a single ring of the armchair surface was found to have an activation energy of 344 ± 30 kJ mol⁻¹ and form a stable, exothermic product with cyano groups. This demonstrates that at least one channel exists for the high-temperature incorporation of N₂ into a char which could give rise to the observed increase in NO release in subsequent char oxidation.     

Magnitudes and Orientations of the N Chemical Shift Tensor of [1-N]-2′-Deoxyguanosine Determined on a Polycrystalline Sample by Two-Dimensional Solid-State NMR Spectroscopy

The magnitudes and orientations of the ¹⁵N chemical shift tensor of [1-¹⁵N]-2′-deoxyguanosine were determined from a polycrystalline sample using the two-dimensional PISEMA experiment. The magnitudes of the principal values of the ¹⁵N chemical shift tensor of the N1 nitrogen of [1-¹⁵N]-2′-deoxyguanosine were found to be ς₁₁ = 54 ppm, ς₂₂ = 148 ppm, and ς₃₃ = 201 ppm with respect to (¹⁵NH₄)₂SO₄ in aqueous solution. Comparisons of experimental and simulated two-dimensional powder pattern spectra show that ς_33N is approximately collinear with the N–H bond. The tensor orientation of ς_33N for N1 of [1-¹⁵N]-2′-deoxyguanosine is similar to the values obtained for the side chain residues of ¹⁵N_ε1-tryptophan and ¹⁵N_π-histidine even though the magnitudes differ significantly.     

Nitrogen isotope pattern in Mongolian larch stands at the southern Eurasian boreal forest boundary

ABSTRACT

In the last decades a drastic increase in air temperature but a stable precipitation regime in Mongolia has led to gradual drying conditions. Thus, we evaluated the effect of spatial and climatic characteristics on the soil–plant nitrogen dynamics in three representative larch stands (Larix sibirica) with different geographical and climatic conditions using stable nitrogen isotopes. The results showed significant differences in the soil inorganic N content among sites and consequently a different isotopic composition in the plant–soil system. Litter, bark and wood had the lowest δ¹⁵N values for all sites, slightly higher δ¹⁵N values for needles, while the highest δ¹⁵N values were observed for roots and soil. These differences could be the result of the larch stands age themselves, but were in agreement with the spatial and climatic characteristics of the sites. Based on the δ¹⁵N value a higher reliance on ectomycorrhizal fungi (ECMF) was observed in the warmest and driest site, while lower dependency was shown in the cooler northern site with higher soil inorganic N content. In both sites, the rate of air temperature increase has been similar in the last decades; however, their soil–plant N dynamics showed different characteristics.     

氮化钽团簇阴离子Ta3N3-解离吸附N2中的15N/14N同位素交换研究

氮气分子的吸附和活化是固氮研究中的重要过程. 近年来过渡金属氮化物由于在合成氨催化研究中的优异表现而受到广泛关注. 但是,氮化物物种与氮气分子在高温下反应的微观机制仍然不清楚,而该过程对于认识反应中的温度效应以及缩小气相团簇体系和凝聚相体系间的差距具有重要意义. 本文使用质谱观测到氮化钽团簇阴离子Ta₃¹⁴N₃^-和¹⁵N₂在高温下(393∽593 K)发生¹⁵N/¹⁴N同位素交换而产生¹⁴N₂/¹⁵N¹⁴N. 结合理论计算,阐述了同位素交换反应的微观机理以及升高温度对于N₂在Ta₃N₃^-上解离吸附的促进作用. 而在对比实验体系Ta₃¹⁴N₄^-/¹⁵N₂中,观察到升高温度只能加速¹⁵N₂在吸附产物Ta₃¹⁴N₄¹⁵N₂^-上的脱附. 这是由于氮空位是氮化物物种活化氮气的必要条件,而Ta₃N₄^-中由于不存在氮空位因此不能活化和解离氮气. 该研究为合成氨中氮化物物种中氮空位的作用提供了重要信息并且为固氮研究中高效催化剂的设计提供了线索.     

Experimental plant for simultaneous production of 14N and 15N by 15N/14N exchange in NO,NO2–HNO3 system under pressure

An experimental study on ¹⁴N and ¹⁵N simultaneous separation using the chemical exchange in NO, NO₂–HNO₃ system under pressure is presented. The influence of the pressure and of the interstage 10 M HNO₃ flow rate on the separation of ¹⁴N and ¹⁵N was measured on a packed column with product and waste refluxers. At steady state and 1.8 atm (absolute), the isotopic concentration at the bottom of the separation column was 0.563 at% ¹⁵N, and in the top of the column was 0.159 at% ¹⁵N. The height equivalent to a theoretical plate and interstage 10 M HNO₃ flow rate values, obtained in these experimental conditions, allows the separation of ¹⁴N highly depleted of ¹⁵N and of ¹⁵N at 99 at% ¹⁵N concentration.     

Tree species of the central amazon and soil moisture alter stable isotope composition of nitrogen and oxygen in nitrous oxide evolved from soil

The use of stable isotopes of N and O in N₂O has been proposed as a way to better constrain the global budget of atmospheric N₂O and to better understand the relative contributions of the main microbial processes (nitrification and denitrification) responsible for N₂O formation in soil. This study compared the isotopic composition of N₂O emitted from soils under different tree species in the Brazilian Amazon. We also compared the effect of tree species with that of soil moisture, as we expected the latter to be the main factor regulating the proportion of nitrifier- and denitrifier-derived N₂O and, consequently, isotopic signatures of N₂O. Tree species significantly affected δ ¹⁵N in nitrous oxide. However, there was no evidence that the observed variation in δ ¹⁵N in N₂O was determined by varying proportions of nitrifier- vs. denitrifier-derived N₂O. We submit that the large variation in δ ¹⁵N-N₂O is the result of competition between denitrifying and immobilizing microorganisms for NO 3 m . In addition to altering δ ¹⁵N-N₂O, tree species affected net rates of N₂O emission from soil in laboratory incubations. These results suggest that tree species contribute to the large isotopic variation in N₂O observed in a range tropical forest soils. We found that soil water affects both ¹⁵N and ¹⁸O in N₂O, with wetter soils leading to more depleted N₂O in both ¹⁵N and ¹⁸O. This is likely caused by a shift in biological processes for ¹⁵N and possible direct exchange of ¹⁸O between H₂O and N₂O.     

A Dual 13C and 15N Long Term Labelling Technique to Investigate Uptake and Translocation of C and N in Beech (Fagus sylvatica L.)

Abstract

A continuous dual ¹³CO₂ and ¹⁵NH₄ ¹⁵NO₃ labelling experimental set-up is presented that was used to investigate the C and N uptake and allocation within 3-year old beech (Fagus sylvatica L.) during one growing season. The C and N allocation pattern was determined after six, twelve and eighteen weeks of growth. The carbon uptake was distinctly different in the three phases examined: The first six weeks after budbreak were dedicated to leaf growth with a R/S (root to shoot) ratio of 0.14 for the new carbon. The second growth phase showed a balanced R/S ratio of C allocation and after week 13, the root compartment was the main carbon sink (R/S = 6.97).

Nitrogen allocation was more basipetal as compared to carbon. In the second growth phase, R/S of N_new was 5.57 but fell to 3.54 for the third growth phase probably due to formation of reserves in buds and stem.     

Using the natural 15N abundance to assess the main nitrogen inputs into the sand dune area of the North-Western Negev desert (ISRAEL)

The variation of the natural ¹⁵N abundance is often used to evaluate the origin of nitrogen or the pathways of N input into ecosystems. We tried to use this approach to assess the main input pathways of nitrogen into the sand dune area of the north-western Negev Desert (Israel). The following two pathways are the main sources for nitrogen input into the system:

1. Biological fixation of atmospheric nitrogen by cyanobacteria present in biological crusts and by N₂-fixing vascular plants (e.g. the shrub Retama raetam);

2. Atmospheric input of nitrogen by wet deposition with rainfall, dry deposition of dust containing N compounds, and gaseous deposition.

Samples were taken from selected environmental compartments such as biological crusts, sand underneath these crusts (down to a depth of 90?cm), N₂-fixing and non-N₂-fixing plants, atmospheric bulk deposition as well as soil from arable land north of the sandy area in three field campaigns in March 1998, 1999 and 2000. The δ¹⁵N values measured were in the following ranges: grass ?2.5‰ to +1.5‰; R. reatam: +0.5‰ to +4.5‰; non-N₂-fixing shrubs +1‰ to +7‰; sand beneath the biological crusts +4‰ to +20‰ (soil depth 2–90?cm); and arable land to the north up to 10‰. Thus, the natural ¹⁵N abundance of the different N pools varies significantly. Accordingly, it should be feasible to assess different input pathways from the various ¹⁵N abundances of nitrogen. For example, the biological N fixation rates of the Fabaceae shrub R. reatam from the ¹⁵N abundances measured were calculated to be 46–86% of biomass N derived from the atmosphere. The biological crusts themselves generally show slight negative ¹⁵N values (?3‰ to ?0.5‰), which can be explained by biological N fixation. However, areas with a high share of lichens, which are unable to fix atmospheric nitrogen, show very negative values down to ?10‰. The atmospheric N bulk deposition, which amounts to 1.9–3.8?kg?N/ha?yr, has a ¹⁵N abundance between 4.4‰ and 11.6‰ and is likely to be caused by dust from the arable land to the north. Thus, it cannot be responsible for the very negative values of lichens measured either. There must be an additional N input from the atmosphere with negative δ¹⁵N values, e.g. gaseous N forms (NO _x , NH₃). To explain these conflicting findings, detailed information is still needed on the wet, particulate and gaseous atmospheric deposition of nitrogen.     

Heat capacity of Bio-SiC and SiC/Si ecoceramics prepared from white eucalyptus, beech, and sapele tree wood

This paper reports on measurement of the heat capacity at constant pressure C _p of silicon bio-carbide prepared within the 5–300 K temperature interval from beech tree wood (bio-SiC(BE)), and within 80–300 K, from tree wood of sapele (bio-SiC(SA)), as well as SiC/Si ecoceramics of beech, sapele, and white eucalyptus wood. It has been shown that in bio-SiC(BE) the measured heat capacity contains a significant contribution of surface heat capacity, whose magnitude decreases with increasing temperature. Of the ecoceramics, only SiC/Si(SA) characterized by a high enough porosity has revealed a small contribution to the heat capacity coming from its surface component. The experimental results obtained are discussed.     

Split-root labelling to investigate 15N rhizodeposition by Pinus sylvestris and Picea abies*

We investigated the transfer of ¹⁵N into the soil via ¹⁵N uptake and release by tree roots, which involves the principles of the split-root technique. One half of the root system received an injection of (¹⁵NH₄)₂SO₄ and the other half equivalent amounts of (NH₄)₂SO₄ at ¹⁵N natural abundance level. ¹⁵N was transferred from one side of the root system (¹⁵N side) to the other side (¹⁴N side) and released into the soil. The method was conducted with Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies [L.] Karst). Two concentration levels of (NH₄)₂SO₄ were used, corresponding with annual N deposition in the Netherlands (30 kg N ha^–1) and a twelfth of that (2.5 kg N ha^?1). Samples were taken 3 and 6 weeks after labelling and divided into needles?+?stem, roots, rhizosphere and bulk soil. Already 3 weeks after labelling, Scots pine took up 23.7?% of the low and 9.1?% of the high amounts of ¹⁵N, while Norway spruce took up 21.5 and 32.1?%, respectively. Both species transported proportions of ¹⁵N to the rhizosphere (0.1–0.2?%) and bulk soil (0.3–0.9?%). The method is a useful tool to investigate the fate of root-derived N in soils, for example, for the formation of stable forms of soil organic matter.     

Assessing the subsequent effect of nitrogen released from tobacco-waste on maize crop using a 15N isotope technique

The investigation of the residual effect of nitrogen (N) released from tobacco-waste (TW) using isotope techniques will provide valuable data for sustainable organic farming. For this aim, a pot experiment was conducted using the ¹⁵N isotope technique. The experiment was based on a completely randomised design with four replications and was conducted on a calcareous ustochrepts soil. TW at levels of 0, 10, 20, 30 and 40 t ha^?1 and N fertiliser as (NH₄)₂SO₄ at levels of 0, 20, 40, 60 and 80 kg N ha^?1 were used for the Bezostaja-1 wheat variety. Concerning mineral N fertilisation with 20 and 80 kg N ha^?1, additional treatments with ¹⁵N-labelled (NH₄)₂SO₂ (10 at.% exc.) have been applied. Following harvesting wheat plants, the Pioneer 3377 maize variety was used to see the residual effect of TW. After harvesting, dry matter yields were recorded and total N concentrations were determined. ¹⁵N determinations and calculations were also made for ¹⁵N treatments separately. TW had a significant residual effect on the growth of corn plant under the pot condition. Increasing rates of TW significantly increased the dry matter yield of corn plant following wheat from 3.31 t ha^?1 (at control) to 7.89 t ha^?1 (at the TW treatment of 40 t ha^?1). The ¹⁵N values derived from the ¹⁵N fertiliser decreased with increasing TW application. The average values of N derived from N fertiliser (Ndff) varied from 2.14 to 3.09% at the rates of 20 and 80 kg N ha^?1, respectively. However, N derived from TW (Ndftw) significantly increased from 16.93 to 24.59% (at 20 kg N ha^?1), and it also increased from 23.06 to 28.15% (at 80 kg N ha^?1) with increasing TW applications from 20 to 40 t ha^?1, respectively.     

Equilibrating of 15N-Gases by Electrodeless Discharge: A Method of Indirect Mass Spectrometric Analysis of 30N2 for Denitrification Studies in Soils

Abstract

The estimation of denitrification in soil by the ¹⁵N tracer technique includes isotope analysis of gas samples with a nonrandom distribution of the N₂ mole masses of 28, 29 and 30. In that case the emission of total ¹⁵N is underestimated by calculating ¹⁵N atom fractions from the ²⁹N₂/²⁸N₂ ratio if ³⁰N₂ is not considered. ³⁰N₂ can be measured indirectly in N₂ enriched with ¹⁵N with nonrandom distribution of mole masses by mass spectrometric analysis. The nitrogen fraction of gas samples was transferred to discharge tubes. Microwaves (60 sec) generated an electrodeless discharge of the gas which caused a temporary split-up of N₂ molecules and thus established an equilibrium distribution of the mole masses. The ²⁹N₂/²⁸N₂ ratio was measured in equilibrated and in untreated samples to calculate the real emission of ¹⁵N. The measurements of ¹⁵N standard gases by this method satisfactorily coincided with calculated values for ¹⁵N atom fraction above a concentration of 50 δ‰.