Soil Water Content Research Articles

Dynamic and empirical methods for field capacity estimation in fine textured soils with a coarse interlayer

Field capacity (FC) is an important soil hydraulic concept in soil science and irrigation management. It is generally determined from soil water content in a soil layer when soil profile reaches a steady pressure head or negligible drainage flux from an initially saturated soil. However, the proposed criteria are mainly tested for uniform soils and vary with soil textures. To quantify FC in layered soils, a Richards equation-based model was used to describe water flow in fine-textured soils with a coarse interlayer. With calibrated soil hydraulic parameters for loam and sand from infiltration measurements, drainage from saturation was simulated in the loam with a sand interlayer. A relative drainage rate (δ) was defined as a function of water storage and drainage flux to analyze soil water status at FC. Soil water content in the upper loam layer of layered profiles was improved compared with that in the uniform loam, which was negatively correlated with buried depth but positively correlated with thickness of the sand layer for a specified δ. Under different buried depths and thicknesses, soil water content decreased with the decline of δ and decreased rapidly as δ reduced to 1 % d−1. The drainage flux at δ = 1 % d−1 changed within a range of 0.056–0.26 cm d−1, and soil water content reached to 0.278–0.346 cm3 cm−3, which accounted for 70–87 % of the saturated water content of loam. Although the FC in the upper fine-textured soil layer varied for different buried depths and thicknesses of coarse interlayer, the proposed dynamic method is reliable and universal to estimate the FC in the above layered soils at δ = 1 % d−1. An empirical equation was also developed to calculate the FC in fine-textured soils with different buried depths and thicknesses of a coarse interlayer based on the critical δ value.

Rational optimization of irrigation regimes for drip-irrigated cotton fields without mulch can alleviate the problem of residual film contamination in arid zones

The serious problem of residual film pollution in the arid region of northwestern China has a severe negative impact on both the farmland environment and the benefits of cotton planting. Drip irrigation without mulch (DIWM) has the potential to serve as an effective alternative to mulch drip irrigation and address the issue of residual film pollution. However, there are few studies on how to formulate a rational irrigation regime under DIWM conditions and achieve water savings and productivity gains. Consequently, from 2020 to 2021, we established three DIWM treatments: W4, W6, and W8. None of the treatments were irrigated at the seedling stage, and the irrigation regime was the same for all the treatments at the squaring stage (2 irrigations at an irrigation quota of 45 mm). From the initial flowering stage, the frequency of irrigation was once every 6 d, 8 d, and 12 d for W4, W6, and W8, respectively, and the corresponding total numbers of watering times were 8, 6, and 4, respectively. The irrigation amount was 69 mm at each time point during the flowering and boll-forming stages in all the treatments, and the final irrigation amount was 52.2 mm in W8. The total irrigation amounts were 366 mm, 504 mm and 625.2 mm for W4, W6 and W8, respectively. This study explored the spatiotemporal characteristics of soil moisture via sensors combined with the spatial grid method. Additionally, the growth indices, biomass accumulation, yield components, and water use efficiency (WUE) of cotton were assessed across various treatments. The results revealed that, in 2020 and 2021, the W8 treatment resulted in the highest soil water content (SWC) in the 70–110 cm soil layer and soil water consumption (WC) in the 10–110 cm layer, with the WC in the 10 cm layer being 20 % and 44 % greater than that in W6, respectively. The excessive total irrigation amount (IA) in the W8 treatment led to high vegetative growth of cotton, diminishing the positive impact on yield. Across both years, the WUE observed in the W6 treatment significantly exceeded that of W8, while the seed cotton yield demonstrated only marginal decreases of 5 % and 0.9 % compared with that of W8. The irrigation amount and average WC in the 10–40 cm soil layer were 19 % and 29 % lower in W6 than in W8, respectively, but the economic benefits were only 2 % lower than those in W8. There was a significant positive correlation between the SWC and WC in all the different soil layers, and the effect of the SWC on the WC gradually decreased with increasing soil depth. Overall, the irrigation regime employed in the W6 treatment within the arid zone, devoid of mulch cover, proves to be an effective water-saving strategy, ensuring a consistent cotton yield and enhancing WUE. This study serves as a reference for developing an efficient irrigation system tailored to the DIWM cotton industry in arid zones, contributing to the promotion of green and sustainable agricultural development in this region.

Rising damp in heritage sites under urban expansion: A comprehensive case study of the Jinsha Earthen Site

Rising damp poses a significant threat to cultural heritage, yet its dynamics within actual heritage sites remain inadequately understood, particularly regarding its evolution and the impact of urbanization. The Jinsha Site, an earthen site from the Shang periods, is primarily composed of silt, with a layer of sand beneath and pebbles at the bottom, making it susceptible to rising damp. This study investigates the Jinsha Site as a case, monitoring soil water content and electrical conductivity, tracking changes in groundwater, precipitation, and river water levels, and investigating the relationship between urbanization and rising damp. The study aims to understand the process, causes, and influencing factors of rising damp and evaluate previous preservation strategies. The findings indicate that groundwater level in the sand layer trigger dampness, whereas the pebble layer exhibits dryness. Urban construction from 2006 to 2013 and 2014–2017 caused fluctuating groundwater levels, leading to repeated transitions between dryness and dampness at the site. Rainfall and river levels have negligible effect; even rainfall exceeding 100 mm (frequency <0.0056) only raises groundwater levels by approximately 1 m and increases water content by less than 2 % for a brief duration, typically less than half a month. The 2022 groundwater pumping strategy effectively maintained levels beneath the pebble layer (506 m), decreasing moisture by 12.71 % and conductivity by 0.27 dS/m. This study reflects on previous protection effortsand offers evidence-based strategies for heritage conservation amidst urban expansion.

Integrated Effects of Soil Moisture on Wheat Hydraulic Properties and Stomatal Regulation.

The development of water-saving management relies on understanding the physiological response of crops to soil drought. The coordinated regulation of hydraulics and stomatal conductance in plant water relations has steadily received attention. However, research focusing on grain crops, such as winter wheat, remains limited. In this study, three soil water supply treatments, including high (H), moderate (M), and low (L) soil water contents, were conducted with potted winter wheat. Leaf water potential (Ψleaf), leaf hydraulic conductance (Kleaf), and stomatal conductance (gs), as well as leaf biochemical parameters and stomatal traits were measured. Results showed that, compared to H, predawn leaf water potential (ΨPD) significantly reduced by 48.10% and 47.91%, midday leaf water potential (ΨMD) reduced by 40.71% and 43.20%, Kleaf reduced by 64.80% and 65.61%, and gs reduced by 21.20% and 43.41%, respectively, under M and L conditions. Although gs showed a significant difference between M and L, Ψleaf and Kleaf did not show significant differences between these treatments. The maximum carboxylation rate (Vcmax) and maximum electron transfer rate (Jmax) under L significantly decreased by 23.11% and 28.10%, stomatal density (SD) and stomatal pore area index (SPI) under L on the abaxial side increased by 59.80% and 52.30%, respectively, compared to H. The leaf water potential at 50% hydraulic conduction loss (P50) under L was not significantly reduced. The gs was positively correlated with ΨMD and Kleaf, but it was negatively correlated with abscisic acid (ABA) and SD. A threshold relationship between gs and Kleaf was observed, with rapid and linear reduction in gs occurring only when Kleaf fell below 8.70 mmol m-2 s-1 MPa-1. Our findings demonstrate that wheat leaves adapt stomatal regulation strategies from anisohydric to isohydric in response to reduced soil water content. These results enrich the theory of trade-offs between the carbon assimilation and hydraulic safety in crops and also provide a theoretical basis for water management practices based on stomatal regulation strategies under varying soil water conditions.

Abscisic acid increase correlates with the soil water threshold of transpiration decline during drought.

By regulating carbon uptake and water loss by plants, stomata are not only responsible for productivity but also survival during drought. The timing of the onset of stomatal closure is crucial for preventing excessive water loss during drought, but is poorly explained by plant hydraulics alone and what triggers stomatal closure remains disputed. We investigated whether the hormone abscisic acid (ABA) was this trigger in a highly embolism-resistant tree species Umbellularia californica. We tracked leaf ABA levels, determined the leaf water potential and gravimetric soil water content (gSWC) thresholds for stomatal closure and transpiration decline during a progressive drought. We found that U. californica plants have a peaking-type ABA dynamic, where ABA levels rise early in drought and then decline under prolonged drought conditions. The early increase in ABA levels correlated with the closing of stomata and reduced transpiration. Furthermore, we found that transpiration declined before any large decreases in predawn plant water status and could best be explained by transient drops in midday water potentials triggering increased ABA levels. Our results indicate that ABA-mediated stomatal regulation may be an integral mechanism for reducing transpiration during drought before major drops in bulk soil and plant water status.

Comparing mini-disk infiltrometer, BEST method and soil core estimates of hydraulic conductivity of a sandy-loam soil

Saturated, Ks, and near-saturated, K, soil hydraulic conductivity control many hydrological processes but they are difficult to measure. Comparing methods to determine Ks and K is a means to establish how and why these soil hydrodynamic properties vary with the applied method. A comparison was established between the Ks and K values of a sandy-loam soil obtained, in the field, with the BEST (Beerkan Estimation of Soil Transfer parameters) method of soil hydraulic characterization and an unconfined MDI (mini-disk infiltrometer) experiment and, in the laboratory, with a confined MDI experiment and the CHP (constant-head permeameter) method. Using for the BEST calculations the soil porosity instead of the saturated soil water content yielded 1.4–1.1 times higher estimates of Ks and K, depending on the pressure head, and differences decreased in more unsaturated soil conditions. The confined MDI experiment yielded 22 % - 77 % higher K values than the unconfined MDI experiment, depending on the established pressure head, h0, and differences were not significant for h0 = −1 cm. In the close to saturation region, the soil hydraulic conductivity function predicted with BEST did not generally agree well with the Ks and K values obtained in the laboratory by a direct application of the Darcy’s law. In particular, BEST yielded a 5.6 times smaller Ks value than the CHP method and up to an 8.1 times higher K value than the MDI. Overall, i) the two application methods of the MDI yielded relatively similar results, especially close to saturation, and ii) there was not a satisfactory agreement between the field (BEST) and the laboratory (MDI plus CHP) determination of soil hydraulic conductivity close to saturation, unless a comparison was made with the same soil water content. The detected differences were probably attributable to soil spatial variability, overestimation of Ks in the laboratory due to preferential flow phenomena, underestimation of Ks in the field due to air entrapment in the soil and infiltration surface disturbance, inability of BEST to describe the actual soil hydraulic conductivity function at the sampled field site. Testing BEST predictions of Ks and K in other soils appears advisable and combining the MDI and CHP methods appears a rather simple means to make these checks. These additional investigations could improve interpretation of the differences between methods, which is an important step for properly selecting a method yielding Ks and K data appropriate for an intended use.

Temporal accumulation and lag effects of precipitation on carbon fluxes in terrestrial ecosystems across semi-arid regions in China

Precipitation (PRE) plays a vital role in hydrological processes, ecological vegetation, and land-atmosphere interactions in semi-arid regions. Previous research has mainly focused on the impact of PRE on large-scale regional climate change and ecological evolution. However, there have been few studies on the long-term effects of PRE on carbon fluxes in these regions, especially the time-accumulation and -lag effects. Here, we employed observational data from the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) and integrated multiple data sources, including remote sensing and carbon flux simulation data, to quantitatively assess the lagged response of carbon fluxes to PRE and elucidate the underlying mechanisms from multiple perspectives. Characterization of PRE, soil water content (SWC) and carbon fluxes at SACOL qualitatively reveals the existence of a time-delayed response of carbon fluxes to PRE, both on monthly and finer daily temporal scales. The average lagged response of net ecosystem exchange (NEE) and gross primary productivity (GPP) to accumulated PRE (APRE) is approximately 42 days. When considering time-accumulation and -lag effects, the combined direct and indirect effects of APRE on NEE and GPP increase by 0.37 and 0.58, respectively. Notably, preceding APRE primarily exerts a direct effect on current carbon fluxes, whereas the impact of SWC at a depth of 0.1 m is primarily mediated through the memory effect of preceding APRE, resulting in an indirect effect on carbon fluxes. These findings emphasize the importance of preceding APRE. Significantly, our subsequent study indicates that the delay in NEE and GPP responses to APRE also extends to approximately 40 to 50 days at the regional scale. Our findings emphasize the significant time effects of APRE on carbon fluxes, and considering these effects will contribute to a better understanding of the interplay between PRE and vegetation over semi-arid regions in China.

Soil wetting triggered by selective logging in Bornean lowland tropical rainforests

Aboveground biomass removal and canopy opening by selective logging modifies soil moisture in the main root zone, impacting soil aeration and various biogeochemical processes in tropical production forests. This study investigated the relationship between canopy damage and topsoil (10 cm) moisture in two logged forests in Malaysian Borneo, while simultaneously controlling for logging intensity, time elapsed since historical logging, and spatial autocorrelation. Volumetric soil water content (VSWC), canopy height model (CHM), leaf area index (LAI), and historical logging data were collected from 84 transects placed subjectively in 15 sites exhibiting varying canopies. We generated an index (PC1) quantifying the magnitude of canopy structural degradation from canopy structure metrics (CSM) combining CHM and LAI data within a 20-meter buffer for each transect. PC1 was analyzed for its impact on VSWC across logging periods, and contrasted with topography. Spatial autocorrelation of VSWC was examined regarding to canopy conditions. VSWC was significantly higher in all logged forests (over 0.4 m3 m−3) comparing to non-disturbed forests (0.27 m3 m−3). The immediate wetting could be a result of extracting mature individuals of late-successional species holding large biomass, while the persistent wet condition may be due to retarded canopy and biomass recovery. In the study area, canopy structure was a stronger predictor of soil moisture than topography. The high soil moisture underneath the most degraded canopies presented the largest spatial extent of autocorrelation. This study revealed soil wetting after selective logging in humid tropical forests, driven by reduced transpiration from biomass loss rather than increased evaporative demand resulting from canopy opening. The elevation in soil moisture could have disrupted biogeochemical processes in the below-ground system, which in turn impede forest succession and put stress on the overall vulnerability of disturbed tropical rainforests.

Precipitation-induced soil properties and plant communities mediate root strategies in an alpine meadow

Abstract Plant roots show flexible traits to changing precipitation, but the factors driving root trait covariation remain poorly understood. This study investigated six key root traits, and the potential driving factors, such as the plant community characteristics and soil properties in the Zoige alpine meadow across five precipitation gradients, including the natural precipitation (1.0P), 50% increasing precipitation (1.5P), 30%, 50% and 90% decreasing precipitation (0.7P, 0.5P and 0.1P, respectively). Our results demonstrated distinct root trait responses to changes in precipitation. Both increasing (1.5P) and decreasing precipitation (0.1P, 0.5P, and 0.7P) inhibited root diameter (RD), specific root length (SRL), and specific root area (SRA) compared to 1.0P. Conversely, root tissue density (RTD) and root nitrogen content (RNC) increased under decreasing precipitation but declined under 1.5P. With increasing precipitation, root foraging strategies shifted with thinner RD and larger SRL to that with larger diameter. Shifts in root strategies were primarily influenced by soil properties, specifically soil water content and available nitrogen. Additionally, root strategies in surface soils (0–10 cm) were mainly related to the grass and sedge coverage, whereas in deeper soils (10–20 cm) root strategies were related to overall plant community coverage and biomass. Our findings indicate that root traits variations and strategies in alpine meadows are co-driven by soil properties and plant communities in response to changing precipitation

Fractions of soil phosphorus mediated by rhizospheric phoD‐harbouring bacteria of deep‐rooted desert species are determined by fine‐root traits

Abstract Soil phosphorus (P) availability is a crucial factor determining primary productivity in terrestrial ecosystem. Plant functional traits and microbes under P‐deficient conditions can respond positively to increase soil P bioavailability. Whether and/or how the fine‐root traits (FRTs) of deep‐rooted desert species affect the rhizosphere and bulk soil community of phoD‐harbouring bacteria and thus improve the availability of soil P, however, remains unclear. We conducted a three‐year artificial outdoor pot experiment of P supply using Alhagi sparsifolia Shap. (hereafter Alhagi) to address this gap. Fine‐root samples from 1‐ and 3‐year‐old Alhagi seedlings and samples of the rhizospheres and bulk soil were collected. High‐throughput sequencing, sequential extraction and root system scanning were used to determine soil phoD‐harbouring bacteria community, Hedley‐P fractions and the FRTs. Fine‐root surface area (RSA), specific root length, foliar Mn concentration (indicating the quantities of root carboxylates that are released) and acid phosphatase (APase) activity were significantly higher in the no‐P supply compared with the high‐P supply conditions. APase activity was significantly higher by 27%, but the foliar Mn concentration was remarkably lower by 26%, in the 3‐ than the 1‐year‐old seedlings. The rhizospheric concentrations of labile P, moderately labile P, inorganic P and organic P in the no‐P supply condition were 5%, 11%, 10% and 21% higher, respectively, in the 3‐ than the 1‐year‐old seedlings. RSA and the foliar Mn concentration were dominated root predictors for the rhizospheric phoD‐harbouring bacteria community for the 1‐year‐old seedlings, whereas fine‐root P concentration was the dominated root predictor for the rhizospheric and bulk soil phoD‐harbouring bacteria communities for the 3‐year‐old seedlings. Soil water content, as the most dominant soil factor driving the variation of phoD‐harbouring bacteria community, notably could not be ignored. FRTs were the main factors that directly and positively determined rhizospheric phoD‐harbouring bacteria community and thus influenced soil P availability, but bulk soil phoD‐harbouring bacteria community were dominated by inorganic P concentration. The importance of fine‐root morphological traits to soil P availability gradually increased as the plants grew. Overall, our results emphasize the significance of rhizospheric phoD‐harbouring bacteria determined by the effect of FRTs on the bioavailability of soil P. Read the free Plain Language Summary for this article on the Journal blog.

Durability of Slag Based Geopolymer Stabilized Clay with High Moisture Condition

Clay soils, characterized by their cohesiveness and water retention capacity, exhibit low aeration and tend to swell when water is absorbed, leading to subsequent contraction. The moisture content significantly affects the properties of marine clay, resulting in low strength and high compressibility. Traditional stabilizers such as lime and cement have been extensively studied for their ability to enhance the compressive strength, reduce swelling potential, and improve the overall durability of the soil. These stabilizers offer numerous benefits in terms of soil properties and have been extensively researched. However,due to environmental concerned, geopolymer has been explored as an alternative replacement to the traditional stabilizer. In this research, stabilized clay soil using ground granulated blast furnace slag(GGBS) based geopolymer were prepared and tested for the compressive strength and durability characteristic. Different percentages of GGBS (10%, 20% and 30%) were used to stabilize the clay soil with different activator/binder ratio (0.5, 0.75 and 1.0) and initial moisture content (0.75wL, 1.0wL, and 1.25wL). Cement stabilized specimen were also prepared for comparison. Unconfined compression test and wet-dry cycle were performed to evaluate the compressive strength and durability of treated soil. It was found that the strength of treated sample decreased with increment of initial moisture content. Increasing the binder dose was necessary to achieve the strength requirements for high water content soils. Thus, it shows that the use of a GGBS based geopolymer binder for the purpose of stabilizing soft soil is an alternative that is both effective and environmentally friendly.

Modeling the response of sesame (Sesamum indicum L.) to different soil fertility levels under rain-fed conditions in the semi-arid areas of western Tigray, Ethiopia

Sesame, a crucial oilseed crop in Ethiopia, ranks second only to coffee in its importance as an exported agricultural commodity. However, inadequate soil fertility management has hampered its productivity despite its substantial international market demand. Hence, this study was conducted to model the response of sesame to different nitrogen fertilizer levels using the AquaCrop model, and to assess the capability of the model as a decision-support tool for optimizing soil fertility management strategies in the study area. The experiment was laid out in a randomized complete block design, consisting of four nitrogen fertilizer rates (0, 23, 46, and 69 kg/ha nitrogen) and three distinct sesame varieties (Setit-1, Setit-2, and Humera-1). Over the course of the three cropping seasons, data on soil physical and chemical properties, crop growth, yield and yield components were collected for each treatment. Evaluation of model performance relied upon established metrics of coefficient of determination (R2), root mean square error (RMSE), normalized root mean square error (N-RMSE), model efficiency (E), and degree of agreement (D). Analysis of results revealed the AquaCrop model appropriately calibrated for simulation of soil water content, showing R2 values ranging from 0.92 to 0.98, RMSE values varying from 6.5 to 13.9 mm, E values from 0.78 to 0.94, and D values from 0.95 to 0.99. Similarly, simulation outputs for aboveground biomass (AB) demonstrated good accuracy of the model, with R2 values varying from 0.92 to 0.98, RMSE values ranging from 0.33 to 0.54 tons/ha, and D values from 0.9 to 0.98. Notable accuracy was also observed in the simulation of canopy cover (CC), revealing R2 values between 0.95 and 0.99, and RMSE values ranging from 5.3 to 8.6 %. In conclusion, this study substantiates the successful calibration and validation of the AquaCrop model for predicting sesame response to diverse nitrogen fertilizer levels. The performance of the model in predicting soil water content, CC, AB, and yield highlights its potential as a valuable tool for optimizing soil fertility management and enhancing sesame cultivation practices in Ethiopia.

Soil water dynamics and plant water uptake: Primeval mature vs. debris flow-developed half-mature subalpine fir stands in the eastern Tibetan Plateau

Natural disaster can disrupt soil structure and replace established vegetation with younger plants, altering the local hydrological processes. We used hydrogen and oxygen stable isotopes to examine soil water dynamics and plant water uptake patterns in two adjacent fir stands in the eastern Qinghai-Tibet Plateau: a primeval mature stand (MF, finer- textured soil) and a debris flow-developed half-mature stand (HMF, coarser-textured soil). Our results showed that the isotopic composition and soil gravimetric water content (SWC) in deep soil water in MF exhibited a more pronounced hysteresis pattern in response to precipitation compared to HMF, indicating lower turnover rate of soil water in MF. This was also confirmed by a smaller contribution of preferential flow to deep soil water in MF compared to HMF. The higher water storage (higher SWC values) and lower turnover rate of soil water suggest a higher soil water buffer capacity in MF. Additionally, both stands showed no significant difference in plant water sources, but plants in MF used more winter precipitation due to the lower soil water turnover rate. These differences suggest MF may be more vulnerable to water disasters, while HMF may be more susceptible to seasonal droughts under climate change. Our insights enhance understanding of hydrological processes linked to changing surface conditions and offer valuable information for managing forest water resources in mountainous regions.

Differences in Metabolic Characteristics of Rhizosphere Fungal Community of Typical Arboreal, Shrubby and Herbaceous Species in Oasis of Arid Region.

Populus euphratica, Tamarix ramosissima, and Sophora alopecuroides are, respectively, typical arboreal, shrubby, and herbaceous species in oases of arid regions. It is important to study the difference in metabolic characteristics of the rhizosphere fungal community of these plant species and their relationships with soil factors for the preservation of delicate arid oasis ecosystems with future environmental changes. In this study, we, respectively, collected 18 rhizosphere soil samples of P. euphratica, T. ramosissima, and S. alopecuroides to explore the difference in rhizosphere fungal metabolic characteristics of different plant life forms and their underlying driving factors. The results showed that (1) soil physicochemical properties (including soil water content, pH, etc.) were significantly different among different plant species (p < 0.05). (2) Rhizosphere fungal metabolic characteristics were significantly different between S. alopecuroides and T. ramosissima (ANOSIM, p < 0.05), which was mainly caused by the different utilization of carboxylic carbon. (3) The RDA showed that the main driving factors of the variations in rhizosphere fungal metabolic characteristics were different among different plant species. The main explanatory variables of the variations in the metabolic characteristics of the rhizosphere fungal community were carbon to nitrogen ratio (23%) and available potassium (17.4%) for P. euphratica, while soil organic carbon (23.1%), pH (8.6%), and total nitrogen (8.2%) for T. ramosissima, and soil clay content (36.6%) and soil organic carbon (12.6%) for S. alopecuroides. In conclusion, the variations in rhizosphere fungal metabolic characteristics in arid oases are dominantly affected by soil factors rather than plant life forms.

Comprehensive analysis of correlations between soil electrical resistivity and index geotechnical properties

This study investigates the relationships between soil electrical resistivity and key geotechnical properties to develop predictive models for designing grounding systems in electrical substations. Conducted on 30 soil samples from various different regions of Thailand, the research evaluates resistivity in relation to soil water content, plasticity index, and dry density. Using a comprehensive laboratory setup, the soil samples were evaluated under controlled conditions, including temperature, humidity, and salt content of the soil samples, to establish robust correlations between the measured resistivity and the index geotechnical parameters. The results reveal a significant inverse relationship between soil resistivity and water content, confirming that water content is a dominant factor influencing resistivity. Further analysis using multiple non-linear regression demonstrated strong correlations, indicating that a combination of water content, soil dry density, and plasticity index can predict soil resistivity with high reliability. This approach enables optimization of substation grounding designs to ensure operational safety and regulatory compliance. The study suggests that integrating these geotechnical assessments into standard grounding system design procedures can significantly improve the effectiveness and safety of electrical infrastructure. Recommendations for future research include expanding the dataset to encompass a broader range of soil types and investigating the effects of particle size and electrolyte content on soil resistivity. These enhancements aim to refine the predictive models and address the broader applicability of the results in diverse geological settings.

Metabolic and Biochemical Performances of Abaca (&lt;i&gt;Musa textilis&lt;/i&gt; Née) under Intermediate and Advanced Phase Agroforestry System

Abaca, one of the potential fiber crops with high-quality fiber and promising economic value, is mainly established under the agroforestry system, for it is considered a non-primary crop. The study aims to observe the metabolic and biochemical performance as well as the fiber quality of abaca under the agroforestry system. The experimental design used in this study was nested with two types of agroforestry systems, i.e., intermediate phase (Fase Tengah, FT) and advanced phase (Fase Lanjutan, FL) and was conducted during the rainy season. Parameters observed in this study were divided into edaphic and climatic parameters, oxidative response parameters, foliage macro- and micronutrient, and fiber quality. Despite poor soil quality compared to FL, higher relative humidity (4.35%), lower temperature (2.73%), and lower shading intensity were observed in FT. Improved soil characteristics in FL, viz. soil water content (19.64%), organic carbon (72.89%), porosity (4.29%), cation exchange capacity (13.77%), and pH (35.13%), were unable to compensate plant stress induced by the high shading intensity at 83.99%. Consequently, it contributed to higher levels of malondialdehyde, superoxide anion, hydrogen peroxide, superoxide dismutase, peroxidase, and phenol by 0.07%, 1.86%, 32.66%, 0.08%, 14.63%, and 35.08%, respectively, due to shading stress. Nevertheless, ascorbic acid content in FL was lower (18.90%) compared to FT. Higher fiber diameter (23.53%) and tensile strength (18.77%) of abaca in FT were observed compared to FL. The improved microclimatic conditions under FT promoted the high adaptability of abaca to poor soil quality. Therefore, it contributed to enhanced growth and fiber quality compared to FL. Pruning is pivotal to managing shading intensity.

Impact of mechanical weed control on soil N dynamics, soil moisture, and crop yield in an organic cropping sequence

Mechanical weed control is a major element of weed suppression in organic farming systems. In addition to the direct effect on weed growth, mechanical weeding, such as harrowing or hoeing, is known to induce side effects on several soil- and crop-related properties. In this study, we investigated the impact of mechanical weeding on soil mineral nitrogen (SMN), soil moisture, and crop yield in an organic crop rotation of grass-clover (Lolium multiflorumLam., Trifolium pratense L.), silage maize (Zea mays L.) and winter barley (Hordeum vulgare L.). The experiment was conducted in two consecutive years (2021, 2022), where each crop was grown in each year on a Plaggic Anthrosol with sandy loam in North-West Germany. Two weed control treatments (mechanical: harrowing, hoeing; chemical: herbicide application) were implemented in a randomized block design with four replications. Greater net nitrogen (N) mineralization in maize compared to winter barley were attributed to the incorporation of grass-clover residues before sowing of maize and greater mineralization potential during the maize growing season. Higher weed growth in maize after mechanical weeding resulted in a reduction of up to 47% in SMN content in the topsoil. In barley, no differences in weed suppression were observed between the treatments and only small effects on SMN were determined after mechanical weeding. The soil water content in the mechanically weeded plots was significantly higher at several events in both years and for both crops, which was attributed to increased water infiltration by disrupting the soil crust. Neither crop yield nor N uptake in harvest products was affected by the different treatments.

Physical property responses of soils subjected to different degrees of erosion and seasonal freeze-thaw cycles in Northeast China

Changes in soil pores and aggregate stability due to freeze-thaw cycles (FTCs) are important causes of increased soil erosion during snowmelt. Soil erosion causes spatial redistribution of soils, enhancing soil heterogeneity and potentially impacting soil responses to FTCs. Nonetheless, there is minimal knowledge of the responses of soils subjected to different degrees of erosion to seasonal FTCs. To reveal the impact of seasonal FTCs, the dynamic variations of pore characteristics and aggregates of soils with four different degrees of erosion (original, degraded, deposited and parent soil) were measured, and the connections between influencing factors and soil properties were analyzed. The results showed that FTCs altered the structure of the soils and weakened their resistance to erosion and that soils with different degrees of erosion responded differently to FTCs. After seasonal FTCs, soil porosity increased (0.4 %-11.9 %) to some extent in all soils, with greater changes observed in the more eroded soils. Notably, capillary porosity exhibited a complex changing trend compared to total porosity. Degraded and parent soils showed a stable bulk density, while the original soil showed a decrease (2.1 %) in bulk density and the deposited soil showed an increase (18.4 %) in bulk density. With the increase of FTCs, the field capacity of original, degraded, and deposited soils exhibited a gradual decrease (15.1 %-18.5 %), while that of the parent soil slightly increased (0.9 %). After seasonal FTCs, the saturated hydraulic conductivity decreased for original and deposited soils (19.5 %-41.5 %), while it increased for degraded and parent soils (29.2 %-41.6 %). Throughout the FTCs, the proportion of the large aggregates decreased and the small aggregates increased, and the transformation was greater on the less eroded soils. The mean weight diameter and geometric mean diameter of the soils gradually decreased with increasing FTCs, while the change was smaller for the more eroded soils. After seasonal FTCs, the less eroded soils were at greater risk of erosion. Our results demonstrated that the number of FTCs had a more significant impact on soil physical properties compared to the temperature difference and soil water content. Overall, freeze-thaw action reinforced the spatial heterogeneity of soil properties, potentially intensifying soil erosion. These findings help reveal the effects of FTCs on the physical properties of soils with different degrees of erosion and deepen the understanding of the mechanism of FTCs on soil erosion processes.

Intraspecific trait variation of carrion beetle species and communities across elevations

Abstract Filtering processes across environmental gradients can structure patterns of trait variation within communities. The community‐weighted mean (CWM) is a metric that is commonly used to indicate the directionality of such filtering processes and the optimal adaptive strategy of taxa within community. Proximity to the CWM indicates higher fitness, and deviations from this optimal value result in changes in the relative abundances of coexisting species. We investigated patterns of intraspecific trait variation in four coexisting carrion beetle species (Coleoptera: Silphidae) across elevational gradients. The study was conducted in temperate forest ecosystems with distinct natural vegetation zones ranging from 950 m to 1700 m above sea level. Of the 12 traits measured, we found that intraspecific variation ranged from 34% (body length) to 100% (ratio of elytra length, head length and head width to body length) and accounted for a larger proportion of variation than interspecific variation in 7 traits. For most traits, trait range, which indicates the niche breadth of species at a given elevation, was positively correlated with relative abundance. The CWMs of traits associated with long‐distance dispersal decreased with elevation, whereas those associated with microhabitat use showed the opposite trend. Soil temperature influenced tibia length after controlling for the effects of species identity, but soil water content had no effect on trait variation. Patterns of variation in body width and thorax width of two beetle species supported the CWM‐optimality hypothesis; however, patterns of trait variation in body width and thorax length of another species showed an opposite trend. Our study identifies several traits that can be highly variable within carrion beetle species. Such high levels of intraspecific trait variation may enable populations to adapt across a wide range of elevations and vegetation types.

Moderate Drought Stress Interferes with the Physiological State and Promotes the Accumulation of Isoflavone in Reproductive Iris domestica Rhizomes

Drought stress is one of the main factors affecting the growth and secondary metabolism of plants. Iris domestica, rich in isoflavones, is a common herbal medicine in China. In this study, the effects of drought stress and rehydration on resistance physiological characteristics and the secondary metabolism of two-year-old I. domestica during the vegetative and reproductive growth period were investigated. The results showed that the dry weight and fresh weight of rhizomes and roots under severe drought stress were significantly decreased, while those under moderate drought stress were not significantly changed. Meanwhile, the SOD activities, POD activities, MDA content and Pro content increased to resist drought at D1 and D2. In the vegetative growth period, the changes in isoflavone concentration and the expression levels of genes in isoflavone synthesis were more dramatic. Isoflavone accumulation was promoted, to some extent, in the reproductive growth period under the D1 drought treatment. In the actual production process, different measures, namely short-term stress regulation in the vegetative growth period and moderate drought stress (13.44% &lt; soil water content ≤ 16.8%) in the reproductive growth period, need to be adopted to regulate isoflavone biosynthesis.