Moisture Fluctuations Research Articles

Impact of drying-wetting cycles on the small strain behaviour of compacted clay

Small strain shear modulus (Gmax) is an important parameter for assessing the performance of compacted soils that underlie typical transport infrastructure assets such as railway tracks. This is particularly important when considering changes in climate patterns, which are expected to yield larger seasonal soil-atmosphere moisture fluctuations. This in turn results in the progressive variation of the small strain properties of compacted soils during their service life (i.e. drying and wetting). In this study, the small strain shear behaviour was evaluated for an intermediate plasticity clay (i.e. kaolin) in a series of drying and wetting cycles. Four different dying and wetting boundaries were considered to explore a wide range of moisture amplitudes during 10 drying-wetting cycles. Drying and wetting was controlled using gravimetric water content in order to mimic realistic field conditions typically observed at substructure level. An ultrasonic pulse transmission method was used to capture the change in small strain stiffness and volume at discrete points during the drying-wetting cycles. The results reveal clear distinctions in behaviour for all four boundaries considered, with wetting boundaries having the greatest influence on behaviour. In this instance, specimens brought to full saturation during wetting exhibited an increase in the small strain shear modulus during progressive drying-wetting cycles. However, a reduction was observed when the wetting boundary was restricted to the compacted state. Measured volume changes were also in agreement with these findings, however there was some evidence of volume increase when drying to residual conditions. The results suggest that this is associated with the formation of the partial pendular state where a loss of capillary contacts between particles occurs. Furthermore, when all data for 10 drying-wetting cycles is plotted in the e-Gmax space, a linear relationship is observed for different constant water content levels. Remarkably, this trend is shown to be independent of the boundary conditions considered in this study or number of drying-wetting cycles.

Seasonal variation in soil algal community structure in different forest plantations in subtropic China.

Algae exert great impact on soil formation and biogeochemical cycling. However, there is no full understanding of the response of soil algal community structure to the seasonal fluctuations in temperature and moisture and changes of soil physicochemical properties across different forests. Here, based on 23S rRNA gene sequencing, we analyzed soil algal community structure in four different forest plantations in two seasons and examined soil physiochemical properties. The results showed the significantly seasonal variation in soil algal community structure, with the higher overall diversity in summer than in winter. In addition, there existed significant correlations between soil algae (species composition, relative abundance, diversity index) and physicochemical properties (pH, total phosphorus, organic matter and nitrate nitrogen), suggesting that edaphic characteristics are also largely responsible for the variation in soil algal community. Nevertheless, the seasonal variation in algal community structure was greater than the variation across different forest plantations. This suggest temperature and moisture are more important than soil physicochemical properties in determining soil algal community structure. The findings of the present study enhance our understanding of the algal communities in forest ecosystems and are of great significance for the management and protection of algal ecosystem.

Collembola community contains larger species in frequently flooded soil

Climate change is increasingly affecting biotic communities, including soil fauna. Extreme weather events such as the incidence of heavy rainfall or prolonged drought can cause strong fluctuations in soil moisture. In river floodplains such extreme events determine the flooding intensity of the river bank grassland soils, and their communities. The diversity and distribution of many soil fauna groups depends on soil moisture content, so changes in inundation frequency and duration will impact soil fauna communities. We used the natural fluctuations in water levels of large Dutch rivers to investigate the effect of flooding intensity on the composition and traits of Collembola species, a key group of the soil fauna community. At five locations along large rivers in The Netherlands, we sampled Collembola communities at six levels of decreasing elevation and increasing flooding intensity. We identified all Collembola to species level and calculated species richness, composition and abundance values. Moreover, to understand the observed taxonomic changes across elevation we used the traits body size and life form to explain the change in Collembola community composition. Our results show that high flooding intensity favors larger Collembola species in the community. We hypothesize that high soil moisture in frequently flooded soil favors larger Collembola, which tolerate flooding. Life form, i.e. the preferred depth in the soil column, was significantly correlated with flooding intensity. There is an optimum in species richness and abundance at intermediate flooding intensity. These results can help predict the impact of climate change on soil fauna.

Geochemical record of Lake Sabakty: Electrical conductivity and reconstruction of the Lateglacial and Holocene environments in the Southern Urals (Russia) steppe

Research subject. The Lake Sabakty sediments core, as a source of data on the Holocene and Lateglacial environments in the Southern Urals.Aim. To obtain a multiple regression model for quantitative reconstructions of the electrical conductivity of water based on the geochemistry of lake sediments and to reconstruct the Late Glacial and Holocene environments based on the study of the Lake Sabakty geochemical record.Materials and methods. After determination of correlations between the content of chemical elements in lake sediments and hydrochemical parameters of 107 Ural lakes, multiple regression models were obtained. Reconstructions were performed based on the results obtained by accelerator mass spectrometry (AMS 14C), 210Pb activity determination, and an analysis of chemical elements and organic matter contents in the sediment core.Results. Three multiple regression models using the concentrations of Na, Ca, Li, and Sr were obtained for electrical conductivity of water reconstruction. In the cold and dry Lateglacial (>12.0 ka cal BP), Lake Sabakty was a slightly brackish reservoir. During the transition from the Lateglacial to the Holocene (12–11.6 ka cal BP), the Lake Sabakty became more productive. In the Early (11.6–8.2 ka cal BP) and Middle (8.2–4.2 ka cal BP) Holocene, the electrical conductivity of water varied under the action of fluctuations in effective moisture. In the Late Holocene (4.2 ka cal BP – present), the Lake Sabakty became less saline due to an increase in effective moisture.Conclusions. The proposed multiple regression models enable rapid quantitative reconstructions of the electrical conductivity of water, which are particularly relevant for Lateglacial–Early Holocene sediments with a low number of microfossils. The Lake Sabakty geochemical record reflects global and regional climatic fluctuations, being more informative compared to the geochemical records of forest lakes in the Southern Urals. The decrease in the electrical conductivity of water of Lake Sabakty of approximately 7.9 and 4.2 ka cal BP coincides with similar data for several other lakes in the Urals.

Development and propagation of hydrologic drought from meteorological and agricultural drought in the Mekong River Basin

AbstractMekong River Basin (MRB) experiences extreme droughts and floods frequently, due to the precipitation deficit across the basin. The meteorological droughts will have a profound impact on the distribution of soil moisture and hence agricultural productivity, which will lead to the reduction of surface water resources. It is therefore important to evaluate the deficits in hydrometeorological extremes, that is, precipitation, soil moisture, and streamflow to help decipher how one drought results in the other. In this study, a streamflow deficit index (SDI) has been proposed and applied to understand the changes in hydrology due to the fluctuations in precipitation and soil moisture in the Mekong River Basin (MRB). The study used percent normal (PN), a precipitation deficit index, and soil moisture deficit index (SMDI) to identify the initiation and sustenance of hydrological drought using SDI. The SMDI was obtained from soil moisture simulated using the soil and water assessment tool (SWAT) for the periods of 1980–2008. The study results suggested that the proposed index was able to represent the historical river flow deficit that persisted in the basin in the year 1992. Increasing variation in the streamflow deficit in parts of Thailand, Lao PDR, Vietnam, and Cambodia from the year 1992 was also captured by SDI. The flooding year 2000, which resulted in an economic loss of over 200 million USD, was also effectively captured by the proposed index. The lengthening of the streamflow drought, a metric used to represent drought propagation, was shorter by at least 2 months in forested catchments compared with that of agricultural catchments, which implies that any deficit in precipitation and soil moisture, will have a severe impact on agricultural basins. Similarly, the attenuation of both agricultural and hydrological drought was found to be smaller in forested subbasins than those in agricultural subbasins. The findings of the study will be useful for the timely identification of extreme hydrological events and for planning mitigation measures.

Estimation of Surface Soil Moisture from Agricultural Lands Using Multi-Spectral Optical Satellite Data: A Study of Bhagwanpur-I CD Block, East Medinipur, West Bengal, India

The spatiotemporal fluctuation of Surface Soil Moisture (SSM) is important for prediction of weather, modeling of hydrological cycle, water management, agricultural managing and making strategy. Optical remote sensing has demonstrated significant promise for precise surface soil moisture estimate. The study aimed to estimate the moisture content in the upper layer of agricultural fields using Landsat 8 OLI, Sentinel-2A multi-spectral satellite data as well as TVDI [Temperature Vegetation Dryness Index] data. The spatial resolution of the Landsat OLI and Sentinel-2A images was 30m and 10m, respectively. The spectral Thermal Infrared (TIR 10.9µm ), TIR (10.9µm) and along with the Short-Wave-Infrared (SWIR 2.2µm) band of the Landsat 8 and the Shore-Wave-Infrared (SWIR 2.2 µm) band of sentinel 2B satellite imagery was utilized to estimate how moist was topsoil of the agricultural lands. The soil moisture estimates using remote sensing based model were acquired and compared with in-situ soil moisture. In a depth of 10cm below the surface, the field-based soil moisture was measured. Normalized Difference Vegetation Index (NDVI), Land Surface Temperature (LST) and TVDI were measured to estimate moisture content. The reflectance values of the TVDI show over the study area generally low, with the values ranging from -0.07 to 1.37. The statistical tests of TVDI values and gravimetric soil moisture values presented a positive correlation with RMSE= 0.17. The results of the study can give insight of better hydrological modeling, management of agriculture and policy making. However, further research is required to validate the methodology over a larger geographical area and to evaluate the preciseness of the assessed SSM at various depths of the soil.

High-Resolution Lacustrine Records of the Late Holocene Hydroclimate of the Sikhote-Alin Mountains, Russian Far East.

There is little information about moisture changes in different altitudinal belts in mountainous regions of the southern Russian Far East. We present ecological and taxonomic compositions of the diatom flora and identify the botanical composition of peat in small mountain lake/mire complexes located in the Central Sikhote-Alin Mountains, within large landslides on the paleovolcanic slopes. Frequent changes in diatom assemblages and peat-forming plants indicate unstable hydroclimatic conditions with varying degrees of wet and dry conditions up to the overgrowth of the lakes. Frequent change in sphagnum mosses with different trophic preferences was identified. The chronology is based on 11 radiocarbon dates. Accumulation rates reached 1.7-1.9 mm/year, and the temporal resolution for the reconstructions was up to 30-40 yr. The tendencies of lake evolution depended on different scale hydroclimatic changes over the last 4400 yr. The most detailed data for the last 2600 yr were obtained from the Nizhnee Lake sequence, which is more sensitive to climatic changes. The main reason for the change in the hydrological regime of the lakes was variations in precipitation during short-term climatic changes. The sediment record of moisture fluctuations is relatively well correlated with regional patterns reflecting summer monsoon intensity and cyclogenesis activity.

Embeddable Soil Moisture Content Sensor Based on Open-End Microwave Coaxial Cable Resonator

In this paper, we propose and demonstrate a novel corrosion-resistant, embeddable open-end coaxial cable soil moisture sensor. This microwave resonator is constructed using two reflectors along the coaxial line. The first reflector is a metal post at the signal input end, short-circuiting the inner conductor to the outer conductor. The second reflector comprises a welded metal plate parallel to the open-end of the coaxial line, maintaining a fixed gap. A moisture-sensitive Polyvinyl Alcohol (PVA) film is inserted into this gap. The resonance frequency of the open-end coaxial cable resonator is highly dependent on the fringe capacitance, which varies with soil moisture levels. As such, tracking resonance frequency changes allows for correlation with soil moisture fluctuations. We provide a detailed discussion of the embeddable open-end microwave coaxial cable resonator (EOE-MCCR) mathematical model and a proof of concept for soil moisture measurement. The demonstration experiments investigate soil moisture content ranging from 4% to 24%. The prototype device exhibits a soil moisture measurement sensitivity of 0.76MHz/% for soil moisture between 4% and 10%, and 1.44MHz/% for soil moisture between 10% and 24%. The soil moisture sensor presented here is robust, easy to manufacture, chemically resistant, low-cost, and suitable for long-term applications and potential industrial uses. This innovative sensor is ideal for sensing applications in harsh environments, advancing the field of chemical trace sensing.

Surface‐driven amplification of Madden–Julian oscillation circulation anomalies across East Africa and its influence on the Turkana jet

AbstractIn semi‐arid environments, rainfall‐driven soil moisture fluctuations exert a strong influence on surface turbulent fluxes. Intraseasonal rainfall variability can therefore impact low‐level atmospheric temperatures and influence regional circulations. Using satellite observations and an atmospheric reanalysis, we investigate whether rainfall variability induced by the Madden–Julian oscillation (MJO) triggers land–atmosphere feedbacks across East Africa.We identify that surface fluxes during the East African wet seasons (March–May and October–December) are sensitive to MJO‐induced precipitation variations across low‐lying regions of South Sudan and highland regions of Uganda and southwest Kenya. For example, during MJO phases 6 to 8, when rainfall is suppressed, surface temperatures and sensible heat fluxes increase, whilst evapotranspiration decreases. Spatial variations in the surface flux response to rainfall variability feed back onto the atmosphere through amplifying MJO‐associated pressure anomalies. During dry MJO events for instance, surface warming across the exit region of the Turkana channel increases the low‐tropospheric along‐channel pressure gradient and intensifies the Turkana jet. We conclude that average surface‐driven temperature fluctuations during a single day are responsible for approximately 12% of MJO‐associated variability of the Turkana jet speed. However, we expect that the accumulation of heat over multiple days to the west of the East African Highlands further amplifies anomalies in the pressure gradient and jet intensity. Modelling experiments are required to quantify the accumulated impact of the surface forcing. Surface‐driven Turkana jet variations influence the East African moisture budget and affect the intensity and inland propagation of coastal convection. Not only is this the first study to investigate the importance of intraseasonal land–atmosphere feedbacks across East Africa, but it is also the first to show that Turkana jet characteristics are partly driven by surface conditions. This work motivates an investigation into whether subseasonal forecast models fully harness the predictability from surface‐induced jet variations.

Dry Matter Production of Two Rice Cultivars with Contrasting Root Plasticity Expression Under Different Topographic Conditions Subjected to Soil Moisture Fluctuation

In rainfed lowland rice fields characterized by sloping terrains and the presence of a hardpan in a flat topography, plants are often exposed to soil moisture fluctuation (SMF) stress due to erratic rainfall patterns. Root plasticity is one of the key traits that play important roles in plant adaptation under such conditions. In this study, two contrasting genotypes, KDML105 and IRAT109, were examined to quantify the expression of plasticity in root branching at different positions in the toposequence (TP) and in a flat topography with a hardpan, both without a groundwater table, and subjected to SMF. Results showed that KDML105 exhibited improved adaptation to SMF conditions due to its greater root system because of the promoted nodal root production and development of lateral roots in the upper soil layer (0 – 20 cm soil depth) along the TP and above the hardpan in a flat topography, which led to the maintenance of its stomatal conductance and dry matter production. IRAT109, on the other hand, did not express root plasticity in deep-rooting due to the absence of groundwater table, particularly in the upper TP, as well as branching ability above the hardpan in a flat topography, which resulted in less water uptake and reduced dry matter production under SMF. Overall, the results indicated that root plasticity in the upper soil layer could be an important trait for the adaptation of rice, both in a sloping TP without a hardpan or in a flat topography with a hardpan, experiencing SMF.

Evaluation of red soil-bentonite mixtures for compacted clay liners

Compacted clay liners are an integral part of the waste landfills, which are provided to contain the leachate within the landfills and protect the surrounding environment. Generally, locally available natural soils are used for the construction of compacted clay liners if they satisfy the design criteria. However, not all soils in their natural state satisfy all the design criteria for the liner materials. Thus, there is a definite need to modify the locally available natural soils by blending with bentonite to meet the required design criteria for the liners. In view of this, the present study evaluates the suitability of an Indian red soil enhanced with bentonite as a liner material. To achieve this, a series of experiments were carried out using locally available red soil and bentonite. First, the suitability of the red soil was evaluated as a liner material. The experimental results showed that the red soil met all the selection criteria stipulated by the Environmental Protection Agencies (EPAs) for the liners except the hydraulic conductivity criterion. Therefore, the red soil was mixed with bentonite contents of 10%, 20% and 30%, and the red soil-bentonite mixtures were evaluated for their suitability for liners in their compacted state. Further, as the liners in the arid and semi-arid regions are subjected to moisture variations due to seasonal moisture fluctuations and other factors, the red soil-bentonite mixtures were subjected to wet-dry cycles, and their suitability was evaluated after wet-dry cycles. The experimental results revealed that all the red soil-bentonite mixtures met the stipulated EPA criteria for the liners in the as-compacted state. However, the red soil-bentonite mixtures with 20% and 30% bentonite contents only satisfied the hydraulic conductivity requirement even after wet-dry cycles. The experimental findings were supplemented with the microstructural insights captured through digital camera images, scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP) studies.

Assessing soil temperature and moisture fluctuations under irrigated banana (Musa spp.) cultivation in response to coconut coir mulch cover

The semiarid is characterized by extreme heat, which affects agricultural production by limiting the soil's ability to retain water. The objective of this study was to investigate the influence of mulch on soil temperature and soil moisture in a drip irrigated banana plantation in a Brazilian semiarid region. Six thermocouples and three soil moisture probes were used, with coconut coir as mulch. Daytime and nighttime surface temperatures were compared for two mulch densities (4 and 8 t ha-1) and bare soil. Soil temperature and moisture were measured at three depths (0.1, 0.3 and 0.5 m). The study was conducted from November 2014 to March 2015. Mulch had a buffer effect on soil temperature fluctuation. Drip irrigation management associated with mulch provided a uniform moisture profile close to field capacity.

Metal–Organic Frameworks (MOFs) Based Electrospun Nanofiber Membrane for Passive Indoor Moisture Control

Metal–organic frameworks (MOFs), an emerging class of porous sorbents, have become one of the most promising functional materials for indoor moisture regulation. However, the practical application of MOFs in building environments is challenging. Common shaping forms of MOFs (e.g., pellets, tablets, monoliths, granules, coating, etc.) may lead to agglomeration of MOF particles, higher usage costs, low efficiency, and material waste. Here, we report a new MOF-based electrospun nanofiber membrane with high porosity, light weight, and a large surface-area-to-volume ratio. MOF nanoparticles distributed on the fibers can fully contact moisture in the air, thus significantly enhancing MOFs’ utilization and performance. The results of the moisture adsorption test show that the improved MOF membrane has significantly higher water vapor uptake than most conventional hygroscopic materials and textiles in built environments. A building energy model was established to evaluate the MOF membrane’s effect on building energy consumption under different climates worldwide. The simulation results show that the MOF membrane can efficiently moderate indoor moisture fluctuation and has excellent energy-saving potential. The latent heat load reduction rate in summer can be up to 80–90% in arid/semi-arid climates and around 50% in temperate climates in a purely passive manner.

Quantifying the Coupled Effect between Soil Moisture and Climate in the Desert Steppe Environment of Inner Mongolia, China

Soil moisture is an important variable affecting land surface and climate interactions. This study used cross-wavelet and wavelet coherence methods to analyze the relationship between soil moisture and climatic factors in the study area based on the soil moisture data sequence and corresponding meteorological data observed on the surface of the desert steppe in Inner Mongolia. The results showed that soil moisture had a relatively high- or low-value period for months or even years. Soil moisture was significantly different between different slope positions and soil layers. The fluctuation and mean of soil moisture decreased gradually with the deepening of soil depth. The relationship between soil moisture and meteorological factors varied with time scales. The influence of precipitation on soil moisture was significant at time scales of 1–6 months and 10–15 months, while air temperature and soil temperature showed stable and continuous periodic influence on soil moisture at the time scale of 10–15 months. Climate indexes for the Pacific region, Pacific Decadal Oscillation (PDO), and North Atlantic Oscillation index (NAO) were the main climatic factors controlling soil moisture in the Inner Mongolia desert steppe and strongly correlated with soil moisture primarily on time scales of 4–7 months and 10–15 months. Pacific Decadal Oscillation (PDO) and Indian Ocean basin-wide warming (IOBW) showed a strong lag effect on soil moisture.

Nonprecipitating Shallow Cumulus Convection Is Intrinsically Unstable to Length Scale Growth

Abstract Condensation in cumulus clouds plays a key role in structuring the mean, nonprecipitating trade wind boundary layer. Here, we summarize how this role also explains the spontaneous growth of mesoscale [>O(10) km] fluctuations in clouds and moisture around the mean state in a minimal-physics, large-eddy simulation of the undisturbed period during BOMEX on a large [O(100) km] domain. Small, spatial anomalies in condensation in cumulus clouds, which form on top of small moisture fluctuations, power circulations that transport moisture, but not heat, from dry to moist regions, and thus reinforce the condensation anomaly. We frame this positive feedback as a linear instability in mesoscale moisture fluctuations, whose time scale depends only on (i) a vertical velocity scale and (ii) the mean environment’s vertical structure. In our minimal-physics setting, we show both ingredients are provided by the shallow cumulus convection itself: it is intrinsically unstable to length scale growth. The upshot is that energy released by clouds at kilometer scales may play a more profound and direct role in shaping the mesoscale trade wind environment than is generally appreciated, motivating further research into the mechanism’s relevance.

Spatially Explicit Linkages Between Redox Potential Cycles and Soil Moisture Fluctuations

AbstractReduction‐oxidation cycles measured through soil redox potential (Eh) are associated with dynamic soil microbial activity. Understanding changes in the composition of, and resource use by, soil microbial communities requires Eh predictability under shifting hydrologic drivers. Here, 50‐cm soil column installations are manipulated to vary hydrologic and geochemical conditions, and are extensively monitored by a dense instrumental deployment to record the depth‐time variation of physical and biogeochemical conditions. We contrast measurements of Eh, soil saturation and key compounds in water samples (probing the majority of soil microbial metabolisms) with computations of the relevant state variables, to investigate the interplay between soil moisture and redox potential dynamics. Our results highlight the importance of joint spatially resolved hydrologic flow/transport and redox processes, the worth of contrasting experiments and computations for a sufficient understanding of the Eh dynamics, and the minimum amount of biogeochemistry needed to characterize the dynamics of electron donors/acceptors that are responsible for the patterns of Eh not directly explained by physical oxic/anoxic transitions. As an example, measured concentrations of sulfate, ammonium and iron II suggest coexistence of both oxic and anoxic conditions. We find that the local saturation velocity (a threshold value of the time derivative of soil saturation) exerts a significant hysteretic control on oxygen intrusion and on the cycling of redox potentials, in contrast with approaches using a single threshold saturation level as the determinant of anoxic conditions. Our findings improve our ability to target how and where hotspots of activity develop within soil microbial communities.

Moisture-dependent response of soil carbon mineralization to temperature increases in a karst wetland on the Yunnan-Guizhou Plateau.

Wetlands are facing gradual drying, leading to large carbon loss due to the transformation from anaerobic to aerobic conditions, but the temperature and drought effects from the temperature and moisture fluctuation on soil organic carbon (SOC) mineralization remain uncertain. An incubation study with three moisture levels (100%, 60%, and 40% WHC, marked as W100, W60, and W40, respectively) and four temperature levels (5, 10, 15, 20°C, marked as T5, T10, T15, and T20, respectively) was conducted to determine the effect of temperature and moisture interactions on SOC mineralization in the karst wetland of the Yunnan-Guizhou Plateau. Compared with T5, the cumulative mineralization CO2 in T20 increased by 83.18% (W40), 154.63% (W60), and 148.16% (W100), respectively. The mineralized CO2 at W60 and W40 significantly decreased compared to that at W100 at the four temperature levels. Temperature, moisture and their interactions had significant positive effects on SOC mineralization rates and cumulative mineralized CO2. The temperature sensitivity of SOC mineralization rates (Q10) under W40 and W60 increased by 22.03% and 24.52%, respectively, compared to that under W100. The cumulative mineralized CO2 was positively related to soil urease activity and negatively related to soil pH, N-NH4+, SOM, and catalase activity. Temperature and moisture fluctuation and soil properties explained 85.40% of the variation in SOC mineralization, among which temperature and moisture fluctuation, soil properties, and their interactions explained 19.71%, 4.81%, and 60.88%, respectively. Our results indicated that SOC mineralization is influenced by the joint effect of temperature and drought, as well as their induced changes in soil properties, in which higher temperatures can increase soil CO2 emissions by enhancing the SOC mineralization rate, but the positive effect may be weakened from the drying wetland.

Case Study on the Impact of Flooding and Inundation on Pavement Performance

The experimental program was designed to discover the effectiveness of various treatments on mitigating pavement distress (mostly longitudinal cracking issues) caused by normal seasonal volumetric changes in expansive clays. Unfortunately, these objectives were compromised by subsequent flooding events. However, these flooding events offered rare opportunities to evaluate the impact of inundation on the performance of newly constructed pavement sections. Flood-induced pavement movement was monitored with cross-section surveys. Pavement condition data were obtained from regular pavement management activities conducted by the Louisiana Department of Transportation and Development’s Pavement Management System unit. The roadway pavements of test sections experienced significant movement because of the floods, but it is differential movement across the pavement that caused longitudinal cracks. The test section, with a geotextile-wrapped sand layer placed between the pavement structure and subgrade, had the best performance among all test sections with respect to longitudinal cracking; better performance was achieved when this sand layer was extended to the edge of the foreslope. This may be because the geotextile-wrapped sand layer created both a drainage system to minimize moisture fluctuations in the subgrade and a flexible mechanical system to absorb the swelling pressures from the underlying subgrade. Flood-induced structural damage was apparent by comparing falling weight deflectometer data of different test sections. Flood-induced heaves and depressions caused the ride quality of the roadway to deteriorate faster than expected. This may be because the prolonged inundation expedited the transition process of the pavement structure and materials from the newly constructed state to the natural equilibrium state.

Study on Lifespan Prediction of Oil–Paper Bushing Considering the Influence of Moisture-Accelerated Aging

The moisture-dependent parameter in the aging kinetic model is inaccessible due to the fluctuation of moisture during the aging period of bushing insulation. This significantly restricts the adoption of aging kinetics-based approaches for predicting transformer bushing insulation lifespan. Given this issue, an improved aging kinetic model is proposed in this article, where the influence of moisture fluctuation is interpreted by the moisture acceleration coefficient. To obtain the involved parameters in the improved model, the humidity of bushing insulation is determined by recognizing the moisture-related feature, which can be extracted from the logarithmic-derivative method derived from frequency domain spectroscopy (FDS). Finally, the improved aging kinetic model and logarithmic-derivative method are then used to provide a method for predicting the lifespan of bushing insulation. According to verification experiments carried out with this model, the relative errors of the re-created laboratory samples are 8.12%, 8.89%, and 25.15%, respectively. In that regard, this article is likely to serve as a model for predicting the lifespan of oil–paper insulation on genuine condenser bushings.

Sensing and Mapping the Effects of Cow Trampling on the Soil Compaction of the Montado Mediterranean Ecosystem

The economic and environmental sustainability of extensive livestock production systems requires the optimisation of soil management, pasture production and animal grazing. Soil compaction is generally viewed as an indicator of soil degradation processes and a determinant factor in crop productivity. In the Montado silvopastoral ecosystem, characteristic of the Iberian Peninsula, animal trampling is mentioned as a variable to consider in soil compaction. This study aims: (i) to assess the spatial variation in the compaction profile of the 0-0.30 m deep soil layer over several years; (ii) to evaluate the effect of animal trampling on soil compaction; and (iii) to demonstrate the utility of combining various technological tools for sensing and mapping indicators of soil characteristics (Cone Index, CI; and apparent electrical conductivity, ECa), of pastures' vegetative vigour (Normalised Difference Vegetation Index, NDVI) and of cows' grazing zones (Global Positioning Systems, GPS collars). The significant correlation between CI, soil moisture content (SMC) and ECa and between ECa and soil clay content shows the potential of using these expedient tools provided by the development of Precision Agriculture. The compaction resulting from animal trampling was significant outside the tree canopy (OTC) in the four evaluated dates and in the three soil layers considered (0-0.10 m; 0.10-0.20 m; 0.20-0.30 m). However, under the tree canopy (UTC), the effect of animal trampling was significant only in the 0-0.10 m soil layer and in three of the four dates, with a tendency for a greater CI at greater depths (0.10-0.30 m), in zones with a lower animal presence. These results suggest that this could be a dynamic process, with recovery cycles in the face of grazing management, seasonal fluctuations in soil moisture or spatial variation in specific soil characteristics (namely clay contents). The NDVI shows potential for monitoring the effect of livestock trampling during the peak spring production phase, with greater vigour in areas with less animal trampling. These results provide good perspectives for future studies that allow the calibration and validation of these tools to support the decision-making process of the agricultural manager.