Subtropical artificial grasslands play an important role in regional husbandry, yet how plant diversity drives grassland production via changes in plant and soil nutrients remains untested. Here, we established a field biodiversity experiment with 1, 3, 5, and 7 plant species in 2022 and investigated biomass production, nutrient cycling, enzymatic activities, and soil microbial properties in 2023 and 2024. Results showed that the 7 species treatment had the highest aboveground biomass among treatments. The 7 species treatment significantly increased the aboveground biomass by 62.07–70.51
Degraded urban soils often require reconstruction to restore their ecological functions, and earthworms are key ecosystem engineers that can contribute to the development of functional Technosols. Plant development is strongly influenced by earthworm-driven modifications of soil properties, yet the effects of co-occurring earthworm ecotypes remain poorly understood. We hypothesized that assemblages of ecologically distinct earthworm species enhance soil physical structure and promote plant growth through complementary processes. To test this, naturally co-occurring anecic, epigeic, and endogeic species were collected from an urban environment and inoculated, either alone or in combination, into constructed Technosols with increasing compost contents (10
The efficacy of nitrification inhibitors (NIs) varies widely in agricultural soils, influenced by environmental conditions that regulate both NI persistence and microbial activity. In this study, we investigated how soil pH and temperature interact to regulate the efficacy and overall soil ecological impact of three widely used synthetic NIs—dicyandiamide, nitrapyrin, and 3,4-dimethylpyrazole phosphate—and a novel inhibitor, quinone imine (QI). A microcosm experiment was conducted using two agricultural soils with contrasting pH (acidic and alkaline) incubated at 12.5 °C and 25 °C, following urea amendment. In addition to monitoring inorganic N pools and potential nitrification rates, inhibitors persistence and effects on ammonia-oxidizing microorganisms (AOM), nitrite-oxidizing bacteria (NOB), and non-target bacterial and fungal communities were assessed using qPCR and amplicon sequencing. All NIs dissipated faster at higher temperatures and showed greater persistence in the alkaline soil. Despite their reduced persistence at 25 °C, inhibition of nitrification was more pronounced at the higher temperature, reflecting increased nitrification activity under warmer conditions. All NIs significantly reduced potential nitrification rates and nitrate concentrations, particularly in the alkaline soil. Commercial NIs mainly affected ammonia-oxidizing bacteria (AOB), whereas QI exerted a stronger effect on ammonia-oxidizing archaea (AOA) and induced more pronounced shifts in bacterial and fungal communities, indicating stronger off-target effects. Overall, our results suggest that, under the conditions examined, soil pH and temperature jointly regulate NI persistence, functional partitioning of AOM, and microbial community composition, highlighting the importance of environmental context in determining NI performance in agricultural soils.
Soil respiration (Rs), driven by microbial activity, varied with mulching practices, but the microbial mechanisms behind these differences remain unclear. To address this knowledge gap, a three-year (2019–2021) maize field study was conducted to evaluate three treatments: no mulching (CK), plastic film mulching (PM), and straw mulching (SM). This study assessed the effects of these practices on the alpha diversity and composition of the bacterial community and Rs, and explore the roles of soil abiotic and biotic factors in driving Rs. The results indicated that PM significantly increased bacterial alpha diversity (as indicated by ASVs, Chao1, and Shannon indices) in the early growth stage of maize and decreased the bacterial abundance and Shannon index in the late growth stage, whereas SM increased that. Furthermore, PM and SM significantly altered the bacterial community, with PM enriched Chloroflexi and Firmicutes, while SM promoted Gamaproteobacteria and Bacteroidota. Cumulative Rs under PM varied interannually, increasing in 2019 and 2020 but decreasing by 9.1
Grassland degradation threatens global soil carbon (C) stocks, yet the mechanisms by which wind-dispersed tumbleweeds regulate soil C stabilization remain insufficiently resolved, particularly regarding how litter-driven priming effects (PE) and the partitioning of litter-derived C into particulate organic carbon (POC) and mineral-associated organic carbon (MAOC) respond to grazing intensity. We conducted a 13C/15N-labeled litter incubation experiment using soils collected from a long-term grazing intensity gradient (non-grazing, light, moderate, and heavy grazing). Litter derived from two tumbleweed species (Cleistogenes squarrosa and Saposhnikovia divaricata) and the dominant grass Leymus chinensis was added individually and in mixtures to soils from each grazing treatment for incubation. S. divaricata and its mixtures rapidly releases C and nutrients, stimulating microbial activity and thereby suppressing microbial mineralization of native SOC. Compared to L. chinensis, its mean PE is reduced by 25.1
Relative to chemical fertilizers, organic fertilizers are well recognized for their soil-improving benefits and other advantages. However, the impact of organic manures, produced by different production techniques, on the composition and diversity of soil microbial communities in paddy fields is not fully understood. To address this knowledge gap, experimental field plots were established in conventional double-cropping rice paddy fields in the Pearl River Delta, China. Five treatments were applied in addition to a no-fertilizer control (CK). These treatments were: two traditional organic fertilizers, namely fresh organic fertilizer (FOF) and successively composted organic fertilizer (SOF); two novel-processed organic fertilizers, including chemically composted organic fertilizer (COF) and chemically composted organic fertilizer with inorganic fertilizer (COIF); and chemical fertilizer (CF). Soil samples at different rice growth stages were collected and genomic DNA was extracted for high-throughput amplicon sequencing. The results showed that the novel-processed organic fertilizer COF significantly increased rice yield in comparison with the chemical fertilizer. Compared with chemical fertilizers and conventional organic fertilizers, COF effectively ameliorated the physicochemical properties of paddy soil and improved soil fertility, as evidenced by increased soil pH, total nitrogen, available nitrogen, and available phosphorus contents. With COF and COIF applications, the alpha diversity of the bacterial communities increased. COF application increased the connectivity of the co-occurrence network of the bacterial communities, and COIF simultaneously increased the connectivity of the co-occurrence networks of bacteria and fungi. Rice growth stage had a significant impact on the diversity and composition of microbial communities in double-cropping rice fields with the application of novel-processed organic fertilizers; dissolved organic carbon content, soil pH, and soil moisture were key factors affecting the microbial community. Overall, these findings deepen our understanding of the composition and diversity of soil microbial communities in response to novel organic fertilizers and of the key driving factors for the associated microbes in rice fields, and contribute to more effective fertilization management and conservation strategies.
Returning plant residues to agricultural soils is an effective strategy to enhance soil organic carbon (SOC) stocks, yet how soil texture interacts with residue composition to regulate microbial priming and residue-derived carbon (C) formation remain poorly understood. Here, we disentangle how the interaction between biochemical composition of residues and addition rate influences soil microbial communities and affects SOC formation across three soil types. We applied ¹³C-labelled residues of wheat [carbon to nitrogen ratio (C/N) = 42.5], pea (C/N = 25.5) and crimson clover (C/N = 15.6) at rates of 1, 2 and 6 Megagrams (Mg) C ha⁻¹ and incubated them to three soils with different clay content (17, 19 and 25
Wildfires alter aggregate microhabitats that regulate microbial access to carbon in volcanic ash soils, but aggregate-scale catabolic responses across contrasting climatic windows remain poorly understood. The hypothesis was that wildfire would reduce cumulative substrate-induced respiration, with declines concentrated in native forest microaggregates and plantation macroaggregates. The MicroResp whole-soil multiple substrate-induced respiration (MSIR) assay quantified cumulative CO2-C production in topsoil (0–5 cm) macroaggregates (2000 –250 μm) and microaggregates (250 –53 μm) from paired burned and unburned Nothofagus forest and Pinus radiata plantation sites in La Araucanía, south-central Chile. The same five georeferenced points per condition were sampled in February 2024 (dry/warm) and August 2024 (wet/cool). Composite dry/warm samples provided chemical, wavelength-dispersive X-ray fluorescence (WDXRF), and X-ray micro-computed tomography (micro-CT) data for analysis. Across campaigns, amino-acid cumulative CO2-C in native-forest microaggregates decreased from 475 to 181 mg kg− 1 in the dry/warm campaign and from 535 to 342 mg kg− 1 in the wet/cool campaign, whereas carbohydrate responses in plantation macroaggregates decreased from 372 to 119 mg kg− 1 and from 419 to 234 mg kg− 1, respectively. Substrate-level log-response ratios and a normalized differential aggregate fire sensitivity (DAFS) index indicated that fire-associated declines were concentrated in native forest microaggregates and plantation macroaggregates. The results indicate that wildfires reorganized microbial substrate use within aggregates in ways that depended on ecosystem/site context and aggregate fraction, while structural and chemical descriptors should be interpreted as contextual information.
Mineral amendments offer a promising strategy for soil carbon sequestration, but the main factors governing their effectiveness across soil depths remain poorly understood. Using a 14C-radiolabelling approach, we quantified the effects of three mineral amendments (iron, calcium, and basaltic rock dust (BRD)) on microbial carbon use efficiency (CUE) and 14C-glucose mineralization across soil depth (0–10, 10–25, 25–50 cm). Our results revealed a pronounced divergence in amendment effects across mineral types and soil depths. Calcium addition significantly increased microbial CUE (from 0.70 to 0.76), while concurrently reducing 14C-glucose mineralization. Conversely, iron addition, especially at 10 to 100 mmol kg-1, decreased microbial CUE (from 0.73 to 0.62) and increased mineralization, whereas BRD had limited effects on both CUE and mineralization. These responses were modulated by depth. Calcium increased microbial CUE only in the topsoil (0–10 cm) with no detectable effect at 10–50 cm, while microbial CUE response to iron or BRD were largely depth-invariant. In addition, iron induced strong positive priming of native 14C-SOM in the topsoil (119 ± 3
Silicon (Si) is increasingly recognized as a crucial modulator of crop health, conferring resistance to a wide range of biotic stresses while influencing soil fertility and microbial communities. In plants, Si enhances structural defenses through cell wall reinforcement and silica deposition, and activates biochemical pathways including antioxidant systems, defense enzymes, and hormone-mediated signaling. Si also reshapes rhizosphere microbiomes, selectively promoting beneficial bacteria and fungi while suppressing pathogens, creating feedback loops that enhance nutrient availability and plant resilience. Conventional Si sources, such as silicate salts and industrial byproducts, provide effective soil and foliar supplementation, whereas emerging nano-silicon formulations offer improved bioavailability and targeted delivery, though their environmental fate and long-term safety require further assessment. Despite robust evidence of agronomic benefits, critical gaps remain in understanding Si perception, molecular signaling, genotype and environment interactions, and long-term ecosystem impacts. Future research should integrate mechanistic studies, multi-omics approaches, long-term field trials, breeding of silicon-efficient cultivars, and precision management tools. When embedded within holistic, agroecological systems, Si represents a promising, sustainable strategy to enhance crop productivity, resilience, and soil health.
Combined application of biochar and silicate rock powder might have synergistic effects on carbon dioxide removal and soil improvement. However, it remains unknown how their combination affects mineralization and stabilization of soil organic carbon (SOC). We compared pure 13C-labeled wheat-straw biochar, pure basanite rock powder, their co-application, and rock-enhanced biochar from co-pyrolysis of wheat and basanite. All amendments were mixed with three agricultural topsoils (temperate silty, temperate sandy, tropical sandy) and incubated for 66 days. The δ13C-signal of the respired CO2 was monitored to determine amendment-induced priming of native SOC. After incubation, a density fractionation was conducted to investigate the potential stabilization of native and biochar-derived SOC as free particulate organic matter (fPOM), occluded POM (oPOM), and mineral-associated organic matter (MAOM). Pure basanite application did not influence short-term SOC dynamics, probably due to limited weathering within the 66-day incubation. In combined applications (co-application and rock-enhanced biochar), the biochar effect was dominant. The effects of biochar-containing amendments (biochar, co-application, and rock-enhanced biochar) were mainly controlled by texture and pH. The sandy soils exhibited positive priming following the application of biochar-containing amendments. In the temperate soils, positive priming occurred in MAOM, while native fPOM was partly shifted to oPOM. Input of biochar-derived SOC compensated losses of native SOC in fPOM and MAOM, resulting in overall SOC gains in most fractions. While priming intensity of all biochar-containing amendments was comparable, rock-enhanced biochar most strongly increased SOC in the density fraction interpreted as MAOM and had a higher short-term stability. These findings demonstrate that short-term effects of combined applications on SOC dynamics were dominated by the biochar component, while highlighting the potential of co-pyrolysis for short-term SOC stabilization.
Evaluating soil storage impacts on aminopeptidase activity can inform the use of aminopeptidase activity in soil N cycling assessments. We evaluated the impact of soil refrigeration (4 °C) and air-drying relative to field-fresh (4 °C for ≤ 3 d) on the activities and sensitivity of eight amino acid-specific aminopeptidase activities across a 42 y N fertilization gradient (0–269 kg N ha− 1) over 1.5, 6, 12 and 24 mo storage. Soil storage generally decreased (7–95
Microbial carbon use efficiency (CUE) is a central parameter for understanding soil carbon cycling and is widely used to predict soil organic carbon (SOC) stabilization and accumulation, microbial metabolic efficiency, and ecosystem carbon balance under global change. The isotope-based approaches currently employed to quantify CUE are grounded on a key assumption that assimilated carbon is predominantly allocated to growth and respiration. This assumption implicitly treats growth-related carbon investment as the dominant pathway linking microbial metabolism to SOC formation. However, in arid environments characterized by chronic water scarcity and nutrient impoverishment, microorganisms often allocate assimilated carbon to “non-growth carbon investments”, defined as carbon expenditures that do not directly generate new biomass but support survival, stress tolerance, and environmental persistence. These investments include maintenance respiration, dormancy, structural carbon allocation and extracellular polymeric substance production. This raises substantial uncertainty regarding whether the foundational assumptions of stable isotope probing-based CUE measurements can be directly applied to drylands. From both microbial ecological and methodological perspectives, this paper argues that isotope-based CUE measurements may systematically underestimate the true metabolic efficiency of microorganisms in drylands. We further examine the ecological mechanisms underlying this bias and outline future research directions. We propose that a “Adjusted CUE framework”—one that explicitly incorporates maintenance metabolism and survival-related carbon investments—should be developed for drylands. We also call for the broader adoption of integrative, multi-method approaches in global dryland carbon-cycle research to avoid misinterpreting microbial carbon allocation strategies and to improve the parameterization of SOC models under increasing aridity.
High temperatures and humidity in tropical climates reduce the effective accumulation of soil organic carbon (SOC) during fallow periods. Planting and returning leguminous green manure can facilitate the development and long-term stability of SOC fractions through the microbial carbon (C) pump mechanism. However, the mechanisms of microbial C sequestration at the functional gene level under different management stages of green manure remain unclear. Here, we systematically analyzed the effects of Crotalaria juncea (CJ), Crotalaria pallida (CP), and Sesbania cannabina (SC) on SOC fractions, microbial metabolic activity, and carbohydrate enzyme (CAZymes) encoding gene abundance during cultivation and incorporation stages. Results indicate that compared to the fallow control (CK), both CP and SC significantly increased SOC and microbial biomass C (MBC) during the planting and incorporation stages. Notably, during the incorporation stage, the SC treatment resulted in greater increases in SOC and MBC, by 51.3
Drought severely constrains plant growth and impairs soil microbial activity, and urban lawns act as a vital reservoir of soil organic carbon (SOC). Nevertheless, how drought regulates rhizosphere bacteria to mediate SOC fractions in turfgrasses remains poorly understood. We established a microcosm experiment and found that the contents of lignin and amino sugars in rhizosphere soil of Carex leucochlora (a native species of China) and Poa pratensis (an introduced species) decreased significantly with declining soil water-holding capacity (WHC). At 30
The conversion of crops to pastures has the potential to mitigate soil organic carbon (SOC) losses associated with long-term intensive cropping. Despite increasing evidence of pasture-induced SOC accumulation, microbial mechanisms governing the spatial sequestration of SOC within aggregate fractions throughout the soil profile of Mollisols under long-term monoculture remain largely unknown. Given the vigorous and deep rooting system of alfalfa, we investigated how the initial conversion of a > 50-year maize monoculture to alfalfa pasture influences SOC sequestration within aggregate fractions across the soil profile and associated microbial communities over the growing season. Alfalfa establishment significantly increased SOC in the mineral-associated aggregate fraction (P < 0.05), with the most pronounced accumulation at 40–50 cm depth (P < 0.01). Correspondingly, alfalfa cultivation markedly shifted microbial community composition. At the flowering stage, copiotrophic taxa such as Subgroup 10 and nitrogen-cycling groups including Nitrospira were enriched across aggregate fractions. At maturity, oligotrophic taxa including Pseudoxanthomonas, Massilia, and Moraxellaceae became more abundant. Notably, alfalfa-driven shifts in microbial community assembly were consistent across aggregate fractions. These findings demonstrate that conversion from maize to alfalfa promotes SOC accumulation in mineral-associated aggregates of deep soil layers. The enrichment of plant species-specific microbial taxa across aggregates suggests enhanced transformation and stabilization of fresh plant-derived carbon inputs.
Rhizosphere priming effects (RPE) are often assumed to accelerate soil organic matter turnover and drive net carbon loss from soils, thereby amplifying climate warming via CO2-feedbacks. Here, this paradigm is challenged combining empirical evidence and a stoichiometric model to show that co-occurring positive and negative RPE can cancel each other over time, resulting in neutral or positive net effects on the soil carbon balance. Then, several data streams are united to caution against upscaling reductionist laboratory soil incubations to ecosystem processes, because they consistently overestimate RPE, related to sieving disrupting the physical integrity of soil minerals and because food webs in natural ecosystems buffer the effects of labile C-inputs so that priming in nature has less extreme magnitudes than in soil incubations. Monte-Carlo simulations further demonstrate that even modest isotopic and flux measurement errors can generate spurious priming estimates when isotopic contrast is weak, highlighting the need for improved methodical accuracy to draw robust conclusion about priming in vivo. In conclusion, it is suggested RPE might function as a mechanism to synchronize carbon and nutrient supply and demand in the rhizosphere, rather than a consistent driver of soil carbon loss, with more modest effects in the field than in the lab. Future research prioritizing experiments with living plants at high labelling intensities, linking C and N fluxes and holistically accounting for the net carbon balance with respect to plant, soil and biota pools and fluxes will provide a more accurate foundation for the conceptualization of rhizosphere contributions to ecosystem carbon and nutrient cycling.
Soil inorganic carbon (SIC), a predominant carbon (C) reservoir in arid ecosystems, is conventionally viewed as geogenic and inert on biological timescales. Whether and how contemporary plant-fixed C actively contributes to this pool remain unresolved, creating a critical gap in our understanding of the terrestrial C cycle. Here, we traced the fate of photosynthetic C via in-situ 13CO2 pulse-labeling of the deep-rooted subshrub Alhagi sparsifolia in a hyper-arid desert ecosystem on the southern fringe of the Taklimakan Desert. We detected significant and persistent 13C enrichment in both soil organic C (SOC) and SIC pools throughout the 0–200 cm profile over 360 days. The incorporation of photosynthetic C into SIC was strongly correlated with biomarkers of living microorganisms (i.e., phospholipid fatty acid-13C) and the abundance of functional genes such as carbonic anhydrase (can). Random forest and correlation analyses identified nutrient availability (available phosphorus, available potassium, and nitrate nitrogen), rather than Ca2+ and pH, as the primary regulator of this microbial-mediated C flow. Shallow soils (0–60 cm) were hotspots for rapid C transformation, while deeper layers (60–200 cm) acted as a long-term SIC sink. Our study offers evidence consistent with an active, microbially driven pathway that transfers atmospheric CO2 fixed by plants into the stable SIC pool. This “microbial bridge” mechanism, governed by nutrient availability, reveals a previously overlooked but potentially rapid biological component of C sequestration in drylands, with profound implications for global C cycle models.
Soil degradation constitutes a primary constraint to global ecosystem services, making restoration a critical objective aligned with the United Nations Sustainable Development Goals 13 and 15. While anaerobic digestate is increasingly recognized as a promising amendment for restoring degraded soils within regenerative agriculture and circular bioeconomy frameworks, the mechanistic relationships between digestate quality and soil microbial restructuring remains insufficiently characterized. In this context, the objective of this study was to assess how psychrophilic digestate application influences soil physicochemical properties and microbial community dynamics, and to explore its role in the recovery of degraded soil under field conditions. Results revealed that alleviation of soil chemical stress, primarily associated with acidity, exchangeable Al toxicity, and nutrient imbalance was the primary regulatory factor. The input of exchangeable base cations, coming from digestate, drove a critical increase in pH, mitigating Al toxicity and unlocking P reserves. The observed soil recovery may be associated with the organic matter inputs from the digestate, which can support microbial activity and contribute to improved soil functioning. This was supported by an observed shift in the main soil microbial groups, from Gram-negative to Gram-positive bacteria, which are often associated with higher carbon use efficiency. These findings provided a detailed field-based framework supporting the use of digestate from low-tech digesters working under psychrophilic conditions as a strategic amendment for improving soil chemistry and microbial community composition, while enhancing soil organic C retention. Furthermore, it may offer a viable solution for digestate management aligned with regenerative agriculture and circular bioeconomy goals.
