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Soil shrinkage characteristic curves are used to describe the shrinkage behavior and hydraulic properties of unsaturated soils. To construct soil shrinkage characteristic curves, a high‐data‐density measurement method is needed that relates water content to soil volume changes. We present a fully automated soil shrinkage measurement setup, based on the simplified evaporation method, to characterize the shrinkage behavior of undisturbed natural expansive clay soils. The high data density creates the opportunity to produce soil shrinkage characteristic curves without the need for a mathematical model. The technique allows for resaturation of the samples after drying, enabling differentiation between reversible and irreversible shrinkage. The setup consists of the commercialized HYPROP2 apparatus combined with optical distance sensors to measure the horizontal and vertical dimensions of the samples, yielding data on the sample volume, weight, and soil water suction. The measurement frequency is once per 10 min, and the measurement period is up to 4 weeks, providing a detailed time series of the drying and shrinkage characteristics. The setup can capture the different shrinkage phases and offers the opportunity to relate the soil shrinkage characteristic curve to soil water suction. The measurement data acquisition rate and accuracy enable detailed interpretation of soil water retention curves for nonrigid soils and are shown to be essential for understanding and quantifying the shrinkage potential of several types of deposits. [ABSTRACT FROM AUTHOR]

Compound warm extremes exert profound impacts on environment, health, and socioeconomics. Yang et al. (2024) indicated a shift or transition from warm‐dry extremes (WDEs), common in non‐ice‐covered areas, to warm‐wet extremes (WWEs) in ice‐covered zones. Utilizing ERA5 reanalysis data, this study determined the duration and frequency of WDEs and WWEs across ice‐covered and non‐ice‐covered regions. A comprehensive analysis uncovers the physical mechanisms responsible for the paradigm differences and attributes them to the weakening of land‐atmosphere interaction caused by ice‐cover, which inhibits soil moisture feedback and reduces the intensity and duration of warm events in ice‐covered areas. Both WDEs and WWEs are associated with high‐pressure systems (HPs). WDEs, situated directly beneath HPs, intensify due to adiabatic warming from subsidence motions. Conversely, WWEs, located beneath the poleward fringes of HPs, emerge from advective warming and moistening associated with poleward intrusions of warm‐moist air. Plain Language Summary: Significantly rising temperatures can coincide with extreme weather events such as droughts or rainstorms to form compound warm‐dry extremes (WDEs) or warm‐wet extremes (WWEs), leading to more severe consequences than just hot weather alone. Recent findings indicate that WDEs are more prevalent in non‐ice‐covered regions where people reside and crops are cultivated, while WWEs are more common in ice‐covered areas. This study seeks to comprehend the reasons behind the paradigm differences of extreme events by analyzing the conditions during hot summers. Our research has identified two primary causes for the paradigm differences. First, in non‐ice‐covered regions, the ground warms the overlying air, which in turn dries out the soil, leading to even higher temperatures. This explains why more WDEs are observed in these areas. However, in ice‐covered regions, this process is inhibited by ice. Second, the high‐pressure systems accompanying these extreme events behave differently based on the presence or absence of ice. In non‐ice‐covered regions, these systems are located directly above the regions, exacerbating the hot‐dry conditions by pushing air downwards. Conversely, hot‐wet conditions occur in ice‐covered regions because these areas are situated beneath the poleward fringes of the systems, which transport warm and moist air from the lower latitudes. Key Points: In contrast to midlatitude regions where warm‐dry extremes are common, warm‐wet extremes prevail over polar regionsPoleward circulation associated with high pressure systems, rather than subsidence, produces warm‐wet conditionsSnow‐ and ice‐covered surfaces neutralize the land‐air interaction feedback loop that reinforces hot‐dry spells in midlatitude regions [ABSTRACT FROM AUTHOR]

Existing approaches for predicting total water storage (TWS) rely on land surface or hydrological models using meteorological forcing data. Yet, such models are more adept at predicting specific water compartments, such as soil moisture, rather than others, which consequently impedes accurately forecasting of TWS. Here we show that machine learning can be used to uncover relations between nonseasonal terms of Gravity Recovery and Climate Experiment (GRACE) derived total water storage and the preceding hydrometeorological drivers, and these relations can subsequently be used to predict water storage up to 12 months ahead, and even exceptional droughts on the basis of near real‐time observational forcing data. Validation by actual GRACE observations suggests that the method developed here has the capability to forecast trends in global land water storage for the following year. If applied in early warning systems, these predictions would better inform decision‐makers to improve current drought and water resource management. Plain Language Summary: Traditional methods for predicting short‐term/seasonal variations in land total water storages rely on hydrological models. However, these models have a drawback—they are better at predicting water stored in specific parts of the land system like soil moisture than giving an accurate forecast for the overall integrated land total water storage. In this study, we demonstrate the applicability of machine learning in uncovering relationships between the de‐season and de‐linearized terms of global water storage variability as observed by the Gravity Recovery and Climate Experiment (GRACE) satellites, and the preceding hydrometeorological variables such as sea surface temperature. These relationships can then be utilized to forecast monthly changes in land total water storage up to 1 year ahead, and even to predict exceptional drought events based on near real‐time observational forcing data. The validation by actual GRACE observations, lends further credence to the effectiveness of the method developed here, showcasing its potential to forecast trends in global land total water storage for the upcoming year. The potential applications of these predictions in early warning systems are highly promising, and we anticipate that they can assist decision‐makers in enhancing current drought and water resource management practices. Key Points: We identify a stable lag relationship between hydrometeorological variables and the GRACE derived total water storage change (TWSC)Using this stable lag relationship, we are able to forecast the global TWSC up to 1 year ahead with solely observational data as inputsOur forecasts exhibit high consistency with actual GRACE data in terms of global mean land water storage trends for the following year [ABSTRACT FROM AUTHOR]

The atmospheric activity on Kalimantan Island (KI) is important for regulating regional weather and climate. This study investigates the effect of autumn soil moisture over KI on following winter precipitation over southern China (SC) during 1968–2014. The results show that the autumn soil moisture over the KI has a significant negative correlation with subsequent winter precipitation over SC. The correlation remains statistically significant when using partial correlation to filter out the concurrent influences of El Niño–Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) signals. The soil moisture anomalies over KI, which initiate in the autumn and persist into the winter, lead to changes in local thermal conditions and atmospheric temperature. Negative soil moisture anomalies over KI will result in positive heating anomalies of the atmosphere above the land surface. This atmospheric heating causes ascending motion, which creates a semi‐closed vertical circulation from KI to the tropical northwest Pacific. This vertical circulation would strengthen the northwest Pacific anticyclone and weaken the East Asian winter monsoon (EAWM). Consequently, southwesterly water vapour flux prevails in the SC as well as the South China Sea (SCS), facilitating the transportation of more water vapour into the SC. Simultaneously, water vapour convergence in the SC. Collectively, these contribute to an addition of precipitation over SC. [ABSTRACT FROM AUTHOR]

In semiarid areas, the positive feedback effect of vegetation and soil moisture plays an indispensable role in the water absorption process of plant roots. In addition, vegetation can absorb water through the nonlocal interaction of roots. Therefore, in this article, we consider how the interactions between cross‐diffusion and nonlocal delay affect vegetation growth. Through mathematical analysis, the conditions for the occurrence of the Turing pattern in the water–vegetation model are obtained. Meanwhile, using the multi‐scale analysis method, the amplitude equation near the Turing bifurcation boundary is obtained. By analyzing the stability of the amplitude equation, the conditions for the appearance of Turing patterns such as stripes, hexagons, and mixtures of stripes and hexagons are determined. Some numerical simulations are given to illustrate the analytical results, especially the evolution processes of vegetation patterns depicted under different parameters. [ABSTRACT FROM AUTHOR]

ABSTRACT The driving forces of transpiration are not only atmospheric evaporation but also root zone water supply and stomatal regulation among species. However, the biophysiological drivers of transpiration remain incompletely understood in heterogeneous karst habitats. This study investigated the commonly coexisting tree species Mallotus philippensis and Celtis biondii in two typical karst habitats: rock‐dominated (RD) habitat and control soil‐dominated (SD) habitat. Over 2 years, soil moisture, transpiration, root distribution, and leaf water potential were measured. The results showed that soil moisture in the RD habitat was significantly lower than in the SD habitat. Transpiration patterns also differed between habitats, with species‐specific distinctions driven by biophysiological traits. M. philippensis showed small hydroscape areas and its root system mainly distributed in the soil zone in both habitats. The isohydric behaviour and lower root density in the RD habitat drove M. philippensis to reduce transpiration in response to soil water deficiency. Conversely, C. biondii had large hydroscape areas and roots capable of penetrating bedrock. It transpired higher relying on ample accessible water through anisohydric behaviour and having a more robust root system both in soil and bedrock zones in the RD habitat. Our study highlights the critical role of root water accessibility and leaf iso/anisohydric tendencies in driving transpiration. [ABSTRACT FROM AUTHOR]

ABSTRACT Polyploid varieties have been suggested as an alternative approach to promote drought tolerance in citrus crops. In this study, we compared the responses of diploid and tetraploid Sunki ‘Tropical’ rootstocks to water deficit when grafted onto ‘Valencia’ sweet orange trees and subjected to water withholding in isolation or competition experiments under potted conditions. Our results revealed that, when grown in isolation, tetraploid rootstocks took longer to show drought symptoms, but this advantage disappeared when grown in competition under the same soil moisture conditions. The differences in drought responses were mainly associated with variations in endogenous leaf levels of abscisic acid (ABA), hydrogen peroxide (H₂O₂) and carbohydrates among treatments. Overall, tetraploids were more affected by drought in individual experiments, showing higher H₂O₂ production, and in competition experiments, rapidly increasing ABA production to regulate stomatal closure and reduce water loss through transpiration. Therefore, our results highlight the crucial importance of evaluating diploid and tetraploid rootstocks under the same soil moisture conditions to better simulate field conditions, providing important insights to improve selection strategies for more resilient citrus rootstocks. [ABSTRACT FROM AUTHOR]

The excessive production and use of plastics increase the release of micro‐ and nanoplastics (MNPs) into the environment. In recent years, research has focused on the occurrence of MNPs in air, soil and water. Nevertheless, there is still a lack of knowledge regarding MNPs in plants. To determine the load, translocation of MNPs and their effects on metabolism, pak choi, tomato, radish and asparagus have been exposed with fluorescent‐labelled poly(methyl methacrylate) or polystyrene (PS) MNPs. The entry of nanoparticles (NPs) of various sizes (100–500 nm) and surface modifications (unmodified, COOH or NH2) into plants has been demonstrated using confocal laser scanning microscopy (CLSM). The translocalization from root to shoot and the accumulation of NP in the intercellular spaces were regardless of the surface modification. In addition, metabolomics was used to evaluate metabolic changes induced by MNPs in pak choi. Changes in phenolic compounds, phytohormone derivatives and other classes of compounds known to be triggered by various environmental stresses have been identified. The present study demonstrates the uptake and translocalization of MNPs in edible parts of vegetables and may pose a hazard for humans. [ABSTRACT FROM AUTHOR]

Plants differ widely in how soil drying affects stomatal conductance (gs) and leaf water potential (ψleaf), and in the underlying physiological controls. Efforts to breed crops for drought resilience would benefit from a better understanding of these mechanisms and their diversity. We grew 12 diverse genotypes of common bean (Phaseolus vulgaris L.) and four of tepary bean (P. acutifolius; a highly drought resilient species) in the field under irrigation and post‐flowering drought, and quantified responses of gs and ψleaf, and their controls (soil water potential [ψsoil], evaporative demand [Δw] and plant hydraulic conductance [K]). We hypothesised that (i) common beans would be more “isohydric” (i.e., exhibit strong stomatal closure in drought, minimising ψleaf decline) than tepary beans, and that genotypes with larger ψleaf decline (more “anisohydric”) would exhibit (ii) smaller increases in Δw, due to less suppression of evaporative cooling by stomatal closure and hence less canopy warming, but (iii) larger K declines due to ψleaf decline. Contrary to our hypotheses, we found that half of the common bean genotypes were similarly anisohydric to most tepary beans; canopy temperature was cooler in isohydric genotypes leading to smaller increases in Δw in drought; and that stomatal closure and K decline were similar in isohydric and anisohydric genotypes. gs and ψleaf were virtually insensitive to drought in one tepary genotype (G40068). Our results highlight the potential importance of non‐stomatal mechanisms for leaf cooling, and the variability in drought resilience traits among closely related crop legumes. [ABSTRACT FROM AUTHOR]

The susceptibility of surface soil to drying when rainfall is scarce has prompted evaluation of deeper placement (20 cm) of fertilizers within the profile to where soil moisture is more likely to be stored. However, concerns arise regarding potential chemical challenges to P availability in the subsurface. This study examined differences in chemical conditions between the soil surface (0–10 cm) and subsurface (15–25 cm), and investigated the effect on the diffusion and extractability of banded P. Analysis of surface and subsurface samples from 15 sites revealed substantial differences in characteristics that influence P behavior between depths. The phosphorus buffering index (PBI) was largely explained by concentrations of amorphous Al and Fe (hydr)oxides and CaCO3. The measured diffusion distance of P from monoammonium phosphate (MAP) granules was found to be inversely related to PBI. Consequently, significant differences in diffusion distances were typically observed between soil layers characterized by marked PBI variations. The measured diffusion radii were used to calculate the mean P concentrations of surface-banded and deep-banded MAP in a field scenario, which were replicated in a 4-week laboratory incubation. The resulting lability of applied P was determined through isotopic exchange, and although significantly higher P recoveries were measured from the subsurface at two sites where large pH differences existed between depths, no significant differences were measured between depths at all other sites. Hence, the subsurface is not a more hostile zone for deep-placed P. [ABSTRACT FROM AUTHOR]

This study addresses the problem of 2D soil water movement under ponding radii of 1, 2, and 3 cm. The soil water movement characteristics (shape parameters of the water content profile, ratio of horizontal wetting front to vertical wetting front, relationship between infiltration time and horizontal wetting front, and relationship between infiltration time and cumulative infiltration) under the above three kinds of water ponding radius were analyzed. On the basis of the assumption that the soil wetting body is a semi-ellipse and the analytical solution of the 1D soil water movement equation at any angle, the approximate analytical solution of the 2D soil water movement equation under ponding conditions is optimized. The function relationships between infiltration time, wetting front, and cumulative infiltration are established. We applied the numerical data simulated by HYDRUS-3D to validate the parameters in proposed analytical solutions and evaluated the relationships between the wetting front and hydraulic parameters. The results indicate that as the water ponding radius increases, the wetting body and 2D water content distribution becomes larger. When the water ponding radius was 2 cm, the numerical and analytical solution of 1D soil water distribution showed the best comparison results, and the model error was the smallest. The ratio of wetting fronts was linearly increased with the increase of air-entry suction with R² = 0.9969. [ABSTRACT FROM AUTHOR]

Field capacity is a dubious soil physical property, but its use continues because of its perceived value for representing a soil’s capacity to store water. Appropriate field capacity estimates can be useful for interpreting data from soil moisture sensors, including those in large-scale monitoring networks, but suitable methods for defining field capacity in this context are unclear. Motivated by the desire to determine optimal field capacity values for the Oklahoma Mesonet, our objectives were (1) to develop and apply an automated time series analysis algorithm to estimate volumetric soil water content at field capacity and corresponding matric potential and (2) to compare the resulting water contents to those calculated from traditional matric potential thresholds (−33 and −10 kPa). Across 118 Oklahoma Mesonet sites and three soil depths (5, 25, and 60 cm), a matric potential threshold of −10 kPa underestimated field capacity water content by 0.010–0.014 cm cm−3 (3–4%) on average, and a threshold of −33 kPa underestimated it for every site and depth by 0.055– 0.078 cm cm−3 (16%−22%) on average. Median matric potentials corresponding to field capacity were −7.6 kPa at the 5-cm depth, −7.2 kPa at the 25-cm depth, and −7.3 kPa at the 60-cm depth. The algorithm developed here can be used to estimate field capacity wherever adequate data are available, and for sites where soil water retention properties are known, matric potentials at field capacity can also be estimated. Using a matric potential of −33 kPa as a standard threshold to represent field capacity is not scientifically justified and should be discontinued. [ABSTRACT FROM AUTHOR]

Soil texture can affect soil temperature, soil moisture, the protection of organic material against microbial degradation, and other soil properties. All these factors potentially influence net nitrogen (N) mineralization. The objective of this analysis is to investigate the relationship between soil texture and net N mineralization using different approaches, including a 10-week laboratory incubation of undisturbed soil cores from 47 sites in California, modeling, and a meta-regression analysis of 461 datasets from 20 studies. In the laboratory incubation as well as in the meta-analysis, total soil N increased significantly with increasing clay content. Net N mineralization expressed in mg kg−1 soil did not change significantly with increasing clay content, but significantly decreased when expressed as a proportion of total soil N. These results are most likely explained by physical and chemical protection of organic molecules by clay minerals. Protection in turn led to the observed increase in total soil N over time. Based on the incubation and measured bulk densities, net N mineralization in the top 15 cm of the soil profile was 30% higher in a sandy loam compared to a clay soil. Model simulations indicated that texture-related differences in soil temperature and moisture have only a small effect on net N mineralization in irrigated agricultural fields under Mediterranean conditions. [ABSTRACT FROM AUTHOR]

The persistence of a soil seed bank influences weed management options. However, for many species, the degree of persistence of a soil seed bank is unknown. We assessed how long seeds remain in the soil for two invasive weeds, Chrysanthemoides monilifera subsp. monilifera (boneseed) and C. monilifera subsp. rotundata (bitou bush), as seeds of these species were predicted to have different longevity in the soil associated with differences in seed coat thickness. Seeds of both subspecies were buried at two depths at two sites in eastern Australia. Seeds were tested for germinability and viability regularly over an 8‐year period. Freshly collected seeds had quite low viability, and there was a rapid decline in viability in the first couple of years after burial, with C. m. rotundata declining faster than C. m. monilifera. Some seeds, however, remained viable in the soil at some sites for up to 8 years, with high site‐to‐site variability. The variability in viability from site to site may be due to the length of time soils remain moist: a combination of rainfall quantity and humidity levels. The low numbers of seeds remaining viable at 8 years indicate progressively lower probabilities of recruitment at sites following weed control but also suggest that monitoring for both subspecies needs to occur for a long period to minimize the risk of reinfestation from the seed bank. [ABSTRACT FROM AUTHOR]

For many drylands, both long‐ and short‐term drought conditions can accentuate landscape heterogeneity at both temporal (e.g., role of seasonal patterns) and spatial (e.g., patchy plant cover) scales. Furthermore, short‐term drought conditions occurring over one season can exacerbate long‐term, multidecadal droughts or aridification, by limiting soil water recharge, decreasing plant growth, and altering biogeochemical cycles. Here, we examine how experimentally altered seasonal precipitation regimes in a mixed shrub grassland on the Colorado Plateau impact soil moisture, vegetation, and carbon and nitrogen cycling. The experiment was conducted from 2015 to 2019, during a regional multidecadal drought event, and consisted of three precipitation treatments, which were implemented with removable drought shelters intercepting ~66% of incoming precipitation including: control (ambient precipitation conditions, no shelter), warm season drought (sheltered April–October), and cool season drought (sheltered November–March). To track changes in vegetation, we measured biomass of the dominant shrub, Ephedra viridis, and estimated perennial plant and ground cover in the spring and the fall. Soil moisture dynamics suggested that warm season experimental drought had longer and more consistent drought legacy effects (occurring two out of the four drought cycles) than either cool season drought or ambient conditions, even during the driest years. We also found that E. viridis biomass remained consistent across treatments, while bunchgrass cover declined by 25% by 2019 across all treatments, with the earliest declines noticeable in the warm season drought plots. Extractable dissolved inorganic nitrogen and microbial biomass nitrogen concentrations appeared sensitive to seasonal drought conditions, with dissolved inorganic nitrogen increasing and microbial biomass nitrogen decreasing with reduced soil volumetric water content. Carbon stocks were not sensitive to drought but were greater under E. viridis patches. Additionally, we found that under E. viridis, there was a negative relationship between dissolved inorganic nitrogen and microbial biomass nitrogen, suggesting that drought‐induced increases in dissolved inorganic nitrogen may be due to declines in nitrogen uptake from microbes and plants alike. This work suggests that perennial grass plant–soil feedbacks are more vulnerable to both short‐term (seasonal) and long‐term (multiyear) drought events than shrubs, which can impact the future trajectory of dryland mixed shrub grassland ecosystems as drought frequency and intensity will likely continue to increase with ongoing climate change. [ABSTRACT FROM AUTHOR]

Mediterranean ecosystems are predicted to undergo longer and more intense summer droughts. The mechanisms underlying the response of herbaceous communities to such drier environments should be investigated to identify the resilience thresholds of Mediterranean rangelands. A 5‐year experiment was conducted in deep and shallow soil rangelands of southern France. A rainout shelter for 75 days in summer imposed drier and warmer conditions. Total soil water content was measured monthly to model available daily soil water. Aboveground net primary production (ANPP), forage quality, and the proportion of graminoids in ANPP were measured in spring and autumn. Plant senescence and plant cover were assessed in summer and spring, respectively. The experimental years were among the driest ever recorded at the site. Therefore, manipulated summer droughts were drier than long‐term ambient conditions. Interactions between treatment, community type, and experimental year were found for most variables. In shallow soil communities, spring plant cover decreased markedly with time. This legacy effect, driven by summer plant mortality and the loss of perennial graminoids, led to an abrupt loss of resilience when the extreme water stress index exceeded 37 mm 10 day−1, characterized by a reduction of spring plant cover below 50% and a decreased ANPP in rainy years. Conversely, the ANPP of deep soil communities remained unaffected by increased summer drought, although the presence of graminoids increased and forage nutritive value decreased. This study highlights the role of the soil water reserve of Mediterranean plant communities in modulating ecosystem responses to chronically intensified summer drought. Communities on deep soils were resilient, but communities on shallow soils showed a progressive, rapid, and intense degradation associated with a loss of resilience capacity. Notably, indexes of extreme stress were a better indicator of tipping points than indexes of integrated annual stress. Considering the role of soil water availability in other herbaceous ecosystems should improve the ability to predict the resilience of plant communities under climate change. [ABSTRACT FROM AUTHOR]

Some taxa of wading birds can locate buried prey by detecting vibratory cues in their foraging substrates while probe‐foraging, using a sensory modality called 'remote‐touch'. As more saturated substrates transmit vibrations better, we predict that these birds can detect prey in wetter substrates more easily. We used sensory assays to test whether substrate water content affects the remote‐touch foraging success rate of Hadeda ibises, Bostrychia hagedash. The birds were more successful at locating prey using vibratory cues than when relying on random direct contact with the beak alone. Their remote‐touch foraging success rate was positively affected by increasing water contents of the soil, but water content had no effect on their direct contact foraging success (indicating this is not an artefact of ease of probing). This may partially explain the link between the range expansion of this species in southern Africa and increased soil irrigation, as it is easier for the birds to detect prey in wetter substrates. Thus, it is likely that the distribution of other remote‐touch foraging birds is affected by substrate water content, and as many of these species are endangered and rely on sensitive wetland habitats, it is vital to understand their sensory requirements for foraging. [ABSTRACT FROM AUTHOR]

Climate change is expected to lead to a drier world, with more frequent and severe droughts, constituting a growing threat to biodiversity, especially in drylands. Positive plant−plant interactions, such as nurse plants facilitating beneficiary communities in their understorey, could mitigate such climate‐induced stress. However, testing the real‐world relevance of nurse facilitation under drought requires accounting for interactions within the diverse beneficiary communities, which may reduce, or amplify the buffering effect of a nurse. Here, we investigated when and how the interactions among nurse plants and beneficiary community members buffered drought effects in a Mediterranean semiarid abandoned cropland. We transplanted sapling beneficiary communities of either one or three species either under a nurse or in open microsites for different soil moisture levels through watering. Net facilitative effects on survival and biomass were only observed when beneficiary communities were species‐diverse and under drought (without watering), meaning that under these conditions, facilitation provided by the nurse had larger positive effects than the negative effects stemming from competition with the nurse and among beneficiary species. Nurses appear to be generating these increases in survival and biomass in drought conditions via two mechanisms commonly associated with watering in open sites: they generate complementarity among the beneficiaries and shift traits to lower stress profiles. Contrasting with watering, which was found to enhance competitive hierarchy, our study shows that nurses appear to alter species dominance, favouring the less competitive species. Our results highlight three mechanisms (complementarity, competitive dominance, and trait plasticity) by which nurse species could mitigate the loss of biodiversity and biomass production due to water stress. Maintaining and supporting nurse species is thus a potentially pivotal approach in the face of projected increase in drought conditions for many drylands across the world. Keywords: biodiversity, dryland, ecosystem functioning, facilitation, functional traits, plant–plant interactions [ABSTRACT FROM AUTHOR]

Drought threatens plant growth and related ecosystem services. The emergence of plant drought stress under edaphic drought is well studied, whilst the importance of atmospheric drought only recently gained momentum. Yet, little is known about the interaction and relative contribution of edaphic and atmospheric drought on the emergence of plant drought stress. We conducted a gradient experiment, fully crossing gravimetric water content (GWC: maximum water holding capacity—permanent wilting point) and vapour pressure deficit (VPD: 1−2.25 kPa) using five wheat varieties from three species (Triticum monococcum, T. durum & T. aestivum). We quantified the occurrence of plant drought stress on molecular (abscisic acid), cellular (stomatal conductance), organ (leaf water potential) and stand level (evapotranspiration). Plant drought stress increased with decreasing GWC across all organizational levels. This effect was magnified nonlinearly by VPD after passing a critical threshold of soil water availability. At around 20%GWC (soil matric potential 0.012 MPa), plants lost their ability to regulate leaf water potential via stomata regulation, followed by the emergence of hydraulic dysfunction. The emergence of plant drought stress is characterized by changing relative contributions of soil versus atmosphere and their non‐linear interaction. This highly non‐linear response is likely to abruptly alter plant‐related ecosystem services in a drying world. Summary statement: Plant drought stress emerges from a nonlinear interaction of soil water availability (here estimated based on gravimetric water content, GWC) and atmospheric water demand (vapour pressure deficit, VPD) with the relative contribution of VPD accelerating below a critical threshold of GWC. [ABSTRACT FROM AUTHOR]

In drylands, grass germination occurs after a large rainfall event. However, trees influence the water requirements for germination either by decreasing the rate of evaporation from soil surface or by interception rainfall with their canopy. The aim of this work was to evaluate the role of Neltuma flexuosa tree on the germination of Leptochloa crinita and Pappophorum caespitosum grasses in response to precipitation events of different sizes. The experiment was conducted in two locations within the Monte desert, Argentina: a semi‐arid location with an average annual precipitation of 345 mm and an arid location with an average annual precipitation of 156 mm. Six microsites were established under N. flexuosa canopies and six microsites in open areas at both locations. Within each microsite, 35 seeds of each grass species were exposed to precipitation events of varying sizes. This procedure was repeated 14 times across two growing seasons. Germinated seeds were counted in the laboratory. Generalized linear mixed models were then applied to evaluate the effects of accumulated precipitation and the microsite on the grass germination in both locations. Results showed that N. flexuosa did not influence the germination of either grass species in the arid location. However, in the semi‐arid location, N. flexuosa facilitated the germination of P. caespitosum only. Large precipitation events would act as an environmental signal for these perennial grasses, allowing them to germinate in favorable years regardless of the microsite or the location. [ABSTRACT FROM AUTHOR]

The global extent of salt‐affected agricultural land, 20% of which is deemed gypsiferous, results in billions of dollars of annual economic loss, a serious problem deserving of attention. However, the analysis of gypsiferous saline soils, such as in the irrigated Lower Arkansas River Valley (LARV) of Colorado, can result in an inflated estimation of soil salinity when using the traditional soil saturated paste extract electrical conductivity (ECe), leading to inaccurate crop yield loss predictions and misguided decisions for remediation. Sparingly soluble gypsum (CaSO4·$\cdot$ 2H2O) in these soils dissolves more readily during laboratory preparation of saturated paste extracts because of excess soil water dilution coupled with sample disturbance. We present a pragmatic linear‐regression approach to correct for this phenomenon, calibrated using two adapted methods for correcting ECe on an individual sample basis. The novel approach used electrical conductivity of pore water samples from saline fields to evaluate the accuracy of the correction methods. The approach was applied on soil samples from two surface‐irrigated, saline fields in the LARV, which were mapped using electromagnetic induction data and analysis of covariance linear regression, calibrated for ECe and ECe corrected for excess gypsum dissoultion (ECeg). Average ECeg values are as much as 26% lower than uncorrected ECe in gypsum‐biased portions of the fields. Estimation of corn salinity hazard in these gypsum‐affected areas using ECeg in lieu of ECe in a traditional yield response function generated mean relative yield values that are higher by up to 13 percentage points. We discuss lessons learned and suggest enhancements to the techniques. Core Ideas: In gypsiferous soils, excess gypsum dissolution biases saturated paste extract (SPE) analysis.Electrical conductivity of SPE (ECe) was corrected with selective dilution and equilibrium geochemical modeling.Linear models were used to estimate gypsum‐corrected ECe values over study fields.Gypsum significantly affects assessment of salinity hazard and crop yield impact. [ABSTRACT FROM AUTHOR]

Croplands have been the focus of substantial investigation due to their considerable potential for sequestering carbon. Understanding the potential for soil organic carbon (SOC) sequestration and necessary management strategies will be enabled with accurate process-based models. Accurately representing crop growth and agricultural practices will be critical for realistic SOC modeling. The MEMS 2 model incorporates a current understanding of SOC formation and stabilization, measurable SOC pools, and deep SOC dynamics and is seen as a highly promising tool to inform management intervention for SOC sequestration. Thus far, MEMS 2 has been developed to represent grasslands. In this study, we further developed MEMS 2 to model annual grain crops and common agricultural practices, such as irrigation, fertilization, harvesting, and tillage. Using four Ameriflux sites, we demonstrated an accurate simulation of crop growth and development. Model performance was strong for simulating aboveground biomass (index of agreement [d] range of 0.89–0.98) and green leaf area index (d from 0.90 to 0.96) across corn, soybean, and winter wheat. Good agreement with observations was also achieved for net ecosystem CO2 exchange (d from 0.90 to 0.96), evapotranspiration (d from 0.91 to 0.94), and soil temperature (d of 0.96), while discrepancy with the available soil water content data remain (d from 0.14 to 0.81 at four depths to 100 cm). While we will continue model testing and improvement, MEMS 2 (version 2.14) has now demonstrated its ability to effectively simulate the growth of common grain crops and practices [ABSTRACT FROM AUTHOR]

Disparities in pH, conductivity, organic carbon (OC), nutrients, and moisture between the Asan Wetland and its periphery in the Western Himalaya, India, highlight the need to investigate influencing factors. This study thus addresses two gaps: (1) identifying key drivers for alkaline pH and elevated wetland concentrations and (2) understanding how different values outside the wetland relate to ecological processes. Asan Wetland soil samples, collected on April 15, 2023, underwent analysis for pH, electrical conductivity (EC), organic carbon (OC), organic matter (OM), available nitrogen (N), available phosphorus (P), potassium (K), sodium (Na), calcium (Ca), moisture content (M), total organic carbon (TOC), and total organic matter (TOM) using standard laboratory procedures, APHA, CPCB, and standard manual techniques. Within the wetland, results indicated that the soil is more alkaline (pH 8.50 ± 0.13) than the periphery in the concentrations of EC, N, K, and M were found to be higher compared to the corresponding concentrations outside the wetland, with mean values of 1.10 ± 0.15 ds/m, 364 ± 117.13 kg/ha, 86.42 ± 21.64 kg/ha, and 20.87 ± 1.50%, respectively. Conversely, outside the wetland, higher values of OC, OM, P, Na, Ca, TOC, and TOM were recorded (0.39 ± 0.23%, 0.66 ± 0.39%, 0.82 ± 0.35 ppm, 80.45 ± 8.46 ppm, 268.12 ± 61.12 ppm, 56.80 ± 0.33%, and 97.70 ± 0.57%, respectively). pH, EC, K, Ca, Na, and moisture content variations indicate location‐based differences. pH, TOM, TOC, and soil moisture were positively correlated within wetlands but negatively correlated with Na and N. In addition, moisture was positively correlated with pH and N but negatively correlated with Ca, K, Na, and P. The study concluded that the Asan Wetland exhibits distinct soil characteristics compared to its periphery, exhibiting location‐based differences while emphasizing these factors' interconnectedness. [ABSTRACT FROM AUTHOR]

Green surfactants–based bioremediation of polycyclic aromatic hydrocarbons (PAHs) from the environment is a promising technique. Rhamnolipids are a class of glycolipid surfactants that belong to the category of green surfactants and have distinctive characteristics. PAHs, which are hazardous toxins, are commonly found in polluted soil, water, and air. PAHs are difficult to break down because they are resistant to degradation and typical methods of cleaning up pollution are not very effective. In recent years, there has been a growing interest in the capacity of specific microorganism species to produce rhamnolipids, which can enhance the process of PAH biodegradation. Rhamnolipids can dissolve and enhance the accessibility of PAHs, thereby boosting the effectiveness of microorganisms that break down PAHs. The presence of rhamnolipids can be attributed to the equilibrium between hydrophobic and hydrophilic properties, as well as their positive charge. Rhamnolipids have biosurfactant properties, making them beneficial for the bioremediation of polluted soil and water. In general, rhamnolipids have proven to be a highly efficient means of removing PAHs from the environment, providing a viable alternative to conventional chemical approaches. Nevertheless, additional investigation is necessary to gain a deeper comprehension of the fundamental principles behind rhamnolipid‐assisted bioremediation and to enhance its implementation in larger real‐world scenarios. This study provides a concise overview of recent research on the utilization of rhamnolipids for bioremediating PAHs in the environment. The article covers the underlying mechanisms, the specific microorganisms employed, and the overall efficacy of the bioremediation process. The utilization of rhamnolipids as a bioremediation tool is examined, along with the difficulties and restrictions of its implementation. The review's conclusion is followed by a discussion on the future directions for studying this topic. [ABSTRACT FROM AUTHOR]

BACKGROUND: Poly‐γ‐glutamic acid (γ‐PGA) is employed extensively in agriculture to enhance soil water retention; however, the underlying mechanism by which γ‐PGA improves soil structure and soybean productivity in arid regions remains poorly understood. A micro‐scale field experiment was conducted in the arid region of northwest China, employing five concentrations of γ‐PGA to investigate its impacts on soybean yield, photosynthesis, and water‐use efficiency, as well as soil aggregates and water distribution. The five levels of γ‐PGA were 0 (CK), 10 (P1), 20 (P2), 40 (P3), and 80 kg ha−1 (P4). RESULTS: The results demonstrated that the application of γ‐PGA significantly improved soybean yield, photosynthesis, and chlorophyll content. It resulted in a decrease in soil aggregate content with a maximum diameter of less than 0.053 mm and an increase in the stability of soil aggregates in the uppermost layer of the soil (0–30 cm). The application of γ‐PGA significantly increased soil water content, particularly in the uppermost layer of the soil, and effectively reduced water consumption and improving water use efficiency in soybeans. Overall, the P3 treatment exhibited the most pronounced improvement of soybean yield, photosynthesis, water‐use efficiency, as well as distribution of soil aggregates and water. The correlation matrix heatmap also revealed a strong correlation between improvement of soybean yield or photosynthesis at various γ‐PGA application levels and the enhancement of soil stability or soil water content. CONCLUSION: The multivariate regression analysis revealed that an optimal application level of 46 kg ha−1γ‐PGA could enhance effectively both yield and water use efficiency of soybean in the arid region of northwest China. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

The two most important abiotic plant stressors that impact plant development and crop yields are water stress and salinity stress. These issues are particularly important in arid and semi‐arid regions. According to a 2019 research paper, “thirty crop species provide 90% of our food, most of which display severe yield losses under moderate salinity.” Moderate salinity is defined as extracted pore‐water salinity in the range of 4–8 dS m−1. Currently, commercially available soil moisture and bulk soil electrical conductivity sensors can estimate in situ soil pore‐water electrical conductivity with suitably calibrated soil moisture and electrical conductivity models for a wide range of soil types and growing media. With knowledge of the pore‐water electrical conductivity it is possible to estimate osmotic tension. Furthermore, there are commercially available dielectric tensiometers that provide soil water tension measurements from the water content of a porous matrix component that is in equilibrium with the water capillary forces in the surrounding soil or growing media. Combining soil moisture and soil water tension measurements enables water retention curves and the hydraulic properties of a soil to be determined. However, the overall ability of a plant to extract water from a soil or substrate is typically dominated by water tension and osmotic tension. Currently, while the technology blocks exist in different commercial offerings, the combination of a water tension and osmotic tension in an integrated sensor does not exist. A key benefit of the porous matrix in a dielectric tensiometer is that electrical measurements include a component of extracted water from the soil or growing media. With the appropriate dielectric characterization of the porous matrix, there should be no need for soil‐specific calibrations. The aim of the paper is to outline the measurement processing that could be implemented into an integrated water tension and osmotic tension sensor. [ABSTRACT FROM AUTHOR]

Ecosystem‐scale photosynthetic efficiency (EPE) is proposed as an effective indicator to quantify gross primary productivity (GPP), but how the coupling between EPE and GPP varies as vegetation resilience decreases has not been evaluated. Here, we quantified forest resilience with optimized Bayesian models. With the use of multisource satellite and modeling data, our study revealed that forests on the Loess Plateau and in the Qinba Mountains in China are experiencing rapid resilience loss and are already facing mortality warnings after 2010. Reductions in resilience also drove the marked decoupling of GPP from EPE. Notably, the decline in resilience was accompanied by a decrease in EPE in about 74% of the forests while GPP increased. The mechanism underlying this decoupling could be attributed to enhanced atmospheric water demand and soil water constraints. The dynamic relationships found here could help to improve forest mortality models and enhance photosynthesis‐based GPP evaluation. Plain Language Summary: The persistence and functionality of forest ecosystems highly depend on their resilience. Low‐resilience forests may be unable to absorb changes and achieve system variable stabilization under perturbations in external drivers and may undergo irreversible system shifts. Reduced resilience is often caused by impaired physiological functions, which inevitably affects forest photosynthetic processes and carbon sinks. Our study on fragile ecosystems in China revealed that forests are rapidly losing resilience and are already facing mortality warnings after 2010. This phenomenon has also led to significant decoupling of carbon sinks from photosynthesis, driven by an elevated atmospheric water demand and soil water deficits. These findings demonstrate that forests will exhibit greater risk of mortality across broad scales under global warming and that photosynthetic proxies cannot be consistently used for evaluating carbon sequestration in ecosystems. Key Points: Early mortality warning signals have been detected for different forest types since 2010A reduction in forest resilience weakens the relationship between the gross primary productivity and photosynthetic efficiencyThe decoupling of forest photosynthesis from carbon sinks exhibits different response patterns to soil water and atmospheric drying [ABSTRACT FROM AUTHOR]

Understanding the dynamics of δ13C and δ18O in modern resin is crucial for interpreting (sub)fossilized resin records and resin production dynamics. We measured the δ13C and δ18O offsets between resin acids and their precursor molecules in the top‐canopy twigs and breast‐height stems of mature Pinus sylvestris trees. We also investigated the physiological and environmental signals imprinted in resin δ13C and δ18O at an intra‐seasonal scale. Resin δ13C was c. 2‰ lower than sucrose δ13C, in both twigs and stems, likely due to the loss of 13C‐enriched C‐1 atoms of pyruvate during isoprene formation and kinetic isotope effects during diterpene synthesis. Resin δ18O was c. 20‰ higher than xylem water δ18O and c. 20‰ lower than δ18O of water‐soluble carbohydrates, possibly caused by discrimination against 18O during O2‐based diterpene oxidation and 35%–50% oxygen atom exchange with water. Resin δ13C and δ18O recorded a strong signal of soil water potential; however, their overall capacity to infer intraseasonal environmental changes was limited by their temporal, within‐tree and among‐tree variations. Future studies should validate the potential isotope fractionation mechanisms associated with resin synthesis and explore the use of resin δ13C and δ18O as a long‐term proxy for physiological and environmental changes. [ABSTRACT FROM AUTHOR]

Summary Soil moisture shapes ecological patterns and processes, but it is difficult to continuously measure soil moisture variability across the landscape. To overcome these limitations, soil moisture is often bioindicated using community‐weighted means of the Ellenberg indicator values of vascular plant species. However, the ecology and distribution of plant species reflect soil water supply as well as atmospheric water demand. Therefore, we hypothesized that Ellenberg moisture values can also reflect atmospheric water demand expressed as a vapour pressure deficit (VPD). To test this hypothesis, we disentangled the relationships among soil water content, atmospheric vapour pressure deficit, and Ellenberg moisture values in the understory plant communities of temperate broadleaved forests in central Europe. Ellenberg moisture values reflected atmospheric VPD rather than soil water content consistently across local, landscape, and regional spatial scales, regardless of vegetation plot size, depth as well as method of soil moisture measurement. Using in situ microclimate measurements, we discovered that forest plant indicator values for moisture reflect an atmospheric VPD rather than soil water content. Many ecological patterns and processes correlated with Ellenberg moisture values and previously attributed to soil water supply are thus more likely driven by atmospheric water demand. [ABSTRACT FROM AUTHOR]

The impact of land variables on temperature forecasts in atmospheric cycling is often underestimated or overlooked. This oversight primarily occurs due to the abundance of meteorological measurements available for assimilation and partly because soil states are assumed to be quickly reset by atmospheric forcing, such as precipitation, justifying no spin‐ups or no updates of soil states during cycling. In this study, by updating soil moisture every 6 hr using different analysis data sets for May 2019, considerable discrepancies were found, highlighting large uncertainties in soil moisture analysis. Different soil moisture analyses produced systematically different temperature forecasts, with errors growing over cycles to be comparable to a typical error magnitude of 2‐m temperature observations (∼2°K). This study demonstrates that temperature forecasts are significantly influenced by whether and how soil moisture is updated, not only near the surface but also up to the low‐mid troposphere and throughout the cycles. Plain Language Summary: This study examines the impact of soil moisture on temperature forecasts in the context of atmospheric cycling. During the 6‐hr cycling for May 2019 over the CONUS domain, updating soil moisture systematically affects temperature forecast bias (>±1°K) in the low‐mid troposphere throughout the cycles. We also observe significant uncertainties across state‐of‐the‐art soil moisture analysis data sets, highlighting the challenges of land data assimilation. Key Points: Temperature forecast errors are significantly affected by whether or how soil moisture is updated in atmospheric cyclingLarge uncertainties are found across different soil moisture analysis data setsUpdating soil moisture alone can mitigate temperature forecast bias in the low‐mid troposphere, systematically improving forecast accuracy [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In root research, hydroponic plant cultivation is commonly used and soil experiments are rare. We investigated the response of 12‐day‐old barley roots, cultivated in soil‐filled rhizotrons, to different soil water potentials (SWP) comparing a modern cultivar (cv. Scarlett) with a wild accession ICB181243 from Pakistan. Water potentials were quantified in soils with different relative water contents. Root anatomy was studied using histochemistry and microscopy. Suberin and lignin amounts were quantified by analytical chemistry. Transcriptomic changes were observed by RNA‐sequencing. Compared with control with decreasing SWP, total root length decreased, the onset of endodermal suberization occurred much closer towards the root tips, amounts of suberin and lignin increased, and corresponding biosynthesis genes were upregulated in response to decreasing SWP. We conclude that decreasing water potentials enhanced root suberization and lignification, like osmotic stress experiments in hydroponic cultivation. However, in soil endodermal cell suberization was initiated very close towards the root tip, and root length as well as suberin amounts were about twofold higher compared with hydroponic cultivation. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This paper addresses the challenge of testing the hypothesis of what the authors call a nested block circular‐compound symmetric (NBCCS) covariance structure for the population covariance matrix. This is a covariance structure which has an outer block compound symmetric structure, where the diagonal blocks are themselves block circular matrices, while the off‐diagonal blocks are formed by all equal matrices. The NBCCS null hypothesis is decomposed into sub‐hypotheses, allowing this way for a simpler way to obtain a likelihood ratio test and its associated statistic. The exact moments of this statistic are derived, and its distribution is carefully examined. Given the complicated nature of this distribution, highly precise near‐exact distributions were developed. Numerical studies are conducted to assess the proximity between these near‐exact distributions and the exact distribution, highlighting the performance of these approximations, even in the case of very small sample sizes. Furthermore, three datasets, on bone mineral content, metabolic rates of glucose, and soil moisture are used to exemplify the practical application of the methodology derived in this study. [ABSTRACT FROM AUTHOR]

Background Aims Methods Results Conclusion Incorporation of cover crop (cc) shoot and root biomass can have different effects on nitrogen (N) dynamics and the transformation of soil‐derived N and cc N.The objective was to determine the effects of different ccs, cc compartments (roots and shoots), and pretreatment of cc biomass (fresh vs. dried) on mineralization processes and on the transformation of soil and cc N following incorporation into a silty loam soil.Soil columns with incorporated 15N‐labeled root and shoot biomass of two cc species (winter rye and oil radish) and different pretreatments (dried and fresh) were incubated for 70 days at a constant temperature and soil moisture (8°C, 40% water‐filled pore space). Carbon and N transformation dynamics were determined repeatedly, distinguishing between N originating from cc biomass and from soil.Net CO2 emission was related to the amount of soluble cell components added with ccs. Net N mineralization was negatively related to the C:N ratio of cc biomass. The incorporation of dried cc biomass caused higher initial soil respiration and N immobilization than fresh biomass. All treatments with cc incorporation showed increased N2O emission. Emitted N2O‐N consisted mainly of cc N (55%–57%) in treatments with fresh shoot biomass, whereas soil N was the main source of N2O (75%) in the treatment with fresh oil radish roots. Recovery of cc 15N was affected by crop compartment and pretreatment. At the end of the incubation, it was 17.5%–42.3% in soil NO3−, 0.1%–8.1% in microbial biomass N, and less than 0.23% of cc N was found in cumulative N2O emission.The incorporation of cc roots and shoots had different effects on N mobilization and immobilization processes and on the partitioning of cc N. These processes can be influenced significantly by pretreatment of the added plant biomass (dried vs. fresh). [ABSTRACT FROM AUTHOR]

Numerical modeling of the recovery of moisture by injecting warm air in the unsaturated zone in a 100 m × 100 m plot of agricultural land in Kuwait, a country located in an arid environment, was conducted to provide “proof of concept” of the technique. If technically and economically feasible, it will be a potential additional source of water that could be exploited for farming activities and other uses. The COMSOL software was used to develop the model and, based on the results of the scenario runs, the effects of different hydraulic and operational parameters, including that of well spacing, on moisture recovery were assessed. In general, the results suggested that the recovery should increase with the increase in the hydraulic conductivity of the unsaturated zone, the amount of heat input, and the pressure differential between the unsaturated zone and the well head. Within the period examined (0 to 11 days), the recovery decreases with the increase in the soil moisture content, possibly due to the fall in relative permeability to moisture‐rich air with the increased water contents in the pore spaces, although the effects may change over a longer period as water contents decrease with moisture recovery. The moisture recovery from the unsaturated zone through the injection of warm air appears to be a feasible proposition from this study that should be demonstrated through a pilot scale experiment in the field. [ABSTRACT FROM AUTHOR]

Invasive plants disrupt the structure and function of ecosystems, causing a decline in their diversity. The coexistence of Solidago canadensis and Erigeron canadensis within shared habitats is a common phenomenon, and the frequent occurrence of co‐invasion has substantial implications for ecosystems. However, the effects of the co‐invasion of two plants on the soil ecosystem across varying degrees of invasion remain uninvestigated. Therefore, we investigated how the co‐invasion of S. canadensis and E. canadensis affects soil physiochemical properties and microorganisms across various degrees of invasion. The invaded regions exhibited significantly lower soil moisture content and pH values than those in the uninvaded areas (p < .05). Additionally, co‐invasion resulted in higher soil organic matter (OM), total nitrogen (TN), total phosphorus (TP), and available phosphorus (AP) contents compared to single invasion by E. canadensis. Furthermore, the invaded regions exhibited a greater diversity of soil bacterial and fungal communities than the uninvaded regions. Under diverse invasion conditions, Actinobacteria and Ascomycota emerged as the predominant phyla of soil bacteria and fungi, respectively, leading to a shift in the soil microbial community structure. Moreover, homogenizing dispersal significantly influenced bacterial community succession, while ecological drift influenced the progression of fungal communities. Using structural equation modeling, this study established significant correlations between soil properties (pH, TN, and nitrate nitrogen) and bacterial interactions (diversity and community assembly) relative to microbial composition. This study revealed the influence of S. canadensis and E. canadensis co‐invasion on soil microbial communities, thereby contributing a theoretical framework delineating the impact of these two invasive plant species. [ABSTRACT FROM AUTHOR]

Fine roots and absorptive roots play key roles in acquiring resources throughout soil profiles and determining plant functions along environmental gradients. Yet, the geographical pattern of carbon allocation in fine roots, particularly in absorptive roots, and their relations with plant sizes and evironment are less understood. We sampled 243 xerophytic shrubs from 63 species distributed along the latitudinal gradient (23°N to 32°N) in dry valleys of southwest China and synthetically measured biomass fractions of plant organs, especially fine roots and absorptive roots (1st to 3rd root order). We identified latitudinal patterns of biomass allocation fractions of organs and their relationships with plant sizes and environmental factors. The latitudinal patterns of both absorptive root and fine‐root fractions followed weak unimodal distributions; stem biomass fraction increased with the latitude, while the leaf biomass fraction decreased. The fraction of fine‐root biomass had negative relationships with plant height and root depth. The fractions of root, fine root, and absorptive root biomass were largely explained by soil moisture. Furthermore, fraction of fine‐root biomass increased in a relatively humid environment. Overall, soil moisture was the most important factor in driving latitudinal patterns of biomass fraction. Our study highlighted that functional redistribution of root system biomass was the critical adaptive strategy along a latitudinal gradient. [ABSTRACT FROM AUTHOR]

Overgeneralization and a lack of baseline data for microorganisms in high‐latitude environments have restricted the understanding of the microbial response to climate change, which is needed to establish Antarctic conservation frameworks. To bridge this gap, we examined over 17,000 sequence variants of bacteria and microeukarya across the hyperarid Vestfold Hills and Windmill Islands regions of eastern Antarctica. Using an extended gradient forest model, we quantified multispecies response to variations along 79 edaphic gradients to explore the effects of change and wind‐driven dispersal on community dynamics under projected warming trends. We also analyzed a second set of soil community data from the Windmill Islands to test our predictions of major environmental tipping points. Soil moisture was the most robust predictor for shaping the regional soil microbiome; the highest rates of compositional turnover occurred at 10–12% soil moisture threshold for photoautotrophs, such as Cyanobacteria, Chlorophyta, and Ochrophyta. Dust profiles revealed a high dispersal propensity for Chlamydomonas, a microalga, and higher biomass was detected at trafficked research stations. This could signal the potential for algal blooms and increased nonendemic species dispersal as human activities increase in the region. Predicted increases in moisture availability on the Windmill Islands were accompanied by high photoautotroph abundances. Abundances of rare oligotrophic taxa, such as Eremiobacterota and Candidatus Dormibacterota, which play a crucial role in atmospheric chemosynthesis, declined over time. That photosynthetic taxa increased as soil moisture increased under a warming scenario suggests the potential for competition between primary production strategies and thus a more biotically driven ecosystem should the climate become milder. Better understanding of environmental triggers will aid conservation efforts, and it is crucial that long‐term monitoring of our study sites be established for the protection of Antarctic desert ecosystems. Furthermore, the successful implementation of an improved gradient forest model presents an exciting opportunity to broaden its use on microbial systems globally. [ABSTRACT FROM AUTHOR]

The sustainability of global agriculture at higher productivity level is a concern owing to climate change, serious environmental footprints, dipping factor productivity and shrinking availability of natural resources, especially. The situation is worsening in the 'Food Bowl of India'—Indo‐Gangetic plains (IGP) by several amalgamated factors, such as declining groundwater, unpredictable precipitation owing to climate change and cultivation of heavy water duty crops. To neutralise these issues, a field experiment was executed for the period 2019–2021 to assess the efficacy of indigenous hydrogels (P‐hydrogel and Superabsorbent polymer hydrogel‐1118) and their application methods viz., seed treatment, slurry application and soil application on crop yield and water productivity, soil moisture dynamics and profitability in a soybean–wheat cropping system under irrigation and rainfed conditions. In both study years (2019–2020 and 2020–2021), due to higher seed germination percentage, irrigation application together with seed treatment and slurry application of superabsorbent polymer hydrogel‐1118 improved system productivity by 8.1%–26.7% and system water productivity by 17.6%–33.8% over control. Wheat grain yield was enhanced by 8.0% (2019–2020) to 32.2% (2020–2021) due to superabsorbent polymer hydrogel‐1118 hydrogel with 10 cm lesser use of irrigation water compared with control (no‐hydrogel). Soil moisture content in 0–15 cm soil layer was also found higher by 1.8%–2.4% in superabsorbent polymer hydrogel‐1118 and P‐hydrogel slurry‐applied plots. Therefore, higher gross profitability (31.8%), net profitability (89.8%) and B:C (26.9%) in wheat could be attributed to increased crop yields when seeds were treated with superabsorbent polymer hydrogel‐1118. Therefore, the utilisation of modified hydrogel application, in the form of seed treatment (seed coating) and slurry application has demonstrated improvement in seed germination, crop yield and water productivity and made soybean–wheat cultivation more economical. This approach presents a feasible solution to achieving a viable production system of soybean and wheat crops by reducing irrigation amounts in the IGP of India, as well as other comparable ecological places worldwide. [ABSTRACT FROM AUTHOR]

Chickpeas are well adapted to rainfed conditions, but a lack of moisture during the reproductive phase can result in lower pod setting and ultimately reduced grain yield. The exact reasons for this reduction are not fully understood, partly because of the lack of information on soil moisture content (SMC) and water use during podding. This study aimed to address this knowledge gap by quantifying the impact of gradual drought on various yield components of desi‐type genotypes using the fraction of transpirable soil water (FTSW) method. Two water treatments were applied at the start of anthesis: well‐watered (WW) and drought‐stressed (DS). The WW was maintained at 24% SMC, whereas the DS was dried to 3% SMC. The results showed that DS caused early podding (3.3 days less), with reductions in plant height (11.4 cm), leaf area (1249.5 cm2), flowers (18.6), pods (27.4), seeds (37.0), grain yield (0.2 g), aboveground dry biomass (11.4 g) and harvest index (0.2 g), while increasing flower abortion (14.6) and seed biomass (1.5 g). However, diverse genotypic responses were observed to treatments, as well as water usage, FTSW and SMC that triggered pods which ranged from 1.12 to 1.89 L, 0.05 to 0.43 and 4.0% to 12.2%, respectively. A positive association between days taken and the amount of water used to terminate pods indicated that quicker‐triggering genotypes, such as Rupali and Genesis 836, consumed less water to develop pods than Flipper, ICCV_06109 and PBA Slasher did. Conversely, the negative association between the amount of water used and the number of pods triggered, seeds and grain yield explained the superior performance of Rupali and Genesis 836. These genotypes extracted less water (FTSW = 0.36 and 0.43; SMC = 10.3% and 12.2%, respectively) to develop pods and maintained favourable photosynthesis at lower transpiration rates for longer periods, allowing them to use residual moisture more efficiently. Our research offers crucial insights that can be beneficial to breeders and physiologists, paving the way for future studies aimed at developing drought‐tolerant genotypes. [ABSTRACT FROM AUTHOR]

Peruvian watergrass (Luziola peruviana J.F. Gmel.) is a perennial weed often found in paddy fields in the southern region of Brazil. Its chemical control is performed mainly by herbicides such as glyphosate in burndown, whose efficacy depends on soil moisture. Under excess‐water soil conditions, glyphosate efficacy is reduced, probably due to reduced translocation and the involvement of photoassimilates partition. Furthermore, little is known about the stress tolerance of these plants subjected to water deficit. Based on that, we performed experiments to verify the effect of soil moisture on the biochemical parameters of Peruvian watergrass and glyphosate translocation to the stolon and roots. Total soluble sugars, sucrose, starch, and glyphosate concentrations in leaves, culms, roots, and glyphosate partitioning were quantified. The malondialdehyde content and the lipid peroxidation increased with the drainage. Under drainage conditions, superoxide production was higher in roots than leaves, while peroxide production was lower in roots than leaves. The electrolyte leakage increased with the drainage and glyphosate application. The total soluble sugar content varied in each organ with a significant increase in the culm 14 days after application in the draining treatment. Sucrose varied considerably and reached its maximum concentration at 21 days after herbicide application. The starch accumulation in the culm was 7 days after applying the highest glyphosate dose. The presence of glyphosate in the roots subjected to soil drainage indicates the movement of this herbicide. In conclusion, soil drainage profoundly impacts Peruvian watergrass physiology, increasing the photoassimilates and glyphosate translocation to the stolon and root. This explains why glyphosate efficacy is higher under drainage conditions. [ABSTRACT FROM AUTHOR]

Watershed water quality modeling to predict changing water quality is an essential tool for devising effective management strategies within watersheds. Process‐based models (PBMs) are typically used to simulate water quality modeling. In watershed modeling utilizing PBMs, it is crucial to effectively reflect the actual watershed conditions by appropriately setting the model parameters. However, parameter calibration and validation are time‐consuming processes with inherent uncertainties. Addressing these challenges, this research aims to address various challenges encountered in the calibration and validation processes of PBMs. To achieve this, the development of a hybrid model, combining uncalibrated PBMs with data‐driven models (DDMs) such as deep learning algorithms is proposed. This hybrid model is intended to enhance watershed modeling by integrating the strengths of both PBMs and DDMs. The hybrid model is constructed by coupling an uncalibrated Soil and Water Assessment Tool (SWAT) with a Long Short‐Term Memory (LSTM). SWAT, a representative PBM, is constructed using geographical information and 5‐year observed data from the Yeongsan River Watershed. The output variables of the uncalibrated SWAT, such as streamflow, suspended solids (SS), total nitrogen (TN), and total phosphorus (TP), as well as observed precipitation for the day and previous day, are used as training data for the deep learning model to predict the TP load. For the comparison, the conventional SWAT model is calibrated and validated to predict the TP load. The results revealed that TP load simulated by the hybrid model predicted the observed TP better than that predicted by the calibrated SWAT model. Also, the hybrid model reflects seasonal variations in the TP load, including peak events. Remarkably, when applied to other sub‐basins without specific training, the hybrid model consistently outperformed the calibrated SWAT model. In conclusion, application of the SWAT‐LSTM hybrid model could be a useful tool for decreasing uncertainties in model calibration and improving the overall predictive performance in watershed modeling. Practitioner points: We aimed to enhance process‐based models for watershed water‐quality modeling.The Soil and Water Assessment Tool‐Long Short‐Term Memory hybrid model's predicted and total phosphorus (TP) matched the observed TP.It exhibited superior predictive performance when applied to other sub‐basins.The hybrid model will overcome the constraints of conventional modeling.It will also enable more effective and efficient modeling. [ABSTRACT FROM AUTHOR]

Various factors influence biocrust effects on infiltration and soil moisture. On China's Loess Plateau, well‐developed moss‐dominated biocrusts reduce infiltration and suppress shrub growth, however, the interrelationships between rainfall conditions and disturbance management to alleviate these impacts are unknown. In a semiarid watershed on the Loess Plateau, we applied two forms of disturbance, scarification (controlled harrowing) and compaction (simulated grazing), at four intensity levels (control‐intact, light, moderate, and heavy) to well‐developed moss‐dominated biocrusts and a bare soil (BS) for comparisons to form eight treatments with three replications. Rainfall intensity and depth, soil moisture, run‐off, and sediment yield were measured during the rainy season (July–October). In total, well‐developed biocrusts did not significantly affect infiltration but reduced soil moisture at depths of 120–180 cm (p < 0.05), and disturbance increased infiltration and deep soil moisture beneath biocrusts (p < 0.05). Rainfall conditions changed the effects of biocrusts and disturbance. Under long, low‐intensity rainfall, moss‐dominated biocrust infiltration was slightly greater than BS, but scarification increased infiltration and compaction reduced it (p < 0.001). Under short, high‐intensity rainfall, biocrusts reduced infiltration, and disturbance intensity increased infiltration and sediment yields (p < 0.001). Light grazing or using light or moderate scarification improves well‐developed moss‐dominated biocrust infiltration in the pastures during May–June before the rainy season during July–October on the Loess Plateau, while avoiding increased soil erosion. [ABSTRACT FROM AUTHOR]

Restoring biological crust (biocrust) in disturbed drylands is challenging due to the difficult environmental conditions, such as limited soil moisture, low soil nutrients, and extreme temperatures, that impede growth. Understanding how the key components of biocrust—mosses, lichens, and cyanobacteria—react to different environmental factors informs the optimal timing, locations, and species composition for biocrust reintroduction, thereby increasing the likelihood of establishment. Here, we inoculated soils with a diverse range of biocrust organisms, analogous to seeding an area with diverse vascular plant seeds, and varied environmental conditions to observe how these changes influenced the development and functions of reintroduced biocrust. We found that by manipulating soil texture and time spent wet, we can change the proportional cover of biocrust within a restoration‐like setting. Specifically, we found that 4 months after inoculation, finer textured soils that received more water become dominated by moss cover, while coarser textured soils with less water remained dominated by cyanobacteria cover, and the interactions between texture and time spent wet strongly influenced cover. We found biocrust morphological group cover had a small, but detectable, effect on ecosystem functions (soil stability and nitrogenase activity, a proxy for nitrogen fixation), but that environmental conditions had a stronger impact on the functions we measured. Manipulative experiments in controlled environments, like this one, can help elucidate the mechanisms underlying the establishment rate and patterns of biocrusts post‐inoculation, and inform implementation of inoculations in the field. [ABSTRACT FROM AUTHOR]

Nutrient cycling in desert ecosystems is heavily reliant on the fine root turnover and litter decomposition processes of dominant plant species. Based on field investigations and laboratory experiments, we explored fine root production (FRP) and turnover of Salsola passerina in Alxa steppe desert, and assessed fine root and leaf litter input and its correlation with soil C and N stocks, and then compared the variability of soil physicochemical properties at the site below and the interspace of S. passerina canopy. Results showed that fine root biomass dynamics of S. passerina were consistent with soil water content. Annual FRP of S. passerina was 243.3 g m−2 yr−1 and the turnover rate was 2.0 per year. S. passerina contributed 172.2 g C m−2 and 6.8 g N m−2 to soil from its fine root senescence and leaf litter input annually. Compared to the canopy interspace, the soil texture and fertility beneath the shrubs significantly improved, while the soil salinity decreased. The results indicated that the activities of desert shrub growth provided the degraded soil with abundant nutrients through fine root turnover and litter decomposition processes, which promoted soil texture and nutrition heterogeneity at the stand scale, and played an important role in degraded dryland restoration. [ABSTRACT FROM AUTHOR]

Spring‐fed wetlands within arid and semiarid systems are hotspots for endemism and distribution of rare plants. Interactions among groundwater and the geomorphic and climatic features of the setting control the abiotic conditions, particularly soil salinity and moisture, that support these plants. However, water uncertainty and land use change challenge the persistence of conditions necessary to support rare plant communities. Wetland management can be implemented to sustain abiotic processes that support rare plant communities, but key information is needed to guide management practices. In this study, we evaluate the relationships of rare plants to abiotic conditions in a managed spring‐fed arid wetland. Soil salinity and moisture conditions were monitored and related to the presence and abundance of rare plants within management units. Soil salinity and moisture variability were related to groundwater dynamics near springs, but wetland management influenced variability in seasonally flooded areas. Permanently saturated conditions and low soil salinities during the spring season supported higher plant diversity and the presence and greater abundance of rare plants. Rare plant presence and abundance were negatively related to low soil moisture, particularly in the summer. Results indicate that increases in soil salinity during the early establishment of plants may affect their distribution and abundance, an important management consideration in arid landscapes and hydrologically altered systems. Our findings inform the restoration and management of rare plant communities and contribute to the management of spring‐fed arid wetlands. [ABSTRACT FROM AUTHOR]

Previous studies have demonstrated that saturated normally consolidated and lightly over‐consolidated clays undergo contraction when heated due to a reduction in preconsolidation pressure. A linear constitutive model is proposed to describe the thermal contraction, with this model, governing equations are developed for the coupled thermo‐hydro‐mechanical (THM) consolidation induced by a prefabricated vertical thermo‐drain (PVTD). Corresponding semi‐analytical solutions are derived employing the Laplace transform and validated via comparison with experimental results, existing numerical model, and custom finite element method (FEM) model. Subsequently, comprehensive parametric analyses are carried out to investigate the THM coupling consolidation behaviors of the clays. Outcomes show that aside from surcharge load, generation of excess pore water pressure in soils can also be induced by thermal contraction, difference in thermal expansibility between pore water and soil grains, and thermo‐osmosis, where the influence of thermal contraction on the excess pore water pressure is the most prominent among the three factors. [ABSTRACT FROM AUTHOR]

This research used the Revised Universal Soil Loss Equation (RUSLE) with Sediment Delivery Ratio (SDR) model. The analytic hierarchy process (AHP) method, while also incorporating the use of a geographic information system (GIS) and remote sensing (RS) to predict the annual soil loss rate and spatialise the processes of water erosion at the scale of the Loukkos Watershed, Morocco. The RUSLE model and AHP parameters were estimated using RS data, and the erosion vulnerability zones were determined using GIS. We used five parameters, including precipitation erosivity, soil erodibility, slope length and steepness, vegetation cover, and soil erosion control practices in the RUSLE. For the AHP technique, we used seven geo‐environmental factors, including annual average precipitation, drainage density, lineament density, slope, soil texture, land use/land cover and landform maps. The results of RUSLE indicated that the average annual soil loss varied from 0 to 2388.27 t·ha−1·year−1. The total estimated annual potential soil loss was approximately 40 790 220.11 t·ha−1·year−1, and a sediment yield estimated by RUSLE‐SDR was 8 647 526.66 t·ha−1·year−1, equivalent to 6.65 Mm3. This value is very close to the measured value of 6.81 Mm3, for a difference of 0.16 Mm3. Furthermore, the results of the AHP indicate that the soil erosion potential index varies from 0 to 0.205315 t·ha−1·year−1. Overall, nearly 13.7% of the area suffered from severe soil erosion exceeding 50 t·ha−1·year−1. Approximately 80% of the Loukkos Watershed area experienced only slight erosion, while the remaining 6% incurred moderate erosion. Integrating GIS and RS into the RUSLE model and AHP helped us robustly estimate the extent and degree of erosion risk. Territorial decision‐makers should adopt our results to develop soil conservation strategies, water management plans and other necessary soil and water conservation measures for this region. [ABSTRACT FROM AUTHOR]

The timing and progression of the spring thaw transition in high northern latitudes (HNL) coincides with warmer temperatures and landscape thawing, promoting increased soil moisture and growing season onset of gross primary productivity (GPP), heterotrophic respiration (HR), and evapotranspiration (ET). However, the relative order and spatial pattern of these events is uncertain due to vast size and remoteness of the HNL. We utilized satellite environmental data records (EDRs) derived from complementary passive microwave and optical sensors to assess the progression of spring transition events across Alaska and Northern Canada from 2016 to 2020. Selected EDRs included land surface and soil freeze‐thaw status, solar‐induced chlorophyll fluorescence (SIF) signifying canopy photosynthesis, root zone soil moisture (RZSM), and GPP, HR, and ET as indicators of ecosystem carbon and water‐energy fluxes. The EDR spring transition maps showed thawing as a precursor to rising RZSM and growing season onset. Thaw timing was closely associated with ecosystem activation from winter dormancy, including seasonal increases in SIF, GPP, and ET. The HR onset occurred closer to soil thawing and prior to GPP activation, reducing spring carbon (CO2) sink potential. The mean duration of the spring transition spanned ∼6 ± 1.5 weeks between initial and final onset events. Spring thaw timing and maximum RZSM were closely related to active layer thickness in HNL permafrost zones, with deeper active layers showing generally earlier thawing and greater RZSM. Our results confirm the utility of combined satellite EDRs for regional monitoring and better understanding of the complexity of the spring transition. Plain Language Summary: The transition from winter to spring in high northern latitudes coincides with warming and thawing temperatures, the release of soil moisture, and the start of the growing season. The pattern of spring transition events is hard to monitor due to vast size and remoteness of Arctic tundra and boreal forest. Here, we used environmental data records (EDRs) from recent satellite observations (2016–2020) to map spring transition events across Alaska and Northern Canada. The EDRs included surface and soil freeze‐thaw status, soil moisture, vegetation productivity and soil respiration, and evapotranspiration. The EDRs were used to classify the timing and order of spring activation in these processes. Spring thawing was closely linked with increased soil moisture, which coincided with the start of growing season. Rising carbon dioxide (CO2) emissions from thawing soils generally preceded ecosystem uptake of CO2 from photosynthesis, reducing the spring carbon sink for atmosphere greenhouse gas emissions. On average, the spring transition spanned ∼6 weeks between initial and final onset events, with earlier timing in boreal forests than tundra. Earlier spring thawing and greater soil moisture levels also coincided with more extensive permafrost thawing. The satellite EDRs were effective in capturing multiple spring transition events and their climate sensitivity. Key Points: Satellite monitoring of complex of spring transition events in high northern latitudesSpring metrics linked with thaw‐related shifts in soil moisture and respiration, productivity, and water and energy fluxesSpring transition spans almost 6 weeks between initial landscape thaw and final growing season onset [ABSTRACT FROM AUTHOR]