Biology and Fertility of Soils最新文献

It is widely accepted that old-aged forest can accumulate soil organic carbon (SOC). How microbial physiological traits respond to forest age and whether they drive SOC sequestration in old-aged forest remain elusive. Therefore, we compared the microbial C use efficiency (CUE), biomass turnover rate (rB), microbial biomass C (MBC) and necromass C (MNC) across soil profiles from middle and old-aged forest and evaluated how these microbial traits are related to SOC storage. The results revealed that both forests could accumulate SOC and old-aged forest supported higher SOC storage than middle-aged forest from 2005 to 2020. Moreover, SOC was concentrated on the surface soils of middle-aged forest, whereas it was more distributed across the deeper soil profile in old-aged forest. Compared with middle-aged forest, the O, A and B soil layers of old-aged forest presented increases in microbial CUE (17.8%, 36.9% and 25.0%, respectively), rB (43.7%, 39.7% and 10.8%, respectively), MBC (114.8%, 81.1% and 122.9%, respectively), and MNC content (47.0%, 22.2% and 21.6%, respectively). Random forest analysis suggested that SOC accumulation is controlled mainly by microbial physiological traits rather than other factors including environmental variables. Specifically, microbial CUE and turnover rates increased in old-aged forest, resulting in higher MBC and MNC contents, which in turn led to SOC accumulation. Moreover, the effects of plant and soil properties on SOC storage are regulated mainly by microbial-physiological parameters and the size of microbial C pools. Our findings provide valuable insights into the microbial mechanisms underlying SOC storage in old-aged forest.

Utilising the rhizosphere microbiota as a biological control agent is a promising strategy to protect plants against pathogens, although its efficacy in fungal hosts is uncertain. This study investigated the efficacy of Pseudomonas chlororaphis, a bacterial strain, in mitigating Paecilomyces penicillatus, a soil-borne pathogenic fungus responsible for white mould disease (WMD) in cultivated morels, such as Morchella importuna. Soils with chronic WMD, inoculated with or without P. chlororaphis, were utilised for M. importuna cultivation. In P. chlororaphis-inoculated morel soil beds, P. chlororaphis colonised both the mycelial surface and ascocarp matrix of M. importuna, increasing the abundance of Morchella in soil and the α-diversity of the soil fungal community. Additionally, P. chlororaphis inoculation decreased the abundance of detrimental P. penicillatus and mitigated the WMD incidence, which correspondingly increased the morel yield. Metagenomics revealed that increasing the pseudomonads in the M. importuna mycosphere altered the functionalities of the M. importuna soil microbiota, enhancing the abundances of genes encoding chitinase and alkaline protease and reducing the abundances of genes encoding glucanase and laccase. Under P. chlororaphis inoculation, pathways associated with pathogenic invasion were under-represented in the soil microbiota. These results enhance our understanding of bacterial–fungal interactions within soil ecosystems and demonstrate the potential for disease suppression through microbiota manipulation within the fungal mycosphere. These insights may lead to innovative approaches to combat fungal pathogens and enhance the health and productivity of valuable fungal crops such as morels.

The dissolution of fertilisers is the initial process that takes place in soils following fertiliser application and influences the fate and effectiveness of fertilisers. Currently, there are only a few methods for studying fertiliser dissolution in soil. These approaches typically do not accurately represent real soil-fertiliser systems and are susceptible to errors, since they are influenced by processes associated with the loss or retention of the trace ions of the fertiliser. Low field NMR or time-domain NMR (¹H-TDNMR) is typically employed for studying ¹H in fluids (or mobile ¹H), however, special pulse sequences enable the selective detection of ¹H in solids. Furthermore, it is possible to filter out undesired signals like ¹H from minerals and from soil organic matter. This allows for the detection and monitoring of ¹H only from protonated fertilisers (e.g., ammonia, (di)-hydrogen phosphates, etc.). The aim of this study is to present an efficient procedure which monitors the dissolution of fertilisers in soils using ¹H-TDNMR. For this, six contrasting New Zealand soils and four protonated fertilisers - NH₄Cl, NH₄NO₃, NaH₂PO₄.H₂O, and (NH₄)₂HPO₄ - were utilised. The proposed method efficiently, accurately, and precisely, monitored the dissolution of the studied fertilisers in all the tested soils under different rain regimes, from violent rain (60 mm h^− 1) to light rain (2 mm h^− 1) with a time interval (temporal resolution) as short as 5 s.

Despite the rapid development of microbial inoculants use, their effectiveness still lacks robustness, partly due to our limited understanding of the factors influencing their establishment in soil. Recurrent inoculation can temporarily increase their abundance, but the effect of this inoculation strategy on plant growth and on the resident microbial community is still poorly studied. Here, we investigated maize growth and soil bacterial community responses under recurrent inoculation of the plant-beneficial bacterium Pseudomonas fluorescens B177. We further assessed how the effect of recurrent inoculation was modulated by the inoculant dose, the application timing and the soil type. Recurrent inoculation at high dose transiently increased the abundance of P. fluorescens B177 and resulted in larger shifts in the resident bacterial community compared to a single inoculation event. Moreover, recurrent inoculation prior to sowing had the strongest effect on maize growth, with increased shoot dry weight by 47.4%, likely due to an indirect effect of the inoculant through early changes in the resident community. Altogether these findings highlight the significance of recurrent pre-sowing inoculations as an alternative strategy for promoting plant growth.

The impact of plant litter on soil carbon (C) cycling is influenced by external nitrogen (N) deposition and plant litter chemistry. While previous research has mainly focused on inorganic N deposition and its effect on plant litter decomposition and soil C cycling, the influence of organic N remains poorly understood. In this study, we conducted a 180-day incubation experiment to investigate how different N forms (NH₄NO₃, Urea 50% + Glycine 50%) and litter chemistry (varying lignin/N ratios) affect CO₂ emissions from an acidic Moso bamboo (Phyllostachys edulis) forest soil. Our findings indicate that litter addition increased soil CO₂ emissions and the proportion of CO₂-C to Total C (considering added litter-C as a part of total C). Specifically, Moso bamboo leaf litter with a lower lignin/N ratio led to higher soil CO₂ emissions and CO₂-C/Total C ratios. The combined addition of litter and N exhibited an antagonistic effect on soil CO₂ emissions, with inorganic N having a more pronounced effect compared to organic N. This antagonistic effect was attributed to the N addition-induced soil acidification, thereby inhibiting microbial activities and reducing soil respiration promoted by litter input. This effect was confirmed by random forest analysis and partial least squares path modeling, which further identified soil dissolved organic C and pH as critical factors positively influencing soil CO₂ emissions. Overall, our study suggests that atmospheric N deposition can mitigate litter-induced soil CO₂ emissions, particularly under inorganic N forms and when leaf litters with high lignin/N ratios are introduced.

Intercropping, based on the interplay between cereals and legumes, might be an encouraging approach to improve soil fertility and crop productivity and to guarantee more sustainable farming systems. However, plant consociation is also influenced by the interaction between roots and soil microbial communities, and different plant genotypes might differently respond to this management. Here, a 2-year field study was carried out, verifying the impact of intercropping and the inoculation with arbuscular mycorrhizal fungi (AMF) on two varieties of durum wheat, using a lentil variety as intercropped plant species, on wheat agronomic parameters and grain features, as well as on microbial communities of soil, rhizosphere and wheat roots. Results showed a genotype effect on diverse agronomic parameters, gluten quality and grain elemental concentrations. Additionally, intercropping and AM fungal inoculation affected and shaped the microbial alpha diversity and composition, especially for the AMF community, at root level. Overall, the effects of the considered treatments (intercropping with lentil and AM fungal inoculation) were noticeably influenced by the specific wheat genotype, suggesting the importance to conduct a careful selection of intercropped genotypes.

Understanding the impact of agricultural land use on the soil prokaryotic communities in connected downslope sites is crucial for developing sustainable strategies to preserve ecosystem properties and mitigate agriculture’s environmental impacts. In this study, we investigated topsoil samples collected at three time points in 2022 (March, June, and November) from two adjacent catenas, reaching from hillslope to floodplain. The catenas differed in land use (extensive grassland vs. extensive cropland) at the top and middle parts, while the floodplain remained an extensive grassland due to legal restrictions. Using quantitative real-time PCRs and metabarcoding, we assessed prokaryotic abundance and prokaryotic community composition. Results show higher bacterial abundance in the cropland-influenced floodplain part across all time points compared to the grassland-influenced floodplain part. Temporal dynamics revealed a progressive decrease in the shared prokaryotic communities of the floodplain parts, peaking at the summer sampling time point, indicating a significant influence of the respective management type of the agricultural sites over the bacterial and archaeal communities of the floodplain parts. Differential abundance analyses identified several nitrifying taxa as more abundant in the cropland-influenced floodplain. Upstream land use also influenced the prokaryotic network of the cropland-floodplain, with some cropland taxa becoming keystone taxa and altering network morphology, an effect not observed in the grassland-influenced floodplain. These findings suggest that upstream agricultural land use practices have exerted a long-term influence on the floodplain prokaryotic communities over the past three decades. Moreover, there is evidence suggesting that these prokaryotic communities may undergo a potential reset during winter, which requires further investigation.

The root-associated type II methanotrophs significantly contribute to CH₄ oxidation-dependent N₂ fixation. However, it is unclear whether type I methanotrophs are involved in CH₄ oxidation and N₂ fixation, especially in natural wetlands. So far, limited attention has given to root-associated active microorganisms. Here, metatranscriptomic analysis of root-associated microbes has been proposed to reveal the aerobic methanotrophs contributing to CH₄ and nitrogen cycles in the roots of Phragmites australis grown in a natural wetland. Results showed Methylocystaceae (type II methanotrophs) and Methylococcaceae (type I methanotrophs) as major taxa (relative abundance, 14%) at transcription level. However, based on 16S rRNA gene sequencing, contribution of these taxa was < 1% at DNA level. Genes encoding methane monooxygenase (enzyme responsible for the first step of CH₄ oxidation) were detected in Methylomonas (pmoCBA) and Methylosinus (mmoXYZCB). Furthermore, genes related to methanol dehydrogenase, formaldehyde dehydrogenase, and formate dehydrogenase were also detected in Methyosinus and Methylomonas, while mcrA gene was observed in Methanospirillum and Methanofollis. Moreover, nitrogenase structural genes, such as nifHDK, were found in Methylosinus (Methylocystaceae) and Methylomonas (Methylococcaceae). Minor nitrogenase genes were detected in Cyanothece, Lyngbya, Pelobacter and Smithella of Cyanobacteriaceae family. In addition, N₂ fixing activity of P. australis was determined by analyzing the natural abundance of δ¹⁵N from June to August. The N₂ fixing activity of P. australis increased in presence of CH₄ in root system under ¹⁵N-N₂ feeding. Metatranscriptomic analysis revealed that not only type II methanotrophs, but also type I methanotrophs oxidize CH₄ and fix N₂.

In the absence of an appropriate formulation, the population of plant growth-promoting bacteria (PGPB) inoculated into soil may be significantly reduced. These unprotected introduced bacteria must compete with the often-more adapted native microflora and are susceptible to predation by soil microfauna. This opinion paper addresses the significance of proper formulation in creating an effective inoculant, discusses the primary challenges associated with current liquid and dry formulations, and emphasizes the rationale for bioencapsulation as the optimal approach for protecting PGPB in a successful inoculant.

Using two kinds of microbial inoculations extracted from soil cropped to rice and peanut, we conducted a swap-inoculation experiment to explore the relative importance of microbial inoculation and soil properties on CO₂ emissions from soil. Inoculated microorganisms into a soil different from their origin (swap inoculation) were partially successful and reduced CO₂ emissions, namely according to home-field advantage (HFA); The success of invasive microorganisms depended on molecular composition of soil organic matter (SOM) compared to inoculation of native microbes (inoculated microorganisms into origin soil). The different habits screened the fewer microorganisms to undergo respiration for energy and life-sustaining activities, thus decreasing CO₂ emissions from SOM. However, the effect of HFA diminished with incubation time, as the invasive microorganisms reshaped SOM molecular diversity and composition during microbial community assemblage, which fits with the Gaia effect (GE). Specific microbial communities, such as Bacteroidetes and Actinobacteria, drove the conversion of persistent molecules to labile molecules, thereby increasing the chances of SOM mineralization by microorganisms. We found there was positive correlation between labile SOM molecules and SOM mineralization. In addition, MBC increased in swap inoculation compared to native inoculation after 60 days, which also resulted in higher CO₂ emissions from SOM. HFA and GE provide new perspectives to help decipher the interaction between microorganisms and the habitat under microbial invasion, and the mechanism of influence on CO₂ emissions from SOM.