Shallow Soil Layers Research Articles

Spatial analysis of the electrical conductivity of the subsoil in various production technologies

The cultivation technology that is used has a very large impact on changes in the physical and chemical properties of the soil. Depending on the machines used and doses of added fertilizers, the changes may concern shallow or deep soil layers. The most commonly used method to quickly determine spatial variability is the measurement of the electrical properties of the soil using the EM38 conductivity meter. The aim of the study was to analyse the spatial variability of the electrical conductivity of the subsoil in fields where traditional cultivation technology and precision farming technology were used. The research consisted of scanning the soil with the EM38 probe at 4 experimental sites and subjecting the results to spatial analysis in the GIS software. The analysis of the obtained results showed that the soil electromagnetic conductivity variability testing method identifies the actual soil variability very well. It should be noted, however, that the lack of additional classical validation measurements may lead to erroneous conclusions. Even with similar soils in the fields, there may be significant differences in mean values (103 - 190 mS · m−1) and variability (18 - 41%).

Soil desiccation trends after afforestation in the Loess Plateau of China

Soil moisture is the main factor limiting the growth of vegetation in semiarid areas. A large area of the Loess Plateau has undergone vegetation restoration efforts following an afforestation program initiated in 1999. Understanding how soil moisture responded to afforestation is important for long-term sustainability of ecological restoration measures in this area, especially because the tree planted were non-native species. The effects on soil moisture content (SMC) of afforestation (Robinia pseudoacacia and Caragana korshinskii) were measured for different plantation ages (10, 20, 30, and 40 years) on the Loess Plateau. Meanwhile, a comparative with natural restoration grassland for the same age intervals was conducted. SMC of R. pseudoacacia plots on south-facing slopes and R. pseudoacacia and C. korshinskii plots on north-facing slopes was lowest when vegetation coverage was greatest after 20 and 30 years, respectively; SMC increases over time following natural grassland restoration; soil moisture consumption of all vegetation types was greater in the shallow soil layer (20–200 cm) than in the deep soil layer (200–500 cm) in each recovery period; and based on a three-way ANOVA, the interaction among afforestation year, vegetation type, and soil depth had significant effects on SMC. In response to societal demand for wood, existing plantations should be thinned, with afforested lands located on north-facing slopes being thinned every 10–30 years (approximately 20 years).

Origin, distribution and enrichment of selenium in oasis farmland of Aksu, Xinjiang, China

This study aims to investigate the selenium (Se) distribution in the soils of the vast cultivated areas of Aksu Prefecture in mid-Western Xinjiang of Northwest China. The study of the origin and enrichment mechanism of Se in the soils of alluvial fans of these areas (also known as oasis areas) are of great importance for the conservation and development of Se-rich resources. Geological genetic analyses and elemental abundance comparisons confirmed that the Se-rich basement rocks (i.e., the Xiyu Group) are the primary source material of Se in the oasis farmlands. The study, carried out on samples taken along two transects that cross each other, showed that, from the peripheral to the core farmland of the investigated area, the Se concentration increases significantly, accompanied by a decrease in pH and increases in organic matter and clay particles. The peripheral farming land in Aksu showed low median Se concentration of 0.19 mg/kg that represent the regional soil background, high alkalinity (pH = 8.1–9.4), high silica content (SiO2 = 47.8–72.0 wt%) and low organic matter content (OrgC = 0.17–0.76 wt%). The core farming land, representing the intensely cultivated farmland, showed a median Se content of 0.56 mg/kg, and is characterized by low alkalinity (pH = 7.3–8.5) and silica content (SiO2 = 33.5–52.5 wt%), and is rich in organic matter (OrgC = 0.87–9.8 wt%). Based on the vertical soil section investigation, we found that the soil mineralogical and geochemical variations from the deep to the shallow soil layers is similar to that from the peripheral to the core farming land. Thanks to soil acidification and accumulation of organic matters and clay particles, the oasis-type farming activities transfer Se from the Se-enriched parts of the peripheral farming land and the deep soil layers to the upper soil layers of the core farming land. This Se-enrichment mechanism made the core farming land and its topsoil the most Se-rich part of the investigated area.

Seasonal changes in the water-use strategies of three herbaceous species in a native desert steppe of Ningxia, China

Frequent periods of drought conditions are known to limit plant performance, primary production, and ecosystem stability in arid and semi-arid desert steppe environments. Plants often avoid competition by shifting their water use seasonally, which affects the water-use patterns of dominant species as well as the composition and structure of plant communities. However, the water-use strategies of dominant herbaceous species, which grow under natural field conditions in the desert steppe region of Ningxia Hui Autonomous Region, China, are poorly known. Here, we explored the possible sources of water uptake and water-use efficiency (WUE) of three dominant herbaceous plant species (Stipa breviflora, Agropyron mongolicum, and Glycyrrhiza uralensis) in a native desert steppe in the semi-arid area of Ningxia through an analysis of multiple parameters, including (1) the stable isotopic oxygen and hydrogen (δ18O and δ2H) compositions of precipitation, soil water, and stem water, (2) the carbon isotope (13C) composition of leaves, and (3) the soil water contents, based on field sampling across varying water conditions from June to September, 2017. Frequent small precipitation events replenished shallow soil water, whereas large events only percolated down to the deep soil layers. Changes in soil water availability affected the water-use patterns of plants. Generally, during light precipitation periods, the deep root system of G. uralensis accessed deeper (>80 cm) soil water, whereas S. breviflora and A. mongolicum, which only have shallow roots, primarily absorbed water from the shallow and middle soil layers. As precipitation increased, all three plant species primarily obtained water from the shallow soil layers. Variation in soil water uptake between the dry and wet seasons enabled plants to make better use of existing satoil water. In addition, the δ13C values of G. uralensis and S. breviflora were higher than those of A. mongolicum. The δ13C values of the three plant species were significantly negatively correlated with soil water content. Therefore, G. uralensis and S. breviflora maintained a higher WUE through their conservative and water-saving strategies across the entire growing season. In contrast, A. mongolicum, with a relatively low WUE in the wet season but a high WUE in the dry season, exhibited a more flexible water-use strategy. The different water-use strategies of these dominant plant species demonstrated the mechanisms by which plant communities can respond to drought.

Effect of planting methods and plant population on productivity of turmeric (Curcuma longa L.) and soil physical properties

Turmeric (Curcuma longa L.) is largely used in diversifed forms as a condiment, favouring and colouring agent and as a principal ingredient in Indian culinary as curry powder. For the higher productivity, identifcation of location specific production technologies is of prime importance. A study was conducted at the Department of Agronomy, Punjab Agricultural University, Ludhiana, Punjab for three consecutive years during kharif seasons of 2013–2015 to appraise the effect of planting methods and plant population on growth and yield of turmeric, and physical properties of the soil. The experiment was arranged in split plot design with four planting methods viz., fatbed, ridge spaced at 45 cm, ridge spaced at 60 cm and bed of 67.5 cm (2 rows per bed) in main plots and three plant populations viz., 1, 33, 334; 1, 66, 667 and 2, 00, 000 plants ha−1 in sub plots with four replications. The results revealed that bed (67.5 cm) planting method registered signifcantly better growth and yield attributes like plant height, leaf area index, dry matter accumulation, number of rhizomes per plant and consequently fresh and dry rhizome yields than other planting methods except than fatbed during frst year. Plant height and leaf area index were signifcantly improved while dry matter accumulation and number of rhizomes per plant were signifcantly less with higher plant population than lower plant population. Fresh and dry rhizome yield were signifcantly higher with plant population of 2, 00, 000 and 1, 66, 667 plants ha−1 than plant population of 1, 33, 334 plants ha−1 due to more plants per unit area under higher plant population. Soil bulk density was signifcantly lowered under ridge and bed planting methods than fatbed planting method at shallow (0–15 and 15–30 cm) soil layers, however, no signifcant effect was observed at deeper soil layers of 30–45 and 45–60 cm. Water infltration rate was recorded in the lessening order of ridge spaced at 60 and 45 cm, bed 67.5 cm and fatbed planting methods, respectively.

No-tillage with mulching improves maize yield in dryland farming through regulating soil temperature, water and nitrate-N

Nitrogen (N) losses from cropland soils contribute to a series of ecological problems. No-tillage and mulching are widely regarded as practices that can minimize the disturbance of the agro-ecosystem and regulate the water cycle in dryland farming. However, detailed understanding of water and nitrate-N transport in soil and their effects on the soil ecosystem under no-tillage with mulching is lacking. To improve our understanding, a long-term continuous maize field experiment was conducted in the southern Loess Plateau, China. This article reports experimental data form a complete growth year for spring-sowing maize, including the fallow period (from October 2017 to April 2018) and the growth period (from May 2018 to September 2018) after 15 years maize planting. Treatments included conventional tillage (CT), no-tillage (NT), no-tillage with biochar (NB), no-tillage with straw mulching (NS), no-tillage with plastic film mulching (NP), and no-tillage with straw-plastic film mulching (NSP). Overall, the results revealed that the effect of different treatments on soil temperature gradually weakened with increased maize growth and increased soil depth. The NP had the highest average temperature during the whole growth period, and NS had the lowest. Average soil profile water content (SWC) and the soil water storage (SWS) of the mulching treatments (NSP, NP, NS) were higher than the non-mulching (CT, NT, NB) at each stage. The SWS of NSP in the maturity period was significantly greater by 7.1 % compared with CT. Our results indicated that there was no nitrate-N leaching in NSP and NP below 40 cm, and the nitrate-N accumulation followed the order of CT > NT > NS > NB > NP > NSP. Conventional tillage exhibited a nitrate-N accumulation peak in deep soil layers (140−180 cm), while nitrate-N peaks of the NT, NS, and NB treatments in the shallow soil layers (40−90 cm) decreased with seasonal variation. However, the NSP and NP increased yields by 36.5 % and 34.1 %, NT decreased yields by 14.8 %, respectively, compared to CT. These suggest that no-tillage alone (NT) does not effectively improve soil water use efficiency and may even reduce yields, but reduce nitrate leaching. No-tillage with straw-plastic film mulching (NSP) was the most effective measure to facilitate the sustainable development of agriculture in dryland farming.

Modeling the effect of salt-affected soil on water balance fluxes and nitrous oxide emission using modified DNDC

Soil salinity restricts plant growth, affects soil water balance and nitrous oxide (N2O) fluxes and can contaminate surface and groundwater. In this study, the Denitrification Decomposition (DNDC) model was modified to couple salt and water balance equations (SALT-DNDC) to investigate the effect of salinity on water balance and N2O fluxes. The model was examined against four growing seasons (2008–11) of observed data from Lethbridge, Alberta, Canada. Then, the model was used to simulate water filled pore space (WFPS), salt concentration and the N2O flux from agricultural soils. The results show that the effects of salinity on WFPS vary in different soil layers. Within shallow soil layers (<20 cm from soil surface) the salt concentration does not affect the average WFPS when initial salt concentrations range from 5 to 20 dS/m. However, in deeper soil layers (>20 cm from soil surface), when the initial salt concentration ranges from 5 to 20 dS/m it could indirectly affect the average WFPS due to changes of osmotic potential and transpiration. When AW is greater than 40%, the average growing season N2O emissions increase to a range of 0.6–1.0 g-N/ha/d at initial salt concentrations (5–20 dS/m) from a range of 0.5–0.7 g-N/ha/d when the salt concentrations is 0 dS/m. The newly developed SALT-DNDC model provides a unique tool to help investigate interactive effects among salt, soil, water, vegetation, and weather conditions on N2O fluxes.

A nurse shrub species helps associated herbaceous plants by preventing shade‐induced evaporation in a desert ecosystem

AbstractXeric shrubs often play an important role in reversing desertification and promoting ecological restoration of degraded dryland ecosystems. However, how shrubs affect their associated herbaceous species and environmental conditions remains largely unknown. In this study, we conducted a removal experiment along with stable isotope analysis to determine the water use strategy of a shrub species (Artemisia ordosica) and its associated perennial graminoids (PG) in the Mu Us Desert, northern China. We observed that in the intact plots, both shrubs and PG predominantly utilized water from the shallow soil layer (0–20 cm, 54.36%, and 63.63%, respectively). Compared to this, when shrubs were removed, soil water content decreased, the main water source of PG switched to the middle soil layer (20–60 cm, 48.25%), and their water use efficiency (WUE) increased. However, the removal of PG had no significant impacts on the soil water content in any layer or on the water source of shrubs but for slightly decreased WUE. We highlighted that rather than hydraulic lift, shade‐induced evaporation decline is the primary mechanism by which shrubs facilitate the growth of associated herbaceous plants in desert ecosystems, indicating that the facilitated herbaceous plants have more flexible water use strategies than shrubs, which probably drives the community succession from being shrub‐dominated to herb‐dominated.

Geothermal Energy Use in Western Siberia and Prospects for Its Innovative Application in Construction

The article gives an overview of the use of low-temperature geothermal energy sources for heat and cold supply of buildings in areas of Western Siberia. The experience of using geothermal heat pumps shows their economic efficiency and environmental friendliness. An innovative application of the low-temperature energy of the shallow subsurface soil layers is the double use of the underground foundation of a building or another structure as energy active elements of the heat-pumping system. The paper analyzes the problems why green technologies are not developing as dynamically as indicated in the Energy Program of Russia and barriers that prevent the wider use of heat pumps and systems in the heat and cold supply of buildings in the Siberian region. These include considerable regulatory and investment barriers, as well as lack of awareness about renewable energy and energy efficiency. Further, market entry remains challenging in Russia that has not fully liberalised its energy market. Furthermore, entrenched interests in conventional energy resources represent a significant barrier to effective legislation and policy implementation. Thus, huge conventional resources of oil, gas and coal in Siberia region, neighboring to Novosibirsk, Omsk and Altay districts are other obstacles to the introduction of renewable green technologies. Some examples on the limitation of barriers to geothermal heat pumps systems application in building construction are given.

Multiple processes contribute to methane emission in a riparian cottonwood forest ecosystem.

Methane emission from trees may partially or completely offset the methane sink in upland soils, the only process that has been regularly included in methane budgets for forest ecosystems. Our objective was to analyze multiple biogeochemical processes that influence the production, oxidation and transport of methane in a riparian cottonwood ecosystem and its adjacent river. We combined chamber flux measurements on tree stems, forest soil and the river surface with eddy covariance measurements of methane net ecosystem exchange. In addition, we tested whether methanogens were present in cottonwood stems, shallow soil layers and alluvial groundwater. Average midday peak in net methane emission measured by eddy covariance was c. 12nmolm-2 s-1 . The average uptake of methane by soils (0.87nmolm-2 s-1 ) was largely offset by tree stem methane emission (0.75nmolm-2 s-1 ). There was evidence of methanogens in tree stems but not in shallow soil. Growing season (May-September) cumulative net methane emission (17.4mmolCH4 m-2 ) included methane produced in cottonwood stems and methane input to the nocturnal boundary layer from the forest and the adjacent river. The multiple processes contributing to methane emission illustrated the linked nature of these adjacent terrestrial and aquatic ecosystems.

Vertical distribution and seasonal variation of soil moisture after drip-irrigation affects greenhouse gas emissions and maize production during the growth season

Providing enough food for the increasing global population is difficult due to water shortages, which can be partially resolved by regulating soil moisture. Soil moisture influences soluble nutrient uptake and microbial activity, which determine crop growth, but also affects greenhouse gas (GHG) emissions. Farming is increasingly contributing to GHG emission, but little is known about the effects of the vertical soil moisture distribution on GHG or maize (Zea mays L.) yield over the growth season. In this study, there were five irrigation treatments: no irrigation (NI), and irrigation of the top (0–30 cm) (TI), middle (30–60 cm) (MI), bottom (60–90 cm) (BI), and all (0–90 cm) (AI) soil layers. The results showed that TI, MI, BI, and AI increased CO2 (25–60%), CH4 (80–270%), and N2O (17–96%) emissions, and the global warming potential (25–63%), while also increasing grain yield (13–119%) and reducing GHG intensity by 12–27%. While higher soil moisture in the shallow soil layer increased grain yield and GHG emissions, GHG intensity was lowest. Subsurface irrigation or control of the “drip irrigation interval” improve grain yield and resource use efficiency with lower environmental costs contributing agricultural sustainable development.

Water use of Salix in the variably unsaturated zone of a semiarid desert region based on in-situ observation

Soil water and groundwater are important water resources for vegetation survival and growth in arid and semiarid regions, and their contributions to water use over a whole growth period are difficult to quantify with limited observations. Additionally, the root water uptake (RWU) processes of groundwater-dependent xeric vegetation are specific and aggravate the complexity of these issues. In this paper, Salix is selected to study the interaction among atmosphere, soil water, groundwater, and RWU from the sprout to withered stage based on an observation within the ‘In situ Monitoring Lysimeter System of the Atmosphere-Plant-Unsaturated Zone-Groundwater Continuum’. Two lysimeters with a diameter of 2 m and depths of 1.2 m and 4.2 m were implemented with Salix. The initial water table depth was 0.7 m in case 1 and 2.2 m in case 2. The results show that: Water use of Salix is the main contribution to actual evapotranspiration (ETa), no less than 80%. ETa was 462.75 mm in case 1 with a shallower soil layer and limited groundwater, during the entire growth period, 2016. Contrastively, it was 619.70 mm in case 2 with relatively abundant soil water and groundwater. The soil water and groundwater contribution were 89.6% and 10.4%, 74.3% and 25.7% for both cases. The selective water use by Salix in different soil layers was subject to temporal moisture availability. Salix extended to utilize groundwater in drought period and shifted back to wetter upper layers in case of rainfall. The access to groundwater significantly alleviates water stress, although rainfall replenishment can also play a part. Salix can not only intercept rainfall infiltration in the root zone, but also cause the decrease of water level, implying that the replanting of Salix should be carried out in a reasonable mode to ensure rainfall infiltration and reduce the ineffective loss of groundwater. Our results provide a practical reference for groundwater management and ecology restoration in semiarid desert regions.

Sweet orange acclimatisation to water stress: a rootstock dependency

The diversification of rootstocks is of great importance for the survival of the citrus industry in order to reduce and mitigate risks caused by abiotic factors, primarily related to drought. The present study aimed to investigate the effects of ‘Pera’ sweet orange Citrus sinensis (L.) Osbeck interactions with eight rootstocks on soil water extraction, physiological responses and field productivity. Eight rootstocks combined with the ‘Pera’ sweet orange were evaluated in the field to study the effects on the following factors in response to soil water availability: matric potential (Ѱm) at depths of 0.25 m, 0.50 m and 0.90 m; physiological responses of the plants: leaf water potential (Ѱw), stomatic conductance (gs) and temperature (Lt); and plant productivity. Significant differences (p ≤ 0.05) were observed in the dry period for scion-rootstock interactions on the parameters Ѱm, Ѱw and gs. There were also significant differences for yield and productive efficiency (p ≤ 0.05). However, contrasting individuals concerning soil water extraction showed similar physiological responses in the driest periods. Different mechanisms of acclimatization to periods of drought stress that resulted in different soil water extractions and different physiological responses were not strongly related to plant productivity and were dependent on the characteristics of the deficit event. Water extraction from the shallow layer of soil is best correlated with plant water status Ѱw, it is not associated with the effective use of water in deeper soil layers for the scion-rootstock combinations studied, and explains the variation on productivities of genotypes. Scion-rootstock interactions that induce a smaller canopy volume and higher productive efficiency (kg fruit/volume canopy) and lower water use are more appropriated in high planting densities.

Decade of experimental permafrost thaw reduces turnover of young carbon and increases losses of old carbon, without affecting the net carbon balance.

Thicker snowpacks and their insulation effects cause winter-warming and invoke thaw of permafrost ecosystems. Temperature-dependent decomposition of previously frozen carbon (C) is currently considered one of the strongest feedbacks between the Arctic and the climate system, but the direction and magnitude of the net C balance remains uncertain. This is because winter effects are rarely integrated with C fluxes during the snow-free season and because predicting the net C balance from both surface processes and thawing deep layers remains challenging. In this study, we quantified changes in the long-term net C balance (net ecosystem production) in a subarctic peat plateau subjected to 10years of experimental winter-warming. By combining 210 Pb and 14 Cdating of peat cores with peat growth models, we investigated thawing effects on year-round primary production and C losses through respiration and leaching from both shallow and deep peat layers. Winter-warming and permafrost thaw had no effect on the net C balance, but strongly affected gross C fluxes. Carbon losses through decomposition from the upper peat were reduced as thawing of permafrost induced surface subsidence and subsequent waterlogging. However, primary production was also reduced likely due to a strong decline in bryophytes cover while losses from the old C pool almost tripled, caused by the deepened active layer. Our findings highlight the need to estimate long-term responses of whole-year production and decomposition processes to thawing, both in shallow and deep soil layers, as they may contrast and lead to unexpected net effects on permafrost C storage.

Numerical investigation of dynamic soil response around a submerged rubble mound breakwater: II. Loose sandy seabed

Low-crested structures such as submerged rubble mound breakwaters (RMB) are commonly used as successful examples of coastal protection measures. This study addresses foundation issues related to the performance of a submerged RMB constructed on a liquefiable site where the foundation soils have been loosely deposited; these issues were investigated using an integrated numerical model proposed by Zhao et al. (2018). Unlike previous work in Zhao et al. (2018), the dynamic features of loose sand deposits (i.e. build-up of pore water pressures, development of plastic strains, degradation of soil stiffness) due to the fluid–seabed-structure interactions, accompanied by the onset of liquefaction, were simulated. The reliability of this model to predict the liquefaction susceptibility of loose sand deposits was validated against the experimental results available in literature. This study shows that the submerged RMB constructed on a liquefiable seabed experienced progressive and asymmetric downward settlement under successive loading cycles. The opposing currents in the wave field tended to enhance this asymmetric settlement whereas the following currents did the opposite. Regardless of changes to the magnitude and direction of current velocities, ignoring the currents in the wave field may lead to an overestimation of the increased rate of residual pore water pressures in the region underneath the breakwater, particularly in shallow soil layers where the maximum relative differences can reach up to 120% of (p̄current−p̄no-current)∕P0 at t∕T=25.

CFD-Based Framework for Analysis of Soil–Pipeline Interaction in Reconsolidating Liquefied Sand

Submarine buried pipelines interact with shallow soil layers that are often loose and prone to fluidization/liquefaction. Such occurrence is a possible consequence of pore pressure build-up induced by hydrodynamic loading, earthquakes, and/or structural vibrations. When liquefaction is triggered in sand, the soil tends to behave as a viscous solid–fluid mixture of negligible shear strength, possibly unable to constrain pipeline movements. Therefore, pipelines may experience excessive displacement, for instance, in the form of vertical flotation or sinking. To date, there are no well-established methods to predict pipe displacement in the event of liquefaction. To fill such a gap, this work proposes a computational fluid dynamics (CFD) framework enriched with soil mechanics principles. It is shown that the interaction between pipe and liquefied sand can be successfully analyzed via one-phase Bingham fluid modeling of the soil. Postliquefaction enhancement of rheological properties, viscosity, and yield stress can also be accounted for by linking soil–pipe CFD simulations to a separate analysis of the pore pressure dissipation. The proposed approach is thoroughly validated against the results of small-scale pipe flotation and pipe dragging tests from the literature.

Rising Temperature May Trigger Deep Soil Carbon Loss Across Forest Ecosystems.

Significantly more carbon (C) is stored in deep soil than in shallow horizons, yet how the decomposition of deep soil organic C (SOC) will respond to rising temperature remains unexplored on large scales, leading to considerable uncertainties to predictions of the magnitude and direction of C‐cycle feedbacks to climate change. Herein, short‐term temperature sensitivity of SOC decomposition (expressed as Q 10) from six depths within the top 1 m soil from 90 upland forest sites (540 soil samples) across China is reported. Results show that Q 10 significantly increases with soil depth, suggesting that deep SOC is more vulnerable to loss with rising temperature in comparison to shallow SOC. Climate is the primary regulator of shallow soil Q 10 but its relative influence declines with depth; in contrast, soil C quality has a minor influence on Q 10 in shallow soil but increases its influence with depth. When considering the depth‐dependent Q 10 variations, results further show that using the thermal response of shallow soil layer for the whole soil profile, as is usually done in model predictions, would significantly underestimate soil C‐climate feedbacks. The results highlight that Earth system models need to consider multilayer soil C dynamics and their controls to improve prediction accuracy.

Application of Graphics Processing Units for Self-Consistent Modelling of Shallow Water Dynamics and Sediment Transport

In this paper, we describe a numerical algorithm for the self-consistent simulations of surface water and sediment dynamics. The method is based on the original Lagrangian-Eulerian CSPH-TVD approach for solving the Saint-Venant and Exner equations, taking into account the physical factors essential for the understanding of the shallow water and surface soil layer motions, including complex terrain structure and its evolution due to sediment transport. Additional Exner equation for sediment transport has been used for the numerical CSPH-TVD scheme stability criteria definition. By using OpenMP-CUDA and GPUDirect technologies for hybrid computing systems (supercomputers) with several graphic coprocessors (GPUs) interacting with each other via the PCI-E / NVLINK interface we also develop a parallel numerical algorithm for the CSPH-TVD method. The developed parallel version of the algorithm demonstrates high efficiency for various configurations of Nvidia Tesla CPU + GPU computing systems. In particular, maximal speed up is 1800 for a system with four C2070 GPUs compare to the serial version for the CPU. The calculation time on the GPU V100~(Volta architecture) is reduced by 95 times compared to the GPU C2070~(Fermi architecture).

A field trial to test the efficiency of induced partial saturation and horizontal drains to mitigate the susceptibility of soils to liquefaction

Within the European project LIQUEFACT some activities have been devoted to the experimental verification of the effectiveness of two techniques in the mitigation of soil liquefaction susceptibility: induced partial saturation (IPS) and horizontal drains. After a preliminary check of their efficiency via centrifuge tests, the two techniques have been studied by means of some large scale shaking tests carried out in a field trial located in the Emilia-Romagna Region (Italy). A preliminary extensive in situ and laboratory investigation was necessary to identify the shallow liquefiable soil layer in which the mitigation techniques and the monitoring instrumentations (pore pressure transducers and geophones) had to be installed. Both techniques required the installation of horizontal well screens via a directional controlled drilling technique: the pipes were used as drainage systems (linear HDL and rhomboidal configurations HDR) or for the air injection in the area treated with IPS technique. The in situ experimental evidences showed that both techniques are able to avoid liquefaction triggering, that on the contrary was attained during the tests in the untreated testing area. The processing of in situ data highlighted that the efficiency of the two techniques is strictly related to chosen arrangement of the horizontal drains and the induced degree of saturation.

Using isotopic labeling to investigate root water uptake in an alley cropping system within Taklimakan Desert Oasis, China

Intercropped trees are becoming popular as an ecological protection screen for a desert oasis from wind-blown sand and sand erosion. However, trees also consume a large amount of water and thus could compete for water resources with other crops. Here, we evaluated the water uptake in a typical alley cropping system within an oasis of the South Taklimakan desert. The system consisted of a poplar tree (Populus L.) used for sand protection and a walnut (Juglans regia L.)-corn (Zea mays Linn.) intercropping system. We evaluated root distribution by isotopically-labeled water (δD) and water uptake (δ18O) via SIAR models as well as the direct inference approach for different periods after tracer injection. We found that the different plants used water from different soil layers. While corn used water mostly from the 0–40 cm soil layer during the jointing (61%) and silking–filling periods (58%), respectively, walnut used water mostly from deeper than 40-cm depth (65%), and poplar used water from both shallow (about 30%, 0–40 cm) and deep soil layers (about 40%, 140–200 cm). Furthermore, while walnut roots can reach 200-cm depth, poplar roots can reach down to 400-cm depth. Due to those root differences, we infer that poplar trees do not necessarily compete for water resources with walnut and corn, and, therefore, can provide a valuable ‘safety-net’ service in this alley cropping system.