ALBERT

Description: Dual-phase oxygen transport membranes are fast-growing research interest for application in oxyfuel combustion process. One such potential candidate is CGO-FCO (60 wt% Ce 0.8 Gd 0.2 O 2−δ –40 wt% FeCo 2 O 4 ) identified to provide good oxygen permeation flux with substantial stability in harsh atmosphere. Dense CGO-FCO membranes of 1 mm thickness were fabricated by sintering dry pellets pressed from powders synthesized by one-pot method (modified Pechini process) at 1200°C for 10 h. Microstructure analysis indicates presence of a third orthorhombic perovskite phase in the sintered composite. It was also identified that the spinel phase tends to form an oxygen deficient phase at the grain boundary of spinel and CGO phases. Surface exchange limitation of the membranes was overcome by La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3−δ (LSCF) porous layer coating over the composite. The oxygen permeation flux of the CGO-FCO screen printed with a porous layer of 10 μm thick LSCF is 0.11 mL/cm 2 per minute at 850°C with argon as sweep and air as feed gas at the rates of 50 and 250 mL/min.

Description: Abstract Ba{[Gax,Tax]Ti(1−2x)}O3 ceramics with x equal to 0, 0.0025, 0.005, 0.01, 0.025, and 0.05 have been prepared by conventional solid‐state reaction. Structural and dielectric characterization have been performed to investigate the effect of dipole‐pair substitution concentration on the macroscopic dielectric properties. Ba{[Gax,Tax]Ti(1−2x)}O3 evolves from a classic ferroelectric to a diffuse phase transition (DPT) as x increases. Ba{[Gax,Tax]Ti(1−2x)}O3 for x ≥ 0.01 possesses diffuseness parameters comparable to Pb(Mg1/3Nb2/3)O3‐PbTiO3 (PMN‐PT) and recently reported (Ba0.97Pr0.03)(Ti0.9425Ce0.05)O3 (BPTC), yet it lacks the frequency and temperature dependence of Tm necessary to be a strictly defined relaxor ferroelectric. Additionally, Ba{[Ga0.05,Ta0.05]Ti0.9}O3 possesses a relative permittivity, ɛr, of 700 ± 16% and dissipation factor less than 0.05 at 10 kHz within the temperature range [−75°C, 120°C]. In comparison to BaTiO3, Ba{[Gax,Tax]Ti(1−2x)}O3 possesses enhanced electrical resistivity at and above room temperature. In situ XRD, including Rietveld refinement, have been performed to determine the lattice parameter, coefficient of thermal expansion, and phase transition temperature (Tc) of each composition within the temperature range [RT, 1000°C], thus linking the dielectric properties with the material's structure. These studies have been corroborated by temperature‐dependent Raman spectroscopy to compare the Tc determined by electrical and structural characterization. The properties of Ba{[Gax,Tax]Ti(1−2x)}O3 are discussed in context with available models that describe donor and acceptor dopants spatially separated in the parent matrix, inter‐relating lattice parameter, Curie temperature, and other material properties.

Description: Abstract Despite growing interest in incorporating intraspecific variation of functional traits in community‐level studies, it remains unclear whether species classified into functional groups based on interspecific trait differences are similar regarding their variation in trait expression in response to varying plant diversity and composition in local communities. In a large biodiversity experiment (Jena Experiment) designed on a trait‐based a priori definition of functional groups (grasses, legumes, small herbs, tall herbs), we studied means, extent of variation (coefficient of variation across communities) and plasticity to increased plant diversity (slopes over a logarithmic species richness ranging from 1, 2, 4, 8 and 16 to 60 species) for nine functional traits. Species means and extent of variation in traits related to nitrogen (N) acquisition and N use differed among functional groups and were more similar in phylogenetically closely related species than expected by chance. Species in the same functional group showed a weak phylogenetic signal and varied widely in means and extent of variation in traits related to shoot architecture and to a smaller extent in leaf traits related to carbon acquisition. This indicated that functional groups were less distinguishable in light than in nitrogen acquisition strategies. The direction and degree of trait plasticity to increasing species richness did not show a phylogenetic signal and were not different among functional groups, but varied largely among species within functional groups. Correlation structures in trait means, extent of trait variation and trait plasticity revealed functional tradeoffs in the acquisition of nitrogen and light across species. While correlations between trait means and extent of trait variation varied from trait to trait (positive, negative or unrelated), trait means and trait plasticity were mostly unrelated. Our results suggest that the concept of functional groups is viable, but context‐specific trait measurements are required to improve our understanding about the functional significance of intraspecific trait variation and interspecific trait differences in local plant communities.

Description: Impact of simulated marine heatwaves on foundation macrophytes in the Baltic Sea. Abstract Marine heatwaves have been observed worldwide and are expected to increase in both frequency and intensity due to climate change. Such events may cause ecosystem reconfigurations arising from species range contraction or redistribution, with ecological, economic and social implications. Macrophytes such as the brown seaweed Fucus vesiculosus and the seagrass Zostera marina are foundation species in many coastal ecosystems of the temperate northern hemisphere. Hence, their response to extreme events can potentially determine the fate of associated ecosystems. Macrophyte functioning is intimately linked to the maintenance of photosynthesis, growth and reproduction, and resistance against pathogens, epibionts and grazers. We investigated morphological, physiological, pathological and chemical defence responses of western Baltic Sea F. vesiculosus and Z. marina populations to simulated near‐natural marine heatwaves. Along with (a) the control, which constituted no heatwave but natural stochastic temperature variability (0HW), two treatments were applied: (b) two late‐spring heatwaves (June, July) followed by a summer heatwave (August; 3HW) and (c) a summer heatwave only (1HW). The 3HW treatment was applied to test whether preconditioning events can modulate the potential sensitivity to the summer heatwave. Despite the variety of responses measured in both species, only Z. marina growth was impaired by the accumulative heat stress imposed by the 3HW treatment. Photosynthetic rate, however, remained high after the last heatwave indicating potential for recovery. Only epibacterial abundance was significantly affected in F. vesiculosus. Hence both macrophytes, and in particular F. vesiculosus, seem to be fairly tolerant to short‐term marine heatwaves at least at the intensities applied in this experiment (up to 5°C above mean temperature over a period of 9 days). This may partly be due to the fact that F. vesiculosus grows in a highly variable environment, and may have a high phenotypic plasticity.

Description: In this study, we aim to gain a better insight on how habitat filtering due to urbanization shapes bird communities of Vienna city parks. This may help to derive implications for urban planning in order to promote and maintain high diversity and ecosystem function in an increasing urbanized environment. The structure of wintering bird communities of 36 Vienna city parks – surveyed once a month in January 2009, December 2009, December 2012, and January 2013 – was described by species richness and the functional diversity measurements FRic (functional richness), FEve (functional evenness), and FDiv (functional divergence). Environmental filtering was quantified by park size, canopy heterogeneity within the park, and the proportion of sealed area surrounding each park. Species richness, FRic, and FDiv increased with increasing park size. Sealed area had a strong negative effect on species richness and FDiv. Canopy heterogeneity played a minor role in explaining variance in FDiv data. FEve did not respond to any of these park parameters. Our results suggest a loss of species richness and functional diversity, hence most likely indicate a decline in ecosystem function, with decreasing park size and increasing sealed area of the surrounding urban landscape matrix. The functional diversity of wintering bird communities in city parks of Vienna was quantified to gain a better insight on how habitat filtering due to urbanisation shapes bird communities. Environmental filtering was quantified by park size, canopy heterogeneity within the park and the proportion of sealed area surrounding each park. Our results suggest a loss of species richness and functional diversity, hence most likely indicate a decline in ecosystem function, with decreasing park size and increasing sealed area of the surrounding urban landscape matrix.

Description: ABSTRACT Hydrographic data from the Labrador Sea collected in February - March 1997, together with atmospheric reanalysis fields, are used to explore relationships between the air-sea fluxes and the observed mixed layer depths. The strongest winds and highest heat fluxes occurred in February, due to the nature and tracks of the storms. While greater numbers of storms occurred earlier and later in the winter, the storms in February followed a more organized track extending from the Gulf Stream region to the Irminger Sea where they slowed and deepened. The canonical low pressure system that drives convection is located east of the southern tip of Greenland, with strong westerly winds advecting cold air off the ice edge over the warm ocean. The deepest mixed layers were observed in the western interior basin, although the variability in mixed layer depth was greater in the eastern interior basin. The overall trend in mixed layer depth through the winter in both regions of the basin was consistent with that predicted by a 1-D mixed layer model. We argue that the deeper mixed layers in the west were due to the enhanced heat fluxes on that side of the basin as opposed to oceanic preconditioning. This article is protected by copyright. All rights reserved.

Description: Some forest-related studies on possible effects of climate change conclude that growth potential of European beech ( Fagus sylvatica L.) might be impaired by the predicted increase in future serious drought events during the growing season. Other recent research suggests that not only multi-year increment rates but also growth resistance and recovery of beech during respectively after dry years may differ between pure and mixed stands. Thus, we combined dendrochronological investigations and wood stable isotope measurements to further investigate the impact of neighborhood diversity on long-term performance, short-term drought response and soil water availability of European beech in three major geographic regions of Germany. During the last 4 decades, target trees whose competitive neighborhood consisted of co-occurring species exhibited a superior growth performance compared to beeches in pure stands of the same investigation area. This general pattern was also found in exceptional dry years. Although the summer droughts of 1976 and 2003 predominantly caused stronger relative growth declines if target trees were exposed to interspecific competition, with few exceptions they still formed wider annual rings than beeches growing in close-by monocultures. Within the same study region, recovery of standardized beech target tree radial growth was consistently slower in monospecific stands than in the neighborhood of other competitor species. These findings suggest an improved water availability of beech in mixtures what is in line with the results of the stable isotope analysis. Apparently the magnitude of competitive complementarity determines the growth response of target beech trees in mixtures. Our investigation strongly suggest that the sensitivity of European beech to environmental constrains depends on neighborhood identity. Therefore, the systematic formation of mixed stands tends to be an appropriate silvicultural measure to mitigate the effects of global warming and droughts on growth patterns of Fagus sylvatic a. This article is protected by copyright. All rights reserved.

Description: Abstract Aim Information on the amount of carbon stored in the living tissue of tree stems (sapwood) is crucial for carbon and water cycle applications. Here, we aim to investigate sapwood‐to‐stem proportions and differences therein between tree genera and derive a sapwood biomass map. Location Northern Hemisphere boreal and temperate forests. Time period 2010. Major taxa studied Twenty‐five common tree genera. Methods First, we develop a theoretical framework to estimate sapwood biomass for a given stem biomass by applying relationships between sapwood cross‐sectional area (CSA) and stem CSA and between stem CSA and stem biomass. These measurements are extracted from a biomass and allometry database (BAAD), an extensive literature review and our own studies. The established allometric relationships are applied to a remote sensing‐based stem biomass product in order to derive a spatially continuous sapwood biomass map. The application of new products on the distribution of stand density and tree genera facilitates the synergy of satellite and forest inventory data. Results Sapwood‐to‐stem CSA relationships can be modelled with moderate to very high modelling efficiency for different genera. The total estimated sapwood biomass equals 12.87 ± 6.56 petagrams of carbon (PgC) in boreal (mean carbon density: 1.13 ± 0.58 kgC m−2) and 15.80 ± 9.10 PgC in temperate (2.03 ± 1.17 kgC m−2) forests. Spatial patterns of sapwood‐to‐stem biomass proportions are crucially driven by the distribution of genera (spanning from 20–30% in Larix to 〉 70% in Pinus and Betula forests). Main conclusions The presented sapwood biomass map will be the basis for large‐scale estimates of plant respiration and transpiration. The enormous spatial differences in sapwood biomass proportions reveal the need to consider the functionally more important sapwood instead of the entire stem biomass in global carbon and water cycle studies. Alterations in tree species distribution, induced by forest management or climate change, can strongly affect the available sapwood biomass even if stem biomass remains unchanged.

Description: Abstract Hydrographic data and tracers from several ship‐based sections show the location and structure of a deep eastern boundary current in the Chile Basin. The current is centered above the Peru‐Chile Trench at 2,500–3,400 m and transports up to 6 Sv of low‐potential vorticity, high‐silicate water south toward Drake Passage. Deep current velocities from direct Lowered Acoustic Doppler Current Profiler measurements are up to about 15 cm/s southward. The hydrographic data, as well as potential vorticity and silicate distributions, show that the current is comprised to a large extent of flow from the west moving along the southern flank of the Sala y Gomez Ridge and Nazca Ridge, and to a lesser extent from a flow along the eastern boundary entering directly from the Panama Basin. At the southern edge of the Chile Trench, the current weakens and partly turns offshore to cross the Chile Ridge through a complex region of passages. Above the southern flank of the Chile Rise the flow joins a broader eastward flow; together, these waters return to the eastern boundary before entering Drake Passage.

Description: Recurring Slope Lineae (RSL) are flow-like features on Mars characterized by a local darkening of the soil thought to be generated by the formation and flow of liquid brines. One possible mechanism responsible for forming these brines could be the deliquescence of salts present in the Martian soil. We show that the JSC Mars-1a analogue soil undergoes a darkening process when salts dispersed in the soil deliquesce, but forming continuous liquid films and larger droplets takes much longer than previously assumed. Thus, RSL may not necessarily require concurrent flowing liquid water/brine or a salt-recharge mechanism, and their association with gullies may be the result of previously flowing water and deposited salts during an earlier warmer and wetter period. In addition, our results show that electrical conductivity measurements correlate well with the deliquescence rates and provide better overall characterization than either Raman spectroscopy or estimates based on deliquescence relative humidity (DRH).