Moisture Fluctuations Research Articles

Stabilization of Expansive Clays with Basalt Fibers and Prediction of Strength by Machine Learning

Expansive clays with high plasticity need to be stabilized to prevent hazards that may arise due to the extreme volume changes experienced with moisture fluctuations. Utilizing a kind of natural and eco-friendly sustainable fiber named as basalt fiber into the soils has become a new issue that needs to be expanded in scope. In this paper, a high plastic soil was stabilized by these natural basalt fibers to reduce possible soil-induced disasters. Basalt fibers in different lengths were mixed into the clay at varied amounts. Due to the soil’s sensitivity to water, the samples were prepared at distinct water contents, 2 on the dry and 3 on the wet side of the optimum. To question whether the strength loss due to the moisture change can be regained with basalt fibers or not, the strength tests were performed on both natural and stabilized samples. Through the tests, it was revealed that the strength of the expansive clays can be enhanced up to 280% at a fiber content of 2%. The highest strength was obtained at approximately 880 kPa by mixing 24 mm fibers with 15% water at 1 and 2% ratios. As anticipated, the long fibers (24 mm) supplied a real reinforcement even at high water contents. In addition, the obtained data set was used to train machine learning algorithms (linear, ridge, lasso, support vector, decision tree) that have just started to be applied in geotechnical engineering. Results have proved that, the decision tree regression outperformed the stress and strain with 0.85 R-squared (R2) in stress and 0.91 R2 in strain estimation. Additionally, it was revealed from the feature importance analyses that water content has an importance of approximately 85% on stress and up to 97% on strain.

Profiling the molecular destruction rates of temperature and humidity as well as the turbulent kinetic energy dissipation in the convective boundary layer

Abstract. A simultaneous deployment of Doppler, temperature, and water-vapor lidars is able to provide profiles of molecular destruction rates and turbulent kinetic energy (TKE) dissipation in the convective boundary layer (CBL). Horizontal wind profiles and profiles of vertical wind, temperature, and moisture fluctuations are combined, and transversal temporal autocovariance functions (ACFs) are determined for deriving the dissipation and molecular destruction rates. These are fundamental loss terms in the TKE as well as the potential temperature and mixing ratio variance equations. These ACFs are fitted to their theoretical shapes and coefficients in the inertial subrange. Error bars are estimated by a propagation of noise errors. Sophisticated analyses of the ACFs are performed in order to choose the correct range of lags of the fits for fitting their theoretical shapes in the inertial subrange as well as for minimizing systematic errors due to temporal and spatial averaging and micro- and mesoscale circulations. We demonstrate that we achieve very consistent results of the derived profiles of turbulent variables regardless of whether 1 or 10 s time resolutions are used. We also show that the temporal and spatial length scales of the fluctuations in vertical wind, moisture, and potential temperature are similar with a spatial integral scale of ≈160 m at least in the mixed layer (ML). The profiles of the molecular destruction rates show a maximum in the interfacial layer (IL) and reach values of ϵm≃7×10-4 g2 kg−2 s−1 for mixing ratio and ϵθ≃1.6×10-3 K2 s−1 for potential temperature. In contrast, the maximum of the TKE dissipation is reached in the ML and amounts to ≃10-2 m2 s−3. We also demonstrate that the vertical wind ACF coefficient kw∝w′2‾ and the TKE dissipation ϵ∝w′2‾3/2. For the molecular destruction rates, we show that ϵm∝m′2‾w′2‾1/2 and ϵθ∝θ′2‾w′2‾1/2. These equations can be used for parameterizations of ϵ, ϵm, and ϵθ. All noise error bars are derived by error propagation and are small enough to compare the results with previous observations and large-eddy simulations. The results agree well with previous observations but show more detailed structures in the IL. Consequently, the synergy resulting from this new combination of active remote sensors enables the profiling of turbulent variables such as integral scales, variances, TKE dissipation, and the molecular destruction rates as well as deriving relationships between them. The results can be used for the parameterization of turbulent variables, TKE budget analyses, and the verification of large-eddy simulations.

Earthworms and plants can decrease soil greenhouse gas emissions by modulating soil moisture fluctuations and soil macroporosity in a mesocosm experiment.

Earthworms can stimulate microbial activity and hence greenhouse gas (GHG) emissions from soils. However, the extent of this effect in the presence of plants and soil moisture fluctuations, which are influenced by earthworm burrowing activity, remains uncertain. Here, we report the effects of earthworms (without, anecic, endogeic, both) and plants (with, without) on GHG (CO2, N2O) emissions in a 3-month greenhouse mesocosm experiment simulating a simplified agricultural context. The mesocosms allowed for water drainage at the bottom to account for the earthworm engineering effect on water flow during two drying-wetting cycles. N2O cumulative emissions were 34.6% and 44.8% lower when both earthworm species and only endogeic species were present, respectively, and 19.8% lower in the presence of plants. The presence of the endogeic species alone or in combination with the anecic species slightly reduced CO2 emissions by 5.9% and 11.4%, respectively, and the presence of plants increased emissions by 6%. Earthworms, plants and soil water content interactively affected weekly N2O emissions, an effect controlled by increased soil dryness due to drainage via earthworm burrows and mesocosm evapotranspiration. Soil macroporosity (measured by X-ray tomography) was affected by earthworm species-specific burrowing activity. Both GHG emissions decreased with topsoil macropore volume, presumably due to reduced moisture and microbial activity. N2O emissions decreased with macropore volume in the deepest layer, likely due to the presence of fewer anaerobic microsites. Our results indicate that, under experimental conditions allowing for plant and earthworm engineering effects on soil moisture, earthworms do not increase GHG emissions, and endogeic earthworms may even reduce N2O emissions.

Performance of flooded flexible pavements: A data-driven sensitivity analysis considering soil moisture fluctuations

The design of pavement systems relies on sensitivity of their performance to moisture variations; yet traditional sensitivity analysis have limitations in understanding the complex interplays affecting pavement performance, and they can be computationally expensive. This study introduces a novel approach of employing System Dynamics Models (SDM) to assess the factors influencing flexible pavement performance under moisture variations. A data-driven Global Sensitivity Analysis (GSA) can complement traditional methods such as Local Sensitivity Analysis (LSA) and feature ranking, providing a deeper understanding of interconnections. Utilizing Latin Hypercube Sampling, input variable samples are generated to facilitate data-driven GSA. To balance prediction accuracy with computational efficiency, a Random Forest ensemble is developed as a multitarget surrogate model. Key findings underscore the interplay between resilience modulus and pavement layer thickness as well as the significance of subgrade soil particle size for coarse-grained subgrades, while subbase aggregate properties show negligible influence. In fine-grained subgrades, soil plasticity index plays a vital role in peak surface deflection. Additionally, the study uncovers the critical impact of precipitation variables on deflection timing. By predicting these critical timings, informed traffic management measures can be contemplated, enhancing road user safety. This research highlights the importance of tailoring pavement design strategies to specific subgrade characteristics and environmental conditions. Moreover, the study recommends adoption of the proposed sensitivity analysis workflow to delve into the various parameters interactions in infrastructure system design.

Water storage capacity is inversely associated with xylem embolism resistance in tropical karst tree species.

Tropical karst habitats are characterized by limited and patchy soil, large rocky outcrops and porous substrates, resulting in high habitat heterogeneity and soil moisture fluctuations. Xylem hydraulic efficiency and safety can determine the drought adaptation and spatial distribution of woody plants growing in karst environments. In this study, we measured sapwood-specific hydraulic conductivity (Ks), vulnerability to embolism, wood density, saturated water content, and vessel and pit anatomical characteristics in the branch stems of 12 evergreen tree species in a tropical karst seasonal rainforest in southwestern China. We aimed to characterize the effects of structural characteristics on hydraulic efficiency and safety. Our results showed that there was no significant correlation between Ks and hydraulic safety across the tropical karst woody species. Ks was correlated with hydraulic vessel diameter (r=0.80, P<0.05) and vessel density (r=-0.60, P<0.05), while the stem water potential at 50 and 88% loss of hydraulic conductivity (P50 and P88) were both significantly correlated with wood density (P<0.05) and saturated water content (P=0.052 and P<0.05, respectively). High stem water storage capacity was associated with low cavitation resistance possibly because of its buffering the moisture fluctuations in karst environments. However, both Ks and P50/P88 were decoupled from the anatomical traits of pit and pit membranes. This may explain the lack of tradeoff between hydraulic safety and efficiency in tropical karst evergreen tree species. Our results suggest that diverse hydraulic trait combination may facilitate species coexistence in karst environments with high spatial heterogeneity.

Utilization of Black Cotton Soil Stabilized with Brick Dust-Lime for Pavement Road Construction: An Experimental and Numerical Approach

Black cotton soil is highly susceptible to volume change due to moisture fluctuations. This leads to the deformation of structures built on such soil. Therefore, the aim of this study is to improve the soil-bearing capacity and deformation analysis of black cotton soil. The laboratory tests were done according to the American Association State of highway and Transport Official (AASHTO) and the American Society for Testing and Materials (ASTM). These tests were natural moisture content, grain size distribution, X-ray diffraction test, Atterberg limit test, modified compaction, California bearing ratio, and triaxial test. Soil sample was stabilized with a ratio of 0%, 4%, 8%, 12%, and 16% of brick dust and 0%, 1%, 3%, 5%, and 7% of lime, respectively. The result of the laboratory test at the optimum percentage of 12% brick dust and 5% lime shows that the liquid limit improved from 93.2% to 67.5%, plastic limit improved from 48.71%, to 58.2%. The optimum moisture content improved from 26.76 to18.5% and Maximum dry density improved from 1.42 g/cm3 to 1.58 g/cm3. The California bearing ratio improved from 1.29%, to 13.6%. The deformation analysis result shows that at optimum percentage of stabilizing agent, the deformation reduced from 2.087 mm to 0.973 mm. Therefore, brick dust-lime soil stabilization shows the promising improvement of weak subgrade soil.

Downed woody debris carbon emissions in a European temperate virgin forest as driven by species, decay classes, diameter and microclimate

Downed woody debris (DWD) plays an important role as regulator of nutrient and carbon (C) cycling in forests, accounting for up to the 20 % of the total C stocks in primary forests. DWD persistence is highly influenced by microbial decomposition, which is determined by various environmental factors, including fluctuations in temperature and moisture, as well as in intrinsic DWD properties determined by species, diameter, or decay classes (DCs). The relative importance of these different drivers, as well as their interactions, remains largely unknown. Moreover, the importance of DWD for C cycling in virgin forests remains poorly understood, due to their scarcity and poor accessibility. To address this research gap, we conducted a study on DWD respiration (RDWD), in a temperate virgin forest dominated by European beech and silver fir. Our investigation analysed the correlation between RDWD of these two dominant tree species and the seasonal changes in climate (temperature and moisture), considering other intrinsic DWD traits such as DCs (1, 2 and 4) and diameters (1, 10 and 25 cm). As anticipated, RDWD (normalized per gram of dry DWD) increased with air temperature. Surprisingly, DWD diameter also had a strong positive correlation with RDWD. Nonetheless, the sensitivity to both variables and other intrinsic traits (DC and density) was greatly modulated by the species. On the contrary, water content, which exhibited a considerable spatial variation, had an overall negative effect on RDWD. Virgin forests are generally seen as ineffective C sinks due to their lack of net productivity and high respiration and nutrient turnover. However, the rates of RDWD in this virgin forest were significantly lower than those previously estimated for managed forests. This suggests that DWD in virgin forests may be buffering forest CO2 emissions to the atmosphere more than previously thought.

Utilization of Black Cotton Soil Stabilized with Brick Dust-Lime for Pavement Road Construction: An Experimental and Numerical Approach

Black cotton soil is highly susceptible to volume change due to moisture fluctuations. This leads to the deformation of structures built on such soil. Therefore, the aim of this study is to improve the soil-bearing capacity and deformation analysis of black cotton soil. The laboratory tests were done according to the American Association State of highway and Transport Official (AASHTO) and the American Society for Testing and Materials (ASTM). These tests were natural moisture content, grain size distribution, X-ray diffraction test, Atterberg limit test, modified compaction, California bearing ratio, and triaxial test. Soil sample was stabilized with a ratio of 0%, 4%, 8%, 12%, and 16% of brick dust and 0%, 1%, 3%, 5%, and 7% of lime, respectively. The result of the laboratory test at the optimum percentage of 12% brick dust and 5% lime shows that the liquid limit improved from 93.2% to 67.5%, plastic limit improved from 48.71%, to 58.2%. The optimum moisture content improved from 26.76 to18.5% and Maximum dry density improved from 1.42 g/cm3 to 1.58 g/cm3. The California bearing ratio improved from 1.29%, to 13.6%. The deformation analysis result shows that at optimum percentage of stabilizing agent, the deformation reduced from 2.087 mm to 0.973 mm. Therefore, brick dust-lime soil stabilization shows the promising improvement of weak subgrade soil.

Carbon dynamics as a function of soil moisture following repeated wet-dry cycles in irrigated soils

Drying-rewetting cycles are ubiquitous across natural and managed ecosystems. These cycles are known to mobilize carbon (C) in soils producing dramatic pulses in microbial respiration. While many factors contribute to these pulses, the drying-rewetting history of soils affecting carbon emissions remains unclear, especially in irrigated soils where soil moisture fluctuations are more repetitive and/or frequent than natural, seasonally influenced soils. To understand the controls of repeated wet-up and dry down effects on agricultural soils, we used a systems approach to examine the cross section of a furrow irrigated orchard to delineate soil C dynamics. Specifically, we compared two contrasting water regimes, (1) soils temporarily but repeatedly inundated during water delivery (i.e., furrows) and (2) soils at the base of trees (i.e., berms) that only receive water during precipitation events in a semi-arid Mediterranean climate. Overall, our findings show that the heterogeneous landscape of a furrow irrigated field results in two separate systems within the field scale in gaseous release of C as CO2, microbial selectivity of substrates, and mechanisms for C stabilization. By monitoring soil moisture as a function of depth for over two years, our results reveal that furrow soils undergo dramatic wet-dry cycles, while moisture within the berm is relatively constant. We were able to capture the distinct heterogeneity of soil moisture changes within the furrow and berm soils by continuously monitoring CO2 flux throughout water input events in both the wet and dry season. Soil CO2 efflux is suppressed upon irrigation within furrows, while carbon oxidation in berm soils exhibits pore-connectivity limitations that result in lower fluxes when dry. Solid phase soil C speciation determined by C 1s NEXAFS demonstrated C of higher aromaticity remained in furrow soil compared to berm soils. Microbial community analysis shows significantly different communities reside within berm and furrow soils, where furrow soils support more anaerobic metabolisms and spore-formers while berm soils have relatively higher abundance of aerobic microbes capable of degrading larger, more complex C compounds. Our findings show that water regime (periodic inundation vs episodic rainfall) controlling rewetting history can greatly differentiate C respiration within managed soils.

Dual preservative strategy for facilitating bamboo durability using cinnamaldehyde and diethylenetriamine and its reaction characteristics on bamboo cell wall

Cinnamaldehyde exhibits excellent anti-mold properties that can preserve bamboo. However, establishing a stable bonding linkage (CN) requires cinnamaldehyde modification, which can be used to manipulate cell wall characteristics and improve bamboo durability. In this study, cinnamaldehyde's chemical fixation into bamboo through the Mannich reaction was successfully achieved, resulting in enhanced anti-mold capacity and dimensional stability. The modified bamboo exhibited remarkable anti-mold properties, with a 40.0% increase in resistance to swelling caused by moisture fluctuations. Nanoindentation analysis also revealed that the internal bamboo cell wall's mechanical properties improved following modification, including a significant improvement in surface hydrophobicity from 13.9° to 67.3°. Concerning the impact of the modification on bamboo cells, the sclerenchyma cell of bamboo was determined to be the focus. We used guaiacol as a lignin model compound to elucidate the potential mechanism of cinnamaldehyde modification, specifically Schiff base formation, using nuclear magnetic resonance spectra. This study shows a viable dual preservative strategy to extend bamboo lifespan.

Blockchain-enabled smart agriculture: Enhancing data-driven decision making and ensuring food security

Agriculture plays a vital role in global food security, but conventional practices have led to environmental degradation and health risks due to excessive use of agricultural nutrients and chemicals. In this era of increased consumer awareness and preference for organic food, the challenge lies in making informed choices amidst various crop production options. To address this, the present research introduces a groundbreaking study that utilizes blockchain technology to record and trace information on crop production from seeds to end-user consumption, enabling easy consumer choices. This study introduces a model that integrates Internet of Things (IoT) sensors to monitor the impact of selected chemicals and nutrients used in agriculture to enhance production yields. To ensure sustainability, the study employs the low-energy adaptive clustering hierarchy (LEACH) protocol, which optimizes energy consumption and network stability, thereby avoiding disruptions. Results indicate that different fertilizers affect soil physical properties such as temperature and moisture. These parameters are monitored using the Agriculture Vercel App, equipped with temperature, moisture, and light sensors in agricultural fields. The app provided threshold readings via alert notifications, revealing significant fluctuations in temperature (12%–43%) and moisture (83%–41%) concentrations upon the application of specific fertilizers like “Agricultural lime” and “Calcium Ammonium Nitrate.” Our IoT-based model is linked with private blockchain technology to prioritize consumer choice and facilitate transparency. This integration enhances food security while mitigating environmental degradation risks. By providing a comprehensive record of crop production practices, our model empowers consumers to make informed decisions aligned with their health and environmental concerns. This research demonstrates the potential of combining IoT and blockchain technologies to revolutionize agriculture, ensure sustainable practices, and promote food security. The findings offer significant implications for policymakers, farmers, and consumers, fostering a more sustainable and health-conscious approach to agriculture worldwide.

Potential of processed barnacles shell as soil conditioner using mung bean plants (Vigna radiata L.) growth

Barnacles as periphyte animals often found clinging on the ship’s hull, being unutilized waste that presents in such abundance. Calcium carbonate in barnacle shells would increase the chance of degrading microbial community survival in the soil, indirectly increasing soil fertility. The processing of barnacle shells to be used as a calcium carbonate supplement involves harvesting, drying, powdering, sterilizing, and mixing it to the soil. We want to observe comparison of the performance of control group (K), processed barnacle shells (T), industrial 16-16-16 NPK (Nitrogen, Phosphate, Potassium) fertilizer (P), and the combination of processed barnacle shell with 16-16-16 NPK fertilizer (TP) supplementation to the soil as planting media by the daily temperature, pH, and moisture fluctuation, besides the measurement of the growth of mung bean plant, Vigna radiata L. (VIMA 5 variant) regarding their application to the soil. The growth of V. radiata L. is measured by epicotyl length, number of leaves, and total wet mass increase of each plant individual. Vigna radiata L. in the control group shows the best growth measured by parameters listed above. However, ANOVA analysis shows statistical significance on the correlation of types of soil treatment (K, T, P, or TP supplementation) to daily moisture fluctuation.

Unraveling mechanisms underlying effects of wetting–drying cycles on soil respiration in a dryland

Rewetting of dry soils usually stimulates soil carbon (C) emission, a phenomenon known as the Birch effect. Soil C cycling in drylands, which store approximately one third of terrestrial soil organic C (SOC), is strongly affected by wetting–drying cycles. However, the physical, chemical, and biological mechanisms that link rewetting cycles with dryland soil C cycling have not been comprehensively studied, nor do we understand how these mechanisms interact with each other. Here, we conducted a dryland soil incubation experiment manipulating four factors related to global change (soil moisture content, soil moisture variability, C availability, and prior warming) in a factorial design. The experiment was divided into two periods: a rewetting period consisting of six 14-d wetting–drying cycles; and a recovery period lasting 28 days during which soil moisture content was held stable, allowing for examination of the legacy effects of the wet-dry cycles. Rewetting cycles decreased soil aggregate stability under some conditions, but their effects on soil microbial biomass and fungal communities, soil enzyme activities, soil priming, and soil dissolved C were not significant. We found lower average soil respiration under the wetting–drying treatment than the stable soil moisture treatment, and Birch effects were observed, but only under some conditions. This was probably because moisture variability exacerbated soil microbial metabolic stress, which showed itself as oxygen limitation during the initial precipitation pulse and as water limitation during soil drying. Notably, respiration rates remained low even after moisture fluctuations ceased, suggesting a legacy effect of rewetting cycles on dryland microbial communities. Overall, rewetting inhibited aggregate formation (physical mechanism), and suppressed soil respiration by inducing soil microbial metabolic stress (biological mechanism), ultimately leading to lower soil C loss under rewetting. Our findings indicate that Birch effects are mediated by the magnitude of moisture variability, the availability of C, and the degree of physiological stress microbes experience.

Global vulnerability of agricultural commodities to climate risk: Evidence from satellite data

Using a new dataset of high-resolution satellite readings of soil moisture in conjunction with climate-economy econometric models and machine learning methods, we quantify the risk to global agricultural commodities from climate change. Our climate risk measure based on soil moisture fluctuations has a significantly negative impact on the yield of major cereals, and the effect is greater than temperature and precipitation. This impact concentrates on countries with lower income levels, harsher climate conditions, or less irrigated farmland. Moreover, we show agricultural commodities are less vulnerable to current drought risks in countries with higher frequencies of past droughts, suggesting that countries adapt to climate change through learning from prior experience.

Maize yield reduction is more strongly related to soil moisture fluctuation than soil temperature change under biodegradable film vs plastic film mulching in a semi-arid region of northern China

Maize yield reduction is more strongly related to soil moisture fluctuation than soil temperature change under biodegradable film vs plastic film mulching in a semi-arid region of northern China

Comprehensive utilization of brick waste as a precursor in synthesizing geopolymer for treating black cotton soil

ABSTRACT Black-cotton soil (BCS) exhibit swelling and shrinkage with fluctuations in moisture that affect various geotechnical constructions. Although lime and cement are extensively used for treating BCS, these are energy-intensive and emits-CO2. Geopolymer produced from industrial-wastes as precursor were found as alternative to these stabilizers, as it gives high strength, consumes low-energy, and emits low-CO2. Brick generate huge waste during construction and demolition. Although brick-waste was earlier used for geopolymer synthesis in structural-concrete, no study is dedicated for developing geopolymer from severely-weathered bricks (age > 60 years) i.e. used for stabilizing BCS. Furthermore, the existing studies were limited to curing of 3–7 days. In this study, the weathered-brick based geopolymer was developed using 8–12 M sodium-hydroxide (NaOH) alkali-activator. The BCS treated with geopolymer at 5–20% proportions of brick with activator-to-binder ratio (A/B) of 0.2, 0.35, and 0.5 were tested for unconfined-compressive strength (UCS) under varying curing periods (7 and 28 days). The maximum UCS was obtained at 10 M NaOH with an A/B of 0.35, and it is about three times that of raw BCS, thus paving way for alternate construction material.

Enhancement of a multi-species reactive transport model for cement-based materials under cyclic wetting and drying conditions

To understand the underlying phenomena that drive concrete deterioration under cyclic environmental conditions in the marine environment, a reactive transport model (RTM) for unsaturated cement-based materials has been established in this study, including multi-ionic and moisture transport coupled with a chemical equilibrium computation. The two-phase moisture transport model, which considers pore structure changes, is introduced with capillary pressure as the primary variable parameter. The modified Poisson-Nernst-Planck (PNP) equations were illustrated for multi-ionic transport through pore solution under unsaturated conditions. A modelling approach for moisture conductivity based on the pore structure and moisture storage was presented to account for pore structure changes on the mass transports. The consideration of boundary conditions and moisture flux through the exposed surface is demonstrated for wetting and drying conditions, separately. Numerical results for mortar samples subjected to NaCl solutions under various cyclic wetting and drying conditions were in good agreement with experimentally measured moisture gain and total chloride content. Under more prolonged wetting conditions, the deeper influence depth and a wider range of moisture fluctuation lead to an increase in concrete deterioration. For all cyclic wetting conditions, the precipitation of Friedel's salt is predicted, which subsequently limits the transport of chloride ions to deeper depths from the exposed surface. A peak in the chloride profile is observed near the exposed surface. Meanwhile, the peak region continuously expands and moves deeper into the specimens with increasing wetting time duration and exposure times, consistent with Friedel's salt precipitation. In contrast, the chloride content near the exposure surface shows a significant decrease due to the decomposition of the C–S–H phase caused by ion leaching and carbonation of the exposed surface.

Precipitation patterns and N availability legacy govern microbial response to rewetting in a plant-soil system

Climate change models predict shifts in the frequency and magnitude of rain events (precipitation patterns). We studied how precipitation history shapes microbial community responses to rewetting and how these effects depend on N status. Twelve weeks of contrasting precipitation and N input left a legacy effect by shaping present (DNA-based) and potentially active (rRNA-based) bacterial and fungal communities. This legacy effect determined the microbial response to rewetting, as demonstrated by differences in the post-wet potentially active bacterial and fungal communities as well as the flux of soil-emitted CO2 over a 29-h period. Despite contrasting effects of precipitation and N input history on fungal:bacterial ratio and microbial community composition, the timing of the potentially active bacterial and fungal response to rewetting was not altered. Thus, regardless of precipitation or N input history, potentially active bacteria responded with a small shift in community composition within 1 h of rewetting but did not change further for the remaining 28 h analyzed. The potentially active fungi did not respond to rewetting within 29 h. Even though more extreme fluctuations in soil moisture changed soil microbial community composition, the short-term response of microbial communities to rewetting was conserved. Soil CO2 efflux upon rewetting was higher from systems with a history of frequent precipitation and underline the role of plants in drying-rewetting processes. We suggest that shifts in the fungal:bacterial ratio, as well as N-cycling potentials, may have consequences on food web stability and soil biogeochemical cycling.

Response to water‐deficit following waterlogging varies among ecotypes of subterranean clover (Trifolium subterraneum ssp. yanninicum), a waterlogging‐tolerant annual pasture legume

AbstractThe pasture legume Trifolium subterraneum ssp. yanninicum L. is waterlogging tolerant, but water‐deficit (WD) susceptible. The interactive effect of waterlogged (WL) and WD (soil moisture fluctuation [SMF]) results in a severe stress impact. We studied three diverse ecotypes to identify traits associated with adaptation to SMF. Ecotypes were established in a glasshouse with two treatments imposed at 21 days: well‐watered (WW–WW; 80% field capacity [FC]) and WL to WD (WL–WD). For WL–WD, pots were WL for 28 days (Harvest I), and then transitioned to WD (drained to 40% FC) and maintained for 10 days (Harvest II). For shoot relative growth rates (RGR) at Harvest I, WL had relatively little impact, although there was a greater reduction for Ecotype A (80% of WW) than Ecotypes B (92%) and C (87%). However, between Harvests I and II, the impact of WL–WD varied among ecotypes with Ecotype A being less affected (75% of WW–WW) than Ecotypes B (57%) and C (63%). For root RGR at Harvest I, WL resulted in a greater reduction for Ecotype A (52% of WW) than Ecotypes B (77%) and C (74%), while for WL–WD between Harvests I and II, Ecotype A showed a large increase (117% of WW–WW) compared to Ecotypes B (95%) and C (87%). In conclusion, the response to WD following WL varied among ecotypes, which demonstrates contrasting adaptation responses to SMF unrelated to WL tolerance. High yield under WL together with capacity for rapid growth post‐WL in a drying soil profile could enhance adaptation to SMF.

Dust Outbreaks across East Iran: Application of Multi-Source Remote Sensing Data (AMSR-E and FengYun3-MWRI) on the Effects of Soil Moisture

One of the most significant hydro-meteorological and agricultural variables is soil moisture, yet measuring it remains a difficult task. Due to the significant spatial fluctuation of soil moisture, it is difficult to quantify it in a particular spot or field across a sizable region. Despite the thermal band's limitations in assessing soil moisture, MODIS and AVHRR, which are inappropriate were utilized in this investigation. The study examined the impact of soil moisture on dust outbreak. Soil moisture in the study domain was monitored using field techniques and the hybrid model. It combined multi-sourced remote sensing data, obtained from AMSER-E and FY-3 satellites. AMSER-E satellite measures the light temperature in five frequencies ranging from 6. 9 to 89 GHz based on data obtained from AMSER-E. Findings revealed areas with a spatial scale of 25 km2 has a 12-hour time step or variability in dust storm, thereby influencing soil moisture content within the zone of study. In addition to introducing acceptable potentials of the passive microwave band for accurate and applied monitoring of the soil moisture, the present results are viewed as a reliable source for studies on drought in time scale. The study shows that Zabol in Sistan has the highest annual average of 80.7 dust storm days. Soil moisture estimates serve a great deal for preparing soil moisture maps and the evaluation of temporal and spatial variations of soil moisture in study region to address issues related to dust storms.&#x0D; In order to identify the areas affected by dust storms and understand how dust particles are dispersed in the Sistan region, satellite image processing was employed using MODIS 1 sensor images obtained from the TERRA satellite.