Living and Dead Microorganisms in Mediating Soil Carbon Stocks Under Long-Term Fertilization in a Rice-Wheat Rotation.

Although soil microorganism is an active area of research, we are still in the early stages of understanding how living microorganisms influence the accumulations of soil microbial residues under different agricultural practices. Based on a 39-year fertilization experiment, we characterized the soil microbiota and correlated their compositions to soil microbial residues, which are indicated by amino sugars under a rice-wheat rotation. In the present study, fertilization regimes and crop season all exerted significant impacts on the compositions of soil microbial communities and their residues, although no significant difference in the microbial residues was found between soil depth (0-10 cm vs. 10-20 cm). Compared within fertilization regimes, the long-term fertilization, especially the application of organic manure, stimulated the accumulations of carbon (C) and nitrogen in soils and microbial residues. Upland soils in wheat season accumulated more microbial residues, particularly in fungal residues, than paddy soils in rice season. Our results suggested that the long-term application of organic manure favored the growth of soil microbial communities, and then increased the contents of microbial residues, particularly in fungal residues, leading to an enlargement of soil C pools. The keystone taxa Pseudaleuria identified by network analysis showed a significantly positive potential in soil C sequestration by increasing the accumulation of fungal residues. Thus, this study revealed the strong and close connections between microbial communities and their residues, and provided evidence about the critical role of keystone taxa in regulating C sequestration.

Soil Aggregation Shaped the Distribution and Interaction of Bacterial-Fungal Community Based on a 38-Year Fertilization Experiment in China.

Soil aggregates provide different ecological niches for microorganisms, and in turn, the microbial interactions affect soil aggregation process. The response of the microbial community in bulk soil to different fertilization regimes has been well studied; however, the co-occurrence patterns of bacteria and fungi in different aggregates under various fertilization regimes remain unclear. Based on the long-term field experiment, we found that fertilization regimes contributed more to fungal than to bacterial community composition. Long-term fertilization decreased microbial interactions in large macroaggregates (LM), macroaggregates (MA) and silt and clay (SC) fractions, but increased in microaggregates (MI). The application of manure with inorganic fertilizers (NPKM) significantly increased the intensive cooperation between bacteria and fungi in LM and MA. Microbial communities in LM and MA were well separated and showed strong competition against microbes in MI and SC; hence, we concluded that the microbial habitat could be divided into two groups, large fractions (LM and MA) and small fractions (MI and SC). The bacterial genera Anaerolinea, Nocardioides, Ohtaekwangia, Geoalkalibacter, Lysobacter, Pedomicrobium, and Flavisolibacter were keystone taxa in inorganic fertilization, and Roseiflexus, Nitrospira, and Blastocatella were keystone taxa in NPKM, which were all sensitive to soil aggregation. In this study, we demonstrated that the NPKM decreased the microbial interactions within and between kingdoms in LM, MA, and SC, but enhanced nutrient availability and microbial interactions in MI, leading to the formation of biofilms and the strengthening of stress tolerance, which finally stimulated the formation and stabilization of soil aggregates. Thus, this study revealed how soil microbial competition or cooperation responded to different fertilization regimes at aggregate scales, and provided evidence for the stimulation of soil stability.

COVID-19 and social distancing: Disparities in mobility adaptation between income groups.

In response to the coronavirus disease 2019 (COVID-19) pandemic, governments have encouraged and ordered citizens to practice social distancing, particularly by working and studying at home. Intuitively, only a subset of people have the ability to practice remote work. However, there has been little research on the disparity of mobility adaptation across different income groups in US cities during the pandemic. The authors worked to fill this gap by quantifying the impacts of the pandemic on human mobility by income in Greater Houston, Texas. We determined human mobility using pseudonymized, spatially disaggregated cell phone location data. A longitudinal study across estimated income groups was conducted by measuring the total travel distance, radius of gyration, number of visited locations, and per-trip distance in April 2020 compared to the data in a baseline. An apparent disparity in mobility was found across estimated income groups. In particular, there was a strong negative correlation (ρ = -0.90) between a traveler's estimated income and travel distance in April. Disparities in mobility adaptability were further shown since those in higher income brackets experienced larger percentage drops in the radius of gyration and the number of distinct visited locations than did those in lower income brackets. The findings of this study suggest a need to understand the reasons behind the mobility inflexibility among low-income populations during the pandemic. The study illuminates an equity issue which may be of interest to policy makers and researchers alike in the wake of an epidemic.

High adsorption capacity of Mg-Al-modified biochar for phosphate and its potential for phosphate interception in soil.

In this study, Mg and/or Al modified biochars (MABC1, MBC2, ABC3) prepared by co-precipitation were to explore their phosphate adsorption capacity from aqueous solution and the potential for soil phosphate interception. The results revealed that MABC composites contained more functional groups than MBC and showed a higher surface area than ABC. The surface of MABC contained dispersed MgAl2O4, Mg(OH)2, AlOOH and Al2O3 crystals that were associated with its enhanced maximum phosphate adsorption capacity (153.40 mg g-1). According to Langmuir model, the maximum adsorption capacity of MABC was 15.91, 1.85, and 93.54 times the capacity of MBC, ABC, and raw biochar (BC4), respectively. The addition of MABC in red soil could significantly slow down the release of soil phosphorus, and MABC also had a stronger phosphate interception capacity (59.89%) than other BCs. In summary, MABC exhibits superior phosphate adsorption and interception capacity, making it ideal for treatment and prevention of phosphorus-polluted water.

Soil nutrient and microbial activity responses to two years after maize straw biochar application in a calcareous soil.

Biochar (BC) addition to soil is a strategy to enhance soil fertility, which may also affect microbial activity. However, little information is available on the responses of soil nutrients and microbial activities to BC in a calcareous soil. This study investigated the changes of soil nutrient contents and microbial activities in a calcareous soil two years after application of biochar at rate of 0, 2.5, 7.5 and 22.5 t/ha. The results showed that the contents of soil organic carbon (SOC), total nitrogen (TN), dissolved organic carbon (DOC), total dissolved nitrogen (TDN), and available phosphorus and potassium increased significantly with increasing BC addition rate, but no significant effect on soil pH. Soil microbial biomass carbon and nitrogen (MBC and MBN) had an increased and then decreased trend. BC amendment increased microbial biomass and promoted soil carbon- and nitrogen-cycling enzyme activities, the ratios of ß-glucosaminidase/phosphomonoesterase, N-acetyl-ß-glucosaminidase plus leucine aminopeptidase/phosphomonoesterase increased significantly with increasing BC addition rate. Redundancy analysis confirmed that DOC and MBN were dominant factors affecting soil microbial biomass, and soil pH, TDN, DOC, MBN and SOC were main factors regulating soil enzyme activities. Besides, principal component analysis revealed that difference in microbial community composition in one year after BC addition was mainly associated with the relative abundance of bacteria and fungi, the relative abundance of bacteria increased, while the ratios of Gram-negative/Gram-positive bacteria and fungi/bacteria, and relative abundance of fungi and arbuscular mycorrhizal fungi decreased in BC-amended soils with control. However, BC had no significant effect on microbial community composition after two years. These results suggest that application of maize BC to calcareous soils may have a great potential for improvements in the soil nutrients and enzyme activity, the changes in soil microbial composition deserve further studies.

[Livestock and Poultry Faeces Nitrogen Loading Rate and Its Potential Return to Farmland in China].

To clearly analyze livestock and poultry faeces and the nitrogen loading rate of farmland in different provinces of China and their potential return to agricultural land, the changes of the output of various livestock and poultry faeces in China and the proportion of faeces from all types of livestock and poultry since 1978 were estimated in this paper based on statistical data and literature reviews using the pig manure equivalent (based on nitrogen) and the spatial distribution and pollution risk of livestock and the poultry faeces and nitrogen loading rates. Furthermore, the nitrogen return potential from animal faeces to farmland was analyzed and evaluated for different provinces of China in 2016. The results show that the pig manure equivalent (N) and total N from livestock and poultry faeces in China increases from 1978 to 2005 and is stable from 2005 to 2016. By 2016, the pig manure equivalent (N) and N were 366822.01×104 t and 2024.10×104 t, respectively, reflecting an increase by 105.78%. Approximately 94.03% to 98.34% of the faeces was from poultry, sheep, pigs, and cattle. The livestock and poultry faeces pig manure equivalent (N) and nutrient N were mainly distributed in North-Central China, especially in the Henan Province, accounting for 22.25% and 8.81% of the total in China, respectively, followed by the Sichuan Province. Based on the arable land, planting, and farmland areas, the pig faeces equivalent (N) and its N nutrient per unit area were calculated and the environmental risks were evaluated based on r values. Based on the arable land area, the southwestern and southeastern regions have large loading rates, while the northcentral region has a serious pollution risk of grade Ⅳ. Based on the planting area, the northwestern and southwestern regions have relatively large loading rates, while the northwestern and northcentral regions have pollution risks of grade Ⅲ. Based on the farmland area, the northcentral and southeastern regions have great loading rates and the northcentral region has a pollution risk of grade Ⅲ, Hunan has the largest loading rate, and Beijing, Shandong, and Henan have grade Ⅳ pollution risks. The livestock and poultry faeces pig manure equivalent (N) and amount of N nutrients returning to farmland in China are 113480.75×104 t and 626.15×104 t, respectively, equivalent to 3.07 t·hm-2 and 16.92 kg·hm-2, respectively, and the northcentral region has the largest rates with 8.27 t·hm-2 and 45.62 kg·hm-2, respectively. Based on 50% of the environmental capacity of faeces N, that is, 85 kg·hm-2, the N nutrient return can increase by 2520.21×104 t. The Heilongjiang Province has the greatest potential return, followed by the Sichuan Province.

Short-Term Responses of Soil Respiration and C-Cycle Enzyme Activities to Additions of Biochar and Urea in a Calcareous Soil.

Biochar (BC) addition to soil is a proposed strategy to enhance soil fertility and crop productivity. However, there is limited knowledge regarding responses of soil respiration and C-cycle enzyme activities to BC and nitrogen (N) additions in a calcareous soil. A 56-day incubation experiment was conducted to investigate the combined effects of BC addition rates (0, 0.5, 1.0, 2.5 and 5.0% by mass) and urea (U) application on soil nutrients, soil respiration and C-cycle enzyme activities in a calcareous soil in the North China Plain. Our results showed soil pH values in both U-only and U plus BC treatments significantly decreased within the first 14 days and then stabilized, and CO2emission rate in all U plus BC soils decreased exponentially, while there was no significant difference in the contents of soil total organic carbon (TOC), dissolved organic carbon (DOC), total nitrogen (TN), and C/N ratio in each treatment over time. At each incubation time, soil pH, electrical conductivity (EC), TOC, TN, C/N ratio, DOC and cumulative CO2 emission significantly increased with increasing BC addition rate, while soil potential activities of the four hydrolytic enzymes increased first and then decreased with increasing BC addition rate, with the largest values in the U + 1.0%BC treatment. However, phenol oxidase activity in all U plus BC soils showed a decreasing trend with the increase of BC addition rate. Our results suggest that U plus BC application at a rate of 1% promotes increases in hydrolytic enzymes, does not highly increase C/N and C mineralization, and can improve in soil fertility.

Characteristics of maize biochar with different pyrolysis temperatures and its effects on organic carbon, nitrogen and enzymatic activities after addition to fluvo-aquic soil.

In this study, the characteristics of maize biochar produced at different pyrolysis temperatures (300, 450 and 600°C) and its effects on organic carbon, nitrogen and enzymatic activities after addition to fluvo-aquic soil were investigated. As pyrolysis temperature increased, ash content, pH, electrical conductivity, surface area, pore volume and aromatic carbon content of biochar increased while yield, ratios of oxygen:carbon and hydrogen: carbon and alkyl carbon content decreased. During incubation, SOC, total N, and ammonium-N contents increased in all biochar-amended treatments compared with the urea treatment; however, soil nitrate-N content first increased and then decreased with increasing pyrolysis temperature of the applied biochar. Extracellular enzyme activities associated with carbon transformation first increased and then decreased with biochars pyrolyzed at 450 and 600°C. Protease activity markedly increased with increased pyrolysis temperatures, whereas pyrolysis temperature had limited effect on soil urease activity. The results indicated that the responses of extracellular enzymes to biochar were dependent on the pyrolysis temperature, the enzyme itself and incubation time as well.

Effects of different organic manures on the biochemical and microbial characteristics of albic paddy soil in a short-term experiment.

This study aimed to evaluate the effects of chemical fertilizer (NPK), NPK with livestock manure (NPK+M), NPK with straw (NPK+S), and NPK with green manure (NPK+G) on soil enzyme activities and microbial characteristics of albic paddy soil, which is a typical soil with low productivity in China. The responses of extracellular enzyme activities and the microbial community diversity (determined by phospholipid fatty acid analysis [PLFA] and denaturing gradient gel electrophoresis [DGGE]) were measured. The results showed that NPK+M and NPK+S significantly increased rice yield, with NPK+M being approximately 24% greater than NPK. The NPK+M significantly increased soil organic carbon (SOC) and available phosphate (P) and enhanced phosphatase, ß-cellobiosidase, L-leucine aminopeptidase and urease activities. The NPK+S significantly increased SOC and available potassium (K) and significantly enhanced N-acetyl-glucosamidase, ß-xylosidase, urease, and phenol oxidase activities. The NPK+G significantly improved total nitrogen (N), ammonium N, available P, and N-acetyl-glucosamidase activity. The PLFA biomass was highest under NPK+S, followed by NPK+M and NPK+G treatments. Principal component analysis (PCA) of the PLFA indicated that soils with NPK+M and NPK+S contained higher proportions of unsaturated and cyclopropane fatty acids (biomarkers of fungi and gram-negative bacteria) and soil under NPK+G contained more straight chain saturated fatty acids (representing gram-positive bacteria). PCA of the DGGE patterns showed that organic amendments had a greater influence on fungal community. Cluster analysis of fungal DGGE patterns revealed that NPK+G was clearly separated. Meanwhile, the bacterial community of NPK+M treatment was the most distinct. RDA analysis revealed changes of microbial community composition mostly depended on ß-xylosidase, ß-cellobiosidase activities, total N and available K contents. The abundances of gram-negative bacterial and fungal PLFAs probably effective in improving fertility of low-yield albic paddy soil because of their significant influence on DGGE profile.

[Estimation on the size of men who have sex with men among college students in Beijing through the Network Scale-Up Method (NSUM)].

OBJECTIVE: Network Scale-Up Method (NSUM) was used to estimate the Personal Network Size (C) of college students in Beijing and the size of men who have sex with men (MSM). METHODS: A survey was conducted on Beijing college students to estimate the personal network size (C) through NSUM and then using the back-estimating and attitude adjustment to correct C value and the size of the target population. RESULTS: The mean of C among Beijing college students was 97 and the differences of C between different majors and different grades were both statistically significant. Among Beijing College students, 3.96% of them identified themselves as MSM, with the number as 16 260. CONCLUSION: Using the NSUM to estimate C of Beijing college students and size of MSM seemed to be credible which worth popularized.

Hyperbaric oxygen therapy improves cognitive functioning after brain injury.

Hyperbaric oxygen therapy has been widely applied and recognized in the treatment of brain injury; however, the correlation between the protective effect of hyperbaric oxygen therapy and changes of metabolites in the brain remains unclear. To investigate the effect and potential mechanism of hyperbaric oxygen therapy on cognitive functioning in rats, we established traumatic brain injury models using Feeney's free falling method. We treated rat models with hyperbaric oxygen therapy at 0.2 MPa for 60 minutes per day. The Morris water maze test for spatial navigation showed that the average escape latency was significantly prolonged and cognitive function decreased in rats with brain injury. After treatment with hyperbaric oxygen therapy for 1 and 2 weeks, the rats' spatial learning and memory abilities were improved. Hydrogen proton magnetic resonance spectroscopy analysis showed that the N-acetylaspartate/creatine ratio in the hippocampal CA3 region was significantly increased at 1 week, and the N-acetylaspartate/choline ratio was significantly increased at 2 weeks after hyperbaric oxygen therapy. Nissl staining and immunohistochemical staining showed that the number of nerve cells and Nissl bodies in the hippocampal CA3 region was significantly increased, and glial fibrillary acidic protein positive cells were decreased after a 2-week hyperbaric oxygen therapy treatment. Our findings indicate that hyperbaric oxygen therapy significantly improves cognitive functioning in rats with traumatic brain injury, and the potential mechanism is mediated by metabolic changes and nerve cell restoration in the hippocampal CA3 region.