Soil Water Migration Research Articles

Additional organic and bacterium fertilizer input regulated soybean root architecture and dry matter distribution for a sustainable yield in the semi-arid Region of China.

In the dryland area of the Loess Plateau in northwest China, long-term excessive fertilization has led to soil compaction and nutrient loss, which in turn limits crop yield and soil productivity. To address this issue, we conducted experiments using environmentally friendly organic fertilizer and bacterium fertilizer. Our goal was to investigate the effects of additional organic and bacterium fertilizer inputs on soil water migration, crop root architecture, and yield formation. We implemented six different fertilizer strategies, namely: Nm (mulching, N 30 kg/ha), NPK1m (mulching, N 60 kg/ha; P 30 kg/ha; K 30 kg/ha), NPK2m (mulching, N 90 kg/ha; P 45 kg/ha; K 30 kg/ha), NPKOm (mulching, N 90 kg/ha; P 45 kg/ha; K 30 kg/ha; organic fertilizer 2 t/ha), NPKBm (mulching, N 60 kg/ha; P 30 kg/ha; K 30 kg/ha; bacterium fertilizer 10 kg/ha), and N (N 30 kg/ha; no mulching). The results revealed that the addition of bacterium fertilizer (NPKBm) had a positive impact on soybean root system development. Compared with the other treatments, it significantly increased the total root length, total root surface area, and total root length density by 25.96% ~ 94.89%, -19.63% ~ 36.28%, and 9.36% ~ 28.84%, respectively. Furthermore, NPKBm enhanced soil water consumption. In 2018, water storage during the flowering and podding periods decreased by 12.63% and 19.65%, respectively, while water consumption increased by 0.97% compared to Nm. In 2019, the flowering and harvest periods decreased by 23.49% and 11.51%, respectively, while water consumption increased by 0.65%. Ultimately, NPKBm achieved high grain yield and significantly increased water use efficiency (WUE), surpassing other treatments by 76.79% ~ 78.97% and 71.22% ~ 73.76%, respectively. Subsequently, NPK1m also exhibited significant increases in yield and WUE, with improvements of 35.58% ~ 39.27% and 35.26% ~ 38.16%, respectively. The use of bacterium fertilizer has a profound impact on soybean root architecture, leading to stable and sustainable grain yield production.

Response of Sandy Soil–Water Migration to Different Conditions under Unidirectional Freezing

In order to conserve valuable soil and water resources and avoid problems related to frozen soil, it is important to study the migration of frozen soil water. A greater understanding of frozen soil–water migration can assist with sustainable development and utilization of soil and water resources in frozen areas. This study used an indoor soil column test device to conduct a one-way indoor freezing test of unsaturated soil and the response of soil sample water migration to different freezing temperatures, initial moisture contents, soil densities, freezing times, solute concentrations, and solute types. The experimental and analytical results showed that the temperature field of the soil sample could be divided into three stages: sharp cooling, slow cooling, and stability. After the soil sample had been frozen for 100 h, the temperature field stabilized. The freezing temperature, initial water content, soil density, and freezing time affected water migration in the soil sample. Lower freezing temperatures and greater initial water content resulted in higher levels of water migration. By contrast, greater soil density led to lower water migration levels. In addition, longer freezing times produced smoother soil–water migration curves. The solute concentration and solute type also affected water migration in frozen soil; the higher the solute concentration, the greater the water migration. Compared with CaCl2, NaCl had a stronger effect, causing more water migration and leading to a higher water content. The research findings will aid further studies on soil and water utilization, environmental maintenance, and restoration in areas with seasonally frozen soil, as well as promote the sustainable development of agriculture, water conservancy project development, and the social economy.

High-Resolution Soil Moisture Measurements in Rational Fertilization and Irrigation Methods as Part of the Sustainable use and Management of Soil Under Climate Change - DIY Solutions

Current climate changes, including drought, represent one of the most severe and extreme natural phenomena, directly affecting the environment, economy and society, and increasingly leading to soil degradation. In drought-stricken areas, losses in agricultural production are driving up food prices. The world's demand for water will continue to grow further in the coming decades. In view of the presented facts, there is a tremendous need for a systemic approach to saving water in the process of soil reclamation and conducting multidisciplinary research in this field. The problem of fertilization is linked to reasonable irrigation. These processes ought to be synchronized and run simultaneously, under the control by the system. This paper presents a prototype measurement probe as an element of a measurement network and the results of tests of its application in under use. The purpose of this research was testing a cheap DIY to solution identify the availability of water resources in the soil layer where the major plant root mass is found, i.e., to a depth of up to 110 cm, and to rationalize the management and improve the efficiency of water use during irrigation, as well as to monitor the migration of water in the soil in the era of climate change. The conducted tests have yielded concrete conclusions - current climate change is already resulting in unusual situations, including the different behaviour of water migrating through the soil. Considering that a wide variety of soils and geological systems are present, it is extremely important to understand these mechanisms in great detail, which makes the created solution feasible. Such a detailed analysis of water migration in soil under use can very successfully support, for example, a low-cost precision irrigation (preventing drought), or fertilization, indicating periods when and where to introduce nutrients after rainfall so that they naturally reach the depth of the largest root mass as quickly as possible. The DIY solution can be crucial in Third World countries by conducting at least single, cheap soil moisture measurements, and in many other places affected by the problem of water deficit, it can be an alternative to extend existing monitoring systems.

Soil water migration under three tree species in response to water stress and extreme rainstorms

In arid and semi-arid areas, plant growth and survival are directly related to the soil water content. The soil water content is an important parameter for monitoring land degradation. A better understanding of how forests use soil water is crucial for the quantification how the terrestrial hydrologic cycle adapts to forestry practices and regional climate anomalies in these areas. This study investigated the variation of the water balance under different precipitation patterns (including soil water redistribution patterns under water stress and extreme rainstorms) under three common tree species in a mountainous area of Beijing were investigated. The results showed that soil water storage in the 80–150 cm layer played an important role for the ability of Platycladus orientalis (L.) Franco and Quercus variabilis Blume to survive drought during a dry season. Compared to P. orientalis and Q. variabilis, the duration of water stress was shortest for Pinus tabulaeformis Carr. (15 months). P. tabulaeformis had a higher ability to utilize top soil water but showed a less balanced use of soil water in each soil layer. It also had the strongest ability to replenish groundwater through deep seepage. P. tabulaeformis may resist drought by transferring water to deeper soil horizons, where it is less susceptible to evaporation and where moisture can be temporarily stored. P. orientalis and Q. variabilis are more dependent on soil water storage in response to water stress conditions.

A multiphase model developed for mesoscopic heat and mass transfer in thawing frozen soil based on lattice Boltzmann method

Subgrade engineering in cold region collapsed and settled under the influence of global warming, this was mainly due to the thawing frozen soil. The heat and mass transfers in thawing frozen soils are generally described with continuity equations on the macroscopic scale. However, the processes of ice melting and water migration in soil were rarely described on the mesoscopic scale. In this study, a multiphase pseudo-potential model with enthalpy-based module was developed based on lattice Boltzmann method to predict the distributions of temperature and water content in the thawing process of frozen soil. The force source terms in pseudo-potential model were given as adhesive force, cohesive force, temperature drive force and bulk force to describe the interaction between multiple components in thawing process, and the enthalpy-based module was employed to realize the process of phase transition in soil. The complex initial conditions of thawing process were measured and then set in simulation for the first time. The results showed that as compared with the measured soil temperatures and water contents at different top soil temperature (5 °C and 10 °C) and times (0, 12, and 36 h), the relative errors of model were 0.01 % ∼ 0.72 % and 0.10 % ∼ 19.31 % for the soil temperatures and water contents, respectively. Further, the developed pseudo-potential model can also be used to detail the mesoscopic heat and mass transfers in thawing soils.

Investigating unfrozen water and its components during freeze–thaw action in loess using a novel NMR technique

AbstractFrost heave and thaw settlement are primarily caused by water migration. Variations in liquid water and its components during freezing and thawing are crucial variables for investigating water migration. Here, a novel soil layer‐scanning method based on magnetic resonance imaging cryogenic soil‐moisture analysis (MRI‐CSMA) was applied to measure dynamic changes of liquid water and its components in nine layers (each 11.1‐mm thick) of four loess samples with different initial water contents (9.2%, 15.7%, 20.0%, and 30.0%) in freezing–thawing experiments under a closed system. The ice–water phase transition and water migration were key factors that controlled the liquid water and its components. During freezing, the liquid water content of each layer (except layer 7) decreased. In the frozen zone (layers 1–6), the liquid water content decreased with decreasing temperature owing to the water–ice phase transition. The lower the temperature, the higher the fraction of water that transitioned to ice. In the unfrozen zone (layers 8–9), parts of the liquid water migrated upward owing to the suction generated at the freezing front. The farther away the freezing front, the smaller the suction and quantity of water migration. During thawing, the liquid water content of each layer increased owing to the ice–water phase transition in the frozen zone and infiltrated down to the unfrozen zone. The contents of the free and adsorbed water exhibited similar change trends to the liquid water content during freezing. However, the change degree of free water was much larger than that of adsorbed water because the phase transition and migration of free water is easier than that of absorbed water. Notably, the liquid water content near the freezing front (layer 7) increased in the early stage of freezing, owing to the combined effect of soil compression and the water–ice phase transition. These results provide a reference for research on water migration in the soil during freezing–thawing and validate the advantage of MRI‐CSMA when characterising water migration in large soil samples.Highlights A novel device (MRI Cryogenic Soil‐Moisture Analyzer) was used. Variations in unfrozen water and its components during freezing were studied. Soil consolidation and pore pressure affect the liquid water change during freezing.

Soil Freeze-Thaw and Water Transport Characteristics Under Different Vegetation Types in Seasonal Freeze-Thaw Areas of the Loess Plateau

In the arid and semi-arid regions of the Loess Plateau, seasonal freezing and thawing influence soil water movement, and water movement directly influences vegetation growth. However, currently, research with regard to freezing and thawing processes under various vegetation types and the mechanism of soil water movement is lacking. Therefore, the present study explored soil water migration characteristics of two typical vegetation types [arbor land (AL) and shrub land (SL)] on the Loess Plateau during seasonal freezing and thawing processes using bare land (BL) as a control. We used field measured data for hourly soil temperature (ST) and soil water content (SWC) at a depth of 100 cm below the soil surface from November 2017 to March 2018. Freezing and thawing process was divided into three stages based on ST change (initial freezing period, stable freezing period, and thawing period). Compared with previous studies in this area, ST is lower than expected, and SWC migration characteristics are also different. The results revealed that: 1) the maximum freezing depth of AL and SL was 60 cm, which was 30 cm less than that of BL. The freezing date of each soil layer in BL was the earliest and average ST value was the lowest. BL had the highest degree of freezing. The freezing of all soil layers in AL occurred at a later date than that of SL. ST and the minimum soil freezing temperatures were higher than those of SL, and the capacity of AL to resist freezing was higher; 2) the SWCs in AL and BL at depths of 0–10 cm and 10–30 cm decreased, whereas SWCs of AL and BL at a depth of 60 cm increased by 152 and 146%, respectively. The SWCs of SL at soil depths of 0–10 cm, 10–30 cm, and 30–60 cm increased by 46.3, 78.4 and 205%, respectively. The amount and distribution of soil moisture in SL were optimum when compared to those of AL and BL. The results of the present study could provide a scientific basis for vegetation restoration in arid and semi-arid areas of the Loess Plateau.

Effects of plastic mulch on soil water migration in arid oasis farmland: Evidence of stable isotopes

In arid areas, where water resources are extremely scarce, the consumption of agricultural water resources is generally higher than 80% of the total water resources. Reasonable irrigation practices and effective water conservation methods are critical to the efficient utilization of water resources. In order to analyze the rationality of existing irrigation mode and evaluate the effect of plastic mulch on irrigation water migration, this research monitored the hydrogen and oxygen stable isotopic composition of soil water in Minqin oasis farmland located in the arid area of Northwest China. We used the soil water balance equation and the Craig-Gordon model to quantify the infiltration and evaporation of soil water. The result shows: (1) After irrigations in the corn growing season, the average irrigation water of 29.9 ± 4.2% (29.0 ± 6.7 mm), 29.6 ± 2.9% (28.4 ± 2.7 mm) and 30.3 ± 4.3% (29.0 ± 3.5 mm) penetrated into the soil layer of 0–10 cm, 10–50 cm, and 50–100 cm respectively. The field drainage under plastic film mulching was higher than that of no film mulching. (2) Plastic film mulching is the main reason for the difference in SWlc-excess of the surface layer. The evaporative loss of 0–5 cm soil water in non-mulched soil was generally higher than that of plastic-mulched soil. During the whole corn growing season, plastic film mulching effectively reduces evaporation losses of surface soil water and improves water use efficiency. The results of the reserch are very useful for understanding the hydrological process of agricultural lands in arid oases, improving agricultural irrigation water utilization rates, and optimizing water conservation models.

Fractal and multifractal analysis of soil particle-size distribution and correlation with soil hydrological properties in active layer of Qinghai–Tibet Plateau, China

The soil hydrological properties (HPs) in active layers regulate soil water migration and affect the evolution of permafrost and biogeochemical cycles. There is relatively little understanding of the changes in soil HPs as a result of soil particle-size distribution (PSD) in the permafrost regions of the Qinghai–Tibet Plateau. In this study, different land-cover types, namely alpine wet meadow (AWM), extremely degraded wet meadow (EDWM), alpine meadow (AM), degraded alpine meadow (DAM), alpine steppe (AS), and alpine desert (AD), were used to determine the relationships between soil PSD and HPs. Soil HPs were determined using borehole nuclear magnetic resonance, and soil PSD (0–2 mm) was analyzed using fractal and multifractal theory. The results showed that vegetation degradation caused coarse soil particle accumulation in the root zone, reflected by the soil single-fractal dimension (Dv: 2.12–2.50). The Dv values showed significant positive correlations with soil clay and silt content as well as a negative correlation with sand content. Results from the generalized fractal and singularity spectra suggested an even distribution of soil particles in the root zone of the AWM, AM, and AD sites. Vegetation degradation increased the soil PSD capacity dimension (D0), information dimension (D1), correlation dimension, D1/D0 ratio, and Hölder exponent of order zero. This was indicative of a narrow soil PSD range and non-uniform soil texture in the root zone. Although capillary water dominated the total soil water content in the alpine soils, soil water composition was also dependent on the vegetation type and soil stratigraphic distribution. Soil particle composition and multifractal dimensions were found to be effective parameters for forecasting soil HPs in the non-root zone of alpine soils. However, the presence of vegetation weakens the relationship between soil PSD and HPs. This study contributes to the accurate evaluation of hydrological and biogeochemical cycles in permafrost regions.

Effect of freeze-thaw processes on soil water transport of farmland in a semi-arid area

Seasonal freeze-thaw processes affect soil water migration and distribution, especially in semi-arid agricultural areas. These processes play an important role in mitigating harsh environmental conditions and wind erosion. Soil water content (SWC) and soil temperature (ST) were monitored at different depths (0–2 m) and investigated under freeze-thaw conditions from November 2018 to May 2019 in a semi-arid agro-pastoral region of northern China. The initial SWC was the main factor that affected the freeze-thaw process. During the freeze-thaw process, differences in soil thermal conductivity caused the soil to thaw faster than the freezing process, and the upper soil layer (0–60 cm) was significantly affected by temperature changes. Changes in the potential energy of water and pore pressure gradient caused the migration of soil water to the upper layer, which led to a slight decrease in SWC in each layer before ST dropped to the freezing point. The vertical migration distance of soil water exceeded 70 cm, and the SWC above a depth of 100 cm increased significantly, as water was mainly obtained from the soil layer below a depth of 200 cm. Soil compaction was reduced when affected by freeze-thaw processes and the soil particles were more fragmented, leading to wind erosion and dust events. Our results partially explain the occurrence of wind erosion in spring and provide a scientific basis for predicting soil water status and appropriate farmland management strategies.

Pedogenic processes in loess-paleosol sediments: Clues from Li isotopes of leachate in Luochuan loess

Tracing pedogenic processes is fundamental for reconstructing climatic and environmental changes using loess deposits. Lithium isotopes can serve as a sensitive tracer to unravel these processes, owing to its active behaviors without effect by redox and biological reactions. This study investigated the Li contents and δ7Li values of leachate and residue ([Li]leachate, [Li]residue, δ7Lileachate and δ7Liresidue) of the upper 12.5 m Luochuan loess-paleosol sediment (since the last interglacial) on the Chinese Loess Plateau, in order to better understand pedogenic processes in loess. The [Li]leachate, varying from 0.39 to 1.97 μg/g, is mainly derived from the adsorption phase, with a significant variation in δ7Lileachate, from −6.55‰ to +12.88‰. Both [Li]leachate and δ7Lileachate variations reflect weathering and adsorption processes during different periods. The [Li]residue vary from 34.4 to 46.3 μg/g (averaging 38.4 μg/g) and their δ7Liresidue vary from −3.66‰ to +2.44‰ (averaging −0.22 ± 1.68‰), both in agreement with the upper continental crust values. At initial stage after loess deposited (stage I), high [Li]leachate but low δ7Lileachate are results of preferential adsorption of 6Li by clays and migration of 7Li with soil solution during weathering and eluviation processes. When overlying loess was deposited and experienced pedogenesis as the stage I, 7Li migrated downward and was adsorbed by clays (stage II), resulting in high [Li]leachate and δ7Lileachate in underlying loess. When loess has superimposed pedogenic and adsorption processes as the stages I and II, loess became as paleosol with highest δ7Lileachate in underlying carbonate accumulation layer. A persistent increase in δ7Lileachate indicates dominant control of post-depositional adsorptions on Li fractionation along solution migrations during weathering and eluviation of overlying deposits, and vice versa. These results highlight that variations in [Li]leachate and δ7Lileachate can be used to trace soil water migration processes and the magnitude of pedogenic processes in loess-paleosol sediment at different periods.

Scale transfer and simulation of the infiltration in chestnut soil in a semi-arid grassland basin

Soil infiltration is an inevitable process of the mutual transformation of surface water and groundwater in the ecological hydrologic cycle that helps to transport nutrients required by plants to the root system, thus promoting vegetation growth and maintaining ecological stability. It is of utmost importance to simulate the process of soil infiltration and calculate the key parameters of soil water migration accurately. Yet, a scale effect in the determination of soil infiltration can seldom be avoided. Based on the scale effect law caused by a change in the inner-ring diameter of the double-ring infiltrometer and common infiltration models, empirical models of soil infiltration scale transfer (SIST) are proposed and established to improve the simulation accuracy of the steady infiltration rate, while reducing test difficulty and consumption. The results show that the four SIST models established based on the infiltration models well simulate the infiltration process of five different sizes of double-ring infiltrometers. The simulation Adj-R2 of the three infiltration zones in the study area was between 0.66 and 0.95, and the validation Adj-R2 ranged from 0.72 to 0.94, indicating that the SIST models showed good applicability in the investigated semi-arid grassland. The results further showed that the double-ring infiltrometer with an inner-ring diameter larger than 90 cm and an outer ring buffer coefficient of 0.33 was not accompanied by the scale effect during measurement. Moreover, the SIST models were used to predict the steady infiltration rate in the study area, providing an accurate data basis for the establishment of regional eco-hydrological models.

Biogeochemical Migration of Elements in the System “Atmospheric Precipitation–Crown Waters–Soil Waters–Lake” in the Background Region (Valdai National Park)

The element distribution is analyzed in the “atmospheric precipitation–crown waters–soil waters–lake” system of the Lake Gusinoe drainage system in the Valdaysky National Park. The chemical composition of the atmospheric precipitations, crown, soil, and lacustrine waters, as well as soils is determined. The input and output element fluxes in genetic soil horizons are calculated by months and their budget in the studied soil profile during the summer–autumn period is determined. The enrichment of soils in elements and intensities of their water migration in soil and lacustrine waters are estimated.

The effects of freeze–thaw process on soil water migration in dam and slope farmland on the Loess Plateau, China

The seasonal freeze–thaw process affects soil water migration, which influence spring planting, especially in arid and semi-arid regions that cannot be irrigated on the Loess Plateau. This study was conducted to evaluate differences in the freeze–thaw process and water migration between dam farmland (DF) and slope farmland (SF). To accomplish this, two typical agricultural soils (DF and SF), soil water content (SWC) and soil temperature (ST) were monitored at different depths (15, 30, 60 and 90 cm), were investigated under freeze–thaw conditions from November 2015 to April 2016 in the Northwest China. The results showed that different freeze-thaw process between dam farmland (DF) and slope farmland (SF). The DF can keep soil water content resulting from longer frozen period. Thermal transmission between soil and air in SF is greater than that in DF. The SWC values in DF were higher than in SF at each depth layer under similar soil temperature. Migrated and incremental SWC in the DF is greater than that in SF during the freeze-thaw process. The initial SWC is the main impact on freeze–thaw process in this study. This research can provide useful information to guide the water management of seasonally frozen agricultural soil.

Deformation Prediction and Deformation Characteristics of Multilayers of Mucky Clay under Artificial Freezing Condition

Artificial ground freezing method, is a popular technique applied in coastal soft soil area for underground engineering construction. This method can bring some side effects, like frost heave and thaw settlement, due to the water migration in soil during freezing-thawing process. A self-designed one-dimensional freezing apparatus is used to study the deformation performance of the reconstituted soft clay from Shanghai 4th layer during freezing-thawing process. Test results show that total frost heave amount increases with decreasing boundary freezing temperature while it remains with the variation of initial water content in the test. The deformation of multilayers during freezing process reveals compression phenomenon due to the water migration in the soil samples. The compression area is the main part contributed to thaw settlement. Besides, a prediction model is established with void ratio as a variable to connect frost-heave model with thaw-settlement model. FDM (Finite Difference Method) method is used for computation through compiling code in MATLAB software. Comparison shows that compression phenomenon is necessary to be considered when calculating thaw settlement. This study provides valuable reference to the deformation control of soil in the construction of artificial ground freezing.

Characteristics of water–heat variation and the transfer relationship in sandy loam under different conditions

The soil freezing process affects the distribution of soil water and heat, influencing decisions on the planting of spring crops. To reveal the redistribution characteristics of soil moisture and temperature and their response factors in the unidirectional freezing process, an indoor unidirectional freezing test was carried out. Three levels of initial moisture content (18.84%, 23.43%, 28.78%), three freezing temperatures (−5 °C, −10 °C, −15 °C), and three dry densities (1.33 g·cm−3, 1.45 g·cm−3, 1.58 g·cm−3) were set up. Firstly, the distribution of soil cold structure and the variation in the freezing depth curve during the freezing process were observed under different initial conditions. Additionally, the variation characteristics of soil temperature over time and space scales were analyzed, and the freezing process was divided into the rapid freezing stage and the steady freezing stage according to the rate of soil temperature change. Furthermore, the redistribution effect of soil water under the action of potential energy gradient and the characteristics of water migration in different periods were explored. On this basis, the transfer functions of soil temperature at time and space scales were constructed in accordance with regression theory. On the premise of significance test, the effects of soil moisture content and dry density on soil temperature over time and space scales were explored via function derivation and parameter analysis. With the increase of moisture content, the density of soil temperature contours decreased. However, as the dry density increased and the freezing temperature decreased, the density of soil temperature contours increased. As the soil freezing temperature decreased, the degree of soil freezing increased, the pore structure was blocked by frozen ice, and the amount of soil water migration decreased. At the same time, due to increasing soil dry density, the amount of soil water migration and migration rate also decreased. The parameter analysis showed that on the time scale, the change rate of soil temperature decreased as the moisture content increased, whereas it increased as the soil dry density increased; similarly, on the spatial scale, the soil moisture content was negatively correlated and the dry density of soil positively correlated with the soil temperature change rate. The results of this study are of great relevance for understanding the intrinsic relationships between soil moisture content, temperature and dry density in frozen soil and scientifically guiding the development of water and soil resources in cold regions.

Influence of sloping tea fields on soil moisture migration

In order to explore the influence of sloping tea fields on soil water migration, this paper studied the characteristics of water transport in soil moisture infiltration and redistribution under different slope gradients (0°, 5° and 15°) and with or without tea plants (Camellia Sinensis L). The results of the experiment showed that in the process of water infiltration, the time required for moisture to infiltrate to the same depth varies with different gradients with or without tea plants. In the absence of tea plants, the time required for water infiltration to the same depth increased first and then decreased with the increase of slope. When tea plants were planted, the time required for water to infiltrate to the same depth increased with increasing slope. In the process of water redistribution, under the same depth of infiltration, the moisture depth of without tea plants increased first with the increase of slope, and then decreased. The moisture depth with tea plants increased with the increase of slope. When the slope was in the range of 0° to 5° and moisture infiltrated to the same depth, the final moisture depth without tea plants was deeper than that with tea plants. When the slope was 5° to 15° and the water infiltrated to the same depth, the final moisture depth without tea plants was shallower than that with tea plants.

Soil water migration in the unsaturated zone of semiarid region in China from isotope evidence

Abstract. Soil water is an important driving force of the ecosystems, especially in the semiarid hill and gully region of the northwestern Loess Plateau in China. The mechanism of soil water migration in the reconstruction and restoration of Loess Plateau is a key scientific problem that must be solved. Isotopic tracers can provide valuable information associated with complex hydrological problems, difficult to obtain using other methods. In this study, the oxygen and hydrogen isotopes are used as tracers to investigate the migration processes of soil water in the unsaturated zone in an arid region of China's Loess Plateau. Samples of precipitation, soil water, plant xylems and plant roots are collected and analysed. The conservative elements deuterium (D) and oxygen (18O) are used as tracers to identify variable source and mixing processes. The mixing model is used to quantify the contribution of each end member and calculate mixing amounts. The results show that the isotopic composition of precipitation in the Anjiagou River basin is affected by isotopic fractionation due to evaporation. The isotopic compositions of soil waters are plotted between or near the local meteoric water lines, indicating that soil waters are recharged by precipitation. The soil water migration is dominated by piston-type flow in the study area and rarely preferential flow. Water migration exhibited a transformation pathway from precipitation to soil water to plant water. δ18O and δD are enriched in the shallow (< 20 cm depth) soil water in most soil profiles due to evaporation. The isotopic composition of xylem water is close to that of soil water at the depth of 40–60 cm. These values reflect soil water signatures associated with Caragana korshinskii Kom. uptake at the depth of 40–60 cm. Soil water from the surface soil layer (20–40 cm) comprised 6–12 % of plant xylem water, while soil water at the depth of 40–60 cm is the largest component of plant xylem water (ranging from 60 to 66 %), soil water below 60 cm depth comprised 8–14 % of plant xylem water and only 5–8 % is derived directly from precipitation. This study investigates the migration process of soil water, identifies the source of plant water and finally provides a scientific basis for identification of model structures and parameters. It can provide a scientific basis for ecological water demand, ecological restoration, and management of water resources.

Evaluation of moraine loams' filtration properties

In Lithuania, surface moraine loam, clay and other lithologic varieties with low permeability take around 60% of the territory. Roads, railway tracks, bridges, dumps intended for keeping waste of different level of danger and other overground structures are built in these areas. Moraine formations with low water permeability become the foundation for earth bank, roads, bridge supports, dumps and other engineering structures. Through these foundations water filtration, infiltration, movement of capillary water and evaporation to the atmosphere continue during the entire period of operation. In wintertime, the volumetric changes of water, contained and freezing in these soils, and water migration in soil towards the surface of freezing determine deformations of foundations or road surface and the occurrence of frost cracks. All the mentioned water migration processes in the layers take place in various directions and in different intensity. This determines the change in geomechanical and geofiltration properties of foundation soils. Foundation soil deformations are likely also due to the processes of drying, bloating and filtration of clayey soils. Thus, the goal of the present work is to evaluate the evolution of filtration features and evaporation intensity of moraine loam in time. The continuous duration of laboratory investigations was over 10 months. For filtration, the filtrometer was used containing the Proctor Standard moulds, water deaeration device and pressure measuring stand with three tubes of different diameter (piezometers). Water and air temperature and relative humidity of the laboratory were measured during each experiment.

Characteristics of soil freeze–thaw cycles and their effects on water enrichment in the rhizosphere

The freeze–thaw process can lead to water enrichment in freezing layers of soil, and may have beneficial effects on vegetation restoration efforts in sandy land habitats. This study determined the characteristics of soil water migration in dunes and interdune areas during freeze–thaw process, and discussed its potential application to the restoration and recovery of sandy land plant communities. In this research, the mobile sand dunes and interdune lowlands were chosen as the study objects in Horqin Sandy Land, north China. We investigated the soil temperature and moisture content on depths of 20cm, 50cm, 100cm and 150cm during soil freeze–thaw period (from September 20, 2010 to April 9, 2011), and determined the migrated water during freezing–thawing processes on soil of sand dunes and interdune lowlands, and discussed its potential application on plant recovery processes. Results showed that the soil freeze–thaw process occurred mostly at a depth of 0–100cm, and the longest period of soil that remained frozen is 104days at a depth of 20cm and the shortest period is 39days at a depth of 100cm in sand dunes. The number of freeze–thaw cycles was not different between sand dune and interdune area over winter. Most freeze–thaw cycles occurred in the thawing process, and mostly at a depth of 0–50cm. The freeze–thaw cycles of interdune areas only occurred in the thawing process, but the freeze–thaw cycles of sand dunes occurred both in the process of freezing and thawing. More water of the interdune areas apparently migrated than did in the sand dunes. The range of soil water storage content at depths of 0 to 100cm increased to 92.4mm on interdune, and 10.8mm on sand dunes during the freeze–thaw process. A negative correlation was found between soil temperature and moisture at depths of 100cm and 150cm, and while a positive correlation existed at depths of 20cm and 50cm. The freeze–thaw process can lead to water enrichment in freezing layer of soil on sand dunes and interdune. Soil texture affected the quantity of soil water migrating during the freeze/thaw process, and more water migrated in interdune areas than in sand dune habitat.