Changes In Soil Moisture Content Research Articles

Oilseed rape (Brassica napus L.) potential to remediate Cd contaminated soil under different soil water content

Changes in soil moisture content accompanying ongoing climate change are expected to affect plant growth and contaminants behaviour in the soil. The study was aimed at investigating soil water content impact on the energy crop oilseed rape (Brassica napus L.) efficiency to remediate Cd contaminated soil (1–250 mg kg−1). B. napus growth, Cd accumulation and removal efficiency were evaluated under optimal, reduced and elevated soil water content (SWC). B. napus showed good tolerance to Cd contamination and ability to phytoextract Cd from the soil. Cd accumulation in oilseed rape increased with Cd soil concentration, whereas removal efficiency was regulated by rape growth and Cd soil concentrations. B. napus has demonstrated good efficiency to cope with low and moderate Cd pollution (with tolerance index TI > 0.69), while high Cd soil pollution had a highly significant adverse impact on plant growth (growth was reduced up to 90%) resulting in low Cd removal efficiency. SWC governed plant growth, Cd accumulation and removal from the soil. Oilseed rapes grown under elevated SWC were of higher biomass (18%) compared to those grown under reduced SWC though the detrimental effect of Cd was more severe at elevated SWC. Reduced SWC led to decreased Cd uptake, conversely elevated SWC promoted Cd uptake. The optimal SWC ensures the highest Cd removal efficiency, whereas soil water deficit or excess restricts B. napus potential to remove Cd from the soil and prolongs remediation.

Effect of experimental climate change and soil moisture content on germination and early growth response of Quercus dentata seedlings

This study was conducted to investigate the effect of changes in soil moisture content under climate change conditions on the growth response of Quercus dentata, a representative species of the genus Quercus on the Korean peninsula. The results showed that Q. dentata germination increased by 9.4 days under climate change conditions (RCP 4.5 scenario), whereas the below-ground biomass and plant biomass increased by 1.3 and 1.2 times, respectively. However, the soil moisture treatment condition solely affected the leaf area, below-ground biomass, and plant biomass but not the germination percentage, germination speed, above-ground length, and above-ground biomass. The variance across the measured growth variables was considerably higher in the control group than in the climate change treatment group, whereas the variance was lower for lower soil moisture content. The findings suggested that under climate change conditions, Q. dentata germinated rapidly and exhibited broader leaf area and increased development below ground, which may be advantageous for the early establishment of seedlings. However, the plants may face difficulties in conditions with low soil moisture content. In conclusion, with continuous climate changes, Q. dentata seedlings are predicted to efficiently adapt to the altered soil moisture content to exhibit even more reliable growth than with the current condition. However, the growth of Q. dentata seedlings would be more difficult with severely low soil moisture content than with abundant soil moisture content, which is predicted to be detrimental to population maintenance in the long term.

Construction and calibration of a portable rain simulator designed for the in situ research of soil resistance to erosion

Land degradation caused by erosion processes is a widespread global problem. Rain simulators are one of the tools often used to determine the resistance of soils to erosion processes. The aim of this publication is to present the process of the construction and calibration of a small, portable field simulator which would be implemented in research studies designed to determine the changes in the soils’ shear strength parameters in forested areas (in situ) caused by a change in soil moisture content achieved by the rain simulation. The constructed simulator consists of a metal frame, sprayers (with specific nozzles), a sediment funnel/tray made of metal, water and a sediment collector unit, a water tank and pump, and a set of rubber hoses, manometer, valves, reducers, adapters and other supplementary equipment. The calibration was carried out by using the pluviometric method. The choice of nozzles was based on the criteria of low water consumption (losses), the Christiansen uniformity coefficient (CU) and the possibility of achieving specific downpour intensities for the investigated area. The further calibration of the device consisted of determining the raindrop diameter and the distribution of the rainfall when the simulator is positioned on the slopes (7° and 15°). The achieved rain intensity was 1.7–1.9 mm/min, with a CU of 92.23–93.70% for the raindrop diameters (D<sub>50</sub>) equal to 1.2 mm. The kinetic energy of the simulated rain (Ke) was 2.82∙10<sup>–6</sup> J. The constructed simulator proved itself to be in accordance with all of the given criteria, and it can successfully be implemented in research studies aimed at determining the resistance of forest soils to erosion processes, infiltration, and sediment yield.

Use of Hydrological Models to Predict Risk for Rutting in Logging Operations

Using hydrological models with a high temporal resolution to predict risk for rutting may be a possible method to improve planning of forwarder trails or to schedule logging operations in sites with low bearing capacity to periods when soil moisture content is at a minimum. We have studied whether descriptions of rut variations, collected in 27 logging sites, can be improved by using hydrological data, modeled by Swedish HYdrological Prediction for Environment (S-HYPE). Other explanatory variables, such as field-surveyed data and spatial data, were also used to describe rut variations within and across logging sites. The results indicated that inclusion of S-HYPE data led to only marginal improvement in explaining the observed variations of the ruts in terms of both “rut depths” within the logging sites and “proportion of forwarder trails with ruts” across the logging sites. However, application of S-HYPE data for adapting depth-to-water (DTW) maps to temporal changes of soil moisture content may be a way to develop more dynamic soil moisture maps for forestry applications.

Estimating Evapotranspiration of Maize under Different Management Practices in a Semiarid Tropical Area Using the Soil Water Balance Method

Smallholder farmers in semiarid areas face low and erratic rainfall and need field management practices that conserve water in the root zone. This work evaluated the effect of mulching and DD (deep tillage) practices as a way to conserve soil moisture and thus improve water availability and maize crop yield in this water-scarce environment. The field experiment was carried out in which the soil moisture content (SMC) was monitored and the other water balance components were measured to quantify the crop ET with the soil water balance (SWB) method. The components of the SWB (rainfall, supplemental irrigation, runoff, deep percolation and change of soil moisture content) were measured for three consecutive seasons of 2018-2019, i.e. two long rain seasons (Masika 2018 and 2019) and one short-rains season (Vuli 2018). The estimation of the deep percolation (DP) involved calculating water fluxes from hydraulic properties measured in the laboratory and from hydraulic gradients measured with tensiometers in the field plots. Treatments significantly affected ET (p ’ cultivation, FC), mulching (FCM) reduced evapotranspiration by 14% and 18% during more water-stressed seasons of Vuli 2018 and Masika 2019. The ET reduction among the treatments was in line with the reduction in soil evaporation, as reflected in the results (of the other article of the same work). The crop transpiration was observed higher, which was consistent with the higher canopy cover observations for the two treatments relative to the FC treatment. Also, while the mulch practice did not affect ET during the first and less water-stressed season of Masika 2018, DD reduced it by 9% and showed no effect during other seasons.

Analysis of metamaterial‐inspired soil moisture microwave sensor

AbstractIn this letter, the authors propose a microwave sensor capable to detect soil moisture content parameter for use in precision agriculture and agricultural smart monitoring applications. The novel sensor is based on complementary split‐ring resonator metamaterial topology, microstrip line and was built under biodegradable dielectric substrate of polylactic acid for sustainable purposes. The sensing mechanism relates the sensor's resonant frequency to the soil moisture content changes over time. For experimental validation purposes, a compact sensor prototype (75 mm × 35 mm × 1.55 mm and 12 g) with fundamental resonant frequency at 958 MHz was built and submitted to calibration process on typically sandy and clay soils to get fitting models capable to estimate soil moisture content. Simulated and experimental results are presented together and show good agreement with each other. The calibration data for both soil types were processed using the least‐squares method and the proposed curve‐fitting models are capable to estimate soil moisture content levels from 5% to 20% for sandy soil and from 12% to 23% for clay soil with satisfactory accuracy, proving the device viability.

Strength Characteristics of Compacted Fly Ash Treated Expansive Soil due to Wetting-Drying Cycles Repetition

Due to high swelling-shrinkage caused by climate change, expansive soil is a significant problem in light construction, road embankments, and slope stability (wet and dry). The physical and mechanical properties of the soil are affected by repeated drying and wetting cycles, particularly changes in volume, negative pore water pressure (suction), and compressive strength. Fly ash is used to increase soil strength and reduce plasticity caused by swelling to address this issue. Because of its chemical properties, fly ash is an excellent choice for low-cost soil improvement. The purpose of this investigation is to determine the static mechanical properties of expansive soil fly ash stabilization under Proctor standard compaction conditions. Mechanical properties were investigated due to changes in soil moisture content, saturation, suction, and compressive strength caused by repeated drying and wetting cycles. The soil's suction was measured using Whatman #42 filter paper, and the soil's compressive strength was tested using a free compression test. According to the findings, the fly ash mixture altered the expansion and shrinkage behavior of expansive soils by lowering the consistency limit. At the same moisture content, the addition of 5% to 15% fly ash increases the compressive strength of the soil significantly. Compressive strength (qu) and stress-strain modulus (Ei) decreased in 1-4 cycle cycles, and after four cycles, changes in compressive strength and stress-strain modulus were very small or insignificant. The proposed method effectively reduces the loss of expansive soil strength caused by environmental changes (wetting-drying). As a result, it contributes significantly to the development of materials to reduce structural damage in expansive soils.

Can Neural Networks Forecast Open Field Burning of Crop Residue in Regions with Anthropogenic Management and Control? A Case Study in Northeastern China

Open burning is often used to remove crop residue during the harvest season. Despite a series of regulations by the Chinese government, the open burning of crop residue still frequently occurs in China, and the monitoring and forecasting crop fires have become a topic of active research. In this paper, crop fires in Northeastern China were forecasted using an artificial neural network (ANN) based on moderate-resolution imaging spectroradiometer (MODIS) satellite fire data from 2013–2020. Both natural factors (meteorological, soil moisture content, harvest date) and anthropogenic factors were considered. The model’s forecasting accuracy under natural factors reached 77.01% during 2013–2017. When considering the influence of anthropogenic management and control policies, such as the straw open burning prohibition areas in Jilin Province, the accuracy of the forecast results for 2020 was reduced to 60%. Although the forecasting accuracy was lower than for natural factors, the relative error between the observed fire points and the back propagation neural network (BPNN) forecasting results was acceptable. In terms of influencing factors, air pressure, the change in soil moisture content in a 24 h period and the daily soil moisture content were significantly correlated with open burning. The results of this study improve our ability to forecast agricultural fires and provide a scientific framework for regional prevention and control of crop residue burning.

Snow melting water infiltration mechanism of farmland freezing-thawing soil and determination of meltwater infiltration parameter in seasonal frozen soil areas

In seasonal frozen soil areas, much meltwater is formed during the thawing period, which easily causes snowmelt floods and waterlogging disasters. The meltwater simultaneously replenishes groundwater and produces surface runoff to provide water for crop roots. However, there are insufficient researches on the infiltration process of meltwater under day thaw and night freezing conditions. Meltwater infiltration process and estimation could provide an important reference for spring irrigation, meltwater disaster early warning systems and soil pollution research. In this study, the law of mass conservation was adopted for meltwater infiltration estimation under 15 and 30 cm snow covers. According to the hypothetical curve trend characteristics of meltwater infiltration rate, it is proposed to adopt Boltzmann distribution function and determine the curve parameters through experimental results, and the average daily maximum infiltration rate of frozen soil is 0.0622 cm/hour. During the thawing period, the soil moisture content changes periodically, and the period lasts approximately 10 h. We also put forward the concept of the maximum meltwater storage volume (Ϝ) of farmland meltwater, which provides a new analysis structure for meltwater runoff research. During the thawing periods, when the snow cover thickness in the early stage of thawing period exceeds Z, the amount of meltwater infiltration does not greatly change, and the maximum infiltration volume is between 3.15 and 5.25 cm. The average daily meltwater infiltration amounts to 0.15 cm.

RETRACTED ARTICLE: Rainfall soil erosion based on color image super resolution and rural revitalization design

Based on the super-resolution color image, this paper studies the design of rainfall soil erosion and rural revitalization. The steep slope system of the Loess Plateau is not only an important cause of soil erosion by rain, but also an important area for landslides, debris flows, and other natural disasters. In this study, high and steep slope system was used as the research object. Through indoor artificial rainfall experiments, under the conditions of intermittent rainfall, outflow and sediment yield characteristics, soil moisture content changes, and rainfall erosion dynamic parameters, the appearance of steep slope system under various conditions was studied from the beginning of rainfall to slope crack stage. At the same time, the development of agriculture and rural areas is not only an important foundation and support for the realization of national modernization, but also an important factor affecting economic and social development. At present, the development level of China’s agriculture and rural areas is still relatively backward, which is a significant defect in the development of China’s modernization. According to the relevant research results of domestic and foreign researchers, this study takes the main content of Rural Revitalization Strategy as the starting point, and, based on the explanation of development background and implication, deeply analyzes the development background of rural complex model and local economic revitalization strategy. At the same time, taking the rural complex as the main carrier to implement the rural revitalization strategy, this paper studies the theoretical source of the rural complex model in detail, and briefly summarizes the significance and characteristics of the rural complex model. This paper expounds the important role of the development of rural complex facilities in the implementation of China’s rural revitalization strategy.

Toprak neminin yarı kurak alanlarda çok zamanlı RADARSAT-2 verileri ile incelenmesi

Soil moisture content is a very important factor in terms of energy exchange and water cycle on Earth and has a great impact in many areas regarding assessment of natural risks, hydrology, ecology, agriculture, and climate science. Soil moisture can greatly change spatially and temporally, especially depending on land use changes, and the changing soil moisture may cause various environmental and ecological problems. In this respect, it is an important research subject to examine the spatial change of soil moisture content on large scales. Synthetic Aperture Radar (SAR) sensors play an important role in detecting soil moisture because they are sensitive to soil moisture and they cover large areas. In this study, it was aimed to investigate the determination of the spatial and temporal variation of soil moisture content using fully polarimetric RADARSAT-2 images in wheat cultivated field and fallow land located in The General Directorate of Agricultural Enterprises Gözlü Agricultural Enterprise. The in-situ measurements obtained monthly from field surveys between March and October 2016 were compared with the backscatter values of SAR images. As a result of the study, negative and positive correlation coefficients varying from -0.65 to 0.67 were obtained between backscatter values and in-situ soil moisture values. The highest correlations for soil moisture were obtained in the cultivated area during the May-June period, which is the growing stage of wheat, and the best results for both areas were determined with VV polarimetric data.

Single and ternary competitive adsorption-desorption and degradation of amphenicol antibiotics in three agricultural soils

The widespread usage of veterinary antibiotics results in antibiotic contamination and increases environmental risks. This study was evaluated the single and ternary competitive adsorption-desorption and degradation of three amphenicol antibiotics (AMs): chloramphenicol (CAP), thiamphenicol (TAP), and florfenicol (FF) in three agricultural soils. The adsorption capacity of amphenicol antibiotics in the soil was weak, and the Kf value was in the range of 0.15–3.59 μg1-1/nL1/n kg−1. In the single adsorption-desorption experiment, the ranked order of adsorption capacity was TAP > FF > CAP. However, in the ternary competitive adsorption experiment, the order was changed to be CAP > FF > TAP. The degradation of AMs in soils was performed at various conditions. All AMs were vulnerable to microbial degradation in soils. A higher initial concentration would reduce the degradation rate and enhance the persistence of AMs in soil. The degradation of AMs was positively influenced by changes in soil moisture content and culture temperatures up to 30 °C and decreased at higher temperatures. An equation was used to predict the leachability of AMs in soils and assess their risk to the water environment. The weak adsorption capacity and poor persistence of FF indicated that it may have a strong effect on groundwater based on the equation. It is imperative to further assess the biological impacts of FF at environmentally relevant concentrations given its mobility and extensive use in the livestock industry.

Assessing evapotranspiration and crop coefficients of potato in a semi-arid climate using Eddy Covariance techniques

A correct estimation of crop coefficients (KC) is essential to assess water requirements of crops from weather variables and thereby optimize irrigation management. KC depends on crop type and varies with crop growth stage, and to a limited extent, with climate. KC values are often assumed to be transferable between locations and climates. KC values have not been determined yet for modern potato cultivars grown under South African, semi-arid climatic conditions. The objectives of this study were (i) to quantify evapotranspiration and water use efficiency (WUE) of potato crops in a semi-arid climate under irrigation, (ii) to estimate KC values for these crops at different growth stages, and (iii) to assess the usefulness of the Penman-Monteith equation to estimate evapotranspiration and irrigation requirements. An eddy covariance (ECV) system was used in potato fields planted with the variety Mondial in two production regions of South Africa: Limpopo (crop growing in winter) and North West (spring-summer crop). Additional sensors were added to the system to measure relative humidity, near surface soil temperature, solar radiation, rainfall and irrigation. Decagon 10 HS capacitance sensors installed at varying soil depths were used to measure the change in soil moisture content of the potato rooted zone. Accuracy of the ECV measurements was evaluated by following the energy balance closure method. Seasonal mean crop evapotranspiration (ETC) was 3.2 mm d−1 for the crop in Limpopo and 5.7 mm d−1 in North West. The reference evapotranspiration (ETO) correlated well with the daily patterns in ETC for most of the season. ETO thus serves as a useful indicator of ETC and can be used for irrigation scheduling of potato. Seasonal mean KC value was 0.99 for the crop in Limpopo and 0.78 in North West. While the KC value in Limpopo likely represented that for a crop free of water-stress, the crop growth in North West was likely somewhat limited by water availability. The winter crop had the highest WUE of 3.55 kg dry potato tuber m−3 of water evapotranspired, whilst WUE for the spring-summer crop was 3.03 kg m−3. This difference could be explained by differences in mean vapour pressure deficit between the growing seasons. To optimize WUE of potato growing in semi-arid, water scarce regions such as South Africa, it is advisable to grow crops in the coolest available growing season, outside the frost-prone period.

Xylem Inc, USA

The widespread usage of veterinary antibiotics results in antibiotic contamination and increases environmental risks. This study was evaluated the single and ternary competitive adsorption-desorption and degradation of three amphenicol antibiotics (AMs): chloramphenicol (CAP), thiamphenicol (TAP), and florfenicol (FF) in three agricultural soils. The adsorption capacity of amphenicol antibiotics in the soil was weak, and the Kf value was in the range of 0.15–3.59 μg1-1/nL1/n kg−1. In the single adsorption-desorption experiment, the ranked order of adsorption capacity was TAP > FF > CAP. However, in the ternary competitive adsorption experiment, the order was changed to be CAP > FF > TAP. The degradation of AMs in soils was performed at various conditions. All AMs were vulnerable to microbial degradation in soils. A higher initial concentration would reduce the degradation rate and enhance the persistence of AMs in soil. The degradation of AMs was positively influenced by changes in soil moisture content and culture temperatures up to 30 °C and decreased at higher temperatures. An equation was used to predict the leachability of AMs in soils and assess their risk to the water environment. The weak adsorption capacity and poor persistence of FF indicated that it may have a strong effect on groundwater based on the equation. It is imperative to further assess the biological impacts of FF at environmentally relevant concentrations given its mobility and extensive use in the livestock industry.

Effect of Variation in Moisture Content on Soil Deformation and Differential Settlement of Frame Structures in Nairobi Area and its Environs

Background: The stability of structures to a great extent depends on the foundation. The foundation of a building structure plays a key role in transferring the loading from the structure to the soil underneath. In foundation design, the effect of changes in soil moisture content to soil deformation and subsequent differential settlement during the lifespan of a structure is often ignored. Objective: This research establishes the relationship between soil moisture content and soil deformation for soils in the Nairobi area and its environs. Soil deformation in some foundation supports in a building leads to an unequal settlement resulting in differential settlement. The research further determines the influence of soil deformation on the differential settlement of a typical four-storey reinforced concrete frame structure. Methods: Seven soil samples collected from the Nairobi area and its environs were subjected to moisture content variation. Soil deformation was measured, and the laboratory test results were applied to determine the modulus of subgrade reaction constant for the elastic foundation. A four-storey reinforced concrete frame structure was modelled at varying foundation conditions. The resulting differential settlement for frame structure was evaluated. Two control cases were assessed. The structural behaviour depicted by changes in bending moments, shear forces, differential settlement, and member stresses for varying foundation cases was assessed. Staad Pro software was applied in structural modelling. Results: Increasing soil moisture content from 30% to 50% and 75% by keeping all other factors constant led to increased soil deformation ranging from 17.2% to 34% for the 7 soil samples tested. Structural modelling revealed that increasing soil moisture content at a group of four outer footings in a 16 footings’ building contributes to significant changes in shear forces, bending moments, compressive and tensile stresses, and supports the differential settlement. Differential settlement induced by soil deformation arising from an increase in soil moisture content from 30% to 75% increased by 49.1%. Conclusion: Increase in soil moisture content contributed to soil deformation, which led to a significant differential settlement in a line of foundation’s outer footings in a building. The moisture content-caused differential settlement, which contributed to remarkable changes in the amount and distribution pattern for shear forces, bending moments, compressive and tensile stresses, and node displacement when the soil moisture content was increased from 30% to 75%.An increase in soil moisture content to 50% and above at some footings of a building would lead to structural failure unless the building structure is specifically designed to withstand such differential settlement. Construction stakeholders should consider the differential settlement attributed to variation in soil moisture content during the structure’s lifespan and safety factors adequately at the design stage to avoid potential structural failure and even collapse.

Changes in root xylem anatomy of peanut genotypes with different drought resistance levels under early‐season drought

AbstractDuring the 2014 and 2015 seasons, peanut root anatomy studies were conducted under well‐watered and under drought conditions using three peanut genotypes which are known to differ in their physiological responses to early‐ and mid‐season drought (ICGV 98,305, ICGV 98,324 and Tifton‐8). Cross sections of the newly formed roots revealed that the average vessel diameter and total vessel area in the first‐order roots were significantly reduced under drought in ICGV 98,305 and ICGV 98,324, yet not in Tifton‐8, which had the smallest vessel diameters and total area in both well‐watered and drought treatments. The xylem vessel structure in newly formed roots of ICGV 98,324 was very responsive to changes in soil moisture content. This adaptive capacity of ICGV 98,324 to change xylem structure as soil moisture conditions change may provide plant breeders an important trait which will lead to better water‐use efficiencies in both moist and drought conditions.

Previous and Current Crop Effects on Early-Season Root Growth and Growing Season’s Soil Moisture Under Dryland Agriculture in Temperate Climate

Understanding the root growth and changes in soil moisture content during the growing season for dryland agriculture crops can improve crop production. It was hypothesized that early-season root growth might be influenced by previous crop and current crops, and soil moisture content and depletion pattern during the growing season and residual soil moisture may be affected by the crop type. A study was conducted on the early-season root growth of canola (Brassica napus L.), wheat (Triticum aestivum L.), and flax (Linum usitatissimum L.) in 2015; and changes in soil water content during the 2013, 2014, and 2015 growing seasons under canola, flax, wheat, barley (Hordeum vulgare L.), and pea (Pisum sativum L.). Early-season root growth of the canola and flax crops was better on wheat than canola stubble, while for wheat it was similar on the stubbles of both wheat and canola. Soil moisture depletion started relatively earlier under the barley and wheat and later under the flax compared to the canola and pea crops. Flax continued to deplete soil moisture for a longer period than the other crops. With some exceptions, all crops could deplete soil moisture to a similar level (down to about 15% or somewhat lower) by the end of their growing seasons. Generally, almost equal amounts of residual soil moisture remained after the different crops.

Comparison of Changes in Soil Moisture Content Following Rainfall in Different Subtropical Plantations of the Yangtze River Delta Region

Rainfall is an indispensable link in the atmospheric water cycle, which plays a critical role in forest hydrology. Quercus acutissima and Cunninghamia lanceolata are two fast-growing and economically important tree species in the middle and lower reaches of the Yangtze River. They are extensively applied in the restoration of vegetation, hydraulic engineering, and the development of artificial forests. The primary aims of this study were to describe and compare the changes in soil water content following rainfall events, while elucidating their relationships to environmental factors. From September 2012 to August 2013, we monitored the soil moisture at different depths every 30 min using commercially available soil moisture measuring devices. Hourly meteorological data were monitored over an open area at 200 m from the sample site, including photosynthetically active radiation (Par), air temperature (Ta), relative air humidity (RH), vapor pressure deficits (Vpd), rainfall, and wind speed. The results revealed that variations in the soil moisture content during summer (Cv = 0.231) and autumn (Cv = 0.0.170) were greater than during spring (Cv = 0.0.092) and winter (Cv = 0.0.055), with those in the deep soil moisture (Cv = 0.117) being smaller. The soil moisture content was significantly altered following the cessation of rainfall, where the initial and average moisture content, and the ACR of the soil increased with higher rainfall intensities. The ACR was positively correlated with Ta (γ = 0.16), RH (γ = 0.46) and rainfall (γ = 0.22), but negatively correlated with Par (γ = −0.29), Vpd (γ = −0.23), and wind speed (γ = −0.01). This study provides valuable information regarding the hydrological processes of artificial forests in the middle and lower reaches of the Yangtze River.

Assessing shallow groundwater level using RTI model and long-term MODIS data in Ejina Basin, Northwest China

The present study aims to exploit the thermal inertia model to assess the shallow groundwater level distribution, as an attempt to address agricultural water shortage and ecological degradation in arid and semi-arid regions. Apparent thermal inertia (ATI) model is one of the most commonly used and successfully implemented models, whereas in some cases, the scales of the results achieved on different dates are inconsistent, which poses a serious difficulty when monitoring soil moisture over time. To address this restriction, we introduce a soil moisture indicator, called RTI, which derives an approximation of soil thermal inertia, from flexible multi-temporal MODIS observations covering a 2-year period. Taking the Ejina Basin in arid area as an example, to more accurately assess the shallow groundwater level distribution, ATI and RTI models were adopted based on the long time series MODIS data to assess the multi-temporal soil moisture content in the study area. The data of groundwater level measured by observation well and thermal inertia were employed to generate scatter diagrams. Subsequently, a nonlinear equation was developed. Based on the thermal inertia, the temporal and spatial distribution map of the shallow groundwater level in the whole study area was generated with the inverse calculation of the nonlinear equation. It was found that the shallow groundwater level distribution in Ejina Basin tended to be shallower from south to north, as well as from summer to winter. As revealed from the results, both ATI and RTI models can effectively assess the shallow groundwater level in arid areas. The RTI model could better reflect the seasonal changes of soil moisture content and groundwater level.

Effects of drought stress on soil bacteriall community in the West foot of Daxing’an Mountains

Global warming poses a serious threat to agriculture and natural systems, in part because of the change of soil moisture content, which changes soil microbial communities and ecological processes. Soil water content is the main factor limiting the growth of plants in soil. Microbial communities rely on soil water to complete their activities, and reveal the changes of underground microbial communities under different soil moisture content, which will help us to further understand the potential impact of climate change on soil ecosystem. To investigate the soil bacterial community structure, we established experiment indoor in the West foot of Daxing’an Mountains with manipulative water content treatments consisting of 20%, 15%, 10%, 5%, 0%. Results showed that bacterial community composition varied significantly with altered drought stress , but community richness did not. The relative abundance of Actinobacteria increased with the increase of drought stress, Proteobacteria, Acidobacteria and Gemmatimonadota decreased with the increase of drought stress, actinobacteria was more likely to accumulate or maintain stable under drought stress, bacterial communities can responding directly to changes in soil moisture.