Search

Paulownia fortunei, one of the world's fastest growing timber tree species, is universally applied with fertilizer as a management approach to meet the nutrient requirements for efficient cultivation. The substantial effects of fertilizer on soil microorganisms in Paulownia plantations have been empirically tested; however, the successive chronosequence of soil microbial carbon and nitrogen functional genes under different fertilizer application durations remains limited. The objective of this study was to explore the characteristics of soil microorganisms involved in carbon and nitrogen cycling and greenhouse gas (GHG) production under different fertilizer application durations. Different fertilizer treatments, i.e., the short-term group (SG) versus the long-term group (LG), and durations were applied to subtropical plantations in southern China and compared with zonal evergreen broad-leaved forests. Results showed that fertilizer treatment significantly increased the relative abundance of Acidobacteriota and the expression of nirK and nosZ. The functional groups that dominated metabolism in SG and LG treatments belonged to Actinobacteria and Acidobacteriota, respectively, suggesting that the nutrient preference of microorganisms in forest soil may change from copiotrophs to oligotrophs with increasing fertilizer application duration. Correlation network analysis showed that the communities that dominated the carbon and nitrogen cycles belonged to Actinobacteria and Acidobacteriota, respectively, and were closely related to ammonium nitrogen and available iron. Actinobacteria and Acidobacteriota were likely the major taxa that affected soil GHG production under different fertilizer application durations. We concluded that long-term fertilizer use changed the preference of microbial nutrient uptake into recalcitrant nutrients, and the sensitivity of the microbial community to nutrients gradually decreased with increasing fertilizer application time. The dominant Actinobacteria affected soil carbon and nitrogen cycles largely by stimulating denitrification to increase the release of nitrous oxide, which might lead to the loss of nitrogen components and the intensification of the GHG effect with increasing fertilizer application time. [ABSTRACT FROM AUTHOR]

The characterization of natural fungal diversity impacts our understanding of ecological and evolutionary processes and can lead to novel bioproduct discovery. Russula and Lactarius, both in the order Russulales, represent two large genera of ectomycorrhizal fungi that include edible as well as toxic varieties. Based on morphological and phylogenetic analyses, including nucleotide sequences of the internal transcribed spacer (ITS), the 28S large subunit of ribosomal RNA (LSU), the second largest subunit of RNA polymerase II (RPB2), the ribosomal mitochondrial small subunit (mtSSU), and the translation elongation factor 1-α (TEF1-α) gene sequences, we here describe and illustrate two new species of Russula and one new species of Lactarius from southern China. These three new species are: R. junzifengensis (R. subsect. Virescentinae), R. zonatus (R. subsect. Crassotunicatae), and L. jianyangensis (L. subsect. Zonarii). [ABSTRACT FROM AUTHOR]

Silica diagenesis has been proved to significantly affect rock composition and fabric. However, it still needs to be clarified how silica diagenesis affects the mechanical properties of shales. To further investigate this impact, we collected shale samples from the Upper Ordovician Wufeng and the Lower Silurian Longmaxi formations, southeast Sichuan Basin. The total organic carbon (TOC) content, mineralogical composition, and major oxide concentrations were measured to characterize the shale composition. Thin-section observations and high-resolution imaging techniques were used to characterize the rock fabric and identify quartz types. The Young's modulus, Poisson's ratio, and the measured hardness were used to characterize the shale mechanical properties. Four major lithofacies were identified, namely, siliceous shale, siliceous-argillaceous mixed shale, silty mudstone, and argillaceous shale. Three types of authigenic quartz in the Wufeng-Longmaxi formations were observed, namely, quartz overgrowth, matrix-dispersed microquartz, and microquartz aggregates. Matrix-dispersed microquartz is typically mixed with clay matrix, while microquartz aggregates typically coexist with migrated organic matter. The combined analysis of Fe–Al–Mn ternary diagram, cross-plots of Si versus Al, Rb versus K 2 O, and TOC content versus excess silica demonstrate that the dominant silica source of quartz cementation is biogenic. The cross-plot of excess silica contents versus Young's modulus, Poisson's ratio, and hardness suggest that silica diagenesis significantly affects the mechanical properties of shale rocks. Microquartz aggregates greatly contribute to shale brittleness, while detrital quartz minimally affects shale brittleness if the detrital quartz was enclosed by ductile clay minerals. • Four quartz types were identified in the Wufeng-Longmaxi shales. • Silica cementation could significantly enhance shale rock mechanical properties. • The organic-rich siliceous shale typically manifests the best brittleness behavior. • The evolution patterns of silica diagenesis in different lithofacies were discussed. [ABSTRACT FROM AUTHOR]