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Aims: Plant and soil nitrogen (N) isotope ratios (δ15N) have been used as indicators of N cycling processes of ecosystems. However, the effects of N and Phosphorus (P) addition on δ15N values and their indicative roles in N-cycling in legume-dominated tropical forests remain poorly understood. Methods: We compared leguminous (Acacia auriculiformis) and non-leguminous (Eucalyptus urophylla) forests in terms of N concentration and δ15N in the leaf–litter–soil continuum under long-term N and P addition. Typical soil N-cycling processes, including rates of mineralization, nitrification, and N loss, were also examined to determine the differences between the corresponding 15N signatures observed in the leguminous and non-leguminous forests. Results: The plants in both tropical forests were found to be 15N-depleted. N addition significantly increased the foliage δ15N in understorey species in the non-leguminous but not the leguminous forest. In both forests, the addition of N resulted in an increase in nitrate (NO3−) leaching and nitrous oxide (N2O) emission. Conversely, P addition led to a decrease in NO3− leaching and N2O emission. Additionally, foliage δ15N was positively correlated with soil N loss rates (N2O emission and NO3− leaching) in the non-leguminous forest but showed no correlation in the leguminous forest. Conclusions: In contrast to the traditional convention derived from non-leguminous forests, our results suggest that foliar 15N isotope signals are not applicable for indicating the soil N dynamic status of leguminous forests. This study highlights the importance of distinguishing legumes from other plant species in terrestrial N-cycling models when incorporating 15N isotope signals. [ABSTRACT FROM AUTHOR]

Background and aims: Forest management practices affect soil carbon dynamics, particularly by changing the diversity of aboveground plant functional groups. However, we have a limited understanding of the underlying mechanisms for how plant management affects soil respiration in planted forest ecosystems. Methods: We conducted a 3-year manipulation experiment of plant functional groups that included understory removal, tree root trenching, and fertilization treatments in 2-year-old and 6-year-old Eucalyptus plantations in the subtropical region, to explore the responses of soil carbon emission and microbial community composition. Results: Soil respiration was significantly suppressed by understory removal (-38%), tree root trenching (-41%), and their interactions (-54%), but fertilization alone and in interactions had no significant effect. Soil bacterial and fungal diversity was negatively affected by understory removal and tree root trenching, respectively. Soil respiration and microbial diversity were lower in younger plantations. Reductions in soil carbon emissions were associated with losses of plant functional groups and soil microbial diversity, while increases in soil respiration were associated with soil physicochemical factors, soil temperature, and plantation age. Conclusions: The results indicated that understory removal and tree root trenching strongly affected soil respiration, while the power effects were regulated by soil microbial community and soil properties in contrast plantation ages. Our findings highlight that plant management is of great significance to the soil carbon emission processes in afforested plantations. [ABSTRACT FROM AUTHOR]

New soil organic carbon (SOC) formation in cropland from straw/stover or manure input is a vital source of SOC for climate change mitigation. However, location and variations in the efficiency, specifically the ratio of new SOC formation to organic C input (NCE), remain unquantified globally. In this study, the spatial variability of cropland NCE from straw/stover or manure input and explanatory factors were determined by analyzing 897 pairs of long‐term field measurements from 404 globally distributed sites and by mapping grid‐level cropland NCEs. The global NCE for paddy and upland averaged 13.8% (8.7%–25.1%, 5th–95th percentile) and 10.9% (6.8%–17.3%), respectively. The initial SOC and the clay content of soil, rather than temperature, were the most important factors regulating NCE. A parabola with an apex at approximately 17 g kg−1 between the initial SOC and NCE was resolved, and a positive correlation between soil clay content and NCE was observed. High‐resolution mapping of the global NCE derived from manure/straw and insight into NCE dynamics provide a benchmark for diagnosing cropland soil C dynamics under climate change and identifying priority regions and actions for C management. [ABSTRACT FROM AUTHOR]

The magnitude of terrestrial carbon (C)‐climate feedback largely depends on the temperature sensitivity of soil organic matter (SOM) decomposition (Q10). However, our understanding of determinants of Q10 for SOM fractions such as particulate and mineral‐associated organic matter (POM and MAOM, respectively) is still inadequate. Particularly, it remains unclear whether microbial effects on Q10 are fraction‐dependent, which induces large uncertainties in projecting soil C dynamics. Here, we conducted large‐scale topsoil sampling on the Tibetan Plateau, in combination with SOM fractionation and 300‐day laboratory incubation to assess SOM fraction‐dependent linkages between Q10 and microbial properties. We found that compared with MAOM, POM had larger Q10 and greater microbial diversity, and also structured distinct microbial communities as well as their co‐occurrence patterns. Furthermore, associations of Q10 with microbial properties differed between the two SOM fractions. Bacterial community composition and relative abundance of bacterial keystone taxa affected Q10 for POM and MAOM respectively, while bacterial alpha diversity showed opposite relationships with Q10 for POM and MAOM. These findings highlight the necessity of incorporating SOM fraction‐dependent microbial properties and their linkages with Q10 into Earth system models to accurately predict terrestrial C‐climate feedback. [ABSTRACT FROM AUTHOR]

The spread of Ganoderma disease in oil palm plantations is affected by several factors, one of the most significant being the soil type. Different soil types influence the availability of nutrients and moisture, which can affect the growth and spread of Ganoderma. This study investigates the impact of spodosols and ultisols on soil macronutrient dynamics and their effect on microbial populations, ultimately influencing Ganoderma distribution. Using a nested sampling design, we collected data from 120 palms across 411 hectares. We analyzed the impact of soil type (sand, ultisol) on soil pH, organic carbon, macronutrients (P-total, P-Bray, Exchangeable K, Exc-Mg, Exc-Ca), and bacterial and fungal populations at 1 m, 2 m, and 3 m distances from infected and healthy palms. Data analysis employed Two-Way ANOVA. The results reveal that soil pH and organic carbon positively influenced Ganoderma incidence in spodosol soil. At the same time, macronutrients P-total, P-Bray, and K had positive interactions with the disease in both soil types. Conversely, Exc-Mg and Exc-Ca showed positive interactions in spodosol soil but negative interactions in ultisol soil. Nitrogen had no significant impact on spodosol soil. Regarding microbial populations, ultisol soil exhibited higher bacterial populations around infected palms (23.4% at 1 m and 12.5% at 3 m). Spodosol soil showed higher bacterial populations further away (2.3% at 1m and 41.3% at 3 m). Fungal populations were higher in ultisol soil compared to spodosol soil for infected palms (27.01 x 106 cfu/g and 26.00 x 106 cfu/g, respectively). This study highlights the complex interplay between soil type, macronutrients, microbial populations, and the spread of Ganoderma. These findings inform the development of effective disease management strategies for oil palm plantations. [ABSTRACT FROM AUTHOR]

Vadose zone soil moisture is often considered a pivotal intermediary water reservoir between surface and groundwater in semi-arid regions. Understanding its dynamics in response to changes in meteorologic forcing patterns is essential to enhance the climate resiliency of our ecological and agricultural system. However, the inability to observe high-resolution vadose zone soil moisture dynamics over large spatiotemporal scales hinders quantitative characterization. Here, utilizing pre-existing fiber-optic cables as seismic sensors, we demonstrate a fiber-optic seismic sensing principle to robustly capture vadose zone soil moisture dynamics. Our observations in Ridgecrest, California reveal sub-seasonal precipitation replenishments and a prolonged drought in the vadose zone, consistent with a zero-dimensional hydrological model. Our results suggest a significant water loss of 0.25 m/year through evapotranspiration at our field side, validated by nearby eddy-covariance based measurements. Yet, detailed discrepancies between our observations and modeling highlight the necessity for complementary in-situ validations. Given the escalated regional drought risk under climate change, our findings underscore the promise of fiber-optic seismic sensing to facilitate water resource management in semi-arid regions. A fiber-optic seismic sensing principle provides a spatiotemporal view of vadose zone soil moisture dynamics, offering a scalable solution for enhanced long-term, large-scale water resource management in face of climate variability. [ABSTRACT FROM AUTHOR]

Understanding the alterations in soil microbial communities in response to climate warming and their controls over soil carbon (C) processes is crucial for projecting permafrost C-climate feedback. However, previous studies have mainly focused on microorganism-mediated soil C release, and little is known about whether and how climate warming affects microbial anabolism and the subsequent C input in permafrost regions. Here, based on a more than half-decade of in situ warming experiment, we show that compared with ambient control, warming significantly reduces microbial C use efficiency and enhances microbial network complexity, which promotes soil heterotrophic respiration. Meanwhile, microbial necromass markedly accumulates under warming likely due to preferential microbial decomposition of plant-derived C, further leading to the increase in mineral-associated organic C. Altogether, these results demonstrate dual roles of microbes in affecting soil C release and stabilization, implying that permafrost C-climate feedback would weaken over time with dampened response of microbial respiration and increased proportion of stable C pool. Understanding microbial responses to climate warming is crucial for projecting permafrost carbon-climate feedback. Here, the authors reveal dual microbial roles in promoting both soil carbon release and stable soil carbon accrual under warming scenario. [ABSTRACT FROM AUTHOR]

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Nutrient management in coffee-based agroforestry systems plays a critical role in soil nitrogen (N) cycling, but has not been well documented. The objective of this study was to evaluate the effect of coffee canopy management and fertilization on soil N dynamics. This study used a randomized complete block design (2 × 3 × 2) with four replications. There were three factors: 1) coffee canopy management (T1: Pruned, T2: Unpruned), 2) fertilizer type (O: Organic, I: Inorganic; M: 50% Organic + 50% Inorganic), and 3) fertilizer dose (D1: low, D2: medium, D3: high). Soil N dynamic indicators (i.e., total N, ammonium (NH4+), nitrate (NO3−), net N-NH4+, net N-NO3−, soil microbial biomass N) were measured at two soil sampling depths (0–20 cm and 20–40 cm). Results showed that pruning increased soil total N and microbial biomass N (MBN) by 10–56% relative to unpruned coffee trees. In contrast, the unpruned coffee canopy had 15–345% higher NH4+, NO3−, net N-NH4+, net N-NO3−, and microbial biomass N concentration than pruned coffee. Mixed fertilizer application increased NO3− and net N-NH4+ accumulation by 5–15% relative to inorganic and organic fertilizers. In addition, medium to high dose fertilization led to a 19–86% higher net N-NO3− concentration and microbial biomass N as compared to low dose fertilization. The treatment of no pruning and mixed fertilizer at low to medium doses was the optimal management strategy to maintain soil available N, while pruning combined with organic fertilizer has the potential to improve soil total N and MBN. [ABSTRACT FROM AUTHOR]

By changing the physicochemical and biological properties of soil, erosion profoundly affects soil nitrogen levels, but knowledge about the erosion impact on soil nitrogen (N) dynamics is still rather incomplete. We compared soil N contents at the early stage of vegetation self-restoration in response to soil erosion thickness (0, 10, 20, 30 and 40 cm), by conducting a simulated erosion experiment on sloping arable land in the dry-hot valley of Yunnan Province, southwestern China. The results showed total nitrogen (TN), ammonium nitrogen (NH4+-N) and nitrate nitrogen (NO3−-N) contents reduced with increasing soil erosion thickness and decreased significantly at the soil erosion thickness of 10, 40 and 10 cm in the rainy season and 30, 10 and 10 cm in the dry season compared with 0 cm. Structural equation modeling (SEM) indicated that soil erosion thickness and seasonal variation were the important drivers of mineral nitrogen (NH4+-N and NO3−-N) content. Soil erosion thickness indirectly affected mineral nitrogen through negative on TN, carbon content and Diazotrophs (nifH genes). Dry–wet season change had an effect on mineral nitrogen mediated by arbuscular mycorrhizal fungi (AMF) and nifH genes. We also found AMF had a promotion to nifH genes in eroded soil, which can be expected to benefit nitrogen fixing. Our findings highlight the importance of considering soil erosion thickness and sampling time for nitrogen dynamics, in particular, the investigation of nitrogen limitation, in the early stage of vegetation self-restoration. [ABSTRACT FROM AUTHOR]

Sandbars are commonly encountered in coastal environments, acting as natural protections during storm events. However, the sandbar response to waves and possible shear failure is poorly understood. In this research, a two–dimensional numerical model is settled to simulate the wave-induced sandbar soil dynamics and instability mechanism. The model, which is based upon the Reynolds-averaged Navier–Stokes (RANS) equations and Biot's consolidation theory, is validated using available experiments. Parametric studies are then conducted to appraise the impact of the wave parameters and soil properties on soil dynamics. Results indicate that the vertical distribution of the maximum vertical effective stress in the sandbar is different from that in the flat seabed, which decreases rapidly along the soil depth and then increases gradually. The impact of soil permeability and saturation on the vertical effective stress distribution around the sandbar also differ from that in the flat seabed. Unlike the flat seabed, the vertical distribution of shear stress in the sandbar increases with an increasing wave period. The sandbar soil shear failure potential is discussed based upon the Mohr–Coulomb criterion. Results show that the range of shear failure around the sandbar is wider and the depth is deeper when the wave trough arrives. [ABSTRACT FROM AUTHOR]

Subalpine forests provide crucial ecosystem services and are increasingly threatened by human alterations like bare-cut slopes from highway construction. External soil spray seeding (ESSS) is often employed to restore these slopes, but the cement it introduces can negatively affect soil fungi, which are vital for the ecological sustainability of restored slopes. Despite previous extensive discussions about ESSS-restored slopes, fungal dynamics and their underlying ecological mechanisms during ESSS-based restorations still remain elusive. Here, we conducted a 196-day simulation experiment using natural soils from a subalpine forest ecosystem. By using nuclear ribosomal internal transcribed spacer (ITS) sequencing, we revealed soil fungal dynamics and their ecological mechanisms during simulated ESSS-based restorations. Results showed a decline in fungal α-diversity and significant shifts in community structures from the initial day to day 46, followed by relative stabilities. These dynamics were mainly characterized by ectomycorrhizal, plant pathogenic, and saprotrophic fungi, with ectomycorrhizal fungi being depleted, while saprotrophic and pathogenic fungi showed enrichment over time. Shifts in nitrate nitrogen ( NO 3 − −N) content primarily regulated these dynamics via mediating homogeneous selections. High NO 3 − −N levels at later stages (days 46 to 196, especially day 46) might exclude those poorly adapted fungal species, resulting in great diversity loss and community shifts. Despite reduced homogeneous selections and NO 3 − −N levels after day 46, fungal communities did not show a recovery but continued to undergo changes compared to their initial states, suggesting the less resilient of fungi during ESSS-based restorations. This study highlights the need to manage soil NO 3 − −N levels for fungal communities during ESSS-based restorations. It provides novel insights for maintaining the ecological sustainability of ESSS-restored slopes and seeking new restoration strategies for cut slopes caused by infrastructure in subalpine forests. [ABSTRACT FROM AUTHOR]

Determining soil hydraulic properties is complex, posing ongoing challenges in managing subsurface and agricultural practices. Electrical resistivity tomography (ERT) is an appealing geophysical method to monitor the subsurface due to its non‐invasive, easy‐to‐apply and cost‐effective nature. However, obtaining geoelectrical tomograms from raw measurements requires the inversion of an ill‐posed problem, which causes smoothing of the actual structure. Furthermore, the spatial resolution is determined from the distances in the electrode placement, thus inherently upscaling the obtained structure. This study explores the applicability of physics‐informed neural networks (PINNs) for upscaling permeability and petrophysical relations and monitoring water dynamics at heterogeneous soils using time‐lapse geoelectrical data. High‐resolution numerical simulations mimicking water infiltration were used as benchmarks. Synthetic ERT surveys with electrode spacing 10 times larger than the numerical model resolution were conducted to provide 2D electrical tomograms. The tomograms were fed to a PINNs system to obtain the permeability, petrophysical relations, and water content maps. An additional PINNs system incorporating water content measurements was trained to examine measurement sensitivity. Results have shown that the PINNs system could produce reliable results regarding the upscaled permeability and petrophysical relations fields. Water dynamics at the subsurface was accurately predicted with an average error of ∼3%. Adding water content measurements to PINNs training improved the system outcomes, mainly at the ERT low sensitivity zones. The PINNs system reduced water saturation errors by more than 30% compared to the common practice of directly translating the geoelectrical tomograms to water saturations using known, homogeneous petrophysical relations. Key Points: Physics‐informed neural networks were applied for simultaneously upscaling heterogeneous soil physical propertiesTraining data relied on inverted 2D geoelectrical tomogramsThe PINNs system was able to reproduce the upscaled water saturation maps during an infiltration scenario [ABSTRACT FROM AUTHOR]

The study gives an estimate of the effect of four methods most often used in hydrological models to calculate the potential evapotranspiration—Penman–Monteith, Priestley–Taylor, Oudin, and Hargreaves, which differ in complexity and meteorological data requirements—on the efficiency and the results of simulating the dynamics of water balance components. The methodological base of the hydrological simulation was the widely known HBV conceptual model, in which the actual evapotranspiration is associated with the current state of a storage, which simulates the dynamics of soil moisture content. The objects of the study were 18 catchments with areas from 2.4 to 755 km2, located within the former Primorskaya Water-Balance station, the data of which were used in calculations of potential evapotranspiration and simulations of runoff. The comparison of simulation results with observations showed that the model values of evapotranspiration at the use of physically sound methods are in better agreement with the Budyko's procedure of determination of potential evapotranspiration. The analysis of model sensitivity to the input potential evaportranspiration showed that the use of physically based methods to calculate the potential evapotranspiration has no general effect on the efficiency of runoff hydrograph simulation of the studied objects. At the same time, in the case when empirical models of evapotranspiration are used, the uncertainty in the results of calculation of potential evapotranspiration should be compensated for by model parameters that are less physically substantiated, which, in turn, can lead to distortion of the dynamics of water balance components and runoff genetic components. [ABSTRACT FROM AUTHOR]

This study focused on the hydrophysical characteristics of an abandoned limestone quarry in Czechia. Six sites were examined; two sites were undergoing natural succession (the Quarry Wall and Reed Canary Grass plots, which had undeveloped arboreal layers) and four sites were undergoing managed forest reclamation. Of the four forest reclamation sites, three were classified as prospering (the Prospering Lime, Prospering Maple and Prospering Lime + Oatgrass plots) and one was in decline (the Declining Larch + Lime plot). The arboreal layer included small-leaved lime (Tilia cordata Mill.), sycamore maple (Acer pseudoplatanus L.), and European larch (Larix decidua Mill.). Our results showed that Lime + Oatgrass plot retained more water than other plots. Field soil moisture measurements indicated that throughout the 1096-day monitoring period, only the soils at the successional sites reached the wilting point (Quarry Wall plot: 159 days; Reed Canary Grass plot: 43 days). Soil heterogeneity in the reclaimed areas was due to variation in the soil profile depth, disturbance from mining activities, reclamation efforts, and the availability of quality soil material. Soil conditions and the dynamics at the quarry created less than ideal conditions for tree regeneration. This primarily relates to limiting and significantly heterogeneous successional plots. [ABSTRACT FROM AUTHOR]

Traditional hydrological model calibration using limitedly available streamflow data often becomes inadequate, particularly in dry climates, as the flow regimes may abruptly vary from arid conditions to devastating floods. Newly available remote-sensing-based datasets can be supplemented to overcome such inadequacies in hydrological simulations. To address this shortcoming, we use multi-variable-based calibration by setting up and calibrating a lumped-hydrological model using observed streamflow and remote-sensing-based soil moisture data from Soil Moisture Active Passive Level 4. The proposed method was piloted at the Maduru Oya River Basin, Sri Lanka, as a proof of concept. The relative contributions from streamflow and soil moisture were assessed and optimised via the Kling–Gupta Efficiency (KGE). The Generalized Reduced Gradient non-linear solver function was used to optimise the Tank Model parameters. The findings revealed satisfactory performance in streamflow simulations under single-variable model validation (KGE of 0.85). Model performances were enhanced by incorporating soil moisture data (KGE of 0.89), highlighting the capability of the proposed multi-variable calibration technique for improving the overall model performance. Further, the findings of this study highlighted the instrumental role of remote sensing data in representing the soil moisture dynamics of the study area and the importance of using multi-variable calibration to ensure robust hydrological simulations of river basins in dry climates. [ABSTRACT FROM AUTHOR]

Landslides or slope failure pose a significant risk to human lives and infrastructures. The stability of slopes is controlled by various hydrological processes such as rainfall infiltration, soil water dynamics, and unsaturated soil behavior. Accordingly, soil hydrological monitoring and tracking the displacement of slopes become crucial to mitigate such risks by issuing early warnings to the respective authorities. In this context, there have been advancements in monitoring critical soil hydrological parameters and slope movement to ensure potential causative slope failure hazards are identified and mitigated before they escalate into disasters. With the advent of the Internet of Things (IoT), artificial intelligence, and high-speed internet, the potential to use such technologies for remotely monitoring soil hydrological parameters and slope movement is becoming increasingly important. This paper provides an overview of existing hydrological monitoring systems using IoT and AI technologies, including soil sampling, deploying on-site sensors such as capacitance, thermal dissipation, Time-Domain Reflectometers (TDRs), geophysical applications, etc. In addition, we review and compare the traditional slope movement detection systems, including topographic surveys for sophisticated applications such as terrestrial laser scanners, extensometers, tensiometers, inclinometers, GPS, synthetic aperture radar (SAR), LiDAR, and Unmanned Aerial Vehicles (UAVs). Finally, this interdisciplinary research from both Geotechnical Engineering and Computer Science perspectives provides a comprehensive state-of-the-art review of the different methodologies and solutions for monitoring landslides and slope failures, along with key challenges and prospects for potential future study. [ABSTRACT FROM AUTHOR]

This study investigates the spatial and temporal heterogeneity of soil moisture on slopes of China's northeastern black soil region, focusing on the effects of terrain adjustment and vegetation. Soil moisture dynamics in the 0–60 cm soil layer were measured at 10 cm intervals using the TRIME-PICO64 TDR® device on slopes with similar gradients representing three land use types: transverse ridge tillage (TRT) farmland, terraced fields (TFs) farmland, and pure forest woodland (WL). The results indicate significant variations in soil moisture content and water storage across different land use types in the order of TF > TRT > WL. The study further identified that soil bulk density, porosity, and water-holding indicators were in the order of WL > TF > TRT, inconsistent with the soil moisture results, indicating that soil quality cannot be the sole reason for the differences in moisture. The moisture differences between farmland types (TRT and TF) and WL are substantial, especially during the rainy season. In the rainy season (0–60 cm) and the dry season (30–60 cm), significant differences in moisture content are observed (p < 0.05). Significant differences in moisture content between farmland types are found at 0–40 cm during the rainy season and at 0–10 cm during the dry season. In the rainy season, soil moisture for TRT and TFs first decreases from 26.76% and 30.85% to 22.44% and 25.38%, then slightly increases to 27.01% and 27.07% along the slope. Meanwhile, WL displays the opposite pattern on upper, relatively steep slopes, with soil moisture increasing from 16.66% to 17.81%, and exhibits a pattern of change similar to TRT and TFs on lower, gentler slopes. TFs consistently show higher soil moisture and water storage at all slope positions than TRT and WL. TFs improve soil quality, reduce erosion and sedimentation, and shift the lowest soil moisture content to a lower slope position. During the dry season, soil moisture differences between slope positions for TRT and WL were small. In general, terracing can effectively modulate moisture distribution along slopes, increasing moisture by an average of 0.26~12.43%, while afforestation, despite improving soil quality, leads to an 18.14~31.13% reduction in soil moisture content, with the impact being particularly significant during the rainy season. These findings provide important insights for optimizing land use and ecological construction, including keeping the balance between soil and water conservation, especially for sub-humid slope terrain areas. [ABSTRACT FROM AUTHOR]

Background Aims Methods Results Conclusions The current transformation of the entire energy system leads to a large‐scale expansion of extra‐high‐voltage underground transmission lines (UTL). Knowledge of the impact on soil temperature and soil moisture dynamics is fundamental for environmental evaluation.We investigated the impact of an existing 320 kV underground cable in continuous operation on soil temperature and moisture dynamics.A soil‐monitoring programme was established at four study sites in Western Germany. Data were continuously recorded in soil up to 120 cm depth using soil sensors over a period of 1 year.Soil warming was in a range of 0.6 K in the topsoil, approx. 1–1.3 K in the rooting zone and 1.7 K in the subsoil at 120 cm depth and was restricted mainly to the immediate vicinity of the cable route. Likewise, the impact on soil moisture dynamics was on average in a range of −1.00 wt.‐% in 0–60 cm depth and −2.45 wt. 2‐% in the subsoil relative to control. Although at a calculated maximum load capacity of 100% in regular operation, soil warming might remain moderate, with 1.5 K in the topsoil, 2.3–3.1 K in the rooting zone and 4.1 K in the subsoil.It is assumed that the reasons for the low‐to‐moderate influence of the UTL are to be found in the operational cable load (on average 65%), heat loss of cables (approx. 12 W m−1 per cable) and the quality of the imbedding material for the cables. [ABSTRACT FROM AUTHOR]

In recent years, machine learning (ML) algorithms have gained substantial recognition for ecological modeling across various temporal and spatial scales. However, little evaluation has been conducted for the prediction of soil organic carbon (SOC) on small data sets commonly inherent to long-term soil ecological research. In this context, the performance of ML algorithms for SOC prediction has never been tested against traditional process-based modeling approaches. Here, we compare ML algorithms, calibrated and uncalibrated process-based models as well as multiple ensembles on their performance in predicting SOC using data from five long-term experimental sites (comprising 256 independent data points) in Austria. Using all available data, the ML-based approaches using Random forest and Support vector machines with a polynomial kernel were superior to all process-based models. However, the ML algorithms performed similar or worse when the number of training samples was reduced or when a leave-one-site-out cross validation was applied. This emphasizes that the performance of ML algorithms is strongly dependent on the data-size related quality of learning information following the well-known curse of dimensionality phenomenon, while the accuracy of process-based models significantly relies on proper calibration and combination of different modeling approaches. Our study thus suggests a superiority of ML-based SOC prediction at scales where larger datasets are available, while process-based models are superior tools when targeting the exploration of underlying biophysical and biochemical mechanisms of SOC dynamics in soils. Therefore, we recommend applying ensembles of ML algorithms with process-based models to combine advantages inherent to both approaches. • We evaluated process-based (PB) and machine-learning (ML) models for SOC prediction. • Random forest & support vector machine predicted SOC superior to PB models. • Reduced data availability and quality significantly weakened ML model performance. • ML-assisted PB model ensembles strongly improved model performance. [ABSTRACT FROM AUTHOR]

Introduction: Arbuscular mycorrhizal fungi (AMF) are pivotal in plant resource acquisition, mediating plant interactions, and influencing soil carbon dynamics. However, their biogeographical distribution in Tibetan alpine grasslands remains understudied. Methods: In this research, we examined the distribution pattern of AMF communities and their key determinants along a 2000-km transect across the Tibetan plateau, encompassing 7 alpine meadows and 8 alpine steppes. Results: Our findings indicate that AMF community diversity and composition exhibit similarities between alpine meadows and alpine steppes, primarily influenced by latitude and evapotranspiration. At the genus level, Glomus predominated in both alpine meadow (36.49%±2.67%) and alpine steppe (41.87%±2.36%) soils, followed by Paraglomus (27.14%±3.69%, 32.34%±3.28%). Furthermore, a significant decay relationship of AMF community was observed over geographical distance. Null model analyses revealed that random processes predominantly (>50%) drove the assembly of AMF communities. Discussion: In summary, our study elucidates the spatial distribution pattern of AMF in Tibetan plateau grasslands and underscores the significant influence of geographical and climatic factors on AMF community dynamics. [ABSTRACT FROM AUTHOR]

Among various factors related to the forest carbon pool, the tree stand age, which interacts with soil organic matter, decomposition rates, and microbial activity, is essential and cannot be disregarded. However, knowledge about how tree phases influence soil carbon sinks is not adequate. This study sampled Larix kaempferi (Japanese larch) plantations with different tree stand ages to investigate the temporal dynamics of soil carbon sink in the forest. Physiochemical analyses and high-throughput sequencing results further revealed the interactions of tree stands and their related rhizosphere microbiome. It was found that microbial composition and metabolic activity were significantly affected by different tree ages, whose structures gradually diversified and became more stable from young to mature forests. Many keystone taxa from the phyla Chloroflexi, Proteobacteria, Acidobacteriota, and Nitrospirota were found to be associated with carbon transformation processes. Interestingly, the carbon resource utilization strategies of microbial groups related to tree ages also differed, with near-mature forest soils showing better labile carbon degradation capacity, and mature forests possessing higher degradation potential of recalcitrant carbon. Age-altered tree growth and physiology were found to interact with its rhizosphere microbiome, which is the driving factor in the formation and stability of forest soil carbon. This study highlighted that the tree age-associated soil microbiomes, which provided insights into their effects on soil carbon transformation, were significant in enhancing the knowledge of carbon sequestration in L. kaempferi plantations. [ABSTRACT FROM AUTHOR]

Assessment of the current state of the near-surface part of the geological environment and understanding of its layered structure play an important role in various scientific and applied fields. The presented work is devoted to the application of phasometric modifications of geoelectric control methods to solve the problem of the detailed complex study of the underground layers of the environment in the process of drilling operations with the use of special equipment. These studies are based on the analysis of variations in phase parameters and characteristics of an artificially excited multiphase electric field to assess poorly distinguishable details and changes in the layered structure of the medium. The proposed method has increased accuracy, sensitivity and noise proofness of measurements, which allows for extracting detailed information about the heterogeneity, composition and stratification of underground geological formations not only in the zone where the drill makes contact with the medium, but also in the entire control zone. This paper considers practical mathematical models of phase images for basic scenarios of drill penetration between the layers of the near-surface part of the geological medium with different characteristics, obtained by means of approximation apparatus based on continuous piecewise linear functions, and also suggests the use of modern machine learning methods for intelligent analysis of its structure. Studying the phase shifts in electrical signals during drilling highlights their value for understanding the dynamics of soil response to the process. The observed signal changes during the drilling cycle reveal in detail the heterogeneity in soil structure and its response to changes caused by drilling. The stability of phase shifts at the last stages of the process indicates a quasi-equilibrium state. The results make a significant contribution to geotechnical science by offering an improved approach to monitoring a layered structure without the need for deep drilling. [ABSTRACT FROM AUTHOR]

Phosphorus (P) is found in the soil in organic (Po) and inorganic (Pi) forms and in compartments with different lability, normally being separated into labile, moderately labile, restricted lability and non-labile forms. The different sources of fertilizers used in the long term may change the form and availability of P over time, increasing or not its availability to plants, which can positively influence coffee productivity. This work aimed to evaluate in the field the effects of phosphate fertilizers with associated technology on the availability of P in soil with high P adsorption capacity after successive fertilizations in Coffea canephora Pierre ex A.Froehner crop. In the experiment, three phosphate sources (conventional MAP - MAP, polymer-coated MAP - MAPPOL and MAP + filter cake - MAPTF); two doses (100 and 150 % of the recommendation); and two nitrogen sources (conventional urea - UC and urea coated with polymer and sulfur - UPS) were used. After 3 years of field experimentation, the soil was collected at a depth of 0-10 cm and then, the labile, moderately labile, and restricted lability fractions were determined. Phosphate fertilizers with associated technology obtained better results in relation to MAP in terms of Pi and Po contents for the labile compartment over time, with an average increase of 66.02 mg dm-3 P in the soil. For the moderately labile fraction, fertilizers with associated technology increased the Pi content (HCl 1M) in the soil in relation to MAP, by 2.56 mg dm-3, representing an increase of 37.92%. These compartments are considered an important reserve of available P for crops grown in soils with high adsorption capacity. Phosphate fertilizers with integrated protection (MAPPOL + MAPTF) compared to MAP increased productivity by 6.79 and 11.62 % in the 2017/2018 and 2018/2019 harvests, respectively. Phosphate fertilizers with associated technology promote P dynamics in different soil compartments, increasing Coffea canephora Pierre ex A. Froehner productivity and sustainability [ABSTRACT FROM AUTHOR]

Rhizodeposition fuels carbon (C) and nutrient cycling in soil. However, changes in the dynamics of microbial growth on rhizodeposits with increasing distance from the root is not well studied. This study investigates microbial growth on individual organic components of rhizodeposits and maize root‐derived exudates and mucilage from agricultural soil. By creating a gradient of substrate concentrations, we simulated reduced microbial access to rhizosphere C with increasing distance to the root surface. We identified distinct C‐thresholds for the activation of microbial growth, and these were significantly higher for rhizodeposits than singular, simple sugars. In addition, testing for stoichiometric constraints of microbial growth by supplementing nitrogen (N) and phosphorus (P) showed accelerated and increased microbial growth by activating a larger proportion of the microbial biomass. Early and late season exudates triggered significantly different microbial growth responses. The mineralization of early‐season exudates was induced at a high C‐threshold. In contrast, the mineralization of late‐season exudates showed 'sugar‐like' properties, with a low C‐threshold, high substrate affinity, and a reduced maximum respiration rate of microorganisms growing on the added substrate. Mucilage exhibited the highest C‐threshold for the activation of microbial growth, although with a short lag‐period and with an efficient mucilage degradation comparable to that of sugars. By determining kinetic parameters and turnover times for different root‐derived substrates, our data enable the upscaling of micro‐scale processes to the whole root system, allowing more accurate predictions of how rhizodeposition drives microbial C and nutrient dynamics in the soil. [ABSTRACT FROM AUTHOR]

Knowledge regarding soil wetness dynamics is relevant for its application in hydrological and climatological studies. It is also a parameter that allows the analysis of processes related to land cover and land use. Due to this importance, the spatio-temporal dynamics of the surface soil humidity (SSH) in the southern of the Argentinean Pampean Plains have been analyzed, based on data corresponding to six Argentine localities and in relation to a climatological index that incorporates rainfall and evapotranspiration variables. The methodology includes statistical correlation and multivariate analysis based on modeled and reanalysis data. The results obtained reveal a different response of the SSH at a spatial level, with maximum values in the highest rainfall region, diminishing towards the most arid zone. This allows us to infer the influence of the topographic homogeneity of the area and the predominance of vertical processes in the hydrological balance. At both a spatial and temporal scale, the SSH dynamics concur with the climatological index pattern, confirmed by a Pearson coefficient. It has also been shown that the SSH responds to the climatological parameters and that the highest correlation occurs at a three-month temporal scale. This response may be observed at an interannual and annual level, with maximum and minimum values during the wet and dry years, respectively and a decrease in the SSH during the warmest seasons (summer). The SSH displays the same tendency as the climatological index, from NE to SW, reaching a maximum in the rainiest area and minimum in the arid region. The manuscript, based on diverse sources analysis, pluviometric periods classification and statistical methods application, is a contribution related to the edaphic variable dynamics in a region in which farming activity constitutes the main land use and where the droughts and floods alternance has effects on the flooding risks and the economic losses as a consequence of intensive droughts, respectively. [ABSTRACT FROM AUTHOR]

Phosphorus is one of the major constraints to karst grassland productivity. Understanding the effects of different fertilization practices on soil phosphorus dynamics is essential for enhancing phosphorus bioavailability and rational management of soil phosphorus in karst grasslands. Here, we investigated the effects of fertilizers and manures on soil bioavailability of phosphorus fractions and explored the relationship between soil properties and soil phosphorus fractions. The four fertilizer application designs were as follows: control (CK; no fertilizer or manure); fertilization (F); manure application (M); fertilization and manure application (FM). The results showed that total phosphorus (TP) concentration was elevated by 23%, 1%, and 42% in F, M, and FM treatments, respectively, compared with CK. F and FM treatments enhanced the total inorganic phosphorus (Pi) concentration by 65% and 66%, respectively, while M and FM treatments enhanced the total organo-phosphorus (Po) concentration by 21% and 35%, respectively. FM treatment elevated bioavailable P, active Po, secondary mineral P, primary mineral P, and occluded P by 69%, 39%, 50%, 31%, and 41%, respectively. Fertilizers inhibited soil acid phosphatase activity, whereas alkaline phosphatase did not respond significantly to fertilizer management in low-latitude karst regions. SOM, TN, AP, and MBP are the key factors affecting the bioavailability of phosphorus fractions. The combined application of fertilizer and manure is the most beneficial measure for enhancing soil phosphorus bioavailability. This research helps deepen our understanding of soil phosphorus dynamics in the karst areas and provides a basis for further enhancement of nutrient availability and vegetation productivity of grassland ecosystems. [ABSTRACT FROM AUTHOR]

Phosphorus (P) dynamics in the soil subsurface are relatively unstudied, especially in forest soils, and may be important in areas with groundwater‐fed surface water bodies. Here, we use X‐ray absorption near‐edge P spectroscopy (P‐XANES) and X‐ray fluorescence microprobe mapping (µ‐XRF) to examine P speciation and co‐localization with Fe and Al as a function of depth in soils from coniferous and deciduous forests. P‐XANES revealed similar trends in P speciation with depth for both forest types, with Al‐P and Fe‐P being dominant, whereas Ca‐P and organic P were minor constituents. Correlation plots derived from µ‐XRF mapping revealed a strong correlation between P and both Fe and Al at all depths. At depths of up to 378 cm, a range that includes A, E, and B horizons, the relationships between P and Al/Fe were remarkably consistent, consisting of a population of P diffusely associated with Al/Fe, consistent with Fe‐ or Al‐adsorbed P, as well as P linearly correlated with Al/Fe in several discreet groupings, indicative of the presence of specific P compounds. At depths below 378 cm, the relationships between P and Al/Fe changed dramatically, with correlation plotting indicating the disappearance of any diffuse P:Al/Fe relationships. This change occurred concurrently with a decrease in oxalate extractable P, suggesting that the P present in this deep soil horizon may be present in a more stable form that is less available for transport, as well as potentially indicating that P adsorbed to Fe/Al did not readily pass through the overlaying Bw soil horizon. Core Ideas: Organic P and Ca‐P minor constituents of overall P pool, which was dominated by Al‐P and Fe‐P.Similar trends in deciduous/coniferous soils, suggesting litter composition unimportant at these study sites.Correlation plotting revealed consistent P:Al/Fe relationships from surface down to 378 cm (Bw horizon). [ABSTRACT FROM AUTHOR]

Background and aims: The accumulation of soil organic carbon (SOC) is a crucial process in mitigating climate change and ensuring soil quality. Subtropical plantations in China have shown high potential for enhancing SOC sequestration due to their high carbon sink capacity. However, the dynamics and compositions of SOC after long term afforestation are still poorly understood. Methods: We examined the dynamics of SOC and its fractions of different soil layers (0–5 cm, 5–10 cm, 10–20 cm, 20–40 cm, 40–80 cm, 80–100 cm) in a mixed broadleaf-conifer plantation (BCP), a Masson pine plantation (MP), and a Slash pine plantation (SP), and an enclosed forest (EF) in subtropical China. Both physical fractions (particulate organic carbon (POC), soil clay organic carbon (SOCclay), soil silt organic carbon (SOCsilt)) and chemical fractions (iron-aluminum-bound organic carbon (Fe/Al-OC), and calcium-bound organic carbon (Ca-OC)) were determined. Additionally, soil physicochemical properties were further analyzed. Results: Our results showed the SOC storage in the EF, BCP, MP, and SP in 2019 increased by 82%, 238%, 126%, and 103% respectively compared to 1984. The proportions of MAOC to SOC were respectively as follows: SP (65.9%) > BCP (64.9%) > EF (61.6%) > MP (53.9%). The mean proportions of SOCclay to MAOC were as follows: BCP (71.1%) > EF (66.9%) > MP (58.5%) > SP (51.0%). The mean proportions of Fe/Al-OC to MAOC were as follows: EF (53.3%) > SP (48.3%) > MP (47.9%) > BCP (39.8%). All these proportion increased with soil depth. RDA and PLS-SEM analysis revealed that soil nitrogen content and electrochemical properties (pH and EC) were the main factors that controlled SOC content and fractions. Conclusions: Subtropical plantations have significant soil carbon sequestration capabilities, but they are currently nearing saturation. Soil nitrogen content may be key factor limiting further enhancement of carbon sequestration. Due to the high proportion of MAOC and relative consistent SOC storage, BCP and SP are recommended as priorities for plantation regeneration in subtropical China. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) are prevalent emerging pollutants in soil environments, acting as carriers for other contaminants and facilitating combined pollution along with toxic metals like cadmium (Cd). This interaction increases toxic effects and poses substantial threats to ecosystems and human health. The objective of this study was to investigate the hydrodynamic adsorption of Cd by conducting experiments where polystyrene microplastics (PS) and biochar (BC) coexisted across various particle sizes (10 µm, 20 µm, and 30 µm). Then, soil incubation experiments were set up under conditions of combined pollution, involving various concentrations (0.5 g·kg−1, 5 g·kg−1, 50 g·kg−1) and particle sizes of PS and BC to assess their synergistic effects on the soil environment. The results suggest that the pseudo-second-order kinetic model (R2 = 0.8642) provides a better description of the adsorption dynamics of Cd by PS and BC compared to the pseudo-first-order kinetic model (R2 = 0.7711), with an adsorption saturation time of 400 min. The Cd adsorption process in the presence of PS and BC is more accurately modeled using the Freundlich isotherm (R2 > 0.98), indicating the predominance of multilayer physical adsorption. The coexistence of 10 µm and 20 µm PS particles with BC enhanced Cd absorption, while 30 µm PS particles had an inhibitory effect. In soil incubation experiments, variations in PS particle size increased the exchangeable Cd speciation by 99.52% and decreased the residual speciation by 18.59%. The addition of microplastics notably impacted the exchangeable Cd speciation (p < 0.05), with smaller PS particles leading to more significant increases in the exchangeable content—showing respective increments of 45.90%, 106.96%, and 145.69%. This study contributes to a deeper understanding of the mitigation mechanisms of biochar in the face of combined pollution from microplastics and heavy metals, offering theoretical support and valuable insights for managing such contamination scenarios. [ABSTRACT FROM AUTHOR]

The ecologically and economically vital symbiosis between nitrogen-fixing rhizobia and leguminous plants is often thought of as a bi-partite interaction, yet studies increasingly show the prevalence of non-rhizobial endophytes (NREs) that occupy nodules alongside rhizobia. Yet, what impact these NREs have on plant or rhizobium fitness remains unclear. Here, we investigated four NRE strains found to naturally co-occupy nodules of the legume Medicago truncatula alongside Sinorhizobium meliloti in native soils. Our objectives were to (1) examine the direct and indirect effects of NREs on M. truncatula and S. meliloti fitness, and (2) determine whether NREs can re-colonize root and nodule tissues upon reinoculation. We identified one NRE strain (522) as a novel Paenibacillus species, another strain (717A) as a novel Bacillus species, and the other two (702A and 733B) as novel Pseudomonas species. Additionally, we found that two NREs (Bacillus 717A and Pseudomonas 733B) reduced the fitness benefits obtained from symbiosis for both partners, while the other two (522, 702A) had little effect. Lastly, we found that NREs were able to co-infect host tissues alongside S. meliloti. This study demonstrates that variation of NREs present in natural populations must be considered to better understand legume–rhizobium dynamics in soil communities. [ABSTRACT FROM AUTHOR]

Biofertilizers, consisting of carefully selected microorganisms across various species and genera, exhibit distinct features that enhance soil fertility and promote plant growth. Embracing the principles of eco-friendly agriculture, the use of biofertilizers emerges as a pivotal strategy for sustainable farming, contributing to environmental preservation and the overall health and biodiversity of the soil. In this study, a commercially available biofertilizer, containing a specialized strain of Priestia megatherium with nitrogen-fixing capabilities, was employed alongside chemical fertilizers at two different doses (30 and 40 mg per kg of soil). The primary objective was to evaluate the impact of biofertilizer on the metabolic activity and structure of microbial communities in a short-term experiment involving potted maize plants, utilizing the BIOLOG® EcoPlates technique. Parameters such as average well-color development (AWCD) and substrate utilization across six guilds (SAWCD) were assessed to gauge microbial metabolic activity. Additionally, functional indexes, including Shannon diversity, Shannon evenness, and Simpson diversity, were calculated as indicators of soil microbial community functionality. While statistically significant differences in AWCD among the studied variants were not observed, all estimated functional indexes consistently revealed heightened microbial diversity and evenness following the application of biofertilizer. This noteworthy finding, achieved within a relatively short period of plant cultivation, underscores the necessity for further research to explore the biofertilizer's enduring effects on soil communities, both in controlled laboratory environments and under real-world field conditions. [ABSTRACT FROM AUTHOR]

The designer of irrigation systems must consider a complex combination of emitter type, emitter uniformity, hydraulics, topography, desired water distribution, crop salt tolerance, water requirements, water quality, fertilizer injection, soil salinity, cultural practices, and other site-specific conditions. In contrast to the approaches applied for the hydraulic design of irrigation installations, there is not a clear, general and consolidated design criterion for calculating the number required emitters per plant. In most cases, given the wide spectrum of possible scenarios, only guideline recommendations can be found, and the final decision is often based on the subjective experience of the designer or grower. This paper aims at revising, clarifying and refining the existing published guidelines and methodologies for estimating the required emitters per plant in drip irrigation, focussing on the Montalvo approach. The agronomic design should satisfy, among others, two specific conditions: (i) the emitters should wet at least a minimum threshold of the soil area (or volume) corresponding to the plant for ensuring a proper development of the roots; (ii) overlapping between emitter bulbs is required for merging wetted volumes and avoiding salt concentration near the root zone. Relying on this basis, a thorough theoretical geometric analysis of the overlapping between wet bulbs of contiguous emitters is carried out. As a result, Montalvo's overlapping coefficients are deduced here. This author assumes an identical net wetted area for all emitters in the laterals, but it can be stated that the overlapping areas between emitters differ in extreme emitters and interior emitters, as well as in configurations with one lateral per plant row and two laterals per plant row. Therefore, this study proposes new formulations for the computation of the overlapping coefficient, which need to incorporate the number of emitters as an additional variable, as well as to distinguish between the presence of one or two laterals per plant row, and between grouped and non-grouped emitters. In one lateral per plant row, the original overlapping coefficient underestimates the net wetted area by one emitter and thus overestimates the theoretical number of required emitters. In the case of two laterals per plant row, the original overlapping coefficient overestimates the net wetted area in the interior emitters, and thus underestimates the theoretical number of required emitters per plant. The presented formulations are applied in different practical examples covering a wide range of scenarios. The results allow a general overview of the influence of the soil type, the emitter flow rate, and the selected overlapping ratio in the number of required emitters per plant. The revision of guidelines and methods presented here, complemented with other experimental results and models of soil water dynamics under drip irrigation, might contribute to a better decision making of designers and field engineers. [ABSTRACT FROM AUTHOR]

The cultivation of Cunninghamia lanceolata (Lamb.) Hook. (Chinese fir) plays a crucial role in enhancing ecological security through water resource preservation and carbon sequestration in China. The biotic and abiotic environmental conditions vary across different stages of plantation, thereby influencing soil nutrient levels and microbial dynamics. However, the interconnection between the soil nutrient cycle and microbial communities within Chinese fir plantations throughout their entire life cycle remains inadequately understood. In this study, conducted across various management stages of Chinese fir plantations in China (including the juvenile stage, first thinning stage, second thinning stage, mature stage, and over-mature stage), we examined the associations among soil organic carbon, soil physicochemical properties, soil enzyme activities, and soil microbial dynamics. Our results revealed that forest management practices significantly modify soil physicochemical properties and enzyme activities across all management stages. Specifically, the concentrations of total soil carbon, soil organic carbon, and soil microbial biomass carbon were notably higher in the over-mature stage compared to other management stages. At the genus level, the five highest contributors belonged to Subgroup2, AD3, Xanthobacteraceae, Elsterales, and Acidobacteriales for the bacterial community. For the fungal community at the genus level, the five highest contributors belonged to Ascomycota, Serendipita, Saitozyma, Mortieralla, and Venturiales. Moreover, anthropogenic thinning activities during the management phase substantially altered both stand and soil environments, as well as the structural characteristics of soil microbial communities. Soil cellulase, soil electrical conductivity (EC), and soil available phosphorus (AP) emerged as key factors influencing the relative abundance of major fungal communities, whereas soil total nitrogen, EC, and AP were identified as critical factors affecting the relative abundance of major bacterial phyla. More microbiological groups increased significantly in the juvenile stage and over-mature stage. Our findings elucidate the intricate relationships between the soil nutrient cycle and soil microbiological dynamics across various forest management stages within Chinese fir plantations. [ABSTRACT FROM AUTHOR]

This study investigates the hazardous effect of salinity on plant growth and soil moisture dynamics in the root zone. Field irrigation experiments on paddy (Oryza sativa L.—basmati variety) with varying levels of salinity of irrigation water (0.5, 5, 10, 15, 20, and 25 dS/m) were performed for studying the effect of salt water stress on crop growth. Throughout the crop's growth period, measurements of leaf area index (LAI), root depth (RD), and soil moisture status in the root zone were recorded. For the analysis, a numerical model was developed to simulate root water uptake (RWU) and soil moisture movement in the root zone, accounting for osmotic pressure developed as a result of the salinity. Nonlinear parameters for the RWU model were estimated based on these observations for each salinity level. By incorporating meteorological data and soil–crop parameters, the model simulated RWU and root zone soil moisture. The results of the irrigation experiments revealed that increased salinity levels in the irrigation water significantly hindered crop development, leading to a decrease in LAI and root depth. The maximum LAI in the growth period decreased markedly, from 5.19 m2m−2 at 0.5 dS/m to 2.01 m2m−2 at 25 dS/m, a decline of approximately 61%. Root depth also exhibited a substantial reduction, declining by up to 36%, from 69.5 cm at 0.5 dS/m to 44.5 cm at 25 dS/m. The simulation outcomes further demonstrated that higher salt concentrations in the irrigation water resulted in reduced root water uptake and decreased soil moisture content in the root zone, ultimately affecting crop yield. The reduction in root water uptake becomes notably pronounced, exhibiting an approximate decrease of 81% when salinity level increases from 0.5 to 25 dS/m. These findings shed light on the hazards posed by salinity in agricultural practices and emphasize the importance of effective management strategies to ensure sustainable crop production in the presence of salinity-induced hazards. Practical Applications: The results of our research yield significant insights with practical applications for real-life conditions. We find that increasing salinity levels in irrigation water have a pronounced adverse effect on paddy crop growth and root water uptake. As salinity levels rise, there is a noticeable effect on crop growth i.e., decrease in leaf area index (LAI), root depth (RD), and root water uptake (RWU), which are crucial parameters for crop development. Furthermore, our findings reveal a clear correlation between increasing salinity and reduced soil moisture content, particularly at the critical depths of 20 and 40 cm below the surface. The practical implications of our research are twofold. First, it underscores the importance of carefully managing salinity levels in irrigation practices to mitigate the negative effects on crop growth and water uptake. Secondly, our study provides valuable insights for crop selection, suggesting that paddy crops may be less suitable under high salinity conditions. These results offer practical guidance for agricultural decision makers, highlighting the need for salinity control measures and informed crop selection to optimize agricultural productivity in regions with saline water environments. [ABSTRACT FROM AUTHOR]

Drying of soil impacts land energy and water balance, influences the sustainability of vegetation growth, and modulates hydrological extremes including floods. While satellite soil moisture data are widely used for a range of environmental applications, systematic differences from regional in‐situ data prevent their optimal use as key physical signatures (such as soil moisture recession, also termed drydown) are represented differently. This study investigates differences in drydowns from the Soil Moisture Active Passive (SMAP) level 4 product with reference to in‐situ observations. A bivariate filtering alternative is proposed to minimize the disparity noted by modeling the relationship between the rate of drying and initial soil wetness and representing the same as in‐situ. Considerable improvements are observed in the resulting SMAP soil moisture filtered estimates. Although the algorithm assumes spatial stationarity, improvements exist across different soil properties and climatic conditions, providing a parsimonious alternative to better capture the dynamics of soil moisture loss. Plain Language Summary: Soil drying affects the environment by changing how land uses energy and water. It also affects plant growth and can lead to extreme events like floods. Scientists use data from satellites to understand soil moisture, but this data sometimes differs from what's measured directly on the ground. Our study looks at these differences, focusing on how soil dries out, using data from a satellite program called the Soil Moisture Active Passive (SMAP). We suggest a new method to make satellite data closer to what's observed on the ground by adjusting it based on initial soil wetness and drying rates. This new approach showed better results and worked well in different types of soil and weather conditions. It helps us track how soil moisture decreases at ground level more accurately, which is important for understanding and managing our environment. Key Points: Coarse‐scale satellite‐derived soil moisture dries faster than in‐situ measurementsWe propose a bivariate recursive filtering approach to characterize soil moisture drying rates and initial wetness conditionsThe proposed approach is applied to SMAP L4, eliminating systematic bias in drying rates for varied sand fractions and aridity profiles [ABSTRACT FROM AUTHOR]

High‐resolution modeling of the flow dynamics in fractured soils is highly complex and computationally demanding as it requires precise geometrical description of the fractures in addition to resolving a multiphase free‐flow problem inside the fractures. In this paper, we present an idealized model for saturated–unsaturated flow in fractured soils that preserves the core aspects of fractured flow dynamics using an explicit representation of the fractures. The model is based on Richards' equation in the matrix and hydrostatic equilibrium in the fractures. While the first modeling choice is standard, the latter is motivated by the difference in flow regimes between matrix and fractures, that is, the water velocity inside the fractures is considerably larger than in the soil even under saturated conditions. On matrix/fracture interfaces, the model permits water exchange between matrix and fractures only when the capillary barrier offered by the presence of air inside the fractures is overcome. Thus, depending on the wetting conditions, fractures can either act as impervious barriers or as paths for rapid water flow. Since in numerical simulations each fracture face in the computational grid is a potential seepage face, solving the resulting system of nonlinear equations is a nontrivial task. Here, we propose a general framework based on a discrete‐fracture matrix approach, a finite volume discretization of the equations, and a practical iterative technique to solve the conditional flow at the interfaces. Numerical examples support the mathematical validity and the physical applicability of the model. Core Ideas: Due to the presence of air in dry fractured soils, fractures of large aperture act as capillary barriers.If the capillary barriers are overcome, fractures become fast‐flowing paths for water to travel downward.A flow model based on Richards' equation in the soil and instantaneous ponding in the fractures is proposed.The model is numerically consistent and its physical applicability is showcased in two‐dimensional simulations. [ABSTRACT FROM AUTHOR]

Water uptake by plant roots is an important component of the soil water balance. Predicting to what extent potential transpiration from the canopy, that is, transpiration demand, can be met by supply of water from the soil through the root system is crucial to simulate the actual transpiration and assess vegetation water stress. In models that simulate the dynamics of vertical soil water content profiles as a function of water fluxes and soil water potential gradients, the root water uptake (RWU) distribution is represented by macroscopic sink terms. We present RWU functions that calculate sink terms based on a mechanistic model of water flow in the soil–root system. Based on soil–root hydraulics, we define α‐supply functions representing the maximal uptake by the root system from a certain soil depth when the root collar water potential equals the wilting point, ω‐supply factors representing the maximal supply from the entire root system, and a critical ωc factor representing the potential transpiration demand. These functions and factors are subsequently used to calculate RWU distributions directly from potential transpiration or demand and the soil water potentials. Unlike currently used approaches, which define α‐stress functions and ω factors representing ratios of actual uptake to uptake demand, the supply‐based formulations can be derived directly from soil and root hydraulic properties and can represent processes like root hydraulic redistribution and hydraulic lift. Core Ideas: Functions to calculate root water uptake (RWU) from different soil depths were derived.RWU is calculated directly using soil water potentials and the potential transpiration rate.The functions are derived using soil and root hydraulic properties.Phenomena like RWU compensation, hydraulic redistribution, and hydraulic lift are reproduced.Similarities and differences with currently used uptake functions are discussed. [ABSTRACT FROM AUTHOR]

Water retention and hydraulic conductivity characteristics are key input data in studies on soil water dynamics in the vadose zone. The most well‐known analytical functions to describe these characteristics are those given by Mualem and van Genuchten, where van Genuchten showed that both can be described by a limited set of shared parameters. Analytically, there are no restrictions on the range of pressure heads for which these characteristics can be used. Experience, however, has shown that for certain sets of parameters, the hydraulic conductivity cannot be computed accurately at low‐pressure heads. This is due to the accuracy of (double precision) floating point operations in computer code. It is shown that for low‐pressure heads, the Mualem function approaches a power function. An adapted version of the Mualem–van Genuchten (MvG) expression for the hydraulic conductivity is proposed: between saturation and a soil‐dependent critical pressure head, the classical Mualem expression is valid and below this critical pressure head a power function is used. The power function is defined such that it matches the Mualem value at the critical pressure head. No accuracy problems will occur when using the power function until the result approaches the smallest possible (double precision) floating point value that significantly differs from zero. Core Ideas: Computer calculated hydraulic conductivities K can show anomalous behavior at low‐pressure heads h.Double precision floating point constraints are the main cause.The Mualem–van Genuchten K expression can be approximated by a power function at low h.An extended expression for the Mualem–van Genuchten K(h) equation is proposed.With the extended expression, K can be computed to values as low as floating point precision allows. [ABSTRACT FROM AUTHOR]

Phosphorus (P) cycle plays a vital role in maintaining the structure and function of wetland ecosystems. However, research knowledge on high-altitude wetland ecosystems is very poor. In the present study, plant communities, soil P fractions and other properties and their transformation were investigated under the influence of four types of degradation categories, namely non-, light-, medium-, and severe degraded (ND, LD, MD, and SD, respectively) wetlands of Tibetan Plateau. The degradation of wetlands causes succession in the plant communities from wet to dry mesophytic communities, significantly reducing plant coverage and biomasses. As a result, soil water content (SWC), soil organic carbon (SOC), and soil total nitrogen (TN) contents decrease with increasing degradation. Plant P accumulation usually showed a decreasing trend with increasing levels of degradation. Soil total P, available P, inorganic P, Labile inorganic P, P mineralization rate, and alkaline phosphatase (ALP) concentration increased from non-degradation to light degradation and then declined until severe degradation. The redundancy analysis (RDA) ranking further revealed that labile organic P is the main source of soil available P and soil ALP play important role in P transformation. These results suggest that there prevails a nonlinear change on soil P pool and turnover rate to wetland degradation degree. The study thus provides a mechanistic understanding of alpine wetland degradation driven soil P dynamics and cycling, which would facilitate the restoration of nutrient-based degraded wetlands. [ABSTRACT FROM AUTHOR]

Black wattle is a tree native to Australia and commercially planted in South Africa and Brazil. Replacement of exported nutrients by wood and bark harvesting, associated with the maintenance of harvest residues, increases productivity, thus maintaining production sustainability. Here, we review recent advances in soil nutrient dynamics, harvest residue management (HRM), and soil organic matter in black wattle plantations. Over the 7–11-year cycle of black wattle, N is the most exported macronutrient (458–1509 kg ha− 1), followed by K (200–766 kg ha− 1), Ca (270–717 kg ha− 1), Mg (62–128 kg ha− 1), S (29–57 kg ha− 1) and P (16–40 kg ha− 1). The average increase in bark yield to 20 kg P ha− 1 applications on sandy soils was 2.7–2.9 t ha− 1 and on clay soils from 2.8 to 8.7 t ha− 1. Sandy soils with low K are more responsive to fertilizer, and rates must consider the K content and cation exchange capacity. Ca and Mg addition responses are more likely when in the topsoil they are in low concentrations (< 0.75 and 0.41 cmolc dm− 3, respectively). Micronutrient fertilization reduces the occurrence of gummosis caused by Phytophthora spp, and B deficiency is the most common and can be supplied by fertilization or foliar application (1 g B L− 1). Few studies have evaluated the impact of black wattle HRM on soil organic matter (SOM) and its effects on production. However, conserving SOM should be considered an essential practice for the sustainability of black wattle production. [ABSTRACT FROM AUTHOR]

Ecological study on plant diversity and soil characteristics of two contrasting sites (Prosopis juliflora-invaded and non-invaded) in Hastinapur Wildlife Sanctuary was undertaken to understand the structure of vegetation and soils and implication of exotic dominance in a dry tropical region of India. Seasonal floristic composition was recorded for one year through monthly visits. Phytosociological study of the two sites in each of three seasons was carried out by sampling a total of 120 quadrats (each 1mx1m, n= 20×3×2). Plant species density and abundance was estimated for both sites in each season. Seasonal surface soil (0-10 cm) samples were analyzed for soil pH, moisture content, organic C, and total N. Species occurrences and their relative abundance data were used to estimate alpha and beta diversity. A total of 76 plant species from 29 families were recorded (Malvaceae, Fabaceae and Asteraceae being top dominants). Maximum flora was recorded in rainy season at both sites, higher at non-invaded sites in all seasons. Beta diversity followed similar trend, higher in rainy season and at non-invaded than invaded sites, highest being 13.2 at non-invaded site in rainy season. Dominants changed with site and season. Vegetation patches were distinct in drier seasons compared to rainy months. Soil organic carbon, total nitrogen and C : N ratios were high at invaded sites compared to non-invaded sites except in summer season. While higher diversity and higher similarity amongst different sites in rainy season indicated a homogenization impact in Indian dry tropical regions, higher diversity at non-invaded site suggested implication of diversity-reducing impact of tree invader Prosopis juliflora. [ABSTRACT FROM AUTHOR]

Despite recent research efforts to explore the co-occurrence patterns of diverse microbes within soil microbial communities, a substantial knowledge-gap persists regarding global climate influences on soil microbiota behaviour. Comprehending co-occurrence patterns within distinct geoclimatic groups is pivotal for unravelling the ecological structure of microbial communities, that are crucial for preserving ecosystem functions and services. Our study addresses this gap by examining global climatic patterns of microbial diversity. Using data from the Earth Microbiome Project, we analyse a meta-community co-occurrence network for bacterial communities. This method unveils substantial shifts in topological features, highlighting regional and climatic trends. Arid, Polar, and Tropical zones show lower diversity but maintain denser networks, whereas Temperate and Cold zones display higher diversity alongside more modular networks. Furthermore, it identifies significant co-occurrence patterns across diverse climatic regions. Central taxa associated with different climates are pinpointed, highlighting climate's pivotal role in community structure. In conclusion, our study identifies significant correlations between microbial interactions in diverse climatic regions, contributing valuable insights into the intricate dynamics of soil microbiota. [ABSTRACT FROM AUTHOR]

In recent decades, there has been increasing interest in studying the variability in soil water properties and, specifically, the spatiotemporal variability in the soil water content. This is motivated by the notable theoretical and applied research interests in soil moisture dynamics and their implications for many natural processes. This study aimed to study whether there are variations in the spatial pattern of the temporal stability of soil moisture over time and to analyze the possible influences of certain hydroclimatic (soil water content, precipitation, and evapotranspiration) and soil factors (texture, bulk density, and organic matter content) on these variations. This study was conducted within the Soil Moisture Measurement Stations Network of the University of Salamanca (REMEDHUS, Spain) under Mediterranean conditions, with daily surface moisture data (0-5 cm depth) obtained from 20 stations for the 2006-2023 period. The results showed differences between the average pattern obtained with the 18-year data series and that obtained with the data series for each year. In more than half of the years studied, the representative station differed from that derived from the average pattern. The mean annual precipitation and summer precipitation characteristics seem to be the main factors influencing the variability in the spatial pattern of the temporal stability of soil moisture. [ABSTRACT FROM AUTHOR]

The radiation level, radionuclide distribution, and dependence of radioactivity on physico-chemical parameters of soils have been studied in Belagavi region of Karnataka, India. The gamma dose rates in air were measured using a portable survey metre, and the activity in soils was measured using NaI (Tl)-based gamma ray spectrometer. The measured absorbed dose rate in air ranges from 54 to 77 nGy h−1 with a mean value of 58 nGy h−1. The 40K activity in soil was found to vary from 97.9 to 378.5 Bq kg−1 with an average of 214.2 Bq kg−1. The 226Ra activity varied from 15.3 to 68.8 Bq kg−1 with an average value of 30.5 Bq kg−1 and the activity of 232Th varied from 12.3 to 65.4 Bq kg−1 with an average value of 27.96 Bq kg−1. The activity of 226Ra and 232Th were found to be higher than the world average value in some locations of the study area. A good positive correlation was observed between the activity concentration of radionuclides and physico-chemical parameters of soil. A good positive correlation was observed between the activity of 226Ra and 232Th with clay with a correlation coefficient of r = 0.609 and 0.591, respectively. The frequency distribution curve of 226Ra, 232Th, and 40K are lognormal in nature. The application of cluster analysis and principal component analysis were carried out using IBM SPSS software for better understanding of dynamics of soil matrix and the dependence of soil radioactivity on the physico-chemical parameters of the soil. [ABSTRACT FROM AUTHOR]

Integrated production systems composed of trees, crops and pastures have shown good results in improving soil quality and the capacity to store carbon in the soil, being efficient in mitigating greenhouse gas emissions. Despite this, changes in carbon stocks and soil organic matter fractions in the initial stages of implementing an agroforestry system remain unclear. This study evaluated the carbon balance and the dynamics of soil organic matter fractions in an agroforestry system conducted over a decade. Total carbon, labile carbon, carbon from particulate organic matter, organic carbon associated with minerals and inert carbon were determined at depths 0–10 cm, 10–20 cm and 20–40 cm. Soil carbon stocks were also estimated for the 0–40 cm depth. Total carbon increased in the agroforestry system compared with a low-productivity pasture. The total carbon stock in the last growing season (68.57 Mg ha−1) was close to the original soil stocks under native Cerrado vegetation (76.5 Mg ha−1). After 10 years, there was a positive balance in the soil carbon stock of both the total carbon and the soil organic matter fractions. The successional agroforestry system is a good alternative to increasing soil total carbon stocks and labile and non-labile fractions of soil organic matter. [ABSTRACT FROM AUTHOR]

Simple Summary: The dynamics of the soil bacterial communities in rotational shifting cultivation fields were investigated. A six-year interval of fallow years did not result in any differences in the soil bacterial communities. A recovery in the abundance of the soil bacterial communities was observed during the rainy season. An increase in bacterial richness occurred during the year after a burn. After one year, the diversity of the bacterial communities reverted to pre-burning levels. Fire is a common practice in rotational shifting cultivation (RSC), but little is known about the dynamics of bacterial populations and the impact of fire disturbance in northern Thailand. To fill the research gap, this study aims to investigate the dynamics of soil bacterial communities and examine how the soil's physicochemical properties influence the bacterial communities in RSC fields over a period of one year following a fire. Surface soil samples (0–2 cm depth) were collected from sites with 6 (RSC-6Y) and 12 (RSC-12Y) years of fallow in Chiang Mai Province, northern Thailand at six different time points: before burning, 5 min after burning (summer), 3 months after burning (rainy season), 6 months after burning (rainy season), 9 months after burning (winter), and 12 months after burning (summer). The results revealed a reduction in the soil bacterial communities' diversity and an increase in soil nutrient levels immediately after the fire. The fire significantly influenced the abundance of Firmicutes, Proteobacteria, Acidobacteria, and Planctomycetes, but not that of Actinobacteria. At the genus level, Bacillus, Conexibacter, and Chthoniobacter showed increased abundance following the fire. During the rainy season, a recovery in the abundance of the soil bacterial communities was observed, although soil nutrient availability declined. Soil physicochemical properties such as pH, organic matter, organic carbon, electrical conductivity, cation exchange capacity, nitrate-nitrogen, available phosphorus, exchangeable potassium, total nitrogen, bulk density, sand, and silt contents significantly influenced the composition of bacterial communities. Alpha diversity indices indicated a decrease in diversity immediately after burning, followed by an increase from the early rainy season until the summer season, indicating that seasonal variation affected the composition of the soil bacterial communities. After one year of burning, an increase in bacterial richness was observed, while the diversity of the bacterial communities reverted to pre-burning levels. [ABSTRACT FROM AUTHOR]

Machine learning algorithms are increasingly applied in hydrological studies with promising results. However, these algorithms generally lack the ability for easy interpretability of the results by users. In this study, we compare six different explainable artificial intelligence (XAI) algorithms that help understand the effect of input data on the simulation results. The methods are explored on two distinct approaches for streamflow modeling using a long short-term memory (LSTM) model: a single model approach using only meteorological forcing data and a regional approach including also static catchment attributes. To gain further insight into the internal dynamics of the LSTM models, the relationship between cell states and soil moisture is investigated. A strong correlation suggests that the LSTM models inherently capture the concept of soil moisture as a catchment-scale storage mechanism. The XAI methods are applied to derive a timestep of influence, revealing how many days of input data are relevant for the model output. All XAI methods result in similar seasonal patterns in the timestep of influence, suggesting that the methods are comparable. Setting soil moisture dynamics in context to seasonal development of the timestep of influence suggests resetting LSTM as soon as soil moisture saturation occurs. [ABSTRACT FROM AUTHOR]

Incorporating crop residues into the soil is an effective method for improving soil carbon sequestration, fertility, and crop productivity. Such potential benefits, however, may be offset if residue addition leads to a substantial increase in soil greenhouse gas (GHG) emissions. This study aimed to quantify the effect of different crop residues with varying C/N ratios and different nitrogen (N) fertilizers on GHG emissions, yield, and yield-scaled emissions (GHGI) in winter wheat. The field experiment was conducted during the 2018–2019 winter wheat season, comprising of four residue treatments (no residue, maize residue, soybean residue, and maize-soybean mixed residue) and four fertilizer treatments (control, urea, manure, and manure + urea). The experiment followed a randomized split-plot design, with N treatments as the main plot factor and crop residue treatments as the sub-plot factor. Except for the control, all N treatments received 150 kg N ha−1 season−1. The results showed that soils from all treatments acted as a net source of N2O and CO2 fluxes but as a net sink of CH4 fluxes. Soybean residue significantly increased soil N2O emissions, while mixed residue had the lowest N2O emissions among the three residues. However, all residue amendments significantly increased soil CO2 emissions. Furthermore, soybean and mixed residues significantly increased grain yield by 24% and 21%, respectively, compared to no residue amendment. Both soybean and mixed residues reduced GHGI by 25% compared to maize residue. Additionally, the urea and manure + urea treatments exhibited higher N2O emissions among the N treatments, but they contributed to significantly higher grain yields and resulted in lower GHGI. Moreover, crop residue incorporation significantly altered soil N dynamics. In soybean residue-amended soil, both NH4+ and NO3− concentrations were significantly higher (p < 0.05). Conversely, soil NO3− content was notably lower in the maize-soybean mixed residue amendment. Overall, our findings contribute to a comprehensive understanding of how different residue additions from different cropping systems influence soil N dynamics and GHG emissions, offering valuable insights into effective agroecosystems management for long-term food security and soil sustainability while mitigating GHG emissions. [ABSTRACT FROM AUTHOR]

Investigating the spatial distribution characteristics of the interaction between soil salinity and moisture is crucial in revealing moisture–salinity interaction in semi-arid farmland. The sampling of soil was performed on the second (S1), fifth (S2), eighth (S3), eleventh (S4), and fourteenth (S5) days after the erosive rainfall. The multifractal method was used to analyze spatial distribution parameters of soil moisture and salinity under the different stages. The findings showed that the soil moisture content decreased from 22.44% to 12.73%, while the salinity increased from 0.71 to 1.18 g kg–1 after the rainfall. As the amount of moisture in the soil decreased, the variability in the distribution of moisture initially increased from S1 to S3 and then decreased, while the salinity content also decreased. The spatial distribution of soil moisture and salinity content showed a strong correlation at S3 to S4 (with the relative water content of soil ranging from 0.52 to 0.75), indicating a significant coupling effect in these stages. However, the distribution of soil salinity was not uniform under high moisture content conditions (S1 to S2), as it was leached unevenly by rainfall, and under low moisture content conditions (S5), it precipitated, resulting in a low correlation between the spatial distribution of soil moisture and salinity content. This research has provided insight into the coupling dynamics of soil moisture and salinity content, revealing the mechanisms governing their spatial distribution in dryland agricultural regions. [ABSTRACT FROM AUTHOR]