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Purpose: Phosphorus (P) is the main factor limiting crop production in red soils. Examining the bacterial community harboring phoD gene under different long-term cropping systems may supply meaningful insights for improving soil P availability. Here, we analyzed how the cropping systems affect community structure of phoD-harboring bacteria by changing physicochemical properties in red soils. Materials and methods: Twenty-four soil samples from eight cropping systems (abandoned farmland, corn continuous cropping, mango continuous cropping, taro continuous cropping, zucchini–corn rotation, pea–corn rotation, canola–tobacco rotation, and walnut–tobacco intercropping for > 10 years) were collected from 0 to 20 cm depth in Miyi County, Sichuan Province, China. The abundance of phoD gene was determined by quantitative PCR, and phoD-harboring bacterial community structure was analyzed by high-throughput sequencing. Results and discussion: Available P concentration and phoD abundance were the highest in pea-corn rotation soil, while alkaline phosphatase (ALP) activity was the lowest in this soil. Available P showed a significant positive relationship with phoD abundance, while a negative relationship with ALP activity. Moreover, the dominant phyla of phoD-harboring bacterial community were Proteobacteria and Actinobacteria, with Cupriavidus and Bradyrhizobium being the dominant genera. The relative abundances of Streptomyces, Pseudomonas, and Amycolatopsis were positively related to soil P concentration (total and available P) and negatively related to ALP activity, indicating that these genera may be essential in the mineralization of soil organic P. Redundancy analysis (RDA) showed that ALP, soil organic carbon (SOC), and N:P ratio were the remarkable factors affecting the structure of phoD-containing bacterial community across all cropping system soils. Meanwhile, structural equation model (SEM) showed that the effects of total N and available P on soil phoD-harboring bacterial community structure were stronger than that of SOC. Further, soil texture was also one of the main factors affecting the phoD-harboring bacterial community structure, which had a notable up-regulation effect on abundance and diversity of phoD gene and indirectly regulate gene composition by affecting available P. Conclusions: The long-term cropping systems can affect the community structure of phoD-containing bacteria and ALP activity by altering physicochemical properties, and thus contribute to regulation of the biogeochemical cycle of P in red soils. The main factors driving the changes in phoD-harboring bacterial community structure were soil texture, SOC, total N, and available P. [ABSTRACT FROM AUTHOR]

Agricultural soils have tremendous potential to sequester soil organic carbon (SOC) and mitigate global climate change. However, agricultural land use has a profound impact on SOC dynamics, and few studies have explored how agricultural land use combined with soil conditions affect SOC changes throughout the soil profile. Based on a paired soil resampling campaign in the 1980s and 2010s, this study investigated the SOC changes of the soil profile caused by agricultural land use and the correlations with parent material and topography across the Chengdu Plain of China. The results showed that the SOC content increased by 3.78 g C/kg in the topsoil (0–20 cm), but decreased in the 20–40 cm and 40–60 cm soil layers by 0.90 and 1.26 g C/kg respectively. SOC increases in topsoil were observed for all types of agricultural land. Afforestation on former agricultural land also caused SOC decreases in the 20–60 cm soil layers, while SOC decreases only occurred in the 40–60 cm soil layer for agricultural land using a traditional crop rotation (i.e. traditional rice–wheat/rapeseed rotation) and with rice–vegetable rotations converted from the traditional rotations. For each agricultural land use, SOC decreases in deep soils only occurred in high relief areas and in soils formed from Q4 (Quaternary Holocene) grey‐brown alluvium and Q4 grey alluvium that had a relatively low soil bulk density and clay content. The results indicated that SOC change caused by agricultural land use was depth dependent and that the effects of agricultural land use on soil profile SOC dynamics varied with soil characteristics and topography. Subsoil SOC decreases were more likely to occur in high relief areas and in soils with low soil bulk density and low clay content. [ABSTRACT FROM AUTHOR]

Purpose: Phosphorus (P) fertilizer has been applied in regions with red soils to ensure high crop yield. However, the supply of bioavailable P for crop plants is insufficient due to the strong adsorption and fixing behaviors in red soils. In this study, we explored P adsorption and desorption characteristics in red soils under different long-term cropping systems. We also analyzed how the cropping systems affect P adsorption and desorption through changing soil physicochemical properties under the experimental conditions. Materials and methods: Eighteen red soil samples were collected at depths of 0–20 cm from six cropping systems (abandoned farmland, corn continuous cropping, taro continuous cropping, pea–corn rotation, canola–tobacco rotation, and walnut–tobacco intercropping for at least 10 years) in Miyi County, Sichuan Province, China. Soil physicochemical properties, zeta potentials, and P adsorption and desorption characteristics were evaluated. Results and discussion: The P adsorption capacity of soils increased at a decreasing rate with increasing exogenous P concentration, while the P desorption capacity increased constantly; however, the change in the percentage of desorbed P had no clear trend. The soils under pea–corn rotation and taro continuous cropping had lower P adsorption capacities and higher P desorption capacities compared to those under the other cropping systems. The maximum P adsorption capacities (Qm) of pea–corn rotation and taro continuous cropping soils were 16.1% and 32.4% of abandoned farmland soil, while the corresponding desorption coefficients were 6.93 and 1.62 times higher than that of abandoned farmland soil, respectively. Soil available P (AP), cation exchange capacity (CEC), and clay content were positively correlated with a and readily desorbable P (RDP), while they were negatively correlated with Qm (P < 0.05); opposite trends were found in the sand content. In addition, the zeta potential of soil colloids decreased with increasing soil pH. Among the cropping systems, the absolute value of zeta potential was lowest for tobacco–walnut intercropping, while its isoelectric point was the highest, resulting in the highest P adsorption capacity. Conclusions: The long-term cropping systems affect P adsorption and desorption characteristics and P availability in red soils by influencing soil physicochemical properties. The main factors driving the changes in P adsorption behavior were AP, CEC, free Fe oxides, and sand content, while AP, sand, and clay contents were the major factors for the P desorption. [ABSTRACT FROM AUTHOR]

Soil easily oxidizable organic carbon (EOC) is directly related to CO2 density; dynamics in subsurface EOC have been observed globally in relation to rapid urbanization. However, in the context of rapid urbanization, the factors related to EOC and the response of the EOC pool to urbanization down the profile remain elusive. The aim of the current paper is to investigate possible changes in the distribution of EOC over the soil profile and the impact of land use, socioeconomic, and natural factors on these. The study used samples from 182 soil profiles (0–100 cm) taken in the peri‐urban areas of the megacity Chengdu (a typical megacity with rapid urbanization). Main drivers of changes in soil EOC were analyzed by using spatial and regression analyses. Closer to the centre of the city, soil EOC levels were lower and land‐use factors and socioeconomic factors contributed more to explaining variation in EOC levels in the 0–40‐cm layer, whereas natural factors were most important at larger distance from the city. The effect of land‐use factors and socioeconomic factors on EOC reached down to 60‐cm depths. Moreover, an estimated 20% loss of EOC stock was observed close to the city in comparison with the surroundings, suggesting that the rapid process of urbanization was accompanied by a loss of EOC stock down the profile to depths of 60 cm, and the negative effects on EOC stock became more intensive as the distance to the city decreased. [ABSTRACT FROM AUTHOR]

• SOC mineralization rate increases with increasing incubation temperature. • Soil microorganisms are preferred to mineralize ROC at higher temperature. • Soil ROC, enzyme activity and pH are primary factors controlling SOC mineralization. • SOC stored in lawn soils is less susceptible to climate warming. Green spaces in urban parks are an essential part of urban planning, not only meeting the environmental demands of urban dwellers but also absorbing greenhouse gases generated in urban regions. Mineralization of soil organic carbon (SOC) is one of the most important processes of C cycling, and links C sequestration and emission. However, few studies have been focused on SOC mineralization in urban parks, especially in scenarios involving rising temperature. Here, soils from different ages of deciduous forest (DT), evergreen forest (ET) and lawn (LN) were collected from the urban parks of Chengdu megacity. A soil incubation study (35 days) was conducted to examine SOC mineralization in three temperature regimes (15, 25, and 35 ℃), three vegetation types (DT, ET, and LN) and three vegetation ages (5, 10, and 15yr), making 27 treatments in total. Results demonstrate that increases in temperature stimulated the daily SOC mineralization rate, cumulative SOC mineralization, and mineralization intensity in the soils from urban green spaces, especially in soils under the 5-year-old plantings. Furthermore, results from principal component analysis (PCA) showed that the soil labile organic carbon (LOC) fraction, especially readily oxidizable carbon (ROC), soil enzyme activity and soil pH are the major factors influencing SOC mineralization. During the incubation, the average temperature sensitivity (Q 10) of the SOC mineralization rate at 25−35 °C was higher than at 15−25 °C (P < 0.05), indicating that more C would release from urban green spaces under a warmer climate. However, over all planting ages, the average Q 10 of SOC mineralization rate in lawn soils reduced by 1.87 %–4.04 % and 4.16 %–5.84 % relative to deciduous and evergreen forest soils, respectively. Overall, the SOC mineralization rate was ranked LN > ET > DT, while the Q 10 of the SOC mineralization rate was ranked DT > ET > LN with increasing temperatures. Moreover, the older vegetation showed lower SOC mineralization rates and higher Q 10 values. These findings imply that SOC stored in the soils under grass and young plantations are less susceptible to climate warming, although the mineralization rates are higher. By contrast, SOC in soils under trees is more susceptible to climate warming, but the mineralization rates are lower. Overall, the temperature change is more important for the SOC mineralization in forest soils and older plantation soils in urban green spaces. [ABSTRACT FROM AUTHOR]

[Display omitted] • Long-term rice-vegetable (RV) rotation caused homogenization of microbiome structure. • pH, NO 3 –-N, and SON were key elements contributing to this homogenization. • The conversion to RV increased microbial nitrification and denitrification capacity. • Decreased nosZ and increased nirKS , norBC genes raised potential N 2 O emissions in RV. Land-use change (LUC) caused by agricultural intensification has aggravated soil reactive nitrogen (Nr) pollution in global rice agroecosystems. Microorganisms mediate Nr transformation; however, the structural and functional responses of the microbial community to LUC and soil Nr loading have yet to be synthesized. Simultaneously, rice–wheat (RW) rotations in China have been subjected to high rates of LUC, primarily to intensive rice-vegetable (RV) rotations. Here, 16S rRNA gene sequencing coupled with Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt2) was performed to assess the influence of conversion from RW to RV on soil Nr fractions, microbial communities, and N-cycling genes, especially over longer time scales and at deeper soil depths. Compared to RW, bacterial alpha-diversity increased in the 10-year RV, whereas archaeal alpha-diversity decreased with increasing years under RV rotations. Microbial beta-diversity significantly decreased after the conversion from RW to RV rotations, resulting in reduced heterogeneity in community structure (composition and abundance) across 0–40 cm soil profiles in RV rotations. Redundancy analysis suggested that this homogenization was driven by increased concentrations of nitrate N and decreased soil pH and soluble organic N concentrations in the RV. At 0–20 cm, RV decreased the abundance of Geobacter spp., Candidatus_Nitrosotalea spp., and their related N-fixation genes, whereas it increased the abundance of Streptomyces spp. and their related nitrification genes. Moreover, the 20-year RV significantly increased the potential denitrification and N 2 O emissions from soil at 0–40 cm by decreasing the abundance of bacterial nosZ genes (encoding nitrous-oxide reductase) and increasing archaeal nirK , nirS (nitrite reductase) genes, and bacterial norB and norC genes (nitric-oxide reductase). Collectively, RW-to-RV conversion decreased soil microbial diversity and increased the size of denitrification/N 2 O-producing communities, this homogenization of microbiomes in long-term RV system may be a potential source of N 2 O. [ABSTRACT FROM AUTHOR]

• Subsurface flow was the major runoff pathway in the study sloping land. • Surface flow dominated P transport, subsurface flow dominated TN and NO 3 − transport. • Biochar and fertilizations increased subsurface flow runoff flux. • Biochar treatment showed higher P runoffs in subsurface flow than NPK fertilizations. Nitrogen (N) and phosphorus (P) loss in runoffs has been a serious problem in China due to the amount of chemical fertilizer currently applied to farmland. Biochar has been used as a soil amendment for increasing nutrient retention, water holding capacity, and crop yield. However, little is known about the influence of biochar on the runoff erosion from both surface flow and subsurface flow, especially in sloping regions. Experimental runoff plots were, therefore, set up on Entisols in a sloping farmland, involving four treatments: control (CT), conventional NPK fertilization (CF, based on local practices), optimum NPK fertilization (OF, based on the recommendation from local agriculture committee), and biochar combined with 85% of optimum NPK fertilizer (BF). The effects of the four treatments on the runoff fluxes, sediment yields and the runoff coefficients, as well as the N (ammonium (NH 4 +), nitrate (NO 3 −) and total N (TN)) and P (phosphate (PO 4 3-), total P (TP), dissolved TP (DTP), particulate P (PP)) losses via both surface runoff (i.e., surface flow, 0–20 cm, ploughed layer) and subsurface runoff (i.e., subsurface flow, 20–60 cm, non-ploughed layer) were all monitored and evaluated from April 2018 to September 2019. Results show that, in this sloping farmland, subsurface flow was the main process of runoff and dominated N transport, but surface flow dominated P transport. The three fertilization treatments reduced the runoff erosion by surface flow, while increasing it from subsurface flow (p < 0.05). Compared with two NPK fertilizations, BF treatment significantly increased the total sediment yield, subsurface runoff flux and subsurface runoff coefficient. Among all three fertilization treatments, the differences of grain yields are found not significant (except for the 4th crop). In surface flow, biochar addition increased the loss flux of NH 4 + and P fractions, but reduced the loss flux of NO 3 − with the comparison of the CF and OF treatments. In subsurface flow, biochar addition didn't significantly changed the runoff of N fractions, but increased P runoffs, especially for TP and PP runoffs (p < 0.05). Overall, the risk of N and P loss, and runoff erosion through subsurface flow in biochar incorporated Entisols sloping farmland needs be highlighted. [ABSTRACT FROM AUTHOR]

Background and Aims: Metabolic dysfunction-associated fatty liver disease (MAFLD) was proposed to substitute NAFLD in 2020. This new term highlights the systematic metabolic disturbances that accompany fatty liver. We evaluated the correlations between MAFLD and subclinical carotid atherosclerosis (SCA) based on a nationwide health examination population in China., Methods: We performed a nationwide cross-sectional population and a Beijing retrospective cohort from 2009 to 2017. SCA was defined as elevated carotid intima-media thickness. The multivariable logistic and Cox models were used to analyze the association between MAFLD and SCA., Results: 153,482 participants were included in the cross-sectional study. MAFLD was significantly associated with SCA in fully adjusted models, with an odds ratio of 1.66; 95% confidence interval (CI): 1.62-1.70. This association was consistent in the cohort, with a hazard ratio (HR) of 1.31. The association between baseline MAFLD and incident SCA increased with hepatic steatosis severity. Subgroup analysis showed an interaction between age and MAFLD, with a higher risk in younger groups (HR:1.67, 95% CI: 1.17-2.40)., Conclusion: In this large cross-section and cohort study, MAFLD was significantly associated with the presence and development of SCA. Further, the risk was higher among MAFLD individuals with high hepatic steatosis index and young adults., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Lei, Wang, Wang, Huang, Liu, Qin, Zhang, Ji, She, Cai, Li, Zhang and Li.)

Increasing soil petroleum hydrocarbons (PHs) pollution have caused world-wide concerns. The removal of PHs from soils mainly involves physical, chemical, biological processes and their combinations. To date, most reviews in this field based on research articles, but limited papers focused on the integration of remediation technologies from the perspective of patents. In this study, 20-years Chinese patents related to the remediation of soil PHs were comprehensively analyzed. It showed an increasing number of patent applications and the patents' quantity were positively correlated with Chinese GDP over the years, suggesting the more the economy developed the more environmental problems and corresponding solutions emerged. In addition, chemical technologies were mostly used in a combination to achieve faster and better effects, while the physical technologies were often used alone due to high costs. In all PHs remediation techniques, bacteria-based bioremediation was the most used from 2000 to 2019. Bacillus spp. and Pseudomonas spp. were the most used bacteria for PHs treatment because these taxa were widely harboring functions such as biosurfactant production and hydrocarbon degradation. The future research on joint technologies combining microbial and physicochemical ones for better remediation effect and application are highly encouraged., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Accurate mapping of soil organic carbon (SOC) is critical to improve C management and develop sustainable management policies. However, it is constrained by local variations of the model parameters under complex topography, especially in hills. This study applied a methodological framework to optimize the spatial prediction of SOC in the hilly areas during 1981-2012 by quantifying the relative importance of environmental factors, which include both qualitative factors and quantitative variables. Results showed that SOC increased twofold with a moderate spatial dependence during the past 32 years. During this period, land use patterns, soil groups, topographic factors, and vegetation coverage had significant impacts on the SOC changes (p < 0.01). Specifically, the impact of land use patterns has exceeded the impact of soil groups and became the dominant factor affecting SOC changes. Meanwhile, impacts from the topographic factors and vegetation coverage have substantially declined. Based on those results, a combinatorial approach (LS&#95;RBF&#95;HASM) was developed to map SOC using radial basis function neural network (RBF) and high accuracy surface modelling (HASM), and to generate more detailed spatial mapping relationships between SOC and the affecting factors. Compared with ordinary kriging (OK), land use-soil group units (LS) and HASM combined (LS&#95;HASM), multiple linear regression (MLR) and HASM combined with LS (LS&#95;MLR&#95;HASM); LS&#95;RBF&#95;HASM showed a better performance with a decline of 6.3%-37.7% prediction errors and more accurate spatial patterns due to the quantitative combination of auxiliary environmental variables and more information on the SOC variations within local factors captured by RBF and HASM. Additionally, MLR may partially undermine the relationship of the internal spatial structure due to the highly nonlinear relation between SOC and environmental variables. This methodological framework highlights the optimization of more environmental factors and the calculation of spatial variability within local factors and provides a more accurate approach for SOC mapping in hills., (Copyright © 2021 Elsevier Ltd. All rights reserved.)