Weibo Wang

Aim: The influences of climatic gradients on biodiversity and functionality in arid ecosystems are increasingly evident. While soil microbes are susceptible to precipitation patterns, the mechanisms through which their variations affect the delivery of multiple ecosystem functions via microbial communities are poorly understood. Here, we examined the direct effect of precipitation gradients on multifunctionality and the indirect effect mediated by soil microorganisms and edaphic properties in drylands.Location: Northwestern China.Time Period: Field investigation in 2020.Major Taxa Studied: Multitrophic microbiota in biocrusts.Methods: We analysed 38 years of daily precipitation data to quantify multifaceted characteristics and spatial variations, including gradients of mean amount, frequency, and variability. Community structures of heterotrophic bacteria, fungi, and photoautotrophic cyanobacteria were determined via amplicon sequencing to measure taxonomic and phylogenetic α‐diversity and spatial turnover. Local multifunctional levels (α‐multifunctionality) and their pairwise dissimilarity/asynchrony (β‐multifunctionality) were depicted based on functional variables related to biocrusts. We investigated how precipitation and microbial diversity jointly influence soil multifunctionality.Results: We found historical precipitation variability, rather than mean annual precipitation, emerged as the primary driver promoting functional variance, leading to a convergence of less beneficial microbial species under high precipitation fluctuations. Although species richness across trophic levels positively influenced local functions, phylogenetic dissimilarity was a key predictor for soil photoautotrophs. As a β‐diversity component, species replacement consistently enhanced multifunctional dissimilarity and asynchrony of biocrusts. Notably, a cascading process was identified where the indirect effect of precipitation heterogeneity, regulated by microbial β‐diversity, accounted for a higher proportion of variance in β‐multifunctionality than direct climate influence.Main Conclusions: This study highlights the importance of precipitation variability and indirect climate impact mediated by soil microbiota. It contributes to a deeper understanding of the real‐world consequences of altered precipitation on drylands, providing valuable insights for interventions to mitigate climatic perturbations by managing soil community properties.

Bacterial diversity and its distribution characteristics in sediments are critical to understanding and revealing biogeochemical cycles in sediments. However, little is known about the relationship between biogeochemistry processes and vertical spatial distribution of bacterial communities in sandy sediments. In this study, we used fluorescence quantitative PCR, high-throughput sequencing technology and statistical analysis to explore the vertical distribution pattern of bacterial community diversity and its influencing factors in sandy sediments of the Yangtze River Basin. The aim is to enrich the understanding of the ecological characteristics and functions of bacteria in river ecosystems. The results showed that both sediment bacterial abundance and diversity showed a gradual decrease from surface to bottom in the vertical distribution. The main environmental factors that influenced the bacterial distribution pattern were pore water dissolved oxygen (DO), total nitrogen (TN) concentration and sediment nitrogen (N) content. The dominant bacterial species, Massilia and Flavobacterium, are suitable for growth and reproduction in high oxygen and nutrient-richer environments, while Limnobacter prefers low oxygen or anaerobic conditions. The vertical distribution pattern of bacteria and its influencing factors in river sandy sediment found in this study differ from the results in mud sediment, which may be related to the larger granular gap between sandy sediment and the lower content of organic matter. The findings of this study further our understanding of the distribution patterns and ecological preferences of microbial communities in river sediments, providing insights into how these communities may adapt to varying environmental conditions.

In the Anthropocene, the pervasive impacts of climate change on arid ecosystems are increasingly evident, resulting in significant alterations in both biodiversity and functionality. Although soil microbes are anticipated to be sensitive to changes in precipitation regimes, the mechanisms through which multifaceted precipitation changes impair the delivery of multiple functions by multitrophic microbiota in soils remain largely unexplored. In the drylands of Northwestern China, we examined the direct effects of historical precipitation regimes on the soil multifunctionality of biocrusts, a model system, and their indirect impacts mediated by microbial communities. Among abiotic predictors, precipitation variability, rather than mean annual precipitation, emerged as the primary driver of multifunctionality, leading to a convergence of less functionally beneficial species. By utilizing a biodiversity-ecosystem function relationship framework, our results underscore the crucial roles of α - and β -diversity of heterotrophic bacteria, fungi, and phototrophic cyanobacteria in maintaining soil functionality. However, the underlying mechanisms are distinct. We found that the local richness of heterotrophs and phylogenetic dissimilarity of photoautotrophs exert positive influences on multifunctionality, while species replacement, a component of β -diversity, primarily enhances the variance in soil multifunctionality. Importantly, the findings illuminate the cascading effect of precipitation variability on dryland ecosystems, amplified by microbial diversity, potentially triggering a silent collapse of vulnerable arid habitats. Our study highlights the importance of considering indirect climate impacts via soil microbiota, contributing to a deeper understanding of the real-world consequences of climate change on drylands, and offering valuable insights for the management of biodiversity theory-inspired ecosystem restoration.

Sediment particle size and heterogeneity play an important role in sediment denitrification through direct and indirect effects on, for example, the material exchange rate, environmental gradients, microbial biomass, and grazing pressure. However, these effects have mostly been observed in impermeable sediments. On the other hand, the material exchange of permeable sediments is dominated by advection instead of diffusion, with the exchange or transport rates exceeding those of diffusion by two orders of magnitude relative to impermeable sediments. The impact of permeable sediment particle size and heterogeneity on denitrification remains poorly understood, especially at the millimeter scale. Here, we conducted an in situ control experiment in which we sorted sand sediment into four homogeneous-particle-sizes treatments and four heterogeneous treatments. Each treatment was deployed, in replicate, within the riffle in three different river reaches with contrasting physicochemical characteristics. After incubating for three months, sediment denitrifier communities (nirS, nirK, nosZ), denitrification gene abundances (nirS, nirK, nosZ), and denitrification rates in all treatments were measured. We found that most of the denitrifying microbes in permeable sediments were unclassified denitrifying microbes, and particle size and heterogeneity were not significantly correlated with the functional gene abundances or denitrification rates. Water chemistry was the key controlling factor for the denitrification of permeable sediments. Water NO₃⁻-N directly regulated the denitrification rate of permeable sediments, instead of indirectly regulating the denitrification rate of sediments by affecting the chemical characteristics of the sediments. Our study fills a knowledge gap of denitrification in permeable sediment in a headwater river and highlights that particle size and heterogeneity are less important for permeable sediment denitrification.

In contrast to obligate bacteria, facultative symbiotic bacteria are mainly characterized by genome enlargement. However, the underlying relationship of this feature with adaptations to various habitats remains unclear. In this study, we used the global genome data of Nostoc strains, including 10 novel genomes sequenced in this study and 26 genomes available from public databases, and analyzed their evolutionary history. The evolutionary boundary of the real clade of Nostoc species was identified and was found to be consistent with the results of polyphasic taxonomy. The initial ancestral species of Nostoc was demonstrated to be consistent with a facultative symbiotic population. Further analyses revealed that Nostoc strains tended to shift from facultative symbiosis to a free-living one, along with an increase in genome sizes during the dispersal of each exterior branch. Intracellular symbiosis was proved to be essentially related to Nostoc evolution, and the adaptation of its members to free-living environments was coupled with a large preference for gene acquisition involved in gene repair and recombination. These findings provided unique evidence of genomic mechanisms by which homologous microbes adapt to distinct life manners and external environments.