Archaeal communities perform an important role in maintaining microbial stability under long term continuous cropping systems

Spartina alterniflora Ecosystem Stability: Insights Into the Interplay Between Soil Bacteria and Their Functional Traits

The relationship between soil microbiome stability and diversity remains a topic of debate. Our study aims to investigate the relationship between soil microbiome stability and diversity in different wetland types invaded by Spartina alterniflora and to reveal the mechanisms driving functional influences on this relationship during the later-stage development of the S. alterniflora invasion system. To investigated the structure, diversity, and functional traits of soil bacteria associated with S. alterniflora and their impact on bacteriome stability we conducted 16S rRNA sequencing of soils from two types of wetlands dominated by the invasive plant S. alterniflora at different growth stages, situated in temperate (salt marsh wetland) and subtropical (mangrove wetland) regions, and assessed bacteriome stability and its driving factors. Subsequently, we analyzed environmental and bacterial changes between the two sites and constructed co-occurrence networks among taxonomic groups and functional traits. The differences in the late-stage development of the two S. alterniflora-invaded wetland systems suggest that bacterial communities with higher diversity tend to exhibit greater stability. Keystone genera play both direct and indirect roles in regulating bacteriome stability, and all belong to dominant phyla. Furthermore, biological factors significantly outweigh nonbiological factors in driving stability. In contrast, core functions (broad functions) and specialized functions such as "nitrogen metabolism" and "sulfur metabolism" decrease bacteriome stability. Their enhancement of these metabolic processes correlates with reduced community stability, which is the key to the differences observed in the two invaded systems. This study advances our understanding of the relationship between soil microbial diversity and ecosystem stability, highlighting the importance of keystone taxa and functional traits for soil microbiome stability. It enhances our ability to predict microbial community transitions. It enhances a scientific basis for the management of S. alterniflora invasion.

Consecutive high-efficient water-saving irrigation increase crop yield and decrease soil salinity through reconstructing rhizosphere soil bacterial communities

Roughly 10 % of the world's arable land is affected by salinization, which significantly reducing crop yields, degrading soil health, and posing a serious threat to food security and ecological stability. High-efficient water-saving irrigation (HEI) technologies have showed positive effects on crop yield, especially with long-term application in salinized soil fields. However, the microbial mechanisms and influential pathways that promote crop yield and reduce salinity under consecutive HEI remain unclear. We conducted a 25-year study of long-term consecutive HEI in typical saline oasis areas, utilizing 16S rRNA high-throughput sequencing and structural equation modeling to analyze the results. The results showed that prolonged application of HEI significantly increased the diversity of soil bacterial community, enhanced the survival rate and yield of cotton, and significantly decreased soil salinity in the cotton fields. Compared with the 1 year application, the diversity indices of soil bacterial communities increased significantly (p < 0.05) by 45.41 %-61.64 %. After 5 years of consecutive HEI, the bacterial network interactions were enhanced. These enhanced interactions significantly (p < 0.005) increased the cotton survival rate by 55.27 % and the yield by 69.99 % after 10 years of application. With the joint positive influence of soil bacterial communities and crop growth after 15-25 consecutive years, soil salinity, the sodium absorption ratio, and the Cl- and SO42- equivalence ratio were significantly (p < 0.005) reduced by 88.01 %-90.00 %, 75.52 %-82.66 %, and 48.39 %-56.66 %, respectively. During the process, Acidobacteriota, Nitrospirota and Myxococcota contributed to higher crop yield mainly via nitrogen fixation, while Bacteroidota and Firmicutes reduced soil salinity primarily via nitrate reduction. Interestingly, Verrucomicrobiota, Nitrospirota, and Desulfobacteria, initially discovered in 5, 10, and 15th years, respectively, reappeared after intervals of 10 years. The diversity, complexity, and stability of the rhizosphere soil bacterial communities continuously improved up to 25 years, significantly (p < 0.005) increasing crop yield and decreasing soil salinity, by 71.55 % and 90.00 %, respectively.

Dissecting the role of soybean rhizosphere-enriched bacterial taxa in modulating nitrogen-cycling functions

Crop roots selectively recruit certain microbial taxa that are essential for supporting their growth. Within the recruited microbes, some taxa are consistently enriched in the rhizosphere across various locations and crop genotypes, while others are unique to specific planting sites or genotypes. Whether these differentially enriched taxa are different in community composition and how they interact with nutrient cycling need further investigation. Here, we sampled bulk soil and the rhizosphere soil of five soybean varieties grown in Shijiazhuang and Xuzhou, categorized the rhizosphere-enriched microbes into shared, site-specific, and variety-specific taxa, and analyzed their correlation with the diazotrophic communities and microbial genes involved in nitrogen (N) cycling. The shared taxa were dominated by Actinobacteria and Thaumarchaeota, the site-specific taxa were dominated by Actinobacteria in Shijiazhuang and by Nitrospirae in Xuzhou, while the variety-specific taxa were more evenly distributed in several phyla and contained many rare operational taxonomic units (OTUs). The rhizosphere-enriched taxa correlated with most diazotroph orders negatively but with eight orders including Rhizobiales positively. Each group within the shared, site-specific, and variety-specific taxa negatively correlated with bacterial amoA and narG in Shijiazhuang and positively correlated with archaeal amoA in Xuzhou. These results revealed that the shared, site-specific, and variety-specific taxa are distinct in community compositions but similar in associations with rhizosphere N-cycling functions. They exhibited potential in regulating the soybean roots' selection for high-efficiency diazotrophs and the ammonia-oxidizing and denitrification processes. This study provides new insights into soybean rhizosphere-enriched microbes and their association with N cycling. KEY POINTS: • Soybean rhizosphere affected diazotroph community and enriched nifH, amoA, and nosZ. • Shared and site- and variety-specific taxa were dominated by different phyla. • Rhizosphere-enriched taxa were similarly associated with N-cycle functions.

Peanut-based Rotation Stabilized Diazotrophic Communities and Increased Subsequent Wheat Yield

The introduction of legumes into rotations can improve nitrogen use efficiency and crop yield; however, its microbial mechanism involved remains unclear. This study aimed to explore the temporal impact of peanut introduction on microorganisms related to nitrogen metabolism in rotation systems. In this study, the dynamics of diazotrophic communities in two crop seasons and wheat yields of two rotation systems: winter wheat - summer maize (WM) and spring peanut → winter wheat - summer maize (PWM) in the North China Plain were investigated. Our results showed that peanut introduction increased wheat yield and biomass by 11.6% (p < 0.05) and 8.9%, respectively. Lower Chao1 and Shannon indexes of the diazotrophic communities were detected in soils that sampling in June compared with those sampling in September, although no difference was found between WM and PWM. Principal co-ordinates analysis (PCoA) showed that rotation system significantly changed the diazotrophic community structures (PERMANOVA; p < 0.05). Compared with WM, the genera of Azotobacter, Skermanella, Azohydromonas, Rhodomicrobium, Azospirillum, Unclassified_f_Opitutaceae, and Unclassified_f_Rhodospirillaceae were significantly enriched (p < 0.05) in PWM. Furthermore, rotation system and sampling time significantly influenced soil properties, which significantly correlated with the top 15 genera in relative abundance. Partial least squares path modeling (PLS-PM) analysis further showed that the diazotrophic community diversity (alpha- and beta-diversity) and soil properties (pH, SOC and TN) significantly affected wheat yield. In conclusion, legume inclusion has the potential to stabilize diazotrophic community structure at the temporal scales and increase subsequent crop yield.