European Journal of Soil Biology最新文献

Veterinary antibiotics are increasingly used in the livestock industry annually. Sulfonamides introduced into the soil with manure are usually largely degraded in various pathways. However, the influence of the metabolic intermediate of sulfonamides on nitrogen (N) cycling under anaerobic conditions in soils has been overlooked. To this end, we carried out a microcosm experiment to investigate the potential consequences of ADPD (2-amino-4,6-dimethylpyrimidine, a degradation product of sulfonamide) at five concentration gradients (i.e., 0, 0.01, 0.1, 1, and 10 mg kg⁻¹) on nitrous oxide (N₂O) emissions, associated genes involved in N cycling, antibiotic resistance genes (ARGs), and mobile genetic elements (MGEs) in soils applied with manure or urea. The results showed that ADPD application promoted N₂O emissions under flooded conditions at environmentally relevant concentrations, and the maximum cumulative N₂O emissions were observed at 1 mg kg⁻¹ and 0.1 mg kg⁻¹ ADPD for manure and urea applied, respectively. The main reasons were the imbalance of denitrifying bacteria, which affected N₂O production and reduction, and the increase of antibiotic resistance in soil bacteria. In conclusion, these findings contribute to assessing the eco-environmental risks associated with the prevalence of sulfonamide metabolic intermediates and expand our understanding of the link between antibiotics and N transformation. Further research in the field is warranted to incorporate their recommendations into the greenhouse gas assessment system.

Sustainable agricultural systems, such as integrated crop-livestock (ICL) and no-tillage (NT), aim to sustainably produce crops and livestock while simultaneously conserving soil and its microbial properties, mainly in tropical regions. However, little is known about how microbial properties respond seasonally to management applied in NT and ICL. Thus, this study assessed the seasonal responses of soil microbial biomass C and enzymatic activity comparing both NT and ICL. The experimental area, under a block design with four replicates, with both NT and ICL management, was implemented in December 2022 on Yellow Argisol soil in Maranhao state, Brazil. Soil samples were collected (0–20 cm depth) in March, June, September, December, and March (2023). The results showed an effect size varying between 0.06 and 0.95 for agricultural systems, and 0.63 to 0.95 for sampling time. For the interaction between agricultural systems and sampling time, the effect size was superior to 0.86. NT showed initially higher microbial biomass C (∼50 %), leveling with ICL by the end of the sampling period. Phosphatase and dehydrogenase increased in ICL from March to June (∼200 % and ∼700 % for phosphatase and dehydrogenase, respectively), while fluorescein diacetate hydrolysis fluctuated in NT. Urease was higher (∼100 %) during all sampling times in NT. Linear discriminant analysis revealed distinct responses across sampling times, with a positive effect of pH on enzymatic activity in both systems and soil moisture and P impacting positively on microbial biomass in ICL. Our results revealed significant seasonal responses of soil microbial biomass and enzymatic activity comparing NT and ICL, but with distinct responses to agricultural systems. The study showed seasonal variation of soil microbial biomass and enzymatic activity dependent on the characteristics of NT and ICL. Therefore, understanding these differences helps farmers make better decisions for healthier soil and better crops.

Research on the variations of microbial attributes, C and nutrient properties, eco-enzymatic activities and their stoichiometry in different aged walnut orchards is essential for the sustainable development of walnut gardens. Here, four walnut orchards of various ages (0-, 7-, 14-, and 21-years) were selected in Hebei province, China, to evaluate the temporal changes in the above-mentioned indices within aggregates based on thermal gravimetric analysis, phospholipid fatty acid analysis and fluorometric assays. Results revealed that as the walnut plantation ages or aggregate sizes increased, the quantity and thermal stability of organic C exhibited increasing and decreasing trends, respectively. Long-term walnut plantation could increase C- and P- acquiring enzyme activities, and decrease N-acquiring enzyme activities in larger aggregates. Eco-enzymatic stoichiometry analyses demonstrated that the microbial C and P co-limitation increased with aggregate sizes or walnut plantation ages, although long-term walnut planting (14- and 21-years) and larger aggregates (>0.25 mm) provided more and easily available C resources for microbes. The aggravated C limitation (or P limitation) could be ascribed to the increased the ratio between microbial biomass C and organic carbon content (or the increased fungi/bacteria and soil N/P ratios) in the elder walnut plantations or larger aggregates. Overall, the study's results can provide several valuable insights (e.g., the old orchards can appropriately apply more P fertilizer) into the sustainable development of walnut gardens from the perspective of microbial nutrient demand.

Extracellular polymeric substances (EPS) synthesized by soil microorganisms play a crucial role in maintaining soil structure by acting as binding agents of soil aggregates. Microbial EPS production is governed by C sources, soil nutrient availability, pH, and other local environmental factors. Another important factor is soil management, and particularly, the addition of organic amendments (OAs), has the potential to influence soil EPS as it can change the biotic and abiotic properties of the soil. Yet the response of soil EPS to the addition of OAs, especially in field trials, and its subsequent impact on soil aggregation remains unclear. This study aimed to elucidate the influence of OAs (including compost from organic residues, mown grass from roadsides and parks, and cattle manure) on soil EPS content and aggregate stability in a three-year field experiment with annual OA application. We further investigated factors that govern EPS production in the soil by exploring the relationship between soil EPS (i.e., polysaccharide and protein content), soil physicochemical properties (i.e., pH, dissolved organic carbon, available and total amount of nutrients), and the soil microbial community (i.e., microbial abundance and taxonomic structure). We found that the addition of grass, manure, and the combination of grass and manure led to an increase in soil EPS content compared to unamended and compost-amended soils. EPS content was correlated with soil variables; in particular, a significant positive correlation was observed between EPS concentration and available N in the soil. Furthermore, bacterial and fungal biomass contributed to soil EPS. Specific bacteria (e.g., members of Proteobacteria, Bacteroidetes, and Chloroflexi) and fungi (e.g., members of Ascomycota and Basidiomycota) demonstrated strong and significant correlations with EPS in the soil. The direction of correlation, whether positive or negative, varied at the order level. In addition, our study revealed significant positive correlations between EPS concentration and soil aggregate stability. These findings offer insights into designing sustainable agricultural management practices, and whether the application of appropriate OAs can enhance soil EPS content and, consequently, soil aggregate stability.

Soil microbial indicators help monitor soil quality. Limited studies have determined how land use in drylands affects soil microbial indices. Top soil (0–10 cm) from four land use systems in African drylands: (1) shrubland (natural), (2) grassland (natural), (3) pasture (agricultural) and (4) cropland (agricultural) occurring on two soil types: (1) Vertisol and (2) Acrisol, was used in laboratory incubations (6 days) to assess the effects of land use changes on organic carbon (C_org) mineralization, microbial biomass C (C_mic), mineralization quotient (qM), metabolic quotient (qCO₂), C_mic:C_org ratio and sensitivity indices of these microbial indicators. Experimental plots were organized into a completely randomized design (n = 3) for every combination of land use and soil type. Cumulative CO₂ produced from native C_org mineralization was the highest in Acrisol (108 ± 2.7 μg CO₂–C g⁻¹ soil) and the lowest in Vertisol (53 ± 2.5 μg CO₂–C g⁻¹ soil) croplands. Vertisol shrubland (1.34 ± 0.09 mg C g⁻¹ soil) and Acrisol cropland (0.28 ± 0.07 mg C g⁻¹ soil) had the highest and the lowest C_mic, respectively. Acrisol cropland (1.29 μg CO₂–C g⁻¹ h⁻¹) had the highest qM, approximately five times higher than the lowest qM (0.26 μg CO₂–C g⁻¹ h⁻¹) in a Vertisol cropland. Highest qCO₂ was observed in an Acrisol pasture (12.04 μg CO₂–C g⁻¹ C_mic h⁻¹), which was approximately 30 times higher compared to the lowest qCO₂ observed in a Vertisol shrubland (0.41 μg CO₂–C g⁻¹ C_mic h⁻¹). The C_mic:C_org ratio was the highest in a Vertisol shrubland (0.097), approximately five times higher than the lowest observed in an Acrisol pastureland (0.019). Our study demonstrated that the measured soil quality indicators' magnitude, direction, and sensitivity varied depending on land use and soil type. Higher N availability in Vertisols increased the biological stability of soil organic carbon (SOC) resulting to decreased SOC mineralization than Acrisols. In conclusion, the measured microbial soil quality indicators showed that Acrisols are prone to accelerated SOC mineralization after disturbance than Vertisols in the studied semi-arid dryland ecosystems. Thus, there is a need to manage natural ecosystem conversions to support sustainable crop and pasture production in African drylands.

Large amounts of terrestrial organic carbon (OC) are stored in Arctic permafrost-affected soils. Through processes of cryoturbation and solifluction, the subsoils can contain subducted topsoil material, which largely contribute to the large OC storage in these soils. While the bacterial, archaeal, and fungal communities in such soils have been studied to some degree, information about protists and meso- and macrofauna is scarce, although these groups might substantially contribute to OC processing, through e.g., food web interactions. Different organic and mineral horizons, including subducted topsoil material, of Arctic soils were investigated using a metatranscriptomics three-domain community profiling approach. Soil horizons were compared in regards to their total microbial community composition including all three domains of life. Furthermore, abundances of different pro- and eukaryotic micropredators were examined and a variety of functional groups involved in the carbon (C) and the nitrogen (N) cycle were analyzed in relation to specific taxonomic groups and abiotic soil parameters. Our study showed that RNA yields positively correlated with the OC content of the horizon and that the composition of the microbial community in subducted topsoil material rather matched that of mineral subsoils instead of organic top horizons. Horizon-resolved profiling revealed heterogeneity in the associated microbiomes and showed major differences in microbiomes of topsoil and subducted topsoil. The abundance of protist and nematode micropredators decreased in subducted topsoil, while predatory myxobacteria remained remarkably constant and comprised high proportions of the total communities in all horizons. Correlations analysis between functional guilds and biotic and abiotic parameters suggest a major impact of predatory myxobacteria on carbon and nitrogen cycles of subducted topsoils. The study adds urgently needed information about the total biota structure in permafrost soils and first insights into the associated soil microbial food webs.

Anthropogenic climate change is widely predicted to influence essential ecosystem services such as decomposition and nutrient cycling, but consistent patterns of response to observed or predicted shifts in climate have proven difficult to evidence. We investigated how aspect (i.e., Pole- (PF) and Equator-facing (EF) roadside grassy verges in SW England), a natural model for variation in soil temperature, influenced soil physicochemical conditions, earthworm communities, and oak leaf litter decomposition. Average above-ground daily annual temperatures for EF-slopes were 1.96 °C higher than PF-slopes, with even more marked variation in average mean daily maximum and extreme temperatures (i.e., an average of three-fold more days where temperature exceeded 30 °C). Despite these differences, of the soil physicochemical factors quantified, only soil moisture (0–15 cm deep) varied consistently with aspect, being higher on the cooler PF slopes. Similarly, we detected no significant variation in litter decomposition. Despite low abundances there were, however, differences in earthworm assemblages between PF- and EF- slopes, with 7 of 14 species restricted to cooler, moister PF verges. Consequently, we conclude that despite consistent aspect-linked differences in the local microclimate, soil-based patterns and processes in semi-natural, temperate grassland ecosystems are relatively well buffered from the magnitude of temperature variation within the range predicted by the IPCC SSP1-2.6 emissions scenario. Nonetheless, the restricted distribution of half the earthworm species, and two functional groups to PF-slopes, supports studies suggesting that temperate increases associated with higher emissions scenarios will negatively influence some species, and the vital soil bioturbation processes that they provide.

The enzymic latch theory established the relationships between hydrolases, oxidases and soil organic carbon (SOC) stock in peatlands, desert or agricultural soils. The vital role of phenolics and soil pH still lack experimental evidences and has yet to be addressed simultaneously. The objective of this study was to validate the role of phenolics in SOC mineralization and whether and how pH regulates the role of phenolics through microbial activity. We conducted a 28-day laboratory experiment to tested the effects of three levels of phenol, 0 mg kg⁻¹ (control), 20 mg kg⁻¹ (LPh) and 100 mg kg⁻¹ (HPh), under four pH values (i.e., pH 5.6, 6.4, 7.2 and 7.9) maintaining 20 % soil moisture, on soil phenol oxidase (PO), hydrolases (α-glucosidase (AG), β-glucosidase (BG), β-xylosidase (XYL), cellobiohydrolase (CBH), and total hydrolases (SUM-H)), microbial indices (microbial biomass carbon (MBC) and dehydrogenases (DHA)), and dissolved organic carbon (DOC). The results showed that soil pH and phenol interacted with CBH, XYL and DHA activities. Both hydrolase and PO activities increased with pH and were highest at pH 7.9 (AG: 38.62 mg kg⁻¹ h⁻¹, BG: 258.88 mg kg⁻¹ h⁻¹, SUM-H: 426.93 mg kg⁻¹ h⁻¹, PO: 1.35 mg kg⁻¹ h⁻¹). CBH activity was reduced by up to 17.74 % at pH 6.4, 20.54 % at pH 7.2 and 21.98 % at pH 7.9. LPh and HPh reduced XYL activity throughout the incubation period up to 24.93 % and 19.88 % at pH 6.4 and 23.43 % and 32.38 % at pH 7.2, respectively. DOC increased with hydrolases activities (AG, BG and SUM-H) and microbial indices (DHA and MBC). Phenolic accumulation limited soil hydrolase and microbial activities and slowed down SOC mineralization, especially at nearly neutral soil pH. SOC stability increased with the transformation of soil labile C to MBC at LPh while reduced with the consumption of SOC by microorganisms at HPh. Overall, the inhibition of phenol on hydrolase activities and SOC mineralization was enhanced under neutral soil pH conditions, helping to better understand the SOC accumulation in agroecosystems.

The distribution of earthworm ecological groups in urban areas is not well-known, despite their crucial role in delivering soil ecosystem services such as nutrient cycling and water drainage. Citizen science engages public audiences in the scientific research process and is an excellent tool for collecting biodiversity data in urban areas, where most of the UK population resides. However, a disadvantage is that differing levels of skill and engagement among participants can create statistical challenges. The Earthworm Watch citizen science project used 668 matched-pair surveys to estimate how the abundance and ecological diversity of earthworms respond to land management practices, and soil properties in UK urban habitats. A total of 5170 earthworms were counted during the project with a mean of 8 earthworms per soil pit - equivalent to a density of 198 earthworms per m². Soil moisture and texture were the largest drivers of total earthworm abundance, with habitat borderline statistically insignificant. Endogeic earthworms were found in 71 % of soil pits, epigeic in 62 % and anecic in 33 %. Fertiliser use also had a significant effect on total abundance, but only when organic fertiliser was used. Earthworm ecological groups demonstrated varied responses to habitat, with endogeic earthworms consistently the most abundant group, showing slight preferences for grasslands and vegetable beds. Anecic earthworms had the lowest abundance across all habitats but were more prevalent in grasslands and vegetable beds. Epigeic earthworms were most abundant beneath shrubs and hedges. These findings align with expected patterns of earthworm ecology, underscoring the potential of well-designed citizen science projects to yield valuable insights into urban earthworms and soil health.

Earthworm burrowing is essential for soil functioning in temperate climates. It is known that soil compaction hampers earthworm burrowing, but there is a lack of knowledge on how it affects the energy costs of earthworms. In the present study, we used respirometry and isothermal calorimetry to quantify earthworm respiration rates and heat dissipation in two endogeic species, Aporrectodea caliginosa and Aporrectodea tuberculata, in compacted and non-compacted soils. We put the measured respiration rates and heat dissipation in relation to the burrow volume and cast volume produced by the earthworms. We found that at higher compaction levels, respiration rates and dissipated heat increased for both studied species. The energy costs associated with burrowing were a significant fraction of the total energy costs. Our results indicate that energy costs per burrow volume increase due to compaction, and that the specific energy costs for burrowing (i.e., per gram earthworm) were lower for A. tuberculata than for A. caliginosa. Further studies are needed to confirm our results. We discuss the potential and current limitations of isothermal calorimetry as a method for direct quantification of energy costs of earthworms. There is a need for further studies that quantify how energy costs of burrowing are affected by various soil conditions, to better predict the implications of land use and soil management on soil processes and functions mediated by earthworm burrowing.