[Taxonomic and Functional Diversity of Soil Microbial Communities in Subalpine Meadow with Different Degradation Degrees in Mount Wutai].

Although soil microbes play a key role in grassland ecosystem functioning, the response of their diversity to grassland degradation has not been fully investigated. Here, we used shotgun metagenomic sequencing to analyze the characteristics and influencing factors of soil microbial taxonomic and functional diversity at four different degradation stages[i.e., non-degraded (ND), lightly degraded (LD), moderately degraded (MD), and heavily degraded (HD)]of subalpine meadow in the Mount Wutai. The results showed that there were significant differences in the relative abundances of Actinobacteria, Bacteroidetes, Nitrospirae, and Parcubacteria among the four subalpine grasslands with different degradation degrees (P<0.05).Compared with that in ND, the degraded meadows increased the proportion of genes related to carbon metabolism, biosynthesis of amino acids, pyruvate metabolism, citric acid cycle, propanoate metabolism, butanoate metabolism, and fatty acid metabolism (P<0.05), indicating that the degradation of subalpine grassland changed the metabolic potential of energy metabolism and the nutrient cycle of the soil microbial community. Grassland degradation changed soil microbial taxonomic and functional α diversity, especially in MD and HD.Grassland degradation resulted in significant changes in the taxonomic and functional compositions of the microbial communities. The total nitrogen, pH, and soil organic carbon significantly affected the taxonomic and functional compositions of the microbial communities.The ß diversity of the plant community was significantly correlated with the taxonomic and functional ß diversity of the microbial community (P<0.05), indicating strong coupling. The results of this study revealed the changes and driving mechanisms of subsurface microbial taxonomic and functional diversity during grassland degradation, which can provide a theoretical basis for subalpine meadow protection and ecological restoration.

[Responses of Soil Fungal Communities to Subalpine Meadow Degradation in Mount Wutai].

Grassland degradation has become a worldwide ecological problem. Although soil microorganisms, as the main participants in the process of grassland degradation, play a key role in maintaining ecosystem function and improving soil productivity, little is known about the changes in microbial communities caused by grassland degradation and their relationship with soil properties and plant communities. In this study, we used Illumina MiSeq sequencing to analyze the soil fungal communities of subalpine meadow soil at four different degradation stages[i.e., non-degraded (ND), lightly degraded (LD), moderately degraded (MD), and heavily degraded (HD)] on Mount Wutai. The results showed that Ascomycota, Basidiomycota, and Zygomycota were the dominant phyla of soil fungi in the subalpine meadow, regardless of degradation stage. LEfSe showed that the subalpine meadows with different degradation degrees were enriched with different biomarkers. Compared with ND, MD and HD were enriched with more pathogenic fungi. Moreover, HD apparently decreased the richness and Shannon indexes of soil fungal communities compared with those of ND. Non-metric multidimensional scaling (NMDS) and similarity analysis (ANOSIM) indicated that the compositions and structures of fungal communities were significantly different among meadows with different degradation degrees (P<0.05). Redundancy analysis (RDA) showed that soil water content, total nitrogen, plant richness, and ammonium nitrogen were significantly correlated with the compositions and structures of fungal communities (P<0.05). There were significant correlations between α diversity and ß diversity between plant and fungal communities (P<0.05), indicating strong coupling. The results of our study provide a theoretical basis for further research on the changes in soil fungal communities and their driving mechanism in different degradation stages of subalpine meadows.

[Spatio-temporal Patterns of Microbial Communities and Their Driving Mechanisms in Subalpine Lakes, Ningwu, Shanxi].

Human activities and climate change cause the degradation of subalpine lake ecosystems, which induce the shift of microbial community structure. The spatio-temporal dynamics and the diversity maintenance mechanisms of bacterial communities in Gonghai Lake in Ningwu, Shanxi, were investigated by using Q-PCR and DGGE. The results showed that the temperature), pH, dissolved oxygen, electrical conductivity salinity, and ammonium nitrogen (NH4+) contestation were significantly different among the different sampling depths during different months. Bacterial abundance was the highest in August and the lowest in November, and the abundance was higher in the middle water layer (2 m, 4 m, and 6 m depths), but relatively low in the surface layer and bottom layer (0 m and 8 m depths, respectively). The α diversity index of bacterial communities had significant differences among the different months and depths, and showed an initial decreasing trend and then an increasing trend from April to December. A PERMANOVA test showed that the spatial distribution of bacterial communities was significantly different among depths (P<0.001). The results of redundancy analysis and variation partitioning indicated that environmental selection and diffusion limitation had an effect on the maintenance of the diversity patterns of bacterial communities at the different depths of GH. However, the relative effect of environmental factors was stronger, of which the concentration of NO3-, NO2-, and NH4+ were the main influencing factors. In conclusion, the bacterial communities in GH subalpine lake showed clear spatio-temporal distribution patterns, and environmental variables had a significant effect on shaping the community diversity.

[Distribution Pattern and Diversity Maintenance Mechanisms of Fungal Community in Subalpine Lakes].

The composition and diversity of fungal communities are essential to maintain the ecosystem balance of subalpine lakes. The aquatic fungal communities at different depths from the subalpine Pipahai (PPH, 0, 2, 4 m), Mayinghai (MYH, 0, 2, 4, 6 m), and Gonghai (GH, 0, 2, 4, 6, 8 m) lakes were studied. In addition to that, the distribution pattern and diversity maintenance mechanism (determination process vs. random process) of fungal communities were explored using high-throughput sequencing. The results showed that the physicochemical parameters of the water were significantly different among the three lakes. The pH, electrical conductivity (EC), ammonia nitrogen (NH4+-N), total carbon (TC), and inorganic carbon (IC) of GH were significantly higher than in the other two lakes. The fungal community was mainly composed of Ascomycota (0.82%-21.05%), Basidiomycota (1.26%-11.79%), Chytridiomycota (0.42%-4.26%), and Rozellomycota (0.11%-0.33%). Cystobasidiomycetes, Dothideomycetes, Chytridiomycetes, and Sordariomycetes were the dominant classes shared by the three lakes. The α-diversity index and the relative abundance of dominant classes were significantly different among the three lakes (P<0.05), but there were no significant differences between the various depths on each lake. The results of the ANOSIM analysis showed that the ß-diversity of the fungal communities were significantly different (r=0.99, P<0.01) among the lakes. There was also expressive differences at various depths on MYH (r=0.98, P<0.01) and GH (r=0.25, P<0.05), but no significant difference in PPH (r=0.23, P>0.05). The analysis results of redundancy and variation partitioning showed that the ß-diversity pattern of fungal communities in small region areas (among the three lakes) and local areas (different depths of MYH) were driven by environmental selection and dispersal limitation. However, the relative role of environmental selection was more significant, with water pH, dissolved oxygen (DO), TC, and EC being the main influencing factors. The results of the null model analysis showed that the interspecific interactions promoted the maintenance of the ß-diversity pattern of the fungal community in GH. In summary, the ß-diversity pattern of fungal communities in the subalpine lakes was mainly driven by a deterministic process.

New Insights into the Electron-Collection Efficiency Improvement of CdS-Sensitized TiO2 Nanorod Photoelectrodes by Interfacial Seed-Layer Mediation.

Titanium dioxide (TiO2) nanorods (NRs) are widely used as photoanodes in photoelectrochemical (PEC) solar fuel production because of their remarkable photoactivity and stability. In addition, TiO2 NR electrode materials can be decorated with active CdS quantum dots (QDs) to expand the sunlight photon capture. The overall photoelectric conversion efficiency for TiO2 NR or QD-sensitized TiO2 NR electrode materials in PEC is typically dominated by their interfacial electron transfer (ET) properties. To understand the key factors affecting the ET, the anatase TiO2 seed layer was added into the interface between the rutile TiO2 NRs and fluorine-doped tin oxide (FTO) substrate. This seed layer enhanced the photocatalytic performance of both the TiO2 NR and CdS QD-sensitized TiO2 NR photoanodes in PEC. Time-resolved photoluminescence spectroscopy and PEC analyses, including Mott-Schottky, electrochemical impedance spectroscopy, and photovoltage ( Vph) measurements, were used to study the charge-carrier dynamics at the interfaces between the FTO, TiO2, and CdS QD. Analysis of the results showed that band alignment at the anatase/rutile junction between the TiO2 and FTO promoted electron-collection efficiency ( eEC) at the FTO/TiO2 interface and ET rate constant ( kET) at the TiO2/CdS QD interface. Furthermore, 34% enhancement of the efficiency in hydrogen (H2) generation demonstrated the potential of the TiO2 seed-layer-mediated TiO2/CdS QD NR photoanode in the application of PEC solar fuel production. The current work represents new insights into the mechanism of ET in TiO2 and TiO2/CdS QD NR, which is very useful for the development of photoelectrode materials in solar energy conversions.