This study examines the effects of different organic carrier materials, chicken manure, mill mud, and cow manure on the long-term viability and metabolite profiles of rhizobacterial strains Mesorhizobium sp. and Rhizobium sp. Over one year, growth curve analysis revealed significant differences in bacterial proliferation. Mill mud supported the most robust growth, with a doubling of 11 days, compared to chicken and cow manure, which exhibited growth saturation after five to eight months. Non-targeted 1H-NMR metabolite profiling revealed distinct sugar and amino acid profiles across carriers. Mill mud exhibited a broader range of sugars, including sucrose, maltose, and mannose, while chicken and cow manure primarily contained monosaccharides like glucose, xylose, and mannitol. Amino acids such as lysine and glutamate were higher in chicken manure, followed by cow manure and mill mud. Plant growth-promoting metabolites were detected in all carriers, with Mesorhizobium sp. and Rhizobium sp. enhancing their production by up to 200% in mill mud and cow manure. Both bacterial strains utilized sugars from the carriers, with Mesorhizobium sp. showing more consistent sugar metabolism. These findings suggest that mill mud is an effective carrier for sustaining rhizobacterial viability and enhancing metabolite production, benefiting biofertilizer formulations and soil health.
The alkaline phosphatase (phoD) gene-encoding bacterial communities (phoD-harbouring communities, hereafter) play crucial roles in organic phosphorus (Po) mineralisation across global terrestrial ecosystems. However, their geographic distribution and driving factors remain unclear, largely due to the mosaic temperature and humidity patterns and the lack of comprehensive high-resolution sampling data across the Qinghai-Tibet Plateau. We addressed this gap using amplicon sequencing techniques and analyses of soil properties as well as plant biomass. Plant biomass, soil organic carbon (C), Po content, C:P ratio, alkaline phosphatase (ALP) activity, and the richness and abundance of key soil phoD-harbouring taxa were higher in warmer, more humid regions, such as the southeastern plateau than the northeastern plateau, while soil pH followed an inverse trend. Soil pH and Po content emerged as the key factors shaping the geographic distribution of phoD-harbouring communities. Acidic soils were associated with higher C:P ratios, community richness, ALP activity, and Po content than alkaline soils. Our findings suggest that warmer, more humid regions promote soil acidification, which in turn drive changes in phoD-harbouring communities, enhance ALP activity, and stimulate Po mineralisation. This study provides new insights into the geographic distribution of phoD-harbouring communities and their role in Po mineralisation across the Qinghai-Tibet Plateau.
Granulating fluffy straw into high-density particles is an innovative approach for uniformly incorporating straw into plough layers. However, massive granulated straw incorporation probably causes microbial nutrient limitation, decreasing straw-C accrual and crop yield. Whether nutrient supplement increases straw-C accumulation remains unclear. In this study, we conducted one-year of micro-plot experiments incorporating massive granulated straw with initial C:N ratio (GS) and adjusted the C:N ratio by nutrient supplement (GSN) in infertile upland and paddy. After one year,GS incorporation greatly improved the surface (0–20 cm layer) soil organic C by 91% and 80% in upland and paddy, respectively, compared to their control. In upland, GS led to lower lignin phenols but higher amino sugars than paddy owing to its stronger microbial anabolism. In upland, GSN incorporation decreased soil organic C by 11.3% than GS by reducing lignin phenols and amino sugars. However, GSN incorporation increased organic C by 2.2% in paddy, via promoting microbial necromass accumulation. GSN incorporation improved crop yield by 26.6% in upland and 12.0% in paddy than GS. Collectively, granulated straw incorporation effectively enhances organic C and crop yield but that responses to nutrient supplement depend on soil properties. Tailored nutrient management is crucial to optimizing C sequestration and productivity in diverse soils.
The transformation of mountainous karst forests into urban parks requires a detailed evaluation of its impact on existing ecosystems, particularly in terms of the interplay between soil characteristics and plant diversity. In this study, we examined the species diversity of woody plants and soil characteristics within three established urban parks in Guiyang, China. We analyzed how habitat modification and the age of these parks influence soil properties and the diversity of woody plants. Our study revealed that soil levels of organic carbon, nitrogen, phosphorus, and potassium in artificial green spaces were significantly lower than in remnant forests. Woody plant alpha-diversity exhibited a negative correlation with potassium in remnant forests, but with phosphorus in artificial spaces. Interestingly, the associations between plant α-diversity and soil organic carbon and nitrogen were not significant in older parks, but were evident in newer ones. Furthermore, nitrogen, phosphorus, and potassium content significantly influenced woody plant composition across these parks. Habitat type and soil properties impacted the compositional diversity of woody plants more than park age, with phosphorus exerting the most substantial effect. In order to balance human recreational activities with the conservation of native ecosystems, it is essential to develop strategic management plans that prioritize soil enrichment and the maintenance of biodiversity in urban mountain parks.
The upward shift of the alpine treeline driven by global climate change has been extensively observed across many mountain ecosystems worldwide. However, variations in belowground microbial communities in the treeline ecotone, as well as the influence of microtopographic factors (e.g., slope aspect) on these changes, remain unclear. Here, we collected soil samples from different aspects above or below the treeline and analyzed the microbial communities using high-throughput sequencing. Our study revealed distinct community characteristics, co-occurrence patterns, and assembly processes between bacterial and fungal communities. Especially, homogeneous selection and dispersal limitation played dominant roles in shaping bacterial and fungal communities, respectively. Keystone bacteria were more critical for maintaining network stability above the treeline, while fungi were the keystone taxa for network stability below the treeline. We also found that oligotrophic species such as Acidobacteriota, Chloroflexi, Verrucomicrobiota, and Ascomycota were predominantly enriched above the treeline, whereas copiotrophic species like Proteobacteria, Gemmatimonadota, Actinobacteriota, and Firmicutes were more abundant below the treeline. Our results uncovered that microbial communities responded greatly to treeline shift than slope aspect, and also imply that the upward shift of the alpine treeline may increase the stochasticity of microbial communities. These findings facilitate our understanding of how microbial communities in the treeline transition zones of alpine ecosystems respond to global warming and their potential effects on soil carbon dynamics.
Elucidating the intricate dynamics of microbial communities across soil profiles is essential for deciphering the mechanisms by which microorganisms regulate ecosystem functions. However, previous studies on soil microorganisms have predominantly centered on abundant taxa, neglecting the significant role of rare taxa in maintaining ecosystem functions. This study comprehensively analyzed the diversity and assembly processes of both rare and abundant microbial taxa in the profiles of Udic and Ustic Isohumosols in northeast China. We also explored the relative contribution of rare and abundant microbial taxa in maintaining ecosystem multifunctionality. Results showed that rare microbial taxa exhibited a higher diversity compared to abundant taxa, and rare microbial taxa occupied more central positions within networks. Furthermore, rare taxa displayed narrower ecological niche breadths and stronger phylogenetic signals, and their community assembly was predominantly governed by deterministic processes. In contrast, stochastic processes exert more pronounced influences on the assemblage of abundant taxa. Ecosystem multifunctionality was significantly reduced in deep soil horizons relative to the surface soil horizons. This is accompanied by close cooperation of microorganisms to cope with environmental stress in deep soils. This study highlights the pivotal role of rare microbial communities in shaping multifunctionality of ecosystems across the entire soil profiles.
Organic mulching is widely applied in agricultural and forest ecosystems to improve crop yields and maintain soil quality. However, its long-term impact on soil organic carbon (SOC) stability and the underlying mechanisms remain unclear. An in situ experiment was initiated in 2018 in the subtropical region of China, with the non-mulched treatment serving as the control group (0 year of mulching), to investigate the effects of mulching on the organic carbon components (particulate organic carbon, POC, and mineral-associated organic carbon, MAOC) in Phyllostachys praecox bamboo forests across different mulching durations of 1, 3, and 5 years. Our results indicated that five-year mulching decreased soil POC concentration by 13.36%, while increasing MAOC and SOC by 130.3% and 64.53%, respectively, compared to no mulching. The POC/MAOC ratio dropped, indicating improved SOC stability. Additionally, soil pH decreased with mulching duration, while bacterial and fungal diversity, available phosphorus content, and β-xylosidase activity significantly increased. Structural equation modeling indicated that POC was mainly regulated by available phosphorus and fungal communities. While MAOC was affected by soil pH, which also mediated its response by influencing enzyme activity and bacterial diversity. In bamboo forest ecosystems, long-term organic mulching enhances SOC sequestration and stability, providing insights into SOC management for sustainable forestry. Such information indicates continuous mulching can be used to improve SOC sequestration in subtropical bamboo ecosystems.
