BackgroundSoil microbiomes play an important role in the services and functioning of terrestrial ecosystems. However, little is known of their vertical responses to restoration process and their contributions to soil nutrient cycling in the subsurface profiles. Here, we investigated the community assembly of soil bacteria, archaea, and fungi along vertical (i.e., soil depths of 0–300 cm) and horizontal (i.e., distance from trees of 30–90 cm) profiles in a chronosequence of reforestation sites that represent over 30 years of restoration.ResultsIn the superficial layers (0–80 cm), bacterial and fungal diversity decreased, whereas archaeal diversity increased with increasing soil depth. As reforestation proceeded over time, the vertical spatial variation in bacterial communities decreased, while that in archaeal and fungal communities increased. Vertical distributions of the soil microbiomes were more related to the variation in soil properties, while their horizontal distributions may be driven by a gradient effect of roots extending from the tree. Bacterial and archaeal beta-diversity were strongly related to multi-nutrient cycling in the soil, respectively, playing major roles in deep and superficial layers.ConclusionsTaken together, these results reveal a new perspective on the vertical and horizontal spatial variation in soil microbiomes at the fine scale of single trees. Distinct response patterns underpinned the contributions of soil bacteria, archaea, and fungi as a function of subsurface nutrient cycling during the reforestation of ex-arable land.Electronic supplementary materialThe online version of this article (10.1186/s40168-018-0526-0) contains supplementary material, which is available to authorized users.

Bimetallic nanoparticle catalysts attract extensive attention for relevant catalysis processes due to their flexible structures, while the structure evolution under specific conditions is ambiguous. This paper describes the structure evolution of Pt-Sn bimetallic nanoparticles for catalytic dehydrogenation, especially Sn segregation for surface recovery of a Pt-Sn alloy. An acid etching-reduction process was adopted to investigate the migration of Sn atoms after surface Sn species loss. By acid etching, Sn atoms at the surface of Pt-Sn alloy nanoparticles were removed, leaving nanoparticles with a Pt-rich shell and an unchanged Pt 3 Sn alloy core. Excitedly, during the following reduction process, the Pt 3 Sn alloy surface was recovered due to the migration of Sn atoms from the core to the surface, as confirmed by transmission electron microscopy, quasi in situ X-ray photoelectron spectroscopy, and density functional theory calculations. Subsequent studies on the catalyst performance for propane dehydrogenation (PDH) showed that the recoverable Pt 3 Sn alloy surface structure contributed to the high efficiency with 92% propene selectivity even after 5 cycles of the acid etchingreduction procedure. The recovery of the Pt-Sn alloy through Sn segregation could enable catalysts to overcome component fluctuations, making an efficient catalytic process.

The densities and viscosities of 1-ethyl-3-methylimidazolium bis­(trifluoromethylsulfonyl)­imide ([EMIM]­[NTf2]) + N-methyl-2-pyrrolidone (NMP) and [EMIM]­[NTf2] + ethanol mixtures were investigated over the mole fraction range from (0.1 to 0.9) and at temperatures from (293.15 to 323.15) K at intervals of 5 K. The densities can be well-represented by the quadratic equation, and the viscosities can be represented in the form of the Vogel equation. The excess molar volumes (V E) and viscosity deviations (Δη) were calculated, and the results were fitted to the Redlich–Kister equation using a multiparametric nonlinear regression method. The estimated parameters of the Redlich–Kister equation and standard deviation were also presented. The results showed that the densities and viscosities were dependent strongly on NMP or ethanol content. Comparatively, the viscosity deviation Δη was more sensitive to temperature than the excess molar volume V E.

Three kinds of iron-containing magnetic ionic liquids (ILs), including imidazole-based, pyridine-based, and pyrrolidine-based ILs, were synthesized respectively, and were used to dissolve coal direct liquefaction residues (CDLR) to obtain asphaltene fractions under the conditions of given time, temperature, and mass ratio of ILs to CDLR. The extracts from CDLR were characterized by ultimate analysis, proximate analysis, FT-IR, and 13C NMR. The results show that physicochemical properties of the extracts obtained with different magnetic ILs consisting of different cationic rings are different, and pyridine-based magnetic IL is an effective extractant to extract asphaltenes from CDLR among the three magnetic ILs. The extracts might be good precursors for preparing high-value-added carbon materials because of their higher carbon content, lower H/C, and ash content.