•Contribution of root decay process on soil water replenishment was assessed.•The macropore formed by decayed root increased the infiltration rate at each stage.•The decayed roots maintain rapid ...preferential infiltration by reducing root density.•Soil water replenishment significantly increased with root decay ages.
Large-scale afforestation has seriously aggravated the consumption of soil water and caused soil desiccation and even the dry soil layers, which has been restricting the survival and sustainability of vegetation in semi-arid areas. How to solve soil water deficit reasonably is an important practical problem we are facing. Here, a field experiment of the decayed roots with different times on soil water infiltration processed was conducted in planted forestland by a double-ring infiltration instrument, to determine the contribution of decayed tree roots on soil water infiltration process and replenishment. Results showed that the decayed process of tree roots in forestland could significantly reduce root density (RD) and increase the relative porosity improved by the roots (RPIR) (P < 0.05). The macropore formed by root decay could not only significantly increase the infiltration rate at each stage (P < 0.05), but also reduce the decrease rate of infiltration rate. Compared with bare land, the decayed roots of the 1–4 yr, the 5–8 yr, and the 9–12 yr increased the amount of soil water replenishment by 37.12%, 217.52%, and 259.85%, respectively. Overall, the decayed tree roots could maintain a relatively high and stable infiltration rate by reduced root density, which increased the effective replenishment of soil water of dry soil layers in forestland. These findings have potential implications for understanding the effect of decay process of tree roots on soil water replenishment, and provide a theoretical basis for the solution to dry soil layers and sustainable management of forestland in semi-arid areas.
•Effects of root and soil water on infiltration rate were studied during different stages.•Root diameter became the main factor affecting soil infiltration along infiltration time.•The ...0–2-mm-diameter root was positively correlated with infiltration rate.•The >4.5-mm-diameter root was negatively correlated with infiltration rate.•Fine roots more determine soil infiltration potential than soil water content.
Soil water is the key limiting factor for achieving sustainable revegetation. Soil infiltration rate plays an important role in determining the inputs from precipitation, which is important for the plant growth and groundwater recharge in semi-arid regions. Soil infiltration rate is generally influenced by belowground biomass (BGB), soil water content (SWC) and other soil properties (total soil porosity, soil mean weight diameter and soil organic carbon). The aim of this study is to understand the effects of plant roots, SWC and other soil properties on soil infiltration rate, and to identify the main factor affecting soil infiltration rate. This study investigated the total soil porosity (TP), soil mean weight diameter (MWD), soil organic carbon (SOC), SWC and plant roots of five grasslands (Bromus inermis, Trifolium repens, Panicum virgatum, Medicago sativa and Miscanthus sinensis). An automatic measurement system of point source device was used to quantify the soil infiltration rate. Results showed that SWC significantly affected the initial infiltration rate (P < 0.05), but plant roots gradually became the main factor affecting soil infiltration rate as the increasing infiltration time. The percentage of root volume (PV) of 0–2 mm was positively correlated with infiltration rate, while the PV of >4.5 mm was negatively correlated with infiltration rate. Our results indicated that fine roots could increase soil organic matters and form soil pores, thus more determining the potential of soil infiltration than soil water content during the short-term vegetation restoration in semi-arid regions.
The accurate measurement of soil infiltration rates is a challenging task in hydrological studies, as they are governed by complex interactions between the plant and soil components. To explore the ...effects of plant roots and soil moisture (SM) on infiltration process, an automatic measurement system based on a point source device was used to determine infiltration rates at different cultivated grasslands (leguminous, gramineous and mixed) in an arid region of China. The results showed that SM and plant roots significantly affected the infiltration process at different stages in the three grasslands. The soil infiltration rates were negatively correlated to SM, but a positive correlation was observed with the below-ground biomass (BGB). SM was the main factor influencing the infiltration rates in the initial stage of infiltration, whereas both SM and BGB determined the steady-state infiltration rates. The influence of the combined effects of SM and plant roots decreased over infiltration time. The decreased rate of determining coefficient showed that SM was more influent than plant roots. These results may contribute to interpret the observed higher soil infiltration capacity in the leguminous grasslands than in the gramineous and the mixed grasslands, and were conducive to better understand the effects of plant and soil properties on infiltration processes in arid areas.
•Soil moisture and plant roots determined soil infiltration capacity by stages were studied.•Soil moisture is a main factor to influence negatively infiltration capacity in initial stage.•Soil moisture and plant roots codetermined the infiltration rate in steady stage.•Influences of soil moisture and roots are diminishing with the duration of infiltration time.
As the earliest commercial cathode material for lithium-ion batteries, lithium cobalt oxide (LiCoO
2
) shows various advantages, including high theoretical capacity, excellent rate capability, ...compressed electrode density, etc. Until now, it still plays an important role in the lithium-ion battery market. Due to these advantages, further increasing the charging cutoff voltage of LiCoO
2
to guarantee higher energy density is an irresistible development trend of LiCoO
2
cathode materials in the future. However, using high charging cutoff voltage may induce a lot of negative effects, especially the rapid decay of cycle capacity. These are mainly caused by rapid destruction of crystal structure and aggravation of interface side reaction at high voltage during the cycle. Therefore, how to maintain a stable crystal structure of LiCoO
2
to ensure the excellent long cycle performance at high voltage is a hot research issue in the further application of LiCoO
2
. In this review, we summarized the failure causes and extensive solutions of LiCoO
2
at high voltage and promoted some new modification strategies. Moreover, the development trend of solving the failure problem of high-voltage LiCoO
2
in the future such as defect engineering and high-temperature shock technique is also discussed.
Graphical abstract
•Soil water infiltrability plays a critical role for vegetation restoration in arid areas.•Artificial grassland could improve soil infiltration capacity by their more root biomass.•Soil moisture and ...root biomass were the main factors affecting soil infiltration capacity.•Mixed artificial grassland with more roots improved mine soil infiltration capacity.
Soil water is one of the critical limiting factors in achieving sustainable revegetation. Soil infiltration capacity plays a vital role in determining the inputs from precipitation and enhancing water storage, which are important for the maintenance and survival of vegetation patches in arid and semi-arid areas. Our study investigated the effects of different artificial grasslands on soil physical properties and soil infiltration capacity. The artificial grasslands were Medicago sativa, Astragalus adsurgens, Agropyron mongolicum, Lespedeza davurica, Bromus inermis, Hedysarum scoparium, A. mongolicum+Artemisia desertorum, A. adsurgens+A. desertorum and M. sativa+B. inermis. The soil infiltration capacity index (SICI), which was based on the average infiltration rate of stage I (AIRSI) and the average infiltration rate of stage III (AIRS III), was higher (indicating that the infiltration capacity was greater) under the artificial grasslands than that of the bare soil. The SICI of the A. adsurgens+A. desertorum grassland had the highest value (1.48) and bare soil (−0.59) had the lowest value. It was evident that artificial grassland could improve soil infiltration capacity. We also used principal component analysis (PCA) to determine that the main factors that affected SICI were the soil water content at a depth of 20cm (SWC20), the below-ground root biomasses at depths of 10 and 30cm (BGB10, BGB30), the capillary porosity at a depth of 10cm (CP10) and the non-capillary porosity at a depth of 20cm (NCP20). Our study suggests that the use of Legume-poaceae mixtures and Legume-shrub mixtures to create grasslands provided an effective ecological restoration approach to improve soil infiltration properties due to their greater root biomasses. Furthermore, soil water content, below-ground root biomass, soil capillary porosity and soil non-capillary porosity were the main factors that affect the soil infiltration capacity.
Soil erosion control and water resource protection can closely interact during restoration of terrestrial ecosystems. In semi‐arid ecosystems, an urgent issue is how vegetation restoration can ...achieve the goal of soil erosion mitigation and water conservation, which in turn, feeds back to ecosystem functioning.
We reviewed 78 articles from 22 countries in semi‐arid areas to evaluate the effects of vegetation type (i.e. forest, grassland and scrubland) on runoff and sediment yields across different environmental conditions (i.e. vegetation coverage, rainfall intensity, slope gradient and soil texture).
Our meta‐analysis shows that runoff and sediment reduction both increased as the vegetation coverage increased, and tended to be stable when vegetation coverage exceeded 60%. Vegetation provided a greater benefit for sediment reduction than for runoff control under intense rainfall. Grasslands were generally more effective in reducing sediment than other vegetation types. Forests, grasslands and scrublands were most efficient in soil erosion control on 20°–30°, 0°–25° and 10°–25° slopes respectively. Grasslands and scrublands generally performed better with respect to soil erosion control on moderately coarse soils, whereas forests were most effective on medium‐textured and moderately fine soils.
Synthesis and applications. Effective restoration and soil erosion control in semi‐arid ecosystems strongly depends on the selection of vegetation type. Our study further indicates that, for land managers, it is critical to consider local slope, and soil texture, and maintain appropriate vegetation coverage to achieve ecosystem sustainability. Grasslands might be particularly suitable to optimize the trade‐off between soil erosion control and surface water resource in semi‐arid regions.
抽象
半干旱区水保型植被恢复过程中如何实现水土流失控制且维系地表水资源的目标，并进一步反馈于植被生态系统功能，是目前亟待解决的问题。
本研究基于公开发表的来源于22个国家、78篇关于半干旱区植被对土壤侵蚀影响的文献报道，应用Meta‐analysis方法，系统评价了不同植被类型（林地，草地和灌木地）在不同环境条件（植被盖度、降雨强度、坡度和土壤质地）下对径流量和产沙量的影响。
研究结果表明，植被减流效应和减沙效应均随植被盖度的增加而增加，并在植被盖度达到60%时趋于稳定。强降雨下，植被减沙效应大于其减流效应。总体上，三种植被类型中，草地具有最高的减沙效应。林地、草地和灌木地分别在20°‐30°、0°–25°和10º‐25°坡度范围内表现出较高的减流效应和减沙效应。且草地和灌木地在中等粗糙质地土壤中的减流效应和减沙效应较高，林地在中等质地和中等细密质地土壤中的减流效应和减沙效应较高。
综合应用：半干旱区的水保型植被水土流失调控的有效性很大程度上取决于适宜的植被类型。本研究表明，在全球半干旱区，建设草地植被可有效实现水土流失调控与地表水资源维系的权衡。同时，在水保型植被建设过程中，应综合考虑坡度和土壤质地等实际情况并维持适宜的植被盖度，以实现植被生态系统的可持续性。
Effective restoration and soil erosion control in semi‐arid ecosystems strongly depends on the selection of vegetation type. Our study further indicates that, for land managers, it is critical to consider local slope, and soil texture, and maintain appropriate vegetation coverage to achieve ecosystem sustainability. Grasslands might be particularly suitable to optimize the trade‐off between soil erosion control and surface water resource in semi‐arid regions.
•Effects of root channels on soil water infiltration rates were studied in artificial grassland.•The average diameter of root channels (ADRC) was significant positively related to average ...infiltration rate.•Root channels played a significant role in soil preferential flow and infiltration capacity.
Soil matrix flow plays a critical role in redistributing the precipitation input and enhancing water storage in arid areas. Root channels can result in macropore flow which strongly influences soil infiltration. Prior research has addressed the influence of vegetation on erosion and runoff, but the effects of root channels on infiltration capacity are less studied. In this study, we studied the root channels and soil water infiltration rates in ten artificial grasslands in an arid area. The results showed that the average root channel diameter (ARCD) of leguminous grasslands and of shrub grasslands were greater than that of gramineous grasslands (p<0.05). Importantly, the ARCD and root channel area (RCA) were significantly and positively related to the average infiltration rate in stage I (AIRS I) and the initial infiltration rate (IIR). The IIR and the AIRS I increased at rates of 31.13 and 14.60mmh−1, respectively, and at the same time there was an increase in ARCD. Overall, our results suggest that root channels played a significant role in the matrix infiltration capacity, resulting in a higher infiltration rate in leguminous grasslands and in mixed sown grasslands than in gramineous grasslands. We suggest that leguminous grasslands or the combination of leguminous and gramineous species in grassland should be given greater attention as suitable materials for mine-soil reclamation in arid regions. Our research improve the understanding of the influence of vegetation on soil hydrological processes and of the hydrology of reclaimed mine soils in arid regions.
Display omitted
•Porous polyacrylamide/polystyrene fiber was synthesized by electrospinning.•The composite fiber shows strong hydrophobic property.•Strong sorption ability of fiber was found for ...multiple fresh and used oils.•PAM/PS membrane exhibited effective property of light-oil/seawater separation.•Membrane showed the good stability for 20 cycling.
With increasing demand for the treatment of oil contaminants in wastewater, it was necessary to develop energy-efficient technologies for oil-water separation. In this study, the porous polyacrylamide/polystyrene (PAM/PS) fiber was synthesized by electrospinning method, and the membrane was obtained from fiber by the compression moulding process. The porous structure on the fiber surface was controlled by the content of PAM. The water contact angle of PAM/PS fiber reached 157.6 ± 2.5°, and it still showed good salt resistance and acid/alkali stability. PAM/PS fiber revealed high oil-sorption capacity for the removal of multiple edible and industrial oils. Notably, for the above used oils, the sorption capacity of PAM/PS still reached 154.5–202.2 g/g. In the mixed system of used oil and simulated seawater, PAM/PS membrane exhibited effective property of oil/water separation. Specially, under an applied pressure of 0.01 MPa and mechanical stirring, the light-oil was rapidly separated from mixtures by PAM/PS membrane, which showed good stability in 20 cycles. Hence, PAM/PS membrane was a very promising material for actual application in the large-scale treatment of oil-contaminants wastewater.
Minisci-type reaction is one of the important means to construct C(sp3)–H functionalization of heteroarenes. According to traditional methods, stoichiometric amounts of precious transition metal ...catalysts and chemical oxidants were required at high temperatures. Here, a green and gentle novel Minisci-type method was developed via visible-light-induced cross-dehydrogenative coupling of heteroarenes with aliphatic C(sp3)–H bonds under oxidant-free and transition-metal-catalyst-free conditions. Only the catalytic equivalent of CF3SO2Na and room temperature were required to maintain an efficient reaction.
China has not yet established a national surveillance network such as NHSN from America, so there is still no large-scale investigations on central line-associated bloodstream infection (CLABSI) ...incidence. Several retrospective studies in China reported that the incidence of CLABSI varied due to inconsistent diagnostic criteria. We performed a nationwide survey to investigate the utilization rate of central venous catheters (CVCs) and the incidence of CLABSI in ICUs of different areas of China. This is a prospective multi-center study. Patients admitted to ICUs with the use of CVCs between January 1, 2014 and December 31, 2018 were enrolled in this study. Hospitals were given the definition of catheter-related bloodstream infection as: a laboratory-confirmed bloodstream infection where CVC was in place on the date of event or the day before. The characteristics of patients, information of catheterization, implementation rates of precautions, and CLABSIs were collected. The statistical analysis was performed by SPSS 25.0 software and website of Open Source Epidemiologic Statistics for Public Health. A total of 38,212 patients and 466,585 catheter days were involved in surveillance. The average CLABSI incidence in a thousand catheter days was 1.50, the lowest incidence unit was in pediatric ICU (0/1000 catheter days), and the lowest incidence area was in Northeast China (0.77/1000 catheter days), while the highest incidence unit was in cardiac ICU (2.48/1000 catheter days) and the highest incidence area was in Eastern China (1.62/1000 catheter days). The average utilization rate of CVC was 42.85%, the lowest utilization rate was in pediatric ICU (5.85%) and in Central China (38.05%), while the highest utilization rate was in surgical ICU (64.92%) and in Western China (51.57%). Among the 702 CLABSI cases reported, a total of 735 strains of pathogens were cultured. Staphylococcus spp. was the most common organism isolated (27.07%), followed by Enterobacteriaceae (22.31%). The implementation rates of all precautions showed an upward trend during the study period (P less than or equai to 0.001). The average incidence of CLABSI in ICUs in China is 1.5/1000 catheter days, similar to the rates reported in developed countries but lower than previous reports in China. CLABSI incidence showed regional differences in China. It is necessary to implement targeted surveillance of CLABSI cases by using standardized CLABSI surveillance definitions and methodologies.
PDF
