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Abstract Aerobic methanotrophs in upland soils consume atmospheric methane, serving as a critical counterbalance to global warming; however, the biogeographic distribution patterns of their abundance and community composition are poorly understood, especial at a large scale. In this study, soils were sampled from 30 grasslands across >2000 km on the Qinghai-Tibetan Plateau to determine the distribution patterns of methanotrophs and their driving factors at a regional scale. Methanotroph abundance and community composition were analyzed using quantitative PCR and Illumina Miseq sequencing of pmoA genes, respectively. The pmoA gene copies ranged from 8.2 × 105 to 1.1 × 108 per gram dry soil. Among the 30 grassland soil samples, Upland Soil Cluster Gamma (USCγ) dominated the methanotroph communities in 26 samples. Jasper Ridge Cluster (JR3) was the most dominant methanotrophic cluster in two samples; while Methylocystis , cluster FWs, and Methylobacter were abundant in other two wet soil samples. Interestingly, reanalyzing the pmoA genes sequencing data from existing publications suggested that USCγ was also the main methanotrophic cluster in grassland soils in other regions, especially when their mean annual precipitation was <500 mm. Canonical Analysis of Principal Coordinates including all soil samples indicated that the methanotrophic community composition was significantly correlated with local environmental factors, among which mean annual precipitation and pH showed the strongest correlations. Variance partitioning analysis showed that environmental factors and spatial distance were significant factors affecting the community structure of methanotrophs, and environmental properties were more important factors. Collectively, these findings indicate that atmospheric methane may be mainly oxidized by USCγ in upland soils. They also highlight the key role of water availability and pH in determining the abundance and community profiles of grassland soil methanotrophs. Graphical abstract Unlabelled Image Highlights • Aerobic methanotrophs in 30 grassland soils on the Tibetan Plateau were analyzed. • USCγ dominated the methanotroph communities in the Tibetan grassland soils. • USCγ also dominated in upland grassland soils around the world. • Grassland methanotrophic communities are shaped by precipitation and soil pH. [ABSTRACT FROM AUTHOR]

Abstract The Tibetan plateau is a cold environment at high altitude and is very sensitive to global climate change. Wetlands on this plateau are among the major sources of the important greenhouse gas methane, and temperature is an important factor in controlling CH 4 production. However, it remains unknown how CH 4 production and microbial processes in such wetlands respond to climate warming. Therefore, we anaerobically incubated soil slurries at 10, 20, 30 and 45 °C for 100 days to investigate the effects of temperature on CH 4 production and microbial community structure in the wetland soil next to NamCo, an alkaline lake on the Tibetan plateau. Rates and pathways of CH 4 production were determined by measuring accumulation of CH 4 and stable isotope fractionation, respectively. The microbial community structures were investigated by Illumina sequencing of bacterial and archaeal 16S rRNA and methanogenic mcrA genes and/or transcripts. Increasing the temperature from 10 to 30 °C enhanced CH 4 production, but at 45 °C it almost ceased and the methanogenic precursor acetate accumulated. At lower temperatures, acetate accumulated only if acetoclastic CH 4 production was inhibited with methyl fluoride. The abundance of bacterial and archaeal 16S rRNA genes and mcrA genes were generally around 108 g−1 dry weight soil or higher. Alphaproteobacteria became increasingly abundant with time of incubation (up to 100 days) and temperature increasing from 10 to 30 °C. At 45 °C, however, Firmicutes became the dominant bacterial phylum. While about >70% of CH 4 was produced from acetoclastic methanogenesis at 10–30 °C, hydrogenotrophic methanogenesis was the dominant (>82%) pathway at 45 °C. The acetoclastic genus Methanoseata was the main methanogen at low (10 °C) and moderate (20 °C and 30 °C) temperatures, but the hydrogenotrophic genera Methanoregula and Methanomassiliicoccus dominated at high temperature (45 °C). Bathyarchaeota , with unknown function, dominated next to methanogenic Euryarchaeota the archaeal community, especially on DNA level. The methanogenic archaeal community composition of NamCo soil resembled that of alkaline lake sediments from the Tibetan Plateau. Structure and function of the methanogenic microbial community in alkaline wetlands and their temperature response seem to be different from those found in neutral paddy soil or acidic peatland soil. Highlights • Acetoclastic methanogenesis was the dominant pathway at 10–30 °C but ceased at 45 °C. • Alphaproteobacteria and Methanoseataceae dominated at 10–30 °C. • Firmicutes and Bathyarchaeota dominated at 45 °C. [ABSTRACT FROM AUTHOR]

Biological nitrogen fixation, conducted by soil diazotrophs, is the primary nitrogen source for natural grasslands. However, the diazotrophs in grassland soils are still far from fully investigated. Particularly, their regional-scale distribution patterns have never been systematically examined. Here, soils (0–5 cm) were sampled from 54 grasslands on the Tibetan Plateau to examine the diazotroph abundance, diversity, and community composition, as well as their distribution patterns and driving factors. The diazotroph abundance was expressed as nifH gene copies, measured using real-time PCR. The diversity and community composition of diazotrophs were analyzed through MiSeq sequencing of nifH genes. The results showed that Cyanobacteria (47.94%) and Proteobacteria (45.20%) dominated the soil diazotroph communities. Most Cyanobacteria were classified as Nostocales which are main components of biological crusts. Rhizobiales, most of which were identified as potential symbiotic diazotrophs, were also abundant in approximately half of the soil samples. The soil diazotroph abundance, diversity, and community composition followed the distribution patterns in line with mean annual precipitation. Moreover, they also showed significant correlations with prokaryotic abundance, plant biomass, vegetation cover, soil pH values, and soil nutrient contents. Among these environmental factors, the soil moisture, organic carbon, available phosphorus, and inorganic nitrogen contents could be the main drivers of diazotroph distribution due to their strong correlations with diazotroph indices. These findings suggest that autotrophic and symbiotic diazotrophs are the predominant nitrogen fixers in Tibetan grassland soils, and highlight the key roles of water and nutrient availability in determining the soil diazotroph distribution on the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

In this study, an expert knowledge-based model, a logistic regression model, and an artificial neural network model were compared for their accuracy and portability in landslide susceptibility mapping. Two study areas (the Kaixian and the Three Gorges areas in China) were selected for this comparison based on their well-known, high landslide hazard. To evaluate the performance of these models and to minimize the impact of the particularity of a study area on model performance, cross-applications of three models between the two study areas were conducted. When the Kaixian area was used as a model development area, prediction accuracy for the expert knowledge-based model, the logistic regression model, and the artificial neural network model were 71.5%, 81.0% and 100.0%, respectively. The high prediction accuracy of the two data-driven models were expected because the observed landslide occurrence used in training the models were also used to validate their respective performance, while the expert knowledge-based model did not use these observations for training. The perfect accuracy for the neural network model can also be attributed to its over-prediction of the susceptibility. When breaking the susceptibility into four classes: very low susceptibility (0–0.25), low susceptibility (0.25–0.5), high susceptibility (0.5–0.75), and very high susceptibility (0.75–1), the observed landslide density at the very high susceptibility level is 0.303/km 2 , 0.212/km 2 , and 0.195/km 2 for the expert knowledge-based model, the logistic regression model, and the artificial neural network model, respectively. This suggests that the expert knowledge-based model was much better than the other two data-driven models at evaluating landslide occurrence in very high susceptibility areas. When the three models developed in the Kaixian area were applied in the Three Gorges area without any changes, their prediction accuracy dropped to 44.8% for the logistic regression model and 81.6% for the artificial neural network model, while the expert knowledge-based model maintained its initial accuracy level of 82.8%. The landslide density for the very high susceptibility areas in the Three Georges area was 0.275/km 2 , 0.082/km 2 , and 0.060/km 2 for the expert knowledge-based model, the logistic model, and the artificial neural network model, respectively. These results indicate that the expert knowledge-based model is more effective at predicting areas with very high susceptibility. When the Three Gorges area was used as a model development area and the Kaixian area was used as the model application area, similar results were obtained. Results from the two experiments show that the performance of the logistic regression model and artificial neural network model is not as stable as the expert knowledge-based model when transferred to a new area. This suggests that the expert knowledge-based model is more suitable for landslide susceptibility mapping over large areas. [ABSTRACT FROM AUTHOR]

There is a paucity of knowledge in understanding the effects of warming and grazing on soil microbes and their active counterparts, especially on the Tibetan Plateau which is extremely sensitive to global warming and human activities. A six-year field experiment was conducted to investigate the effects of asymmetric warming and moderate grazing on total and active soil microbes in a Tibetan Kobresia alpine meadow. Soil bacterial abundance and 16S rDNA transcriptional activity were determined using real-time PCR. Total and active soil procaryotic community structures were analyzed through MiSeq sequencing based on 16S rDNA and rRNA, respectively. The results showed that the soil procaryotic community was more sensitive to the warming than the grazing. The warming significantly decreased soil microbial respiration rates, 16S rDNA transcription activity, and dispersion of total procaryotic community structures, but significantly increased the α diversity of active procaryotes. Warming also significantly increased the relative abundance of oligotrophic microbes, whereas decreasing the copiotrophic lineage proportions. The functional profiles predicted from the total procaryotic community structures remained unaffected by warming. However, the rRNA-based predictions suggested that DNA replication, gene expression, signal transduction, and protein degradation were significantly suppressed under the warming. The grazing only significantly decreased the 16S rDNA transcription and total procaryotic richness. Overall, these findings suggest that warming can shift soil procaryotic community to a more oligotrophic and less active status, highlighting the importance of investigating active microbes to improve our understanding of ecosystem feedbacks to climate change and human activities. [ABSTRACT FROM AUTHOR]

Intertidal mangrove wetlands are of great economic and ecological importance. The regular influence of tides has led to the microbial communities in these wetlands differing significantly from those in other habitats. In this study, we investigated the microbiomes of the two largest mangrove wetlands in Hainan Island, China, which have different levels of anthropogenic protection. Soil samples were collected from the root zone of 13 mangrove species. The microbial composition, including key functional groups, was assessed using Illumina sequencing. Bioinformatics analysis showed that there was a significant difference in the microbiomes between the protected Bamen Bay and the unprotected Dongzhai Bay. The overall microbiome was assigned into 78 phyla and Proteobacteria was the most abundant phylum at both sites. In the protected wetland, there were fewer marine-related microbial communities, such as sulfate-reducing bacteria, and more terrestrial-related communities, such as Verrucomicrobia methanotrophs. We also observed distinct microbial compositions among the different mangrove species at the protected site. Our data suggest that the different microbiomes of the two mangrove wetlands are the result of a complex interaction of the different environmental variables at the two sites. [ABSTRACT FROM AUTHOR]

Lakes are widely distributed on the Tibetan Plateau, which plays an important role in natural methane emission. Aerobic methanotrophs in lake sediments reduce the amount of methane released into the atmosphere. However, no study to date has analyzed the methanotroph community composition and their driving factors in sediments of these high-altitude lakes (>4000 m). To provide new insights on this aspect, the abundance and composition in the sediments of six high-altitude alkaline lakes (including both freshwater and saline lakes) on the Tibetan Plateau were studied. The quantitative PCR, terminal restriction fragment length polymorphism, and 454-pyrosequencing methods were used to target the pmoA genes. The pmoA gene copies ranged 10-10 per gram fresh sediment. Type I methanotrophs predominated in Tibetan lake sediments, with Methylobacter and uncultivated type Ib methanotrophs being dominant in freshwater lakes and Methylomicrobium in saline lakes. Combining the pmoA-pyrosequencing data from Tibetan lakes with other published pmoA-sequencing data from lake sediments of other regions, a significant salinity and alkalinity effect ( P = 0.001) was detected, especially salinity, which explained ∼25% of methanotroph community variability. The main effect was Methylomicrobium being dominant (up to 100%) in saline lakes only. In freshwater lakes, however, methanotroph composition was relatively diverse, including Methylobacter, Methylocystis, and uncultured type Ib clusters. This study provides the first methanotroph data for high-altitude lake sediments (>4000 m) and shows that salinity is a driving factor for the community composition of aerobic methanotrophs. [ABSTRACT FROM AUTHOR]

The wetlands of the Qinghai-Tibetan Plateau are believed to play an important role in global nutrient cycling, but the composition and diversity of microorganisms in this ecosystem are poorly characterized. An understanding of the effects of geography and microtopography on microbial populations will provide clues to the underlying mechanisms that structure microbial communities. In this study, we used pyrosequencing-based analysis of 16S rRNA gene sequences to assess and compare the composition of soil microbial communities present in hummock and hollow soils from three wetlands (Dangxiong, Hongyuan and Maduo) on the Qinghai-Tibetan Plateau, the world’s highest plateau. A total of 36 bacterial phyla were detected. Proteobacteria (34.5% average relative abundance), Actinobacteria (17.3%) and Bacteroidetes (11%) had the highest relative abundances across all sites. Chloroflexi, Acidobacteria, Verrucomicrobia, Firmicutes, and Planctomycetes were also relatively abundant (1–10%). In addition, archaeal sequences belonging to Euryarchaea, Crenarchaea and Thaumarchaea were detected. Alphaproteobacteria sequences, especially of the order Rhodospirillales, were significantly more abundant in Maduo than Hongyuan and Dangxiong wetlands. Compared with Hongyuan soils, Dangxiong and Maduo had significantly higher relative abundances of Gammaproteobacteria sequences (mainly order Xanthomonadales). Hongyuan wetland had a relatively high abundance of methanogens (mainly genera Methanobacterium, Methanosarcina and Methanosaeta) and methanotrophs (mainly Methylocystis) compared with the other two wetlands. Principal coordinate analysis (PCoA) indicated that the microbial community structure differed between locations and microtopographies and canonical correspondence analysis indicated an association between microbial community structure and soil properties or geography. These insights into the microbial community structure and the main controlling factors in wetlands of the Qinghai-Tibetan Plateau provide a valuable background for further studies on biogeochemical processes in this distinct ecosystem. [ABSTRACT FROM AUTHOR]

The Zoige Plateau is characterized by its high altitude, low latitude and low annual mean temperature of approximately 1°C and is a major source of atmospheric methane in the Qinghai- Tibetan Plateau. Methanotrophs play an important role in the global cycling of CH4, but the diversity, identity and activity of methanotrophs in this region are poorly characterized. Soils were collected from hummocks and hollows in the Riganqiao peatland and the methanotroph community was analysed by qPCR and sequencing methane monooxygenase ( pmoA and mmoX) genes. The pmoA genes ranged between 107 and 108 copies g−1 fresh soil, with a somewhat greater abundance in hummocks than hollows. The pmoA genes were analysed by amplicon pyrosequencing and the mmoX genes by cloning and sequencing. Methylocystis species were found to be the most abundant methanotrophs, but numerous clades were present including three novel pmoA and three novel mmoX clusters. There were differences between the methanotroph communities in the hummocks and hollows, with the most significant being an increased abundance of uncultivated type Ib methanotrophs in the hollows. The results indicate that aerobic methanotrophs are abundant in Riganqiao peatland and include previously undetected clades in this geographically isolated and distinctive environment. [ABSTRACT FROM AUTHOR]

We used a minirhizotron system to investigate the influence of three major factors-root morphology, root depth, and season of root emergence-on root survivorship and longevity in a Kobresia humilis meadow on the Tibetan Plateau during the growing season of 2009. Root longevity was assessed by survival analysis, Kaplan-Meier analysis, and Cox proportional hazards regression. Root longevity was correlated positively with root diameter. A 17.5 % decrease in the risk of mortality was associated with a 0.1-mm increase in diameter. Roots distributed in the top 10 cm of the soil had significantly shorter longevities than roots at greater depths, with a 48 % decrease of mortality risk for each 10-cm increase in soil depth from the surface to 40 cm. Of all the factors examined, the season of root emergence had the strongest effect on root lifespan. Roots that emerged in May and June had shorter longevity than roots that emerged later in the year, and roots that emerged in September and October were more likely to survive over winter. Our findings indicated that life-history traits of roots in K. humilis meadows are highly heterogeneous, and this heterogeneity should be considered when modeling the contribution of roots to carbon and nitrogen fluxes in this type of meadow ecosystem. Moreover, temporal, spatial, and compositional variations in root longevity must be considered. [ABSTRACT FROM AUTHOR]

Revealing the mechanisms underlying soil microbial community assembly is a fundamental objective in molecular ecology. However, despite increasing body of research on overall microbial community assembly mechanisms, our understanding of subcommunity assembly mechanisms for different prokaryotic and fungal taxa remains limited. Here, soils were collected from more than 100 sites across southwestern China. Based on amplicon high‐throughput sequencing and iCAMP analysis, we determined the subcommunity assembly mechanisms for various microbial taxa. The results showed that dispersal limitation and homogenous selection were the primary drivers of soil microbial community assembly in this region. However, the subcommunity assembly mechanisms of different soil microbial taxa were highly variable. For instance, the contribution of homogenous selection to Crenarchaeota subcommunity assembly was 70%, but it was only around 10% for the subcommunity assembly of Actinomycetes, Gemmatimonadetes and Planctomycetes. The assembly of subcommunities including microbial taxa with higher occurrence frequencies, average relative abundance and network degrees, as well as wider niches tended to be more influenced by homogenizing dispersal and drift, but less affected by heterogeneous selection and dispersal limitation. The subcommunity assembly mechanisms also varied substantially among different functional guilds. Notably, the subcommunity assembly of diazotrophs, nitrifiers, saprotrophs and some pathogens were predominantly controlled by homogenous selection, while that of denitrifiers and fungal pathogens were mainly affected by stochastic processes such as drift. These findings provide novel insights into understanding soil microbial diversity maintenance mechanisms, and the analysis pipeline holds significant value for future research. [ABSTRACT FROM AUTHOR]

• An increase in salinity inhibited soil CH 4 oxidation and methanotroph abundance. • Greater adaptation to soil salt stress in brackish than freshwater lake samples. • A major switchover of active methanotrophs in response to increased soil salinity. • Propagule limitation limits the adaptability of soil microbes to salinity change. The extent to which propagule limitation can govern the responses of microbially-mediated processes (such as methane oxidation) to sudden environmental changes, is poorly understood. Here, we compared the ability of the methanotroph community in lakeshore soils of two lakes to respond to an experimental increase in salinity. One set of samples was taken from lakeshore soils of a freshwater lake (Yang Lake), the other from a slightly brackish lake (Qinghai Lake), both on the Tibetan Plateau. Samples were incubated in microcosms by adding ∼ 5 % 13CH 4 or 12CH 4 and different concentrations of NaCl solution. DNA stable-isotope probing (DNA-SIP) followed by high-throughput sequencing was used to determine how the active methanotrophic populations differed in lakeshore soils with different salinity levels. Samples from saline and freshwater lake initially showed much-reduced methane oxidation ability and methanotrophic activity at increased salinity. For the freshwater samples with the salinity of 25 to 50 g/L after NaCl addition, there was no adaptation and increase in methanotrophy after 7 days. By contrast, samples from the brackish lake showed an initial depression of methane oxidation, followed by greatly increased rates after several days. Sequencing revealed that this recovery of methanotrophy in the brackish lake samples was associated with a major switchover in composition of active methanotroph community. In particular, the relative abundance of Type Ⅰa methanotrophs became more abundant at increased salinity. It appears that in this freshwater lake environment, isolation from any nearby high-salinity-tolerant bacterial sources has prevented the possibility of full adaptation to a high salinity change in the environment, and only a moderate salinity adaptation is possible by species-sorting from within the existing community. By contrast, in the higher-salinity environment, the highly salinity-tolerant Methylomicrobium was able to break the establishment limitation in the high salinity environment and become the dominant methanotroph. Our study provides an instance of propagule limitation preventing adaptation to changed conditions. [ABSTRACT FROM AUTHOR]

Aerobic methanotrophs present in wetlands can serve as a methane filter and thereby significantly reduce methane emissions. Sanjiang wetland is a major methane source and the second largest wetland in China, yet little is known about the characteristics of aerobic methanotrophs in this region. In the present study, we investigated the diversity and abundance of methanotrophs in marsh soils from Sanjiang wetland with three different types of vegetation by 16S ribosomal RNA (rRNA) and pmoA gene analysis. Quantitative polymerase chain reaction analysis revealed the highest number of pmoA gene copies in marsh soils vegetated with Carex lasiocarpa (10 g dry soil), followed by Carex meyeriana, and the least with Deyeuxia angustifolia (10 g dry soil). Consistent results were obtained using Sanger sequencing and pyrosequencing techniques, both indicating the codominance of Methylobacter and Methylocystis species in Sanjiang wetland. Other less abundant methanotrophy, including cultivated Methylomonas and Methylosinus genus, and uncultured clusters such as LP20 and JR-1, were also detected in the wetland. Methanotroph diversity was almost the same in three different vegetation covered soils, suggesting that vegetation types had very little influence on the methanotroph diversity. Our study gives an in-depth insight into the community composition of aerobic methanotrophs in the Sanjiang wetland. [ABSTRACT FROM AUTHOR]

Permafrost wetlands are important methane emission sources and fragile ecosystems sensitive to climate change. Presently, there remains a lack of knowledge regarding bacterial communities, especially methanotrophs in vast areas of permafrost on the Tibetan Plateau in Northwest China and the Sanjiang Plain (SJ) in Northeast China. In this study, 16S rRNA-based quantitative PCR (qPCR) and 454 pyrosequencing were used to identify bacterial communities in soils sampled from a littoral wetland of Lake Namco on the Tibetan Plateau (NMC) and an alluvial wetland on the SJ. Additionally, methanotroph-specific primers targeting particulate methane monooxygenase subunit A gene ( pmoA) were used for qPCR and pyrosequencing analysis of methanotrophic community structure in NMC soils. qPCR analysis revealed the presence of 10 16S rRNA gene copies per gram of wet soil in both wetlands, with 10 pmoA copies per gram of wet soil in NMC. The two permafrost wetlands showed similar bacterial community compositions, which differed from those reported in other cold environments. Proteobacteria, Actinobacteria , and Chloroflexi were the most abundant phyla in both wetlands, whereas Acidobacteria was prevalent in the acidic wetland SJ only. These four phyla constituted more than 80 % of total bacterial community diversity in permafrost wetland soils, and Methylobacter of type I methanotrophs was overwhelmingly dominant in NMC soils. This study is the first major bacterial sequencing effort of permafrost in the NMC and SJ wetlands, which provides fundamental data for further studies of microbial function in extreme ecosystems under climate change scenarios. [ABSTRACT FROM AUTHOR]

Microbial abundance and diversity in river ecosystems are being increasingly investigated, yet a synthesized understanding is still lacking. Here, studies of microbial abundance and diversity along global rivers are systematically reviewed based on 814 investigations performed across 8376 sites. We found that riverine microbial investigations are extremely heterogeneous regarding the spatiotemporal distribution of the sampling sites, the environmental media concerned, the microbial groups and indices targeted, the methods used, and the physicochemical properties examined. More than 72.23% of the studies were performed in the last 8 years, with most studies conducted in Europe, China, and the United States, while other regions were poorly investigated. Most studies have examined microbes in water, but very few studies have systematically investigated microbes in water, sediments, and riparian soils. Bacteria are the most studied microbial taxonomic groups; microbes with resistance genes and nitrogen cycling genes are the most studied microbial functional groups. High‐throughput sequencing has greatly expanded our understanding of microbial diversity along rivers. Nevertheless, the ecological implications of microbial diversity are still poorly understood. Regarding physicochemical properties, researchers tend to examine environmental parameters that are critical for shaping microbial communities, such as pH, nitrogen, and phosphorus. Future research should pay more attention to rivers that have not been well studied, especially large rivers. Additionally, microbial studies along rivers should be conducted in a more systematic way, taking the underinvestigated environmental media, microbial groups, microbial indices, and physicochemical properties into consideration. Advanced microbiology techniques, such as multiple omics technologies, should be increasingly applied. This article is categorized under:Water and Life > Conservation, Management, and AwarenessWater and Life > Nature of Freshwater Ecosystems [ABSTRACT FROM AUTHOR]

To determine whether archived air-dried soils can be potentially used to explore microbial information upon sampling, we examined microbial community dynamics during soil air-drying and long time preserving. Fresh soils from five long-term fertilization treatments were sampled, air-dried, and preserved. Soil microbial community was characterized at specific intervals (from 0 h to 8192 h) by Illumina sequencing. The results showed that both prokaryotic and fungal community profiles did not substantially change during air-drying and long time preserving. The fertilization effects on microbial community structure could still be identified using the air-dried soils. These findings suggest that air-drying and preserving exerts an almost negligible impact on soil microbial community profiles, laying the foundation for utilizing worldwide archived soils to investigate microbial community. • Soil microbial community dynamics during air-drying and preserving were deciphered. • Prokaryotic and fungal community profile was relatively stable during drying. • Microbial community structure was clustered by treatment rather than drying time. • Fertilization effects on microbial profile could be identified by air-dried soils. [ABSTRACT FROM AUTHOR]

[Display omitted] • Static composting with upward and downward aerations were compared. • Aeration directions altered heat and moisture distribution during composting. • Aeration strategies affected the compost quality with the same raw materials. • Mineralization and humification promoted by downward aeration. • The microbial community profiles were insensitive to aeration direction. A composting experiment with sewage sludge and green waste was conducted to explore the effects of aeration directions (i.e., upward and downward) on static composting systems. The compost properties, including humification indexes and organic matter loss rate, and microbial diversity during the composting, were determined. Results showed that the downward aeration promoted the homogenization of temperature and moisture of the static composting system, thereby stimulating microbial metabolism and accelerating mineralization and humification. Microbial community profiles significantly changed among the composting phases. The humification dynamics were significantly correlated with the relative abundance of multiple microbial functional groups. However, no significant effects of aeration direction on the microbial community profiles were observed. The findings indicate that downward aeration is promising to improve the quality of static compost production, by stimulating microbial metabolism rather than altering microbial community profiles. [ABSTRACT FROM AUTHOR]

The cover image is based on the Overview Microbial abundance and diversity investigations along rivers: Current knowledge and future directions by Kexin Li et al., https://doi.org/10.1002/wat2.1547. [ABSTRACT FROM AUTHOR]