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Abstract: Increases in nitrogen (N) deposition and variation in precipitation have been occurring in temperate deserts; however, little information is available regarding plant phenological responses to environmental cues and their relationships with plant growth pattern in desert ecosystems. In this study, plant phenology and growth of six annuals in response to N and water addition were monitored throughout two consecutive growing seasons in 2011 and 2012 in a temperate desert in northwestern China. The effects of N and water addition on reproductive phenology differed among plant species. N and water addition consistently advanced the flowering onset time and fruiting time of four spring ephemerals; however, their effects on two spring‐summer annuals were inconsistent, with advances being noted in one species and delays in another. N and water addition alone increased plant height, relative growth rate, leaf number, flower number, and individual biomass, while their combinative effects on plant growth and reproductive phenology were dependent on species. Multiple regression analysis showed that flowering onset time was negatively correlated with relative growth rate of two species, and negatively correlated with maximum plant height of the other four species. Our study demonstrates that phenological responses to increasing precipitation and N deposition varied in annuals with different life histories, whereby the effects of climate change on plant growth rate were related to reproductive phenology. Desert annuals that were able to accelerate growth rate under increasing soil resource availability tended to advance their flowering onset time to escape drought later in the growing season. This study promotes our understanding of the responses of temperate desert annuals to increasing precipitation and N deposition in this desert. [ABSTRACT FROM AUTHOR]

Nutrient supplies to plants from ants are well known from specialised myrmecophytic symbioses and from plants growing in soil close to ant nests. However, above-ground nutrient pathways may play a largely unrecognised role also in less specialised ant-plant interactions-the numerous facultative relationships, where ants forage on plants., In a laboratory experiment, weaver ants ( Oecophylla smaragdina) were confined to the canopies of coffee ( Coffea arabica) seedlings, excluding any ant-to-plant transfer of nutrients via the soil strata. When ants were fed 15N-labelled glycine and subsequently deposited faecal droplets on the seedlings, coffee leaves showed increased levels of 15N and total nitrogen compared to control plants without ants. This was evident for both exposed leaves and leaves covered in plastic bags (i.e. not directly exposed to ants). Thus, nitrogen from ant excretions was absorbed through the coffee leaves, and subsequently, translocated within the plants and possibly leading to the observed higher shoot/root (wet weight) ratios observed on ant-plants compared to controls., Synthesis. These results reveal an undescribed foliar uptake of ant-provided nutrients. If this is a general mechanism, a vast amount of ant-plant interactions involves fertilisation. Foliar fertilisation by ants may be an important steady benefit to plants, which has driven the evolution of ant-plant mutualisms in parallel with the well-recognised but probably more fluctuating benefit from herbivore protection. Given the world-wide abundance of plant canopies foraged by ants, this nutrient pathway may be of high ecological significance. [ABSTRACT FROM AUTHOR]

We investigated photoinhibition on natural communities of ammonia oxidizing (AO) archaea (AOA) and bacteria (AOB) embedded in complex stream biofilms, and its implications on nitrogen uptake at biofilm scale. Based on the strong photoinhibition previously exhibited by free living and cultured AOA and AOB, we expected AO activity to decrease in biofilms experimentally exposed to light, reducing the contribution of microbial nitrification to ammonium uptake. To test it, we conducted light manipulation experiments in mesocosms using biofilms naturally developed on stream cobbles sides both exposed to light (light-side) and facing the sediment (dark-side). We observed a strong AO photoinhibition in dark-side biofilms, accompanied by either biofilm-scale decreases in nitrification or increases in nitrogen uptake likely by heterotrophic activity. Conversely, in light-side biofilms photoinhibition was not observed suggesting that photoautotrophic layers may protect AO in situ by a sunshade effect. Experimental light and dark alternation cycles stimulated AO, enhancing both nitrification and ammonium uptake. These results support photoinhibition effects on natural AO communities, especially in biofilms developed under ambient dark conditions, whereas this effect seems to be buffered in biofilms developed under light conditions. Therefore, the contribution of nitrification to ammonium uptake at biofilm scale should consider not only the physiological study of AOA and AOB, but also the environmental conditions and community structure at the habitat microscale, since they may counterbalance, among others, the damaging light effects under natural conditions. [ABSTRACT FROM AUTHOR]

Almost all models of plant resource limitation are grounded in either one or both of two simple conceptual models: Liebig's Minimum Hypothesis (LMH), the idea that plants are limited by the resource in shortest supply, and the Multiple Limitation Hypothesis (MLH), the idea that plants should adjust to their environment so that all essential resources are equally limiting. Despite the differences in their predictions, experiments have so far failed to discriminate between them. In a simple factorial nitrogen and water addition experiment in a Minnesota grassland, we observed shifts in allocation that, as in previous studies, are not all explained by a single theory. We found that leaf biomass responded positively to nitrogen additions but did not respond to water additions. We found that fine-root biomass increased in response to water additions, but only at low nitrogen levels, and that fine-root biomass decreased in response to nitrogen additions, but only at high water levels. To understand these responses we built a physiologically based model of plant competition for water, nitrogen, and space to predict plant allocation to fine roots and leaves. Critically, we include in our model the inherent variability of soil moisture and treat light, water, and nitrogen as resources with distinct mechanistic roles. Experimental results showed that plants were nitrogen and water limited. The model explains the experimental results, under conditions of co-limitation, as follows. Foliage increases with nitrogen additions but not water additions because leaf construction is constrained by nitrogen uptake. When water is added, plants spend a larger fraction of the growing season limited by light (and effectively nitrogen) than by water. Thus, water additions cause fine-root biomass to increase because of the increased importance of nitrogen limitation. The response of fine-root biomass to water additions decreases with nitrogen additions because these additions reduce nitrogen limitation. In general, our results are explained by sequential resource limitation. The rate of carbon assimilation may be limited by a single resource at any one moment, but the identity of the limiting resource(s) changes throughout the growing season. [ABSTRACT FROM AUTHOR]

Monodispersed mesoporous silica spheres ( MMSSs) with tunable particle size were successfully synthesized from tetraethyl orthosilicate ( TEOS) and cetyltrimethylammonium bromide ( CTAB) under an alkaline condition. The MMSSs synthesized under different reaction conditions, such as reaction temperature, co-solvent amount, and TEOS and CTAB concentrations, have been investigated by scanning electron microscopy ( SEM), transmission electron microscopy ( TEM), small angle X-ray diffraction ( SAXRD), and nitrogen adsorption-desorption. The average particle size increases with increase in the reaction temperature from 40°C to 90°C, and 80°C is the optimal temperature to synthesize MMSSs with narrow particle size of 75 ± 14 nm. Ethanol plays a role as co-surfactant in low concentration, and then as co-surfactant and co-solvent in high concentration, which results in an increase in particle size from 75 ± 14 nm to 518 ± 30 nm and change of the mesoporous structure from paralleled array type to radially orientated type. The average particle size and yield of MMSSs increase with increase in the TEOS concentration when the TEOS concentration reaches saturated level ( Cs = 0.09 M), but some small silica particles appear when the TEOS concentration is higher than the critical level ( Cs* = 0.134 M). When the CTAB concentration increases, at the same TEOS concentration, the surface area, and pore volume increases, but the monodispersity becomes low. [ABSTRACT FROM AUTHOR]

Surface energy of cerium oxide was measured by differential scanning calorimetry ( DSC). Nanocrystalline CeO2 samples were synthesized by a nonaqueous sol-gel method and their surface and interfacial areas were determined from nitrogen adsorption, X-ray diffraction, and electron microscopy measurements. Three samples were repeatedly heated in a differential scanning calorimeter and the excess enthalpy was obtained from the difference in DSC traces between first heating, during which coarsening occurred, and second heating. Surface enthalpy was calculated from excess enthalpy and from changes in surface and interfacial areas. The measured surface enthalpy for CeO2, 1.2 ± 0.2 J/m2, is consistent with values from oxide melt solution calorimetry on samples with different surface areas. This is the first successful measurement of surface energy using scanning calorimetry. [ABSTRACT FROM AUTHOR]

A green house experiment was designed to test the idea that competition for inorganic nitrogen (N) between plants and heterotrophic microorganisms occurs in soils with high C:N ratios, qualifying for N limited microbial activity, but not at low C:N ratios. The short-term (24 h) 15N uptake by the grass Festuca gigantea and microorganisms in planted and unplanted soils was determined, and the bacterial activity was measured by the 3H-thymidine incorporation technique. Two deciduous forest soils, with C:N-ratios of 20 and 31, and the 20 soil amended with litter to a C:N ratio of 34, were used. A novel and important part of the experimental design was the preparation of the unplanted reference soil with plants present until the competition assay started by the addition of 15N labelled ammonium ( ) or nitrate ). The results suggested that plants and soil microorganisms competed for mineral N but under influence of other factors than the soil C:N ratio. The plants reduced the microbial uptake of and in the soil with low C:N ratio, which also had the lowest bacterial activity. The plants had a larger N uptake than microorganisms in the two natural soils but smaller in the litter-amended, and their presence enhanced the bacterial activity, especially in the latter soil. The litter-amended soil with its high C:N ratio and easily decomposable C was the soil that best fulfilled the criteria for competition, including a net consumption of mineral N during the assay, the lowest plant uptake of mineral N due to the high N immobilization by microorganisms, and a reduced microbial 15N uptake-to-bacterial activity in the presence of plants. Thus, other factors, such as the decomposability of the soil C and the bacterial activity, were more important than the soil C:N ratio to the outcome of plant–microbial competition for N. [ABSTRACT FROM AUTHOR]

• Here, nitrogen (N) uptake and metabolism, and related gene expression, were analyzed in germinating spores of Glomus intraradices to examine the mechanisms and the regulation of N handling during presymbiotic growth. • The uptake and incorporation of organic and inorganic N sources into free amino acids were analyzed using stable and radioactive isotope labeling followed by high-performance liquid chromatography (HPLC), gas chromatography–mass spectrometry (GC-MS) and liquid scintillation counting and the fungal gene expression was measured by quantitative polymerase chain reaction (Q-PCR). • Quiescent spores store Asp, Ala and Arg and can use these internal N resources during germination. Although not required for presymbiotic growth, exogenous N can also be utilized for the de novo biosynthesis of amino acids. Ammonium and urea are more rapidly assimilated than nitrate and amino acids. Root exudates do not stimulate the uptake and utilization of exogenous ammonium, but the expression of genes encoding a putative glutamate dehydrogenase (GDH), a urease accessory protein (UAP) and an ornithine aminotransferase (OAT) were stimulated by root exudates. The transcript levels of an ammonium transporter (AMT) and a glutamine synthetase (GS) were not affected. • Germinating spores can make effective use of different N sources and the ability to synthesize amino acids does not limit presymbiotic growth of arbuscular mycorrhizal (AM) spores. [ABSTRACT FROM AUTHOR]

In waste materials, proximate analysis measuring the total concentration of carbohydrate, protein, and lipid contents from solid wastes is challenging, as a result of the heterogeneous and solid nature of wastes. This paper presents a new procedure that was developed to estimate such complex chemical composition of the waste using conventional practical measurements, such as chemical oxygen demand (COD) and total organic carbon. The procedure is based on mass balance of macronutrient elements (carbon, hydrogen, nitrogen, oxygen, and phosphorus [CHNOP]) (i.e., elemental continuity), in addition to the balance of COD and charge intensity that are applied in mathematical modeling of biological processes. Knowing the composition of such a complex substrate is crucial to study solid waste anaerobic degradation. The procedure was formulated to generate the detailed input required for the International Water Association (London, United Kingdom) Anaerobic Digestion Model number 1 (IWA-ADM1). The complex particulate composition estimated by the procedure was validated with several types of food wastes and animal manures. To make proximate analysis feasible for validation, the wastes were classified into 19 types to allow accurate extraction and proximate analysis. The estimated carbohydrates, proteins, lipids, and inerts concentrations were highly correlated to the proximate analysis; correlation coefficients were 0.94, 0.88, 0.99, and 0.96, respectively. For most of the wastes, carbohydrate was the highest fraction and was estimated accurately by the procedure over an extended range with high linearity. For wastes that are rich in protein and fiber, the procedure was even more consistent compared with the proximate analysis. The new procedure can be used for waste characterization in solid waste treatment design and optimization. [ABSTRACT FROM AUTHOR]

The phase domain of Ti3O5–Ti2O3–Ti(CO) at 1580 K was determined from the formation energies of Ti(C xO y), as calculated via the Gibbs–Duhem equation. An extensive Ti(CO) domain is attributed to the high affinity between TiC and TiO. The phase domain of Ti3O5–Ti2O3–Ti(CN) was obtained at 1673 K using the formation energies of Ti(C xN y). This study shows that the stable region for Ti2O3 is significantly small in the Ti3O5–Ti2O3–Ti(CN) phase domain. It demonstrates the absence of TiO and Ti2O3 in the normal syntheses of TiC and Ti(CN) from TiO2, respectively. [ABSTRACT FROM AUTHOR]

Despite their low primary production, ombrotrophic peatlands have a considerable potential to store atmospheric carbon as a result of their extremely low litter decomposition rates. Projected changes in temperature and nitrogen (N) deposition may increase decomposition rates by their positive effects on microbial activity and litter quality, which can be expected to result in enhanced mass loss and N release from Sphagnum and vascular plant litter. This is the first study that examines the combined effects of increased temperature and N deposition on decomposition in bogs. We investigated mass loss and N release at four bog sites along a gradient from north Sweden to northeast Germany in which both temperature and N deposition increased from north to south. We performed two litterbag experiments: one reciprocal experiment with Eriophorum vaginatum litter and one experiment using recalcitrant ( Sphagnum fuscum) and more degradable ( Sphagnum balticum) Sphagnum litter collected from the most northern site. We measured mass loss and N release during two ( Sphagnum) and three ( E. vaginatum) years. The N concentration and decomposability of the E. vaginatum litter did not differ between the sites. Mass loss from E. vaginatum litter increased over the gradient from north to south, but there was no such effect on Sphagnum litter. N loss of all litter types was affected by collection site, incubation site and time and all interactions between these factors. N release in Sphagnum was positively related to N concentration. We conclude that decomposition of vascular plants and Sphagnum litter is influenced by different environmental drivers, with enhanced temperatures stimulating mass loss of vascular plant litter, but not of Sphagnum. Enhanced N deposition increases Sphagnum litter N loss. As long-term consequences of climate change will presumably entail a higher vascular plant production, overall litter decomposition rates are likely to increase, especially in combination with increased temperature. [ABSTRACT FROM AUTHOR]

- None of the well-established nitrogen-related IR absorption bands, common in synthetic and terrestrial diamonds, have been identified in the presolar diamond spectra. In the carbonado diamond spectra, only the single nitrogen impurity (C center) is identified and the assignments of the rest of the nitrogen-related bands are still debated. It is speculated that the unidentified bands in the nitrogen absorption region are not induced by nitrogen, but rather by nitrogen-hydrides because in the interstellar environment, nitrogen reacts with hydrogen and forms NH+; NH; NH2; NH3. Among these hydrides, the electronic configuration of NH+ is the closest to carbon. Thus, this ionized nitrogen-mono-hydride is the best candidate to substitute carbon in the diamond structure. The bands of the substitutional NH+ defect are deduced by redshifting the irradiation-induced N+ bands due to the mass of the additional hydrogen. The six bands of the NH+ defects are identified in both the presolar and the carbonado diamond spectra. The new assignments identify all of the nitrogen-related bands in the spectra, indicating that presolar and carbonado diamonds contain only single nitrogen impurities. [ABSTRACT FROM AUTHOR]