Mining leads to soil degradation and land subsidence, resulting in decreased soil quality. However, there are limited studies on the detailed effects of mining activities on soil properties, particularly in western aeolian sand. This study, therefore, quantitatively assessed the aeolian sandy soil disturbance induced by mining activities in the contiguous regions of Shanxi, Shaanxi, and Inner Mongolia. The following soil physical quality indices were measured in the pre (May 2015), mid (October 2015), and postmining period (April 2016), such as the soil water content (SWC), particle size (PS), soil penetration (SP), and soil saturated hydraulic conductivity (SSHC). The results showed that mining activities brought irreversible effects on soil structures. In the pre-mining period, land subsidence broke up large soil particles, destroying soil structure, leading to decreased PS (218.33 vs. 194.36 mu m), SP (4615.56 vs. 2631.95 kPa), and subsequently decreased SSHC (1.12 vs. 0.99 cm/min). Rainfall during the midmining period exacerbated this fragmentation. Thereafter, low temperatures and humidity caused the soil to freeze, allowing the small soil particles to merge into larger ones. Meanwhile, the natural re-sedimentation, subsidence, and heavy mechanical crushing in the post-mining period increased PS and SP. The SSHC hence increased to 1.21 cm/min. Furthermore, the evaluation of soil indices from different stress zones showed that the external pulling stress zone always had a higher SSHC than the neutral zone in any mining period, possibly due to the presence of large cracks and high SWC. This study contributes to the understanding of the impact of mining activities on soil physical qualities, providing a theoretical basis and quantitative guidance for the surface damage caused by coal mining in the aeolian sandy area in Western China.
BACKGROUND Chaetanaphothrips orchidii is an invasive thrips of tropical origin that was detected in 2016 in Spanish citrus, where it can damage up to 70% of the fruit. Pupation site and emergence rates are key biological traits for thrips management that are unknown for C. orchidii. Here, we determined the pupation site and period of C. orchidii in citrus and evaluated the effect of soil moisture on adult emergence. RESULTS A two-year field study showed that C. orchidii pupated in the soil from May to December in commercial citrus orchards. Chaetanaphothrips orchidii emergence was very low compared to other harmful thrips species in citrus. Using D/E traps, we demonstrated that the thrips emerged mainly from wet areas near drip irrigation emitters during the summer, and its emergence was strongly related to the soil water content. A laboratory experiment confirmed that C. orchidii did not emerge at RH below 70%, and its emergence peaked at 97% RH. CONCLUSIONS Our results have important implications for the sustainable management of C. orchidii because soil moisture is very low in Mediterranean citrus during summer, except in areas near drip irrigation emitters. Therefore, these and other potential high-humidity areas should be considered crucial targets to manage this pest in citrus during summer, reducing cost and labor.
Drought is one of the most severe environmental stresses affecting soybean growth and development, especially in arid and semi-arid areas. The aim of this experiment is to evaluate the effect of regulated deficit irrigation during the vegetative stages on soybean plants and determine the amount irrigation water can be reduced without affecting the physiological parameters, the crop phenology, and the yield of the soybean crop. The field experiments were conducted during two irrigation crop seasons (2021 and 2022) in Louata, Morocco. The results showed that regulated deficit irrigation regimes during the vegetative stages was combined with high temperatures and low air humidities during the beginning of flowering and the pod filling stage during 2021 in comparison with 2022, especially for 25% CWR (crop water requirements). Regulated deficit irrigation regimes reduced the stomatal conductance by 46% and 52% respectively during the first and second growing seasons by limiting CO2 intake for the Calvin cycle. The stomata closure increased the leaf temperature and affected the functioning of the photosynthetic apparatus by damaging the chlorophyll pigments and impairment of electron transport chains in chloroplasts. The transition from regulated deficit irrigation to 100% CWR at the beginning of flowering (R1) compensated for the photosynthetic loss, improved the growth and development of soybean plants and enhanced the yield and its components for 50% and 75% CWR. The adaptative mechanism such as the remobilization of the carbon reserved in the stems and leaves (vegetative tissues) to the grains improved the grain yield by 36.7% during 2021 and by 32.2% during 2022 and. This consequently improved the water use efficiency, the water productivity of soybean for 50% and 75% CWR and contributed to water saving with an average of 60 mm per growing season. (c) 2024 Crop Science Society of China and Institute of Crop Science, CAAS. Production and hosting by Elsevier B.V. on behalf of KeAi Communications Co., Ltd. This is an open access article under the CC BY-NC- ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
In recent years, the damage caused by thrips has become a key factor impacting the winter and spring production of fruits and vegetables in Hainan Province, China. This study aimed to elucidate the effects of different pupation environments on pupal development and eclosion of chilli thrips (Scirtothrips dorsalis Hood) by analyzing pupal development and eclosion of chilli thrips in an indoor environment with simulated natural soils and water content. Soil type, soil water content, and temperature substantially affected the eclosion of chilli thrips during the pupal stage. Both a low soil water content of 1% and a high soil water content of 15% were not conducive to the pupation and eclosion of chilli thrips. Moreover, the results indicated an interaction between soil type and soil water and temperature and soil water content, affecting the eclosion of chilli thrips. Chilli thrips not only pupated in soil but also completed pupation and eclosion in other soil-less environments, such as tender mango leaves, stalks, plastic mulch, and weed fabric. This study suggests that in addition to adopting pest control measures that target the canopy layer of crops, appropriate measures such as increasing soil water content can also be implemented in the ground layer to enhance the overall effectiveness of pest control.
Generally, nanotechnology plays an very important role in various applied scientific fields. Iron and magnesium nanoparticles (NPs) can cause positive or negative changes in soil physical and mechanical properties, especially in long periods. The aim of this study was to investigate the multi-year effects of NPs on soil water retention and aggregate tensile strength. A wheat farm loamy soil was amended with 1%, 3%, and 5% (weight/weight) of magnesium oxide (MgO) and iron oxide (Fe3O4) NPs in three replications and incubated for three years. Water contents were measured at different matric suctions of 0, 10, 20, 40, 60, 100, 300, 1 000, and 15 000 cm. The van Genuchten model was fitted to the moisture data. Tensile strength was measured on the 2-4 mm aggregates at matric suctions of 300 (i.e., field capacity) and 15 000 (i.e., permanent wilting point) cm. The results showed that the levels of 1% and 3% Fe3O4 NPs significantly increased water retention, compared to the no NP application control and 5% MgO NPs, which is probably due to the increase of adsorption surfaces in the treated soils. Water contents at field capacity and permanent wilting point in the 5% MgO NP treatment decreased compared to those of the other treatments, due to the increased soil vulnerability and reduced soil fine pores. The application of Fe3O4 NPs did not have any significant effect on soil tensile strength. Based on the results of this study, soil physical and mechanical properties could be affected by NP application.
Soil hydraulic properties are mainly governed by the soil's heterogeneity, anisotropy, and discontinuous structural characteristics, primarily when connected soil macropores characterize the structures. Therefore, researchers must document reliable hydrological models to elucidate how the soil medium affects the movement of soil water. This study, utilizing a field-scale staining tracer test, distinguishes between matrix flow and preferential flow areas in the seepage field of Xi'an loess. The Xi'an loess's soil water characteristic curve (SWCC) was explored through field investigations and laboratory analyses. A dual-permeability model that couples matrix and macropore flow was developed using the Hydrus-2D model, enabling simulations of water migration under varying initial soil water content, rainfall intensity, and crack width. The results showed that (1) The SWCC of macropores in the preferential flow area exhibits a bimodal distribution, and the Fredlund & Xing model is applied for sectional fitting to obtain the corresponding soil water characteristic parameters. (2) Initial soil water content and rainfall intensity significantly influence water distribution, while crack width has a relatively minor effect. (3) The cumulative flux under the preferential flow is significantly higher than in the matrix area, and the wetting front depth increases with higher initial water content and rainfall intensity. This study reveals the key characteristics of preferential flow and moisture migration in the matrix zone and their influencing factors in loess. It constructs a two-domain infiltration model by integrating loess's diverse structural characteristics and pore morphology. This model provides a theoretical basis and technical support for simulating preferential flow and studying the moisture dynamics of loess profiles.
Despite the extensive research conducted on plant-soil-water interactions, the understanding of the role of plant water sources in different plant successional stages remains limited. In this study, we employed a combination of water isotopes (delta 2H and delta 18O) and leaf delta 13C to investigate water use patterns and leaf water use efficiency (WUE) during the growing season (May to September 2021) in Hailuogou glacier forefronts in China. Our findings revealed that surface soil water and soil nutrient gradually increased during primary succession. Dominant plant species exhibited a preference for upper soil water uptake during the peak leaf out period (June to August), while they relied more on lower soil water sources during the post-leaf out period (May) or senescence (September to October). Furthermore, plants in late successional stages showed higher rates of water uptake from uppermost soil layers. Notably, there was a significant positive correlation between the percentage of water uptake by plants and available soil water content in middle and late stages. Additionally, our results indicated a gradual decrease in WUE with progression through succession, with shallow soil moisture utilization negatively impacting overall WUE across all succession stages. Path analysis further highlighted that surface soil moisture (0- 20 cm) and middle layer nutrient availability (20- 50 cm) played crucial roles in determining WUE. Overall, this researchemphasizes the critical influence of water source selection on plant succession dynamics while elucidating un- derlying mechanisms linking succession with plant water consumption.
Strong winds, particularly in the absence of disaster-resistant designs, significantly impact the stability of greenhouse foundations and eventually lead to structural damage and potential harm to crops. As a countermeasure, rebar stakes are commonly used to reinforce the foundations of non-disaster-resistant greenhouses. This study evaluates the pull-out resistance (Rpull-out) of rebar stakes considering various factors like soil compaction, embedded length, installation duration and angle, and changes in soil water content against uplift pressure by strong winds. A combination of field (i.e., the cone penetration test and rebar stake pull-out test) and laboratory (i.e., the compaction test, soil compaction meter test, and soil box test) tests are performed for the assessment of Rpull-out. The results indicate that Rpull-out increases with higher soil compaction, greater embedded length, longer installation duration, and an inclined installation angle. The soil compaction exerts the most significant impact; 90% to 100% of the soil compaction rate has approximately 10 folds higher Rpull-out than the 60-70% compaction rate. If the embedded length is increased from 20 cm to 40 cm, there is a two-fold increase in the average of Rpull-out. Inclined installation of rebar stakes increases Rpull-out by 250% to 350% compared to vertical installation, and rebar stakes installed prior to the uplift event have 1.5 to 6.4 fold increases in Rpull-out than those with instant installation. Additionally, we observed variations in the surface soil moisture due to climatic changes introducing variability in Rpull-out. These findings lead to the proposition of efficient rebar stake installation methods, contributing to the enhanced stability of a greenhouse.
This study investigates effects of grass on hydro-thermal-mechanical properties and shallow stability of unsaturated soil slope. A field measurement consisted of two cut slopes, namely bare slope and grassed slope, was carried out. Field measurement results show that grass has effects on reducing the volumetric water content and increasing matric suction. There is a greater gap in matric suction between grassed soil slope and bare soil slope when the snow appears. Besides, the soil temperature in grassed slope is lower than bare slope in warm seasons. However, contrasted result of the soil temperature is recorded in winter. The triaxial tests were conducted for studying mechanical properties of grassed saturated soil with different grass ages. Experimental results reveal that there is an increase in peak shear strength and effective cohesion of grassed soil as the grass age increases, whereas a slightly higher effective angle of internal friction is observed. Furthermore, the volumetric strain decreased with the rise in grass root volume ratio. The approach of coupled nonisothermal-seepage numerical analysis for unsaturated soil slope considering impacts of grass is suggested. It is followed by slope stability analysis considering enhanced shear strength of soil due to grass roots. The good agreement regarding soil temperature and volumetric water content between simulation and field measurement indicates that the proposed approach is feasible to consider the influences of grass on the hydro-thermal behaviors of unsaturated soil slope. Furthermore, the higher values of factor of safety (FOS) of grassed slope present that the grass is effective in resisting the shallow landslide-prone area.
Permafrost degradation alters the flow rate, direction, and storage capacity of soil moisture, affecting ecohydrological effects and climate systems, and posing a potential threat to natural and human systems. The most widely distributed permafrost regions are coastal, high-latitudes and high-altitudes (mainly by the Qinghai-Tibet Plateau). Past studies have demonstrated that permafrost degradation in these regions lacks sorting out regional driving factors, assessing cascading effects on the hydrological environment and monitoring methods. To address this, we reviewed the historical research situation and major topics of permafrost degradation from 1990 to 2022. We analyzed the spatio-temporal dynamics and driving mechanism of permafrost degradation. Then, we comprehensively discussed the effects of permafrost degradation on the soil physical structure and hydraulic properties, soil microorganisms and local vegetation, soil evapotranspiration and stream runoff, and integrated ecohydrological effects. Permafrost field site data were then collected from existing findings and methods for direct or indirect monitoring of permafrost changes at different scales. These results revealed that the research on the hydrological effects of permafrost change was mainly centered on the soil. In addition, regional environmental factors driving permafrost degradation were inconsistent mainly in coastal regions influenced by sea level, high-latitude regions influenced by lightning and wildfire, and high-altitude regions influenced by topography. Permafrost degradation promoted horizontal and/or vertical hydrological connectivity, threatening the succession of high latitude vegetation communities and the transition from high altitude grassland to desert ecosystems, causing regional water imbalances would mitigate or amplify the ability of integrated ecohydrological benefits to cope with climate warming. The never-monitored permafrost area was 1.55x106 km2, but the limitations of using data for the same period remained a challenging task for soil moisture monitoring. Finally, future research should enhance the observation of driving factors at the monitoring site and combine remote sensing data, model simulations or numerical simulations, and isotope tracers to predict the future degradation state of deep permafrost effectively. It is expected that this review will guide further quantifying the driving mechanisms of permafrost degradation and the resulting cascading effects.