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Although Tetracladium species have traditionally been studied as aquatic saprotrophs, the growing number of metagenomic and metabarcoding reports detecting them in soil environments raises important questions about their ecological adaptability and versatility. We investigated the factors associated with the relative abundance, diversity and ecological dynamics of Tetracladium in temperate forest soils. Through amplicon sequencing of soil samples collected from 54 stands in six forest sites across the eastern United States, we identified 29 distinct Amplicon Sequence Variants (ASVs) representing Tetracladium, with large differences in relative abundance and small changes in ASV community composition among sites. Tetracladium richness was positively related to soil pH, soil temperature, total sulphur and silt content, and negatively related to plant litter quality, such as the lignin-to-nitrogen ratio and the lignocellulose index. Co-occurrence network analysis indicated negative relationships between Tetracladium and other abundant fungal groups, including ectomycorrhizal and arbuscular mycorrhizal fungi. Collectively, our findings highlight the ecological significance of Tetracladium in temperate forest soils and emphasize the importance of site-specific factors and microbial interactions in shaping their distribution patterns and ecological dynamics., (© 2024 The Author(s). Environmental Microbiology published by John Wiley & Sons Ltd.)

Volatile reactive nitrogen oxides (NO y ) are significant atmospheric pollutants, including NO x (nitric oxide [NO] + nitrogen dioxide [NO 2 ]) and NO z (nitrous acid [HONO] + nitric acid [HNO 3 ] + nitrogen trioxide [NO 3 ] + ...). NO y species are products of nitrogen (N) cycle processes, particularly nitrification and denitrification. Biogenic sources, including soil, account for over 50% of natural NO y emissions to the atmosphere, yet emissions from soils are generally not included in atmospheric models as a result of a lack of mechanistic data. This work is a unique investigation of NO y fluxes on a landscape scale, taking a comprehensive set of land-use types, human influence, and seasonality into account to determine large-scale heterogeneity to provide a basis for future modeling and hypothesis generation. By coupling 16S rRNA amplicon sequencing and quantitative polymerase chain reaction, we have linked significant differences in functional potential and activity of nitrifying and denitrifying soil microbes to NO y emissions from soils. Further, we have identified soils subject to increased N deposition that are less microbially active despite increased available N, potentially as a result of poor soil health from anthropogenic pollution. Structural equation modeling suggests human influence on soils to be a more significant effector of soil NO y emissions than land-use type.

This article outlines the design and implementation of an internet-of-things (IoT) platform for the monitoring of soil carbon dioxide (CO 2 ) concentrations. As atmospheric CO 2 continues to rise, accurate accounting of major carbon sources, such as soil, is essential to inform land management and government policy. Thus, a batch of IoT-connected CO 2 sensor probes were developed for soil measurement. These sensors were designed to capture spatial distribution of CO 2 concentrations across a site and communicate to a central gateway using LoRa. CO 2 concentration and other environmental parameters, including temperature, humidity and volatile organic compound concentration, were logged locally and communicated to the user through a mobile (GSM) connection to a hosted website. Following three field deployments in summer and autumn, we observed clear depth and diurnal variation of soil CO 2 concentration within woodland systems. We determined that the unit had the capacity to log data continuously for a maximum of 14 days. These low-cost systems have great potential for better accounting of soil CO 2 sources over temporal and spatial gradients and possibly flux estimations. Future testing will focus on divergent landscapes and soil conditions.

Background: The genus Tetracladium De Wild. (Ascomycota) has been traditionally regarded as a group of Ingoldian fungi or aquatic hyphomycetes-a polyphyletic group of phylogenetically diverse fungi which grow on decaying leaves and plant litter in streams. Recent sequencing evidence has shown that Tetracladium spp. may also exist as root endophytes in terrestrial environments, and furthermore may have beneficial effects on the health and growth of their host. However, the diversity of Tetracladium spp. communities in terrestrial systems and the factors which shape their distribution are largely unknown., Results: Using a fungal community internal transcribed spacer amplicon dataset from 37 UK Brassica napus fields we found that soils contained diverse Tetracladium spp., most of which represent previously uncharacterised clades. The two most abundant operational taxonomic units (OTUs), related to previously described aquatic T. furcatum and T. maxilliforme, were enriched in roots relative to bulk and rhizosphere soil. For both taxa, relative abundance in roots, but not rhizosphere or bulk soil was correlated with B. napus yield. The relative abundance of T. furcatum and T. maxilliforme OTUs across compartments showed very similar responses with respect to agricultural management practices and soil characteristics. The factors shaping the relative abundance of OTUs homologous to T. furcatum and T. maxilliforme OTUs in roots were assessed using linear regression and structural equation modelling. Relative abundance of T. maxilliforme and T. furcatum in roots increased with pH, concentrations of phosphorus, and increased rotation frequency of oilseed rape. It decreased with increased soil water content, concentrations of extractable phosphorus, chromium, and iron., Conclusions: The genus Tetracladium as a root colonising endophyte is a diverse and widely distributed part of the oilseed rape microbiome that positively correlates to crop yield. The main drivers of its community composition are crop management practices and soil nutrients., (© 2022. The Author(s).)

Trees associating with different mycorrhizas often differ in their effects on litter decomposition, nutrient cycling, soil organic matter (SOM) dynamics, and plant-soil interactions. For example, due to differences between arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) tree leaf and root traits, ECM-associated soil has lower rates of C and N cycling and lower N availability than AM-associated soil. These observations suggest that many groups of nonmycorrhizal fungi should be affected by the mycorrhizal associations of dominant trees through controls on nutrient availability. To test this overarching hypothesis, we explored the influence of predominant forest mycorrhizal type and mineral N availability on soil fungal communities using next-generation amplicon sequencing. Soils from four temperate hardwood forests in southern Indiana, United States, were studied; three forests formed a natural gradient of mycorrhizal dominance (100% AM tree basal area to 100% ECM basal area), while the fourth forest contained a factorial experiment testing long-term N addition in both dominant mycorrhizal types. We found that overall fungal diversity, as well as the diversity and relative abundance of plant pathogenic and saprotrophic fungi, increased with greater AM tree dominance. Additionally, tree community mycorrhizal associations explained more variation in fungal community composition than abiotic variables, including soil depth, SOM content, nitrification rate, and mineral N availability. Our findings suggest that tree mycorrhizal associations may be good predictors of the diversity, composition, and functional potential of soil fungal communities in temperate hardwood forests. These observations help explain differing biogeochemistry and community dynamics found in forest stands dominated by differing mycorrhizal types. IMPORTANCE Our work explores how differing mycorrhizal associations of temperate hardwood trees (i.e., arbuscular [AM] versus ectomycorrhizal [ECM] associations) affect soil fungal communities by altering the diversity and relative abundance of saprotrophic and plant-pathogenic fungi along natural gradients of mycorrhizal dominance. Because temperate hardwood forests are predicted to become more AM dominant with climate change, studies examining soil communities along mycorrhizal gradients are necessary to understand how these global changes may alter future soil fungal communities and their functional potential. Ours, along with other recent studies, identify possible global trends in the frequency of specific fungal functional groups responsible for nutrient cycling and plant-soil interactions as they relate to mycorrhizal associations.

Volatile nitrogen oxides (N 2 O, NO, NO 2 , HONO, …) can negatively impact climate, air quality, and human health. Using soils collected from temperate forests across the eastern United States, we show microbial communities involved in nitrogen (N) cycling are structured, in large part, by the composition of overstory trees, leading to predictable N-cycling syndromes, with consequences for emissions of volatile nitrogen oxides to air. Trees associating with arbuscular mycorrhizal (AM) fungi promote soil microbial communities with higher N-cycle potential and activity, relative to microbial communities in soils dominated by trees associating with ectomycorrhizal (ECM) fungi. Metagenomic analysis and gene expression studies reveal a 5 and 3.5 times greater estimated N-cycle gene and transcript copy numbers, respectively, in AM relative to ECM soil. Furthermore, we observe a 60% linear decrease in volatile reactive nitrogen gas flux (NO y  ≡ NO, NO 2 , HONO) as ECM tree abundance increases. Compared to oxic conditions, gas flux potential of N 2 O and NO increase significantly under anoxic conditions for AM soil (30- and 120-fold increase), but not ECM soil-likely owing to small concentrations of available substrate ( NO 3 - ) in ECM soil. Linear mixed effects modeling shows that ECM tree abundance, microbial process rates, and geographic location are primarily responsible for variation in peak potential NO y flux. Given that nearly all tree species associate with either AM or ECM fungi, our results indicate that the consequences of tree species shifts associated with global change may have predictable consequences for soil N cycling., (© 2020 The Authors. Global Change Biology published by John Wiley & Sons Ltd.)

Reactive nitrogen oxides (NO y ; NO y = NO + NO 2 + HONO) decrease air quality and impact radiative forcing, yet the factors responsible for their emission from nonpoint sources (i.e., soils) remain poorly understood. We investigated the factors that control the production of aerobic NO y in forest soils using molecular techniques, process-based assays, and inhibitor experiments. We subsequently used these data to identify hotspots for gas emissions across forests of the eastern United States. Here, we show that nitrogen oxide soil emissions are mediated by microbial community structure (e.g., ammonium oxidizer abundances), soil chemical characteristics (pH and C:N), and nitrogen (N) transformation rates (net nitrification). We find that, while nitrification rates are controlled primarily by chemoautotrophic ammonia-oxidizing archaea (AOA), the production of NO y is mediated in large part by chemoautotrophic ammonia-oxidizing bacteria (AOB). Variation in nitrification rates and nitrogen oxide emissions tracked variation in forest communities, as stands dominated by arbuscular mycorrhizal (AM) trees had greater N transformation rates and NO y fluxes than stands dominated by ectomycorrhizal (ECM) trees. Given mapped distributions of AM and ECM trees from 78,000 forest inventory plots, we estimate that broadleaf forests of the Midwest and the eastern United States as well as the Mississippi River corridor may be considered hotspots of biogenic NO y emissions. Together, our results greatly improve our understanding of NO y fluxes from forests, which should lead to improved predictions about the atmospheric consequences of tree species shifts owing to land management and climate change., Competing Interests: The authors declare no conflict of interest.

Rationale: Biochar amendments often decrease N 2 O gas production from soil, but the mechanisms and magnitudes are still not well characterized since N 2 O can be produced via several different microbial pathways. We evaluated the influence of biochar amendment on N 2 O emissions and N 2 O isotopic composition, including 15 N site preference (SP) under anaerobic conditions., Methods: An agricultural soil was incubated with differing levels of biochar. Incubations were conducted under anaerobic conditions for 10 days with and without acetylene, which inhibits N 2 O reduction to N 2 . The N 2 O concentrations were measured every 2 days, the SPs were determined after 5 days of incubation, and the inorganic nitrogen concentrations were measured after the incubation., Results: The SP values with acetylene were consistent with N 2 O production by bacterial denitrification and those without acetylene were consistent with bacterial denitrification that included N 2 O reduction to N 2 . There was no effect of biochar on N 2 O production in the presence of acetylene between day 3 and day 10. However, in the absence of acetylene, soils incubated with 4% biochar produced less N 2 O than soils with no biochar addition. Different amounts of biochar amendment did not change the SP values., Conclusions: Our study used N 2 O emission rates and SP values to understand biochar amendment mechanisms and demonstrated that biochar amendment reduces N 2 O emissions by stimulating the last step of denitrification. It also suggested a possible shift in N 2 O-reducing microbial taxa in 4% biochar samples., (© 2018 John Wiley & Sons, Ltd.)

1-Diphenylphosphinonaphthyl-8-triphenylstibonium triflate ([][OTf]) was prepared in excellent yield by treating 1-lithio-8-diphenylphosphinonaphthalene with dibromotriphenylstiborane followed by halide abstraction with AgOTf. This antimony(v) cation was found to be stable toward oxygen and water, and exhibited exceptional Lewis acidity. The Lewis acidity of [][OTf] was exploited in the catalytic reductive coupling of a variety of aldehydes into symmetric ethers of type in good to excellent yields under mild conditions using Et3SiH as the reductant. Additionally, [][OTf] was found to selectively catalyze the Aldol condensation reaction to afford α-β unsaturated aldehydes () when aldehydes with 2 α-hydrogen atoms were used. Finally, [][OTf] catalyzed the cyclotrimerization of aliphatic and aromatic aldehydes to afford the industrially-useful 1,3,5 trioxanes () in good yields, and with great selectivity. This phosphine-stibonium motif represents one of the first catalytic systems of its kind that is able to catalyze these reactions with aldehydes in a controlled, efficient manner. The mechanism of these processes has been explored both experimentally and theoretically. In all cases the Lewis acidic nature of the antimony(v) cation was found to promote these reactions.

A diamidocarbene was coordinated to an antimony(III) dichloride Lewis acid. Subsequent reduction with magnesium gave a monomeric, formally antimony(I) fragment that is supported by the diamidocarbene. Spectroscopic, crystallographic, and computational analyses demonstrated that the carbene ligand engages the antimony(I) center in π-backbonding resulting in a short (2.068(7) Å) Sb-C interaction that is comparable to those observed in known stibaalkenes., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)