Soil Total Carbon Research Articles

Long-term nitrogen deposition alters the soil bacterial community structure but has little effect on fungal communities

Subtropical Moso bamboo (Phyllostachys edulis) forests have become hot spots for nitrogen (N) deposition in China. However, the effect of long-term N deposition on the structure of soil microbial communities in different horizons of these forests remains unclear. To investigate the influence of extended N deposition on soil bacteria and fungi, a simulated N deposition field study was conducted in Fujian Province with four N deposition levels (0, 20, 40 and 80 kg N hm−2 a−1). The absolute abundances, diversity, community structure, and potential functions of soil bacteria and fungi were investigated after 10 years of simulated N deposition. The results indicated that there was no significant effect of N deposition on the abundance or diversity of soil microbes in either the organic or mineral horizons of Moso bamboo forests. However, under rates of 40 and 80 kg N hm−2 a−1, long-term N deposition altered the structure of the soil bacterial community in the organic horizon. Specifically, there was a 27.75∼36.40 % increase in the relative abundance of Actinobacteria, while that of Acidobacteria decreased by 24.40∼27.52 %. Redundancy analysis (RDA) demonstrated that soil total carbon (TC) was the key variable influencing the bacterial community structure in the organic horizon. Analysis of potential microbial functions showed that in the organic horizon, the rates of chemoheterotrophy significantly decreased under 80 kg N hm−2 a−1. However, N deposition did not noticeably impact the fungal community structure in either soil horizon. Our study suggested that under 10 years of N deposition, only the bacterial community composition and function in the organic horizon was affected, indicating that soil bacteria are more sensitive to N deposition than fungi in subtropical Moso bamboo forests. Therefore, further research is necessary to fully understand the impact of N deposition on fungal community composition in the soil organic horizon and on the microbial community in the mineral horizon of subtropical bamboo forests. This study provides valuable insights for informing future environmental management and conservation strategies.

Methodology for evaluating soil carbon stock changes based on regional geochemical survey data: A case study in Huangpi, China

Soil carbon pools play a crucial role in the Earth's ecosystem, acting as significant carbon sinks and sources. Through a detailed analysis of soil carbon content using data from the Huangpi District in Wuhan, China, this research employs geochemical survey data, field replicates, and spatial autocorrelation information to establish an assessment model for soil carbon stocks. The model addresses the sources of errors and their effects on carbon pool changes, using both traditional statistical theories and geostatistical models to detect changes in carbon density and estimate carbon sources and sinks with minimized error ranges. Key findings indicate that sampling errors, influenced by small-scale spatial variability, are the primary source of observational inaccuracies in assessing total soil carbon and organic carbon, accounting for over 90% of the variation. Meanwhile, analytical errors are more significant when quantifying soil inorganic carbon content due to its lower concentrations. From 2001 to 2022, no significant changes were observed in the soil organic carbon stock in Huangpi District, while a modest increase in inorganic carbon was noted. The study highlights that increasing sample density beyond a certain threshold does not significantly affect carbon stock estimates or their error ranges, emphasizing the stability of the block kriging method in estimating regional carbon stocks.

Polyaspartic calcium improved soil quality and altered nitrification process in saline‐sodic paddy soils

AbstractSaline‐sodic paddy soils in the Songnen Plain suffer from nitrogen loss due to nitrification. The purpose of the study is to explore soil saline improvement and nitrification mitigation effects of polyaspartic calcium (PASP‐Ca) by evaluating changes of soil quality, nitrification, and microbial communities. Four PASP‐Ca application treatments (additions of 0, 500, 1000, and 1500 kg hm−2) were studied in an experiment in saline‐sodic paddy soils of the Songnen Plain, China. Results showed that PASP‐Ca application significantly decreased soil pH, electrical conductivity (EC), and water‐soluble salt ions, and significantly increased soil total carbon (TC), total nitrogen (TN), urease activity (UA), and sucrase activity (SA). PASP‐Ca application significantly slowed down soil nitrification, which was manifested in a significant increase in ammonium nitrogen () and a significant decrease in nitrate nitrogen () and ammonia monooxygenase activity (AMO). The composition and distribution of soil nitrifying microbial communities were affected by soil salinity, nutrient, and enzyme activities. Ammonia‐oxidizing bacteria (AOB) plays an important role in the nitrification process of saline‐sodic paddy soils, while PASP‐Ca application significantly inhibited nitrification by suppressing AOB amoA gene abundance. This study shows that PASP‐Ca, as an effective amendment, can improve soil salinization and slow down nitrification, which has an important role and significance in improving nitrogen utilization and reducing nitrogen loss of saline‐sodic soils.

Soil organic carbon fractions and storage potential in Finnish arable soils

AbstractUnderstanding the factors affecting the total amount and distribution of soil organic carbon (OC) across different functional carbon pools is important to better define the future management of soil OC stocks. The interactions between soil management practices, local physicochemical soil properties and climate are essential for determining the OC content of the soil. Nevertheless, how these factors affect the total amount of OC and its distribution across carbon pools, i.e., more labile particulate (POC) and more stable mineral‐associated (MAOC) organic carbon, is only partly known. In this study, we assessed topsoil (0–20 cm) samples from 93 arable farms in the southern half of Finland to determine the total amount of OC, and its distribution in MAOC and POC, along with relevant soil properties (amount of clay and silt, aluminium and iron oxides and pH), climate (precipitation and temperature) and fertilization (mineral versus organic). The fertilization did not affect the total soil carbon content (12–58 g OC kg−1 soil). The share of OC in the MAOC fraction (on average 86% of total OC) was relatively stable across the large range of OC contents and clay contents (2%–68%). We assessed the highest feasible MAOC of the soils with boundary line analyses and their OC saturation state with Hassink's equation (Hassink, 1997). Only soils with the lowest clay content (<10% clay) were assumed to be carbon‐saturated, suggesting that most of the studied soils have a capacity to accrue more MAOC. Simple linear regression showed that clay, aluminium and iron oxides explained 9%, 21% and 22% of the variation in MAOC, respectively. Multiple regression analyses including the amount of clay, clay+silt, aluminium and iron oxides, pH, type of fertilization, precipitation and temperature as explanatory variables explained 33%–53% of the variation in OC and MAOC. In all soils, aluminium oxides were important explanatory variable for MAOC, whereas Fe oxides were significant only in soils with higher clay content (>30%). In soils with a low clay content (<30%), pH had added value in explaining MAOC. Altogether, it seems that various climatic, edaphic and soil management‐related factors are context‐dependently controlling OC and that soil textural information alone is not necessarily an adequate predictor to assess the MAOC saturation state of the soil.

The Impact of Artificial Afforestation on the Soil Microbial Community and Function in Desertified Areas of NW China

Afforestation is a widely used method of controlling desertification globally as it significantly impacts the soil quality, microbial community structure, and function. Investigating the effects of various artificial vegetation restoration models on soil microbial communities is crucial in understanding the mechanisms involved in combating desertification. However, research on this topic in arid, desertified regions is limited. In this study, we collected soil samples from two types of artificial forests (single species and mixed species) and bare desert soils in desertified areas of Northwest China to explore the impact of afforestation on soil nutrients, the microbial community composition, network relationships, and carbohydrate degradation abilities using metagenomic sequencing techniques. Our findings indicate that afforestation significantly enhances the soil moisture, total carbon, available phosphorus, and total nitrogen levels. The soil under mixed-species forests exhibited significantly higher levels of total carbon, total phosphorus, available phosphorus, and total nitrogen than that under single-species forests. Following afforestation, the populations of Pseudomonadota, Acidobacteriota, and Cyanobacteria increased significantly, whereas Actinomycetota decreased markedly. In single-species forests, Pseudomonadota and Bacillota were enriched, whereas Chloroflexota, Planctomycetota, and Acidobacteriota were more prevalent in mixed-species plantations. Afforestation increases the complexity and stability of microbial community networks. Afforestation enhances microbial metabolic activity, particularly increasing the abundance of carbon degradation functional genes in forest soils compared to bare desert soils. Mixed-species plantations outperform single-species forests in enhancing carbohydrate metabolism, amino acid metabolism, and the biodegradation and metabolism of xenobiotics. The abundance of functional genes associated with the degradation of starch, cellulose, hemicellulose, chitin, and pectin in mixed-species forests was significantly greater than in single-species plantations. Our study shows that mixed-species afforestation effectively improves the soil quality, enhances the stability of soil microbial communities, and bolsters the carbon cycle in arid regions prone to desertification. The reciprocal relationship between microorganisms and plants may serve as an intrinsic mechanism by which mixed-species afforestation more effectively controls desertification.

Exogenous calcium-induced carbonate formation to increase carbon sequestration in coastal saline-alkali soil

Promoting soil carbon sequestration is a possible way to mitigate global warming. To investigate the effects of exogenous calcium on soil carbon sequestration during the application of organic matter to improve coastal saline-alkali soil. In this study, a 30-day incubation experiment was based on the application of corn straw biochar + chicken manure (BM) and rice straw + chicken manure (SM). Usages of exogenous calcium in each treatment under each organic matter combination as follow: CK (No exogenous calcium), CaSi1 (1.24 g CaSiO3, i.e. 4.28 g Ca kg−1 soil), CaSi2 (2.48 g CaSiO3, i.e. 8.56 g Ca kg−1 soil), CaOH1 (0.79 g Ca(OH)2, i.e. 4.28 g Ca kg−1 soil), CaOH2 (1.58 g Ca(OH)2, i.e. 8.56 g Ca kg−1 soil), CaSiOH (1.24 g CaSiO3 + 0.79 g Ca(OH)2, i.e. 8.56 g Ca kg−1 soil). Results showed that exogenous calcium significantly reduced CO2 emission. Organic matter addition promoted the loss of SOC, and exogenous did not significantly affect the mineralization of SOC albeit strongly increased SIC, making up for the loss of SOC, increasing soil total carbon and realizing soil carbon fixation. Soil carbon fixation was mainly realized by the reaction of exogenous calcium with CO2 generated by mineralization and converting it into calcium carbonate. pH and soil CO2 emission are the major controlling factors for soil inorganic carbon sequestration. Therefore, applying organic matter with exogenous calcium can realize soil carbon fixation by generation of calcium carbonate.

Impact of biocrust on soil nitrogen maintenance and microbial composition in citrus orchards under varying urea application rates

Biocrust communities and their effects on soil nitrogen (N) content in natural drylands have been extensively studied. However, their significance in citrus orchards, which are typically managed with N fertilizer, remains unclear. To address this, an investigation was conducted in a citrus orchard subjected to varying levels of urea application (0 %, 70 %, and 100 % of the local N fertilizer application) over three years. The study focused on biocrust communities dominated by bryophytes, examining their community and individual characteristics, and comparing the properties and microbial communities of soils with and without biocrust cover. The results showed that biocrust had the highest percent coverage (56.1 %) in the plot with 70 % local N fertilizer application. Dicranella heteromalla was the dominant biocrust species across all treatments, exhibiting greener and longer leaves with 70 % local N fertilizer application. Biocrust cover significantly (P < 0.01) influenced soil total nitrogen content, soil water content, soil total carbon content, and soil dissolved organic carbon content. In contrast, fertilizer application had non-significant effects on the physicochemical properties of soils, regardless of biocrust cover. A notable difference in bacterial phyla composition was observed between soils with and without biocrust cover (PERMANOVA, P = 0.001), although fertilization did not significantly affect the bacterial diversity index. Additionally, biocrust cover significantly (P < 0.01) influenced predicted soil bacterial functional groups, including ureolysis and nitrogen fixation, while fertilizer application had a weaker impact on these bacterial functional groups. In conclusion, nitrogen application altered the community and dominant species characteristics of biocrust but did not overshadow the effects of biocrust on soil N dynamics. In the citrus orchard with varying levels of urea application, biocrust played a crucial role in soil water retention, N maintenance, and predicted microbial ecological functions related to N cycling.

Enhancing crop production and carbon sequestration of wheat in arid areas by green manure with reduced nitrogen fertilizer

Green manure with appropriate amount of chemical nitrogen fertilizer can increase crop yield, but also aggravate soil carbon emissions. However, it is unclear whether incorporation of green manure into the cropping pattern with reduced nitrogen amount can alleviate this situation and enhance carbon sequestration potential. So, a field experiment with split-plot design was set up in 2018 of northwest China, and studied the effects of nitrogen reduction on crop productivity, carbon emissions, and carbon sequestration potential in 2021–2023. The main plots were two cropping patterns, including multiple cropped green manure after wheat harvest (W-G) and fallow after wheat harvest (W). Three nitrogen application levels formed the split-plots, including local conventional nitrogen amount (N3, 180 kg ha−1), nitrogen amount reduced by 15% (N2, 153 kg ha−1) and 30% (N3, 126 kg ha−1). The results showed that W-G increased grain yield of wheat and energy yield of wheat multiple cropped green manure pattern. The multiple cropped green manure after wheat harvest with local conventional nitrogen amount reduced by 15% (W-GN2) had the significant increasing-effect, and increased grain yield of wheat by 9.6% and increased total energy yields by 39.3% compared to fallow after wheat harvest with local conventional nitrogen amount (W–N3). Relative to W–N3, W-GN2 did not significantly increase carbon emissions of wheat season, and increased total carbon emissions of cropping pattern by 11.1%. Compared to multiple cropped green manure after wheat harvest with local conventional nitrogen amount (W-GN3), W-GN2 decreased carbon emissions by 5.8% in wheat season and decreased by 3.9% in the whole cropping pattern. Therefore, W-GN2 gained high carbon emission efficiency based on grain yield, and were 9.9% and 11.2% higher than W–N3 and W-GN3, respectively. In addition, W-GN2 enhanced soil total nitrogen, carbon, and organic carbon contents, compared with W–N3, thus increasing soil carbon sequestration potential index (net primary productivity/carbon emissions). We conclude that multiple cropped leguminous green manure after wheat harvest with local conventional nitrogen amount reduced by 15% can enhance crop productivity and carbon sequestration potential of farmland in arid areas.

Evaluating annual soil carbon emissions under biochar-added farmland subjecting from freeze-thaw cycle

Straw biochar is a commonly recognized agricultural amendment that can improve soil quality and reduce carbon emissions while sequestering soil carbon. However, the mechanisms underlying biochar's effects on annual soil carbon emissions in seasonally frozen soil areas and intrinsic drivers have not been clarified. Here, a 2-y field experiment was conducted to investigate the effects of different biochar dosages (0, 15, and 30, t ha−1; B0 (CK), B15, and B30, respectively) on carbon emissions (CO2 and CH4) microbial colony count, and soil-environment factors. The study period was the full annual cycle, including the freeze-thaw period (FTP) and the crop growth period (CP). Structural equation modeling (SEM) was developed to reveal the key drivers and potential mechanisms of biochar on carbon emissions. Biochar application reduced soil carbon emissions, with the reduction rate positively related to the biochar application rate (B30 best). During FTP, the reduction rate was 11.5% for CO2 and 48.2% for CH4. During CP, the reduction rate was 17.9% for CO2 and 34.5% for CH4. Overall, compared with CK, B30 treatment had a significant effect on reducing total soil carbon emissions (P < 0.05), with an average decrease of 16.7% during the two-year test period. The study also showed that for soils with continuous annual cycles (FTP and CP), carbon emissions were best observed from 10:00–13:00. After two years of freeze-thaw cycling, biochar continued to improve soil physical and chemical properties, thereby increasing soil microbial colony count. Compared with B0, the B30 treatment significantly increased the total colony count by 74.3% and 263.8% during FTP and CP (P < 0.05). Structural equation modeling (SEM) indicated that, with or without biochar application, the soil physicochemical properties directly or indirectly affected soil CO2 and CH4 emission fluxes through microbial colony count. The total effects of biochar application on CO2 emission fluxes were 0.50 (P < 0.05) and 0.64 (P < 0.01), respectively, but there was no significant effect on CH4 emission fluxes (P > 0.05). Among them, soil water content (SWC), soil temperature (ST) and soil organic carbon (SOC) were the main environmental determinants of CO2 emission fluxes during the FTP and CP. The total effects were 0.57, 0.65, and 0.53, respectively. For CH4, SWC, soil salinity (SS) and actinomycete colony count were the main environmental factors affecting its emission. The total effects were 0.50, 0.45, 0.44, respectively. For freeze-thaw alternating soils, the application of biochar is a feasible option for addressing climate change through soil carbon sequestration and greenhouse gas emissions mitigation. Soil water-heat-salt-fertilization and microbial communities are important for soil carbon emissions as the reaction matrix and main participants of soil carbon and nitrogen biochemical transformation.

Development of near-infrared spectroscopy (NIRS) for estimating organic matter, total carbon, and total nitrogen in agricultural soil

The analysis of soil organic matter (OM), total carbon (TC), and total nitrogen (TN) using traditional methods is quite time-consuming and involves the use of hazardous chemical reagents. Absorbance spectroscopy, especially near-infrared (NIR), is becoming more popular for soil analysis. This method requires little sample preparation, no chemicals, and a single spectral analysis to evaluate soil properties. Thus, this research aimed to develop an NIR spectroscopy method for the analysis of OM, TC, and TN in agricultural soils. These findings can provide a good concept of using PLS regression with NIR techniques. The method is as follows:•Topsoil (0–20 cm) samples were collected from various agricultural fields. OM, TC, and TN were analyzed using traditional methods and NIR spectroscopy.•NIR spectra were obtained using an FT-NIR spectrometer, original spectral including with Savitzky–Golay smoothing, standard normal variate (SNV) and multiplicative scatter correction (MSC) preprocessing method were used to create a predicted model through Partial Least Squares (PLS) regression with 65 % calibration, and the rest 35 % for validation.•The results showed significant relationships between measured soil properties (SOM and TC) and NIR absorbance spectra in agricultural soil (R2 of calibration and validation higher than 0.80).

Response of the soil bacterial community to seasonal variations and land reclamation in a desert grassland

Soil bacteria are important participants in biogeochemical cycles, and the stability of their community structure is not only affected by fluctuations in time and environment, but also by the participation and regulation of anthropogenic interference. With the increasing reclamation of farmland in the agropastoral transitional zone of northern China, it is imperative to understand the characteristics of soil bacterial communities in response to seasonal variations and anthropogenic reclamation. In this study, desert grassland, artificial shrubland, and desert grassland reclaimed farmland on the western side of the Mu Us Sandy Land were used as research objects. The following main results were obtained through soil sampling in April and September, and physicochemical analyses combined with 16S high-throughput sequencing: seasonal variations increased soil pH and soil water content, whereas land reclamation significantly increased soil total carbon, total phosphorus, soil available phosphorus, and soil available potassium contents. Changes in soil physicochemical properties altered the structure of soil bacterial communities to varying degrees, with Actinobacteriota and Acidobacteriota being the differential phyla among the three sampling sites under seasonal variations (p < 0.05). The relative abundance of Actinobacteriota was significantly higher in April than in September at all three sampling sites, and that of Acidobacteriota was significantly lower in April than in September. Therefore, Actinobacteriota and Acidobacteriota are key ecological indicators for predicting changes in the physicochemical properties of desert grassland soils. Actinobacteriota not only affected the complexity of the soil bacterial network, but also had a significant linear relationship with bacterial community stability. Actinobacteriota subgroups (Solirubrobacterales, Propionibacterales, 0319-7L14, and Gaiellales) were also strongly associated with soil bacterial community stability. Solirubrobacter, Gaiella, Nocardioides, Marmoricola, and Kribbella, which play crucial roles in maintaining the stability of bacterial communities, responded positively to changes in pH and soil water content. This study demonstrates the response of soil bacterial communities to environmental changes in a desert grassland and emphasizes the importance of Actinobacteriota as an indicator of soil ecosystem health.

Effects of Biochar and Straw Return on Soil Microbial Community Characteristics and Functional Differences in Saline Water Drip Irrigation Cotton Fields

In arid areas, fresh water resources are insufficient, and agricultural water mainly depends on shallow saline groundwater. However, long-term saline irrigation will cause soil salt accumulation and soil environment deterioration, which is not conducive to crop growth. In this study, based on the long-term irrigation of fresh water (0.35 dS·m-1, FW) and saline water (8.04 dS·m-1, SW), biochar (3.7 t·hm-2, BC) and straw (6 t·hm-2, ST) were added to the soil by an equal-carbon design. The aim was to clarify the effects of biochar and straw returning on the physical and chemical properties and microbial community structure of salinized soil. The results showed that saline irrigation significantly increased soil water content, electrical conductivity, available phosphorus, and total carbon content but significantly decreased pH value and available potassium content. The contents of available phosphorus, available potassium, and total carbon in soil were significantly increased by biochar and straw returning, but the conductivity value of soil irrigated with saline water was significantly decreased. The dominant bacteria in each treatment were Proteobacteria, Actinomycetes, Acidobacteria, Chloromycetes, and Blastomonas. Saline water irrigation significantly increased the relative abundance of Blastomonas and Proteobacteria but significantly decreased the relative abundance of Acidobacteria and Actinobacteria. Under the condition of fresh water irrigation, the relative abundance of Chlorocurvula was significantly reduced by the return of biochar. Straw returning significantly increased the relative abundance of Proteobacteria but significantly decreased the relative abundance of Acidobacteria, Actinomyces, Chloromyces, and Blastomonas. Under saline irrigation, the relative abundance of Chlorocurvula and Blastomonas were significantly reduced by biochar return to field. Straw returning significantly increased the relative abundance of Proteobacteria but significantly decreased the relative abundance of Acidobacteria, Actinomyces, Chloromyces, and Blastomonas. LEfSe analysis showed that saline irrigation decreased the potential markers and functional numbers of soil microorganisms.Under saline irrigation, biochar returning increased the number of potential markers and functions of soil microorganisms. Straw returning to field increases the number of potential markers of soil microorganisms. RDA results showed that soil microbial community and functional structure were significantly correlated with EC1:5, SWC, and pH. Saline water irrigation will deteriorate the soil environment, which is not conducive to agricultural production, among which EC1:5, SWC, and pH are important factors driving changes in soil microbial community and functional structure. Using biochar and straw to return to the field can reduce the harm of salt to soil and crops, laying a foundation for improving agricultural productivity.

Spatiotemporal Simulation and Prediction of Soil Organic Carbon Density in Gannan Grassland Under Future Climate Scenarios

To study the temporal and spatial distribution characteristics of soil organic carbon density in grassland and explore the relationship between organic carbon density and influencing factors is of great significance to the management and maintenance of grassland ecosystems in Gannan Autonomous Prefecture, which is conducive to realizing the goal of "double carbon," promoting carbon sink, and mitigating climate change. Taking Gannan Tibetan Autonomous Prefecture of Gansu Province as the research object, based on data from two CMIP6 future climate scenarios (SSP126 and SSP585), the CENTURY model was used to simulate and predict the temporal and spatial changes in soil organic carbon density in grassland of Gannan during 2023-2100. The main conclusions were as follows:① From 2023 to 2100, total organic carbon density, slow organic carbon density, and inert organic carbon density all showed a downward trend, whereas active organic carbon density fluctuated first and then increased. Meanwhile, the total organic carbon density, active organic carbon density, slow organic carbon density, and inert organic carbon density under the SSP585 scenario were higher than those under the SSP126 scenario. ② Mann-Kendall mutation analysis showed that the abrupt change in the difference of soil total organic carbon density (Δsomtc) occurred in 2030. The abrupt change in the difference of soil active carbon density (Δsom1c) occurred in 2027. ③ During the study period, the average soil organic carbon density of Gannan grassland was 7 505.69 g·m-2 under the SSP126 scenario and 7 551.87 g·m-2 under the SSP585 scenario. Gannan grassland soil organic carbon density was higher in the west and lower in the east, and the coefficient of variation was relatively stable. ④ The results of partial correlation analysis showed that precipitation was positively correlated with soil organic carbon density, whereas temperature was significantly negatively correlated with soil organic carbon density under future climate scenarios. ⑤ The results of the Theil-Sen Median trend analysis and Mann-Kendall test showed that under the two climate scenarios, the soil organic carbon density in Gannan showed an overall downward trend, in which Luqu County showed the fastest downward trend and Dibe County showed the slowest.

Biochar immobilized hydrolase degrades PET microplastics and alleviates the disturbance of soil microbial function via modulating nitrogen and phosphorus cycles

Microplastics (MPs) pose an emerging threat to soil ecological function, yet effective solutions remain limited. This study introduces a novel approach using magnetic biochar immobilized PET hydrolase (MB-LCC-FDS) to degrade soil polyethylene terephthalate microplastics (PET-MPs). MB-LCC-FDS exhibited a 1.68-fold increase in relative activity in aquatic solutions and maintained 58.5 % residual activity after five consecutive cycles. Soil microcosm experiment amended with MB-LCC-FDS observed a 29.6 % weight loss of PET-MPs, converting PET into mono(2-hydroxyethyl) terephthalate (MHET). The generated MHET can subsequently be metabolized by soil microbiota to release terephthalic acid. The introduction of MB-LCC-FDS shifted the functional composition of soil microbiota, increasing the relative abundances of Microbacteriaceae and Skermanella while reducing Arthobacter and Vicinamibacteraceae. Metagenomic analysis revealed that MB-LCC-FDS enhanced nitrogen fixation, P-uptake and transport, and organic-P mineralization in PET-MPs contaminated soil, while weakening the denitrification and nitrification. Structural equation model indicated that changes in soil total carbon and Simpson index, induced by MB-LCC-FDS, were the driving factors for soil carbon and nitrogen transformation. Overall, this study highlights the synergistic role of magnetic biochar-immobilized PET hydrolase and soil microbiota in degrading soil PET-MPs, and enhances our understanding of the microbiome and functional gene responses to PET-MPs and MB-LCC-FDS in soil systems.

Transformation and Sequestration of Total Organic Carbon in Black Soil under Different Fertilization Regimes with Straw Carbon Inputs

In the context of the carbon peak and carbon-neutral era, it is crucial to effectively utilize maize straw as a resource for achieving carbon (C) sequestration and emission reduction in rural agriculture. Maize straw carbon undergoes two processes after being added to the soil: mineralization (decomposition) and humification (synthesis) by soil animals and microorganisms. These processes contribute to the reintegration of carbon into the agroecosystem’s carbon cycle. However, understanding of the transformation and stabilization of straw carbon, as well as the differences in C fixation capacity in soils with various fertilization treatments in black soils, remains limited. This study aims to quantify the relationship between straw carbon input and organic carbon sequestration in various fertilization treatments of black soil. Based on a long-term positional fertilization trial (45 years) in black soil, 13C-labeled maize straw (1.5 g in 120 g of dry soil) was applied and combined with an in situ incubation method using carborundum tubes. Throughout the 360-day trial, we observed the influence of fertilization on soil total organic C levels, organic carbon δ13C values, maize straw addition rate, and straw C fixation capacity. The decomposition of straw was most prominent during the initial 60 days of the incubation period, followed by a gradual decrease in the rate of decomposition. Compared with day 0, the SOC δ13C value and straw C residue rate were highest in the no-fertilization treatment (CK) after 360 days of incubation. The amount of organic carbon transformed and fixed in the soil was significantly higher in the organic fertilizer treatment (M) compared to other treatments, highlighting the stronger decomposition, transformation, and carbon fixation capacity of straw carbon in the M treatment. Moreover, the highest carbon storage of 43.23 Mg·ha−1 was observed in the M fertilization treatment after 360 days, which was significantly different from other treatments (p &lt; 0.05). The study demonstrates that soil with low fertility exhibits increased sequestration potential for straw carbon. Additionally, organic fertilizer input would increase soil organic carbon storage and facilitate straw carbon conversion.

Macrogenomics reveal the effects of inter-cropping perilla on kiwifruit: impact on inter-root soil microbiota and gene expression of carbon, nitrogen, and phosphorus cycles in kiwifruit.

Intercropping systems can improve soil fertility and health, however, soil microbial communities and functional genes related to carbon, nitrogen and phosphorus cycling under the intercropping system of mesquite and perilla have not been studied. Therefore, in the present study, different planting densities and varieties of Perilla frutescens (L.) Britt and kiwifruit were used for intercropping, and changes in soil microbial communities and carbon, nitrogen, and phosphorus cycling genes in kiwifruit inter-roots under inter-cropping conditions were investigated by macro-genome sequencing technology. The results showed that intercropping with Perill caused a decrease in most soil nutrients, soil enzyme activities, and had a significant impact on the microbial (bacteria and fungi) diversity. Inter-cropping increased the relative abundance of the dominant bacterial phylum "Proteobacteria" and "Actinobacteria" by 47 and 57%, respectively, but decreased the relative abundance of the dominant fungal phylum "Chordata" and "Streptophyta" by 11 and 20%, respectively, in the inter-root soil of kiwifruit, and had a significant impact on the microbial (bacteria and fungi) diversity. In addition, inter-cropping could greatly increase the inter-root soil carbon sequestration (PccA, korA/B/C/D, fhs, and rbcl/s), carbon degradation (abfD), organic nitrogen mineralization (GDH2), denitrification (napA/B, nirB, norB), organic phosphorus mineralization (phop, phn), and inorganic phosphorus solubilization (gcd, ppk) gene abundance. The gene co-occurrence network indicated that soil korB, nirB, and gnd key functional genes for carbon, nitrogen, and phosphorus cycling in kiwifruit inter-root soils and their expression was up-regulated in the inter-cropping group. Structural equation (SEM) further showed that soil total nitrogen, organic matter, total carbon and acid phosphatase had significant effects on microbial diversity (p < 0.05) and soil carbon cycling gene korB and phosphorus cycling gene purH (p < 0.001), while korB and purH had positive effects on kiwifruit quality. In conclusion, intercropping perilla in kiwifruit orchards changed the structure of bacterial and fungal communities in the inter-root soil of kiwifruit, but I believe that intercropping perilla stimulates carbon degradation, leading to carbon emission and serious loss of soil nutrients, and that prolonged intercropping may adversely affect the quality of kiwifruit, and thus its limitations should be noted in future studies.

Seasonal Grazing Does Not Significantly Alter the Particle Structure and Pore Characteristics of Grassland Soil

Seasonal grazing is a recognized and sustainable approach to livestock management, but there is still a lack of comprehensive research on its impact on soil structure. This study utilizes advanced scanning electron microscopy technology to quantitatively evaluate the long-term effects of seasonal grazing on grassland soil structure, focusing on soil pore distribution characteristics and particle size. The investigation offers a detailed visual representation of the arrangement of soil particles at a micro-level. In both grazed and ungrazed plots (NG), soil particles ranging from 0.005 to 0.05 mm and 0.075 to 0.25 mm in size were predominant, constituting 20% and 60%, respectively. In plots subjected to seasonal grazing (grazing in June and August, G68, and grazing in July and September, G79), micro-particles (0.002–0.005 mm) and particles sized 0.05–0.075 mm were significantly lower compared to NG. Scanning electron microscope (SEM) images demonstrate structural differences, with NG displaying a higher proportion of small to medium-sized particles, more small pores, and fewer large pores. Analysis of pore size and morphology reveals the prevalence of large pores in both grazed and ungrazed plots. Continuous grazing plots exhibit significantly higher proportions of large pores compared to NG, while seasonal grazing plots show no significant differences. Correlation analyses indicate associations between soil physicochemical properties, particle size, and pore structure. Total soil nitrogen (TN), total soil carbon (TC), and soil moisture positively correlate with 0.005–0.05 mm particle proportions, while EC is negatively correlated with 0.05–0.075 mm particles. This study enhances our understanding of the effects of grazing practices on soil structure and provides scientific evidence for sustainable land management.

Grazing exclusion is more effective for vegetation restoration and nutrient transfer in the heavily degraded desert steppe

BackgroundGrazing exclusion is an efficient practice to restore degraded grassland ecosystems by eliminating external disturbances and improving ecosystems’ self-healing capacities, which affects the ecological processes of soil-plant systems. Grassland degradation levels play a critical role in regulating these ecological processes. However, the effects of vegetation and soil states at different degradation stages on grassland ecosystem restoration are not fully understood. To better understand this, desert steppe at three levels of degradation (light, moderate, and heavy degradation) was fenced for 6 years in Inner Mongolia, China. Community characteristics were investigated, and nutrient concentrations of the soil (0–10 cm depth) and dominant plants were measured.ResultsWe found that grazing exclusion increased shoots’ carbon (C) concentrations, C/N, and C/P, but significantly decreased shoots’ nitrogen (N) and phosphorus (P) concentrations for Stipa breviflora and Cleistogenes songorica. Interestingly, there were no significant differences in nutrient concentrations of these two species among the three degraded desert steppes after grazing exclusion. After grazing exclusion, annual accumulation rates of aboveground C, N, and P pools in the heavily degraded area were the highest, but the aboveground nutrient pools were the lowest among the three degraded grasslands. Similarly, the annual recovery rates of community height, cover, and aboveground biomass in the heavily degraded desert steppe were the highest among the three degraded steppes after grazing exclusion. These results indicate that grazing exclusion is more effective for vegetation restoration in the heavily degraded desert steppe. The soil total carbon, total nitrogen, total phosphorus, available nitrogen, and available phosphorus concentrations in the moderately and heavily degraded desert steppes were significantly decreased after six years of grazing exclusion, whereas these were no changes in the lightly degraded desert steppe. Structural equation model analysis showed that the grassland degradation level mainly altered the community aboveground biomass and aboveground nutrient pool, driving the decrease in soil nutrient concentrations and accelerating nutrient transfer from soil to plant community, especially in the heavily degraded grassland.ConclusionsOur study emphasizes the importance of grassland degradation level in ecosystem restoration and provides theoretical guidance for scientific formulation of containment policies.

Insights into the distribution characteristic of microbiota in alkaline–sandy soil with inorganic and organic fertiliser treatments: contrasting abundance, structure and functionality

ABSTRACT Fertiliser amendment is the most direct method for improving soil properties of ecologically vulnerable areas (e.g. desertification soil area), and then, understanding the response of microbial community activities and growth to different fertilisation treatments is of great significance in sandy soil restoration. Here, a field experiment with different fertiliser treatments in typical alkaline–sandy soil was conducted. In this study, the difference of physicochemical property, microbial communities and functions in different treatments of no fertiliser (CK), (ii) fly ash chemical fertilisers (CF), (iii) humic straw organic fertiliser (OF), (iv) functional microbial fertiliser (FMF), (v) sulphate-reducing bacterial (SRB) fertiliser (MF) and (vi) humic straw organic fertiliser + functional microbial fertiliser + SRB fertiliser (CMF) were evaluated. The result showed that the contents of soil total organic carbon, NO3-N, P and K in the FMF were highest. The abundance of keystone taxa (Gemmatimonadetes and Thaumarchaeota) increased significantly in the treatments of microbial fertiliser. Microbial fertiliser boosted genes for aerobic nitrite oxidation, nitrogen fixation, ammonia oxidation and aromatic compound degradation. The number of methylotrophy and dark sulphur oxidation genes was reduced. The bbove results indicated that the treatments with the inoculation of functional microbes are better than the others for the restoration of alkaline–sandy soil.

Response Mechanism of cbbM Carbon Sequestration Microbial Community Characteristics in Different Wetland Types in Qinghai Lake.

Carbon-sequestering microorganisms play an important role in the carbon cycle of wetland ecosystems. However, the response mechanism of carbon-sequestering microbial communities to wetland type changes and their relationship with soil carbon remain unclear. To explore these differences and identify the main influencing factors, this study selected marsh wetlands, river wetlands and lakeside wetlands around Qinghai Lake as research subjects. High-throughput sequencing was employed to analyze the functional gene cbbM of carbon-sequestering microorganisms. The results revealed that the alpha diversity of cbbM carbon-sequestering microorganisms mirrored the trend in total carbon content, with the highest diversity observed in marsh wetlands and the lowest in lakeside wetlands. The dominant bacterial phylum was Proteobacteria, with prevalent genera including Thiothrix, Acidithiobacillus, and Thiodictyon. Acidithiobacillus served as a biomarker in lakeside wetlands, while two other genera were indicative of marsh wetlands. The hierarchical partitioning analysis indicated that the diversity of cbbM carbon-fixing microorganisms was primarily influenced by the total nitrogen content, while the community structure was significantly affected by the soil total carbon content. Moreover, an increased soil temperature and humidity were found to favor the carbon fixation processes of Thiomicrospira, Thiomonas, Polaromonas, and Acidithiobacillus. In summary, changes in wetland types seriously affected the characteristics of cbbM carbon sequestration in microbial communities, and a warm and humid climate may be conducive to wetland carbon sequestration.