Elevational distribution and occurrence of arbuscular mycorrhizal fungi in non-host Carex capillacea.

Little is known about Arbuscular mycorrhizal (AM) fungal colonization and community composition in non-mycorrhizal (NM) plants, especially along elevational gradients. This study explores this question using a NM plant, Carex capillacea, at Mount Segrila, Tibet. Here, C. capillacea, its rhizosphere soil, and the neighboring mycotrophic plant Poa annua were sampled at four elevations to evaluate and compare their AM fungi colonization and communities. The results showed that AM fungal colonization density of C. capillacea was negatively correlated with elevation and biomass of total NM plants per quadrat. AM fungal diversity and community composition between C. capillacea and P. annua showed a similar pattern. In addition, elevation and soil did not significantly influence the AM community in C. capillacea, while they were important abiotic factors for assemblages in rhizosphere soil and P. annua. These findings support that a broad array of AM fungi colonize the root of C. capillacea, and a mycelial network from a co-occurring host plant might shape the AM fungal communities in C. capillacea along the elevation gradient. The co-occurrence patterns of AM fungi associated with non-mycotrophic species and adjacent mycotrophic species have important implications for understanding AM fungal distribution patterns and plant-AM interactions.

Responses of soil microbial diversity, network complexity and multifunctionality to three land-use changes.

Land-use change is one of the greatest challenges for natural ecosystem services. Soil microbiomes are essential for modulating multiple ecosystem functions. However, little is known about the impact of land-use changes on soil microbial communities and their associated soil functions. In this study, 150 alpine soil samples representing conversion of forests to shrublands or grasslands, and of shrublands to grasslands were investigated for bacterial, fungal and protistan community diversity, co-occurrence network, as well as their relationships with soil multifunctionality via a sampling strategy of space-for-time substitution. The conversion of forest to grassland increased the diversity of fungi and bacteria, and altered the microbial community structures of bacteria, fungi and protists, resulting a greater impact on soil microbiome than other land-use conversions. Cross-trophic interaction analyses demonstrated this conversion increased microbial network complexity and robustness, whereas forest to shrubland had the opposite trend. The land-use induced changes in soil multifunctionality were related with microbial network modules, but were not always associated with variations of microbial diversity. Random forest modeling further suggested the significant role of microbial modules in explaining soil multifunctionality, together with environmental factors. These findings indicate divergent responses of belowground multitrophic organisms to land-use changes, and the potential role of microbial module in forecasting soil multifunctionality.

Experimental investigation of dynamic mechanical characteristics of inhomogeneous composite coal-sandstone combination for coalbed methane development.

In deep resource exploitation, the coal seam and the strata are jointly loaded, forming a systematic combined structure that can have a significant effect on coalbed methane (CBM) development. Therefore, to understand the deformation and damage characteristics due to blasting load of the complex and real ground conditions, the 50 mm split Hopkinson pressure bar (SHPB) was used to study the dynamic performance and energy changes of coal-sandstone combination and sandstone-coal combination as inhomogeneous materials. In addition, high-speed photographic equipment was employed to determine the damage failure mechanisms. The results showed that the dynamic compressive strength and failure strains of two combinations showed polynomial relationships with increasing strain rates. The strain rate effects and likenesses of the two combinations' energy and energy rates were substantial. Furthermore, for the coal-sandstone combination, the initial damage fractures occurred at the end face near the bar, and at the interface for the sandstone-coal combination. Eventually, the improved constitutive model based on the ZWT was significantly consistent with the two combinations. The related theory can perform an effective and practical role in the mining of coal rocks under complex ground conditions for CBM development.