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Understanding the dynamics of soil water content (SWC) is essential for effective land management, particularly in regions affected by underground mining. This study investigates the spatial and temporal patterns of SWC and its interaction with topographic and edaphic factors in coal mining and non-coal mining areas of the Chenghe watershed, located in the southeast of the Chinese Loess Plateau, which is divided by a river. Our findings revealed that the capacity to retain moisture in the top layer of coal mining areas is significantly higher (25.21%) compared to non-coal mining areas, although deeper layers exhibit lower SWC, indicating altered moisture dynamics due to underground mining disturbances. Coal mining areas show greater spatial and temporal variability in SWC, suggesting increased sensitivity to moisture fluctuations, which complicates water management practices. Additionally, underground mining activities introduce more intense effects on the relationship between SWC and topographic factors (i.e., GCVR across soil profile of 0–60 cm; slope at depth of 50 cm) or edaphic factors (i.e., soil organic matter and available potassium at depth of 30 cm; pH at depth of 50 cm) compared to non-coal mining areas. This variability is evident in the temporal shifts from positive to negative correlations, particularly in coal mining areas, reflecting modifications in both soil physical and chemical properties resulting from mining activities. In contrast, non-coal mining areas maintain a more stable moisture regime, likely due to preserved natural soil structures and processes. These contrasting findings emphasize the necessity for tailored management strategies in coal mining regions to address the unique challenges posed by altered soil characteristics and water dynamics. [ABSTRACT FROM AUTHOR]

Mitigation practices for nitrogen leaching losses from livestock agriculture are needed to protect freshwater quality and increase the efficiency of agricultural production. Within New Zealand, the most common pasture type is a twospecies mix of perennial ryegrass (Lolium perenne) and white clover (Trifolium repens). Ecological theory suggests that increasing species and functional diversity improves ecosystem function, including nitrogen (N) retention. Use of more diverse pasture types, including a mix of pasture grasses, legumes and other forbs, particularly plantain (Plantago lanceolata), with functional traits, including winter activity, deep-rooting, N fixation, and biological inhibition of nitrification in the soil, is a potential mitigation practice that requires further verification with long-term field measurements. Here we utilize a network of large lysimeters to make field-based measurements of N leaching from 5-8 species diverse pasture, including plantain, under a range of soil, climate and management conditions, for comparison with losses from traditional ryegrass-clover pasture. Over 3 years of measurements, leaching from fully established diverse pasture was 2-80 kg N ha-1 y-1. No differences were observed in dry matter production or N leaching of diverse pasture compared to ryegrass-clover lysimeters. Large losses, up to 120 kg N ha-1, were observed during periods when pasture was not fully established, including cultivation and sowing of new pasture, depending on season. Timing of management activities could be optimized to minimize these losses. These data provide critical assessment of diverse pasture as a mitigation approach for reducing N losses. Further work on diverse pastures should include higher diversity mixes as well as consideration of animal mediated effects of diverse pasture diets on N inputs. [ABSTRACT FROM AUTHOR]

Biochar is an eco-friendly material that is potentially used in earthworks to prevent stability and serviceability problems under extreme scenarios. This study aims to examine the effects of biochar amended on water infiltration and evaporation under extreme climate. A series of numerical analyzes were conducted to observe the response of pore water pressure (PWP) to extreme climate variation with an application of biochar composition. Moreover, an analysis of variance (ANOVA) has been performed to investigate the effect of biochar on soil water holding capacity at a low suction range. According to the result, biochar amended can maintain the fluctuation of PWP due to wetting and drying processes under extreme climate scenarios. This is due to the fact that the finer particles of biochar may clog large soil pores, reducing the water infiltration rate. Moreover, the addition of biochar can increase water retention capacity at low matric suction ranges, which can prevent flooding during extreme wet conditions. Further to this, the addition of biochar to the soil can maintain PWP fluctuation at the near surface area under extreme climate, preventing soil desiccation cracks. [ABSTRACT FROM AUTHOR]

Relevance. Progressive degradation of farmland soils – erosion, salinization, desertification. Aim. To establish features of water-physical properties of leached chernozem under an apple orchard and associated patterns of soil profile moisture distribution in summer period when precipitation deficiency observed. Methods. Moisture content in soil horizons was determined by the gravimetric method. To determine the granulometric composition of soils, the pipette method was used. The soil bulk density was determined by the cutting ring method. For solid phase density determination the pycnometric method was used. The method of graphic interpolation was used for transition the soil texture classification from Russian to international one. Water infiltration modeling into the soil profile was carried out using the HYDRUS-1D program. The parameters of approximating of the water retention curve of soils by the Van Genuchten equation were obtained by the calculation method of pedotransfer functions «Rosetta Lite» of the RETC program, using data on soil density and soil texture. Results. It has been established that the upper well-structured horizons of leached chernozem under an apple orchard have a greater water-holding capacity; their water-retention curves are more flattened. The water retention curve of the more structureless B2k horizon, the soil texture of which is dominated by sandy fractions, is shifted towards lower humidity. During hot and dry summer period the moisture deficiency in the soil was noted only in the upper twenty-centimeter soil column (14 mm). The moisture of the lower horizons, where the bulk of tree roots are concentrated, is satisfactory. The model demonstrates the smallest discrepancies with the moisture values measured during the soil reclamation experiment one day after the start. The downward moisture penetration into the lower soil layers is prevented by low pressure in the clayey A and AB horizons. Selection of input parameters and debugging of the model based on experimental data allows it to be used to simulate further processes occurring in the soil. It was revealed that the formation of positive (upward) water flows, which ensure the “pull-up” of salts and substances from the lower part of the profile to the upper layers during dry periods of the year, has a significant impact on moisture distribution in the chernozem under the apple orchard.

Accurate measurement of infiltration rate and hydraulic conductivity is important for assessing soil physical health, irrigation management and catchment modelling. Commercially available infiltrometers are often expensive, fragile, and require specialist knowledge to operate and perform complex post-measurement calculations. We developed the Lithosphere Infiltrometer (permeameter) to be usable for both experienced soil researchers, and users without prior technical or scientific expertise in soil science. The Lithosphere Infiltrometer is able measure both surface and subsoil infiltration rate and hydraulic conductivity. It is manufactured using 3D-printed parts and off-the-shelf electronic components. It has a robust, quad-leg design that allows for rapid leveling of the device and accurate setting of water depth via a novel 3D-printed bell chamber. The water level is measured using a U85 JRT laser with ±1 mm accuracy connected to an Adafruit Huzzah 32 microcontroller. Infiltration rate and hydraulic conductivity are calculated at 1 to 10 min time steps, and data is presented in real-time on an OLED display. Data is stored on the device and available for download to a mobile device by Wi-Fi.

This paper discusses the interest in utilizing R, a programming language, in soil physics for enhanced data reproducibility. Reproducibility is challenging across scientific disciplines, including soil science, and it is encouraged by demands for transparency from funding bodies and governments. Open and reproducible soil physics research can benefit the scientific community. With a focus on open science practices, the authors developed {infiltrodiscR}, leveraging existing R knowledge in soil physics. The package facilitates analysis of infiltration data, demonstrated through analysing changes in infiltration using published data. Results align with previous findings, showcasing {infiltrodiscR}'s potential in promoting reproducibility in soil science research.

A study was conducted to investigate the impacts of converting rubber plantations into oil palm plantations on soil properties and soil hydrology. Soil organic carbon (SOC), bulk density (BD), aggregate stability (AS), saturated hydraulic conductivity (Ks), soil water retention, texture, thermal properties, and pH were determined using soil samples collected from different depths of a twelve-year-old oil palm and rubber cultivated fields located in low country wet zone of Sri Lanka. In each field, volumetric water content (VWC) of soil was continuously measured at four soil depths (0-25, 25-50, 50-75, and 75-100 cm) over a seven-month period. While the study revealed a 40% lower SOC in 0-25 cm soil layer of the oil palm field compared to the rubber field, no significant changes were observed in BD, porosity, pore size distribution, AS, and Ks for the two fields. However, the volumetric heat capacity of rubber grown soil was significantly higher than that of the oil palm grown soil. Oil palm utilized the most water from 25-75 cm soil layer; whereas, rubber extracted more water from deeper soil layers (75-100 cm). Soil water depletion in oil palm field was faster during dry periods than in rubber fields highlighting the need to examine the soil water extraction patterns of oil palm during extended dry spells in future studies. Overall, the conversion of rubber into oil palm plantations showed no significant impact on most of the soil properties and soil hydrology after twelve years of conversion. [ABSTRACT FROM AUTHOR]

A power-law formulation rooted in percolation theory has proven effective in depicting the vertical distribution of soil organic carbon (SOC) in temperate forest subsoils. While the model suggests the solute as the primary factor distributing SOC, this may not hold true in the surface soil in which roots contribute significantly to the SOC. This study in the Changbai Mountains Mixed Forests ecoregion (CMMF) evaluates the SOC profiles in three forests to assess the model's efficacy throughout the soil column. Prediction of the SOC profile based on the regional average values was also assessed using field data. The observed scaling aligned well with predictions in mixed broadleaved and broadleaved Korean pine mixed forests, but disparities emerged in birch forest, possibly due to waterlogging. The predicted SOC levels correlate strongly with the field data and align well with the normalized average SOC levels. The findings suggest that the model remains applicable in the CMMF when considering root-derived carbon. However, the hindrance of solute transport may have a greater impact than roots do. The spatial heterogeneity of the SOC means that a single predicted SOC value at a specific depth may not fit all sites, but the overall agreement highlights the potential of the model for predicting the average or representative SOC profiles, which could further aid in regional-scale carbon stock estimation. [ABSTRACT FROM AUTHOR]

Mitigation practices for nitrogen leaching losses from livestock agriculture are needed to protect freshwater quality and increase the efficiency of agricultural production. Within New Zealand, the most common pasture type is a two-species mix of perennial ryegrass (Lolium perenne) and white clover (Trifolium repens). Ecological theory suggests that increasing species and functional diversity improves ecosystem function, including nitrogen (N) retention. Use of more diverse pasture types, including a mix of pasture grasses, legumes and other forbs, particularly plantain (Plantago lanceolata), with functional traits, including winter activity, deep-rooting, N fixation, and biological inhibition of nitrification in the soil, is a potential mitigation practice that requires further verification with long-term field measurements. Here we utilize a network of large lysimeters to make field-based measurements of N leaching from 5–8 species diverse pasture, including plantain, under a range of soil, climate and management conditions, for comparison with losses from traditional ryegrass-clover pasture. Over 3 years of measurements, leaching from fully established diverse pasture was 2–80 kg N ha−1 y−1. No differences were observed in dry matter production or N leaching of diverse pasture compared to ryegrass-clover lysimeters. Large losses, up to 120 kg N ha−1, were observed during periods when pasture was not fully established, including cultivation and sowing of new pasture, depending on season. Timing of management activities could be optimized to minimize these losses. These data provide critical assessment of diverse pasture as a mitigation approach for reducing N losses. Further work on diverse pastures should include higher diversity mixes as well as consideration of animal mediated effects of diverse pasture diets on N inputs.

Abstract Amidst intensifying global agricultural water demand, optimizing management practices and understanding the role of soil amendments, particularly biochar (BC), in modulating soil water dynamics are critical. Here, we review the potential impacts of BC on soil water dynamics, elucidate mechanistic underpinnings, and identify critical research gaps and prospective avenues. In general, BC modifies soil structure, hydraulic properties, surface albedo, and heat fluxes, which influence soil water storage, energy balance, and irrigation paradigms. Depending on soil texture and BC properties, BC demonstrates a greater reduction in bulk density and saturated hydraulic conductivity in coarse-textured soils compared to fine-textured soils. BC application generally increases water holding capacity (WHC) while exhibiting no consistent impact on soil water infiltration. Increased WHC of soils results from increased porosity, surface area, and soil aggregation. Increased porosity arises from a confluence of factors, encompassing new pores formation, reorganization of pores, increased soil aggregation, dilution effects of BC, reduced soil compaction, and biotic interactions, including increased population of burrowing invertebrates. BC tends to increase plant-available water in coarser soils, attributed to its hydrophilic nature, augmented specific surface area, and enhanced overall porosity. However, BC may induce soil water repellency, contingent upon variables such as feedstock composition, pyrolysis temperature, and specific soil attributes. While BC exhibits transformative potential in enhancing soil hydraulic properties, scalability concerns and economic viability pose challenges to its widespread agricultural application. Overall, BC offers promising avenues for sustainable water management. However, it is imperative to explore large-scale applications and conduct long-term field studies across different management, climate, and soil types to fully understand how different types of BC impact soil water dynamics. Graphical Abstract

Understanding the dynamics of soil water content (SWC) is essential for effective land management, particularly in regions affected by underground mining. This study investigates the spatial and temporal patterns of SWC and its interaction with topographic and edaphic factors in coal mining and non-coal mining areas of the Chenghe watershed, located in the southeast of the Chinese Loess Plateau, which is divided by a river. Our findings revealed that the capacity to retain moisture in the top layer of coal mining areas is significantly higher (25.21%) compared to non-coal mining areas, although deeper layers exhibit lower SWC, indicating altered moisture dynamics due to underground mining disturbances. Coal mining areas show greater spatial and temporal variability in SWC, suggesting increased sensitivity to moisture fluctuations, which complicates water management practices. Additionally, underground mining activities introduce more intense effects on the relationship between SWC and topographic factors (i.e., GCVR across soil profile of 0–60 cm; slope at depth of 50 cm) or edaphic factors (i.e., soil organic matter and available potassium at depth of 30 cm; pH at depth of 50 cm) compared to non-coal mining areas. This variability is evident in the temporal shifts from positive to negative correlations, particularly in coal mining areas, reflecting modifications in both soil physical and chemical properties resulting from mining activities. In contrast, non-coal mining areas maintain a more stable moisture regime, likely due to preserved natural soil structures and processes. These contrasting findings emphasize the necessity for tailored management strategies in coal mining regions to address the unique challenges posed by altered soil characteristics and water dynamics.

Introduction: Previous studies have proven that different tillage measures have significant different effects on soil structure, hydrology properties and soil erosion. However, few studies have clarified the dynamic changes in soil aggregate stability and infiltration properties during crop growth under four tillage measures. Methods: Four field plots (150 m x 15 m) managed by four tillage methods including wide ridge tillage (DT), no-tillage (NT), contour ridge tillage (CT) and traditional tillage (CK) were built in 2021 to evaluate their effects on dynamic changes of soil structure and water conductivity during crop growth. Soybean was the seasonal crop. Soil bulk density, soil porosity, soil aggregate stability and soil infiltration characteristics were measured to assess dynamic changes in soil aggregate stability and infiltration from June to October 2022. Results: The results showed that NT significantly increased soil bulk density by up to 21.62% compared with CK, while DT did not show significantly increase in soil bulk density. DT, NT and CT could greatly increase the capillary porosity and proportion of capillary porosity to total porosity. DT and NT also improved the stability of soil water-stable aggregates by 3.37% and 10.6%. In terms of soil infiltration properties, all three tillage methods increased the initial, stable and average infiltration rates by 8.4%-52.94%, of which the DT and NT showed the greatest improvement. The soil infiltration process of four tillage measures could be better fitted by Horton model than Kostiakov and Philip models. Soil saturated hydraulic conductivity (SHC) of CK exhibited a significant negative correlation with soil bulk density and capillary porosity, and showed a positive correlation with total porosity and geometric average diameter of water-stable aggregate (GMD), whereas the other three treatments only displayed a significant correlation with the stability of soil water-stable aggregate. Conclusion: The results suggest that DT, NT and CT have potential to improve soil structure and infiltration capacity compared with CK, and contribute to preventing and controlling soil erosion in sloping farmland of Northeast China. [ABSTRACT FROM AUTHOR]

Understanding the dynamic response of soil moisture to rainfall is crucial for describing hydrological processes at the hillslope scale. However, because of sparse monitoring coupled with the complexity of water movement and steep topography, the findings of rainfall‐related soil moisture dynamics have not always been consistent, indicating a need for systematic investigations of soil moisture dynamics and infiltration patterns following rainfall inputs at multiple topographic positions along a hillslope. This study aimed to examine the nature of these responses by characterizing and quantifying the response amplitude, rate and time for 37 large rainfall events at 25 combinations of topographic positions and soil depths along a steep forested hillslope. Our results showed that soil moisture responses under different rainfall patterns could be attributed to one or the other rainfall characteristics, such as rainfall intensity and amount. However, soil moisture dynamics at different hillslope positions after rainfall varied widely due to the controls of soil properties, topography, and non‐equilibrium flow. Preferential flow was more evident under dry initial soil conditions than under wet initial soil conditions. Findings of this study reveal that the dynamic response patterns of soil moisture to rainfall do not always follow topographic controls, which can improve our understanding of water cycling related to the infiltration process at the hillslope scale, and support water resources management in subtropical mountain ecosystems. [ABSTRACT FROM AUTHOR]

Amidst intensifying global agricultural water demand, optimizing management practices and understanding the role of soil amendments, particularly biochar (BC), in modulating soil water dynamics are critical. Here, we review the potential impacts of BC on soil water dynamics, elucidate mechanistic underpinnings, and identify critical research gaps and prospective avenues. In general, BC modifies soil structure, hydraulic properties, surface albedo, and heat fluxes, which influence soil water storage, energy balance, and irrigation paradigms. Depending on soil texture and BC properties, BC demonstrates a greater reduction in bulk density and saturated hydraulic conductivity in coarse-textured soils compared to fine-textured soils. BC application generally increases water holding capacity (WHC) while exhibiting no consistent impact on soil water infiltration. Increased WHC of soils results from increased porosity, surface area, and soil aggregation. Increased porosity arises from a confluence of factors, encompassing new pores formation, reorganization of pores, increased soil aggregation, dilution effects of BC, reduced soil compaction, and biotic interactions, including increased population of burrowing invertebrates. BC tends to increase plant-available water in coarser soils, attributed to its hydrophilic nature, augmented specific surface area, and enhanced overall porosity. However, BC may induce soil water repellency, contingent upon variables such as feedstock composition, pyrolysis temperature, and specific soil attributes. While BC exhibits transformative potential in enhancing soil hydraulic properties, scalability concerns and economic viability pose challenges to its widespread agricultural application. Overall, BC offers promising avenues for sustainable water management. However, it is imperative to explore large-scale applications and conduct long-term field studies across different management, climate, and soil types to fully understand how different types of BC impact soil water dynamics. Highlights: Biochar generally improves soil water retention in coarse-textured soils. In coarse-textured soils, biochar increases porosity and PAW but decreases bulk density and Ksat. The effects of biochar on infiltration rates vary depending on soil types, as well as biochar particle size, production temperature, and depth of placement. Further studies on the mechanisms governing water retention in biochar-amended soils are warranted. Long-term studies encompassing various soil and biochar types are necessary. [ABSTRACT FROM AUTHOR]

Extreme rainfall events pose a severe challenge to soil and water conservation, even in areas with high vegetation cover on the Loess Plateau. In this study, the artificial extreme rainfalls with cumulative rainfall of 270 mm and intensity of 60 mm · hr−1 were conducted on in‐situ experimental plots (20 × 2.5 m) on a loess gully–slope with gradients of 35°–40° that were treated with different grass coverage: (0%, 30%–40%, 70%–80%, >90%). The ephemeral gully/rill and shallow landslide occurred in plots were analyzed. Revegetation changed the erosion type on gully–slope, reducing gully erosion but promoting shallow landslide due to the change from infiltration–excess runoff to saturation–excess runoff. Under grass coverage of >90%, over 95% of rainfall seeped into the soil, and subsurface flow was generated due to the lower saturated hydraulic conductivity of underlying soil, which increased the possibility of landslides. The average erosion rate (0.36–3.29 g · m−2 min−1; no obvious erosion) in plots with 70%–80% coverage was 95.5% lower than that in bare land plots (27.8–47.5 g · m−2 min−1; ephemeral gully erosion), while due to landslides the average erosion rate in plots with >90% coverage (135.1–184.3 g · m−2 min−1) was 86.5 times higher than that in plots with 70%–80%. For grass, a coverage of 70%–80% was most effective in preventing soil erosion, controlling gully erosion and preventing landslides under extreme rainfall. These results deepen the understanding of the complex relationship between vegetation, gully erosion, and landslides in ecologically sensitive areas. Key Points: Vegetation changed the erosion type on slope from water erosion to gravity erosionHigh‐coverage vegetation promoted shallow landslides under extreme rainfallFor grass cover, a coverage of 70%–80% was most effective in preventing soil erosion [ABSTRACT FROM AUTHOR]

Soil compaction is a threat to agricultural soil function due to constriction of macro- and meso-pores necessary for air and water movement and crop root elongation. Soils are most vulnerable to compaction when moist. Agricultural soils saturated from winter precipitation or from intentional flooding for groundwater recharge may limit growers’ operational access to fields. The objective of this research was to develop guidance for rain-free “time-to-trafficability” (including shallow workability—when a soil is conducive to both tillage and traffic) after deep wetting, using soil survey data, pedotransfer functions, and a hydroclimatological modeling approach. Trafficability is defined as a threshold of field capacity (θfc) at the soil surface (0–10 cm), ranging from 85% of θfc (clays and silty clays) to 95% of θfc (sands and loamy sands). The θfc threshold is guided by the soil texture plasticity index, an indicator of compaction risk. 2911 soil profiles from soil survey databases were subjected to a wetting simulation, followed by drainage and evaporation using HYDRUS-1D across 11 locations representing mean annual potential evapotranspiration (PET) quantiles from 5% to 95%, four months (January-April), and three different years, assuming no precipitation. Rain-free time-to-trafficability was greatest in fine and loamy soils during cold months (January and February). However, seasonal effects on time-to-trafficability were more pronounced in loamy soils. Non-linear predictive functions were developed for each 0–10 cm textural class to enable mapping the typical time-to-trafficability across PET gradients, revealing clear regional and temporal patterns. Model derived estimates can inform agricultural managed aquifer recharge timing decisions and subsequent risk of soil compaction. Additional research is needed for validation and to better constrain time-to-trafficability estimates for loamy and fine textured soils, which show a greater degree of uncertainty amid greater risk of compaction indicated by plasticity indices.

Introduction: Previous studies have proven that different tillage measures have significant different effects on soil structure, hydrology properties and soil erosion. However, few studies have clarified the dynamic changes in soil aggregate stability and infiltration properties during crop growth under four tillage measures.Methods: Four field plots (150 m × 15 m) managed by four tillage methods including wide ridge tillage (DT), no-tillage (NT), contour ridge tillage (CT) and traditional tillage (CK) were built in 2021 to evaluate their effects on dynamic changes of soil structure and water conductivity during crop growth. Soybean was the seasonal crop. Soil bulk density, soil porosity, soil aggregate stability and soil infiltration characteristics were measured to assess dynamic changes in soil aggregate stability and infiltration from June to October 2022.Results: The results showed that NT significantly increased soil bulk density by up to 21.62% compared with CK, while DT did not show significantly increase in soil bulk density. DT, NT and CT could greatly increase the capillary porosity and proportion of capillary porosity to total porosity. DT and NT also improved the stability of soil water-stable aggregates by 3.37% and 10.6%. In terms of soil infiltration properties, all three tillage methods increased the initial, stable and average infiltration rates by 8.4%–52.94%, of which the DT and NT showed the greatest improvement. The soil infiltration process of four tillage measures could be better fitted by Horton model than Kostiakov and Philip models. Soil saturated hydraulic conductivity (SHC) of CK exhibited a significant negative correlation with soil bulk density and capillary porosity, and showed a positive correlation with total porosity and geometric average diameter of water-stable aggregate (GMD), whereas the other three treatments only displayed a significant correlation with the stability of soil water-stable aggregate.Conclusion: The results suggest that DT, NT and CT have potential to improve soil structure and infiltration capacity compared with CK, and contribute to preventing and controlling soil erosion in sloping farmland of Northeast China.

Purpose: Elucidating the effects of vegetation on soil mechanical and hydrological behavior is crucial to understand shallow landslide stability. However, in geohazard-prone regions, quantifying the soil hydrological behavior is challenging because of large variations in soil water. The positive effects of vegetation hydrological effects have not been clearly delineated. The objective of this study was to analyze the contribution of vegetation types to slope stability under different soil matric suction conditions. Methods: The hydrological and mechanical properties of soil were measured and the extended Mohr–Coulomb failure criterion were used to estimate the differences in hydrological reinforcement on slopes under three vegetation types (grasslands, trees, and shrubs). The slope stability was compared using a two-dimensional finite element model. Results: The results showed that the increase in soil hydrological reinforcement of grasslands (16%) was higher than that of shrubs (13%) and trees (9%). The displacement vector and plastic strain cloud map indicated that slope failure was initiated from the foot of the slope; additionally, the plastic strain area of the grasslands was considerably larger than that of the shrubs and trees. Furthermore, with increase in matric suction, the factor of safety (FoS) of slope for trees, shrubs, and grasslands increased from 1.87 to 2.87, 1.50 to 3.53, and 1.47 to 3.32, respectively, with minimum variations in the FoS of slope for trees. Conclusions: This study provides valuable insights for quantifying the contribution of soil matric suction to the hydrological reinforcement of shallow slopes under different vegetation types. To maintain slope stability, understanding the soil hydrological properties is important to select suitable plants that can strengthen slope stabilities, allocate plant communities scientifically and rationally, and guide the implementation of appropriate land management practices. [ABSTRACT FROM AUTHOR]

Background: Vegetation roots are considered to play an effective role in controlling soil erosion by benefiting soil hydrology and mechanical properties. However, the correlation between soil hydrology and the mechanical features associated with the variation root system under different vegetation types remains poorly understood. Methods: We conducted dye-tracer infiltration to classify water flow behavior and indoor experiments (including tests on soil bulk density, soil organic carbon, mean weight diameter, soil cohesion, root density, etc.) to interpret variation patterns in three forest systems (coniferous and broad-leaved mixed forest, CBF; coniferous forest, CF; Phyllostachys edulis, PF) and fallow land (FL). Results: Based on the soil dye-tracer infiltration results, the largest dyeing area was observed in CF (36.96%), but CF also had the lowest infiltration rate (60.3 mm·min−1). The soil under CBF had the highest shear strength, approximately 25% higher than other vegetation types. CF exhibited the highest aggregate stability, surpassing CBF by 98.55%, PF by 34.31%, and FL by 407.41%, respectively. Additionally, PF forests showed the greatest root biomass and length. The results of correlation analysis and PCA reveal complex relationships among hydrological and mechanical soil traits. Specifically, soil cohesion does not exhibit significant correlations with hydrological traits such as the dyeing area, while traits like MWD and PAD show either positive or negative associations with hydrological traits. Root traits generally exhibit positive relationships with soil mechanical traits, with limited significant correlations observed with hydrological traits. Conversely, we found that root biomass contributes significantly to the dyeing area (accounting for 51.48%). Conclusions: Our findings indicate that the reforestation system is a successful approach for conserving water and reducing erosion by increasing soil-aggregated stability and shear strength, causing water redistribution to be more homogenized across the whole soil profile. [ABSTRACT FROM AUTHOR]

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Terraced landscapes represent one of the most widespread human-induced/man-made transformations of hilly-mountainous environments. Slope terracing produces peculiar morphologies along with unusual soil textures and stratigraphic features, which in turn strongly influence slope hydrology. The investigation of the hydrological features of terraced soils is of fundamental importance for understanding the hydrological dynamics occurring in these anthropogenic landscapes, especially during rainfall events. To this purpose, the availability of extensive field monitoring data series and of information on subsoil properties and structure is essential. In this study, multi-sensor hydrological data were acquired over a period longer than 2 years in the experimental site of Monterosso al Mare, in the Cinque Terre National Park (Liguria region, Italy), one of the most famous examples of terraced landscape worldwide. Monitoring data were coupled with accurate engineering-geological investigations to achieve the hydro-mechanical characterization of backfill soils and to investigate their hydrological response at both the seasonal and the single rainstorm scale. The results indicated that the coarse-grained, and anthropically remolded texture of the soils favors the rapid infiltration of rainwater, producing sharp changes in both soil volumetric water content and pore water pressure. Furthermore, the pattern of hydrological parameters showed seasonal trends outlined by alternating phases of slow drying and fast wetting. The study outcomes provide useful insights on the short and long-term evolution of hydrological factors operating in agricultural terraces. These findings represent a useful basis for a better understanding of the time-dependent processes that guide water circulation in terraced systems, which have a key role in controlling the occurrence of erosion and landslide processes. [ABSTRACT FROM AUTHOR]

The rock fragment (RF) has been widely observed in the soil solum or on the soil surface. It regulates soil hydrological processes (SHPs) and thus has great impacts on soil and water conservation. However, responses of SHPs to RF characteristics (position, content, coverage area, mulching thickness, and size) remain unclear. Based on the dataset extracted from 168 published studies, effects of RF characteristics on SHPs (soil loss rate, evaporation rate, surface runoff rate, infiltration rate, soil water content, and soil water storage) and saturated hydraulic conductivity (Ks) were discussed in this study. Results showed that RFs completely inserted into the soil solum (CO_INS) improved the Ks by 6.9%, runoff rate by 12.8%, and soil loss rate by 22.3%, while it reduced the evaporation rate by 30.7%, infiltration rate by 15.4%, and soil water content by 9.9%. With the RF content (kg kg−1) increasing, its effects on these SHPs were strengthened. The RFs resting on the surface and partially covering soil surface (PA_COV) improved the infiltration rate but reduced the evaporation rate by 36.9%, surface runoff rate by 25.4%, and soil loss rate by 59.3%. This in turn enhanced soil water content and storage. However, as the RF coverage (% in area) increasing, the cross-sectional area of water flow decreased, and thus the infiltration rate reduced. The RFs completely mulch on the soil surface (CO_MUL) reduced the evaporation rate by 59.5% and infiltration rate by 76.5% but improved the soil water content and storage. Except the infiltration rate, the effects of CO_MUL on SHPs were strengthened as mulch thickness (cm) increased. The RFs partially embedded into soil surface (PA_EMB) promoted surface runoff rate by 15.3%, soil loss rate by 34.7%, and soil water content by 24.3%, but reduce the infiltration rate. However, the surface runoff rate was reduced at high embedded coverage due to increased tortuosity of water flow. In addition, the RF size exerted weaker effects on SHPs than RF positions, content, coverage, and mulch thickness. Our findings enhanced the understanding of SHP responses to RFs characteristics, which would be important for relate soil and water modeling and management. [ABSTRACT FROM AUTHOR]

Copper and zinc are present in fertilizers, such as copper sulfate and zinc sulfate, and evaluation of their susceptibility to leaching is important, as well as their interaction and competitiveness in soil systems. This article aimed to evaluate the adsorption kinetics of copper and zinc in mono- and multi-component systems in an Oxisol, Inceptisol and Entisol Quartzipsamment using multivariate analyses. Physical, chemical, and mineralogical analyses of the soils were performed, and the batch method was used. Copper and zinc solutions containing the same concentrations of target and competitive ions were used in the sorption kinetics assays, and quantification was performed in an atomic absorption spectrophotometer. The pseudo first-order, pseudo second-order and Elovich models were fitted to the observed data. The results showed that the first principal component was related to the adsorption estimated by the pseudo first-order model and the adsorption properties of the soils. The second principal component was associated with charged adsorptive surfaces, such as clay and organic matter. In the dendrogram, Cluster 1 consisted of the Inceptisol, which contains minerals that enhance the adsorption of ions. Cluster 2 highlighted the similarities in ion adsorption between the Oxisol and Entisol Quartzipsamment, which have lower ion retention capacities. [ABSTRACT FROM AUTHOR]

Terraced landscapes represent one of the most widespread human-induced/man-made transformations of hilly-mountainous environments. Slope terracing produces peculiar morphologies along with unusual soil textures and stratigraphic features, which in turn strongly influence slope hydrology. The investigation of the hydrological features of terraced soils is of fundamental importance for understanding the hydrological dynamics occurring in these anthropogenic landscapes, especially during rainfall events. To this purpose, the availability of extensive field monitoring data series and of information on subsoil properties and structure is essential. In this study, multi-sensor hydrological data were acquired over a period longer than 2 years in the experimental site of Monterosso al Mare, in the Cinque Terre National Park (Liguria region, Italy), one of the most famous examples of terraced landscape worldwide. Monitoring data were coupled with accurate engineering-geological investigations to achieve the hydro-mechanical characterization of backfill soils and to investigate their hydrological response at both the seasonal and the single rainstorm scale. The results indicated that the coarse-grained, and anthropically remolded texture of the soils favors the rapid infiltration of rainwater, producing sharp changes in both soil volumetric water content and pore water pressure. Furthermore, the pattern of hydrological parameters showed seasonal trends outlined by alternating phases of slow drying and fast wetting. The study outcomes provide useful insights on the short and long-term evolution of hydrological factors operating in agricultural terraces. These findings represent a useful basis for a better understanding of the time-dependent processes that guide water circulation in terraced systems, which have a key role in controlling the occurrence of erosion and landslide processes.

In areas with scarce water resources, it is so important to analyze the connection between the different elements of a river basin and the water collected by the basin's reservoir, to determine and predict the spatial and temporal variability of water on it. In this paper, we use the basic principles of hydrological modelling to develop a model for the exploitation of rainfall in reservoir basins in the province of Malaga, Spain. The monthly water input data of the seven reservoirs in the province of Malaga, provided by the Hidrosur Network of the Automatic Hydrological Information System (SAIH), as well as the precipitation and daily temperature of the stations of the State Meteorological Agency (AEMET) associated with the basins of each of these reservoirs were used. We assume that the entrance to a reservoir in a given month must depend on the precipitation produced in its watershed (both the amount of rain and the intensity with which it fell), the precipitation collected from the previous months (and the way in which it was produced) and the evapotranspiration produced during that period. For each reservoir, we propose a model with nine parameters to simulate the arrival of rainfall to the reservoir, covering aspects from the amount and intensity of rain, past and present, to the level of evapotranspiration on a given area for a given date. These nine parameters are optimally adjusted through an artificial intelligence algorithm to maximize the correlation between real and simulated contributions. The results show how this model, adjusted for each reservoir, will let us predict how changes in the rainfall and temperature patterns, predicted, for example, by the IPCC models, will affect the future water levels at the studied reservoirs. [ABSTRACT FROM AUTHOR]

Climate change and unsustainable land management practices have resulted in extensive soil degradation, including alteration of soil structure (i.e., aggregate and pore size distributions), loss of soil organic carbon, and reduction of water and nutrient holding capacities. Although soil structure, hydrologic processes, and biogeochemical fluxes are tightly linked, their interaction is often unaccounted for in current ecohydrological, hydrological and terrestrial biosphere models. For more holistic predictions of soil hydrological and biogeochemical cycles, models need to incorporate soil structure and macroporosity dynamics, whether in a natural or agricultural ecosystem. Here, we present a theoretical framework that couples soil hydrologic processes and soil microbial activity to soil organic carbon dynamics through the dynamics of soil structure. In particular, we link the Millennial model for soil carbon dynamics, which explicitly models the formation and breakdown of soil aggregates, to a recent parameterization of the soil water retention and hydraulic conductivity curves and to solute and O2 diffusivities to soil microsites based on soil macroporosity. To illustrate the significance of incorporating the dynamics of soil structure, we apply the framework to a case study in which soil and vegetation recover over time from agricultural practices. The new framework enables more holistic predictions of the effects of climate change and land management practices on coupled soil hydrological and biogeochemical cycles. Plain Language Summary: Soil degradation due to climate change and unsustainable land management practices is a global phenomenon that threatens food security and Earth livability at large. While soil degradation involves modifications of both physical and biological properties of soils, mathematical models to predict these changes have focused independently on these two aspects, limiting our ability to holistically assess climate and human drivers of soil degradation. Here, we connected recent advances in modeling physical and biological soil processes to develop a unified framework that can account more holistically for potential changes in soil properties over time. The potential of this framework to predict soil changes is illustrated through an analysis of a case study of soil and vegetation recovery from agricultural practices. This work may represent an important step toward predicting the effects of land use and climate changes on soil degradation, hence enabling the design of more sustainable land management strategies. Key Points: A framework linking soil structure, carbon, and hydrology is needed for holistic predictions under environmental and land use changesThe novel Millennial model for soil carbon cycling is linked to a recent soil hydraulic parameterizationAggregated carbon is used as a proxy for soil macroporosity to simultaneously model the changes in soil properties and microbial activity [ABSTRACT FROM AUTHOR]

The soil freeze–thaw process is a transition phase of soil water in cold areas that influences the soil's hydrological behavior. However, dynamic phenomena and corresponding consequences have yet to be studied adequately. Therefore, the present study was planned to comparatively analyze the effects of a freezing–thawing cycle on the hydrologic behaviors of loess soil from northeast Iran. Small-size (0.5 × 0.50 m) erosion plots were subjected to a freezing–thawing cycle under governing conditions of the region of the origin soil. The plots were subjected to a freezing–thawing treatment by inducing cold air until the temperature declined to below − 20 °C and lasted for 3 days using a cooling compartment system and then were kept in the laboratory with an ambient temperature of above 10 °C for 2 days. The treated plots and untreated plots were then exposed to a simulated rainfall with an intensity of 72 mm h−1 and 0.5 h duration while they were placed on a slope of 20%. The results indicated that the hybrid processes of freezing–thawing and splash and inter-rill erosions significantly increased runoff generation and soil loss. The time to runoff, runoff volume, and soil loss were 1.65 times less and 1.38 and 2.90 times more, respectively, compared to those reported for the control treatment with significant differences (p < 0.006). The performance of ice lenses, freezing fronts, and the creation of near-saturation moisture after completing the cycle were identified as the most critical factors affecting the different soil behaviors under the frozen-thawed cycle. [ABSTRACT FROM AUTHOR]

Gypsum (CaSO4∙2H2O) amendment can reduce phosphorus (P) export from agricultural fields and protect water quality. Past studies have examined the impact of gypsum application rate, but limited research has been conducted to assess the effect of the time interval between gypsum application and P fertilization on treatment effectiveness and P mobility. To address this question, a mesocosm-scale experiment was conducted using 36 soil columns packed with either Brookston clay-loam (total phosphorus, TP: 0.46 g kg−1) or Fincastle silt-loam soil (TP: 4.63 g kg−1). For each soil type, 9 columns were treated with gypsum (5 Mg ha−1) and an equal number served as untreated controls. At different time intervals (2, 30, and 58 days after gypsum application), one-third of the columns received P fertilizer (34 kg P ha−1). Rainwater was added to generate leachate that was collected over a 3-week period and analyzed for pH, sulfate (SO4−2), dissolved reactive P (DRP), and TP. At the end of each leaching period, soil columns were sliced (2–5 cm layers), and the amount of water-extractable P (WEP) and Olsen-P was quantified. The gypsum treatment had generally no effect on Olsen-P, but it consistently resulted in lower WEP level (1.8-fold) compared to controls. Likewise, during the later stage of the experiment (> 30 days), the gypsum treatment resulted in DRP concentration reduction (28–52%) in leachate from the Fincastle soil columns (but the effect was marginal in the Brookston columns likely due to limited distribution of surface applied gypsum in this fine-textured soil). These results indicated that the effect of gypsum on DRP leaching varies with the timing of P application. Depending on soil type, an interval of 1–2 months (shorter interval for coarse-textured soils; longer interval if soils are fine-textured) should be adopted before applying P fertilizer in order to optimize the effectiveness of the gypsum treatment. [ABSTRACT FROM AUTHOR]

Soil water storage and movement are highly heterogeneous across landscapes and their response to spatiotemporal variations in meteorological forcing is complex. While different pools of soil water (including bound and mobile water) are observed, the mechanisms of soil water movement in semi-arid and sub-humid regions are not well understood due to high variation in soil water storage conditions. The Taihang Mountain is a headwater region that recharges both groundwater and surface water systems of the North China Plain, where groundwater levels have been declining and water storage loss is serious. Increasing land cultivation in the Taihang Mountain areas has increased evapotranspiration and reduced both surface runoff and groundwater recharge. Although extreme precipitation is critical for groundwater recharge in the headwater regions, the response mechanism of soil water movement and groundwater recharge remains unclear. In this study, soil water movement and groundwater recharge mechanisms in a cultivated farmland (FL) and land under natural vegetation (NV) were determined for a normal and an extreme precipitation year through the combined use of soil water content and stable isotopes of water (18O and 2H). Soil water got enriched in δ18O and δ2H (δ18O changed from −11.2 to −7.0‰ at NV and from −11.1 to −4.4‰ at FL; δ2H changed from −71 to −49‰ at NV and from −73 to −30% at FL) with increasing soil depth during the growing season suggesting that winter precipitation was generally transported via advection dispersion flow mechanism. However, this process was accompanied by the mixing of previously enriched soil water after large rain events (20–50 mm/day) during the rainy season in a normal precipitation year. Water movement changed from translatory flow to preferential flow after extreme precipitation in a wet precipitation year. Cultivation intensified water evaporation in the top soil layer (upper 10–20 cm), and induced preferential flow down to 50 cm soil depth under FL relative to land under NV. Thus, cropping significantly reduced groundwater recharge. Excessive storm during a wet year produced bypass flow after the first rainstorm, which rapidly recharged deep soil layers (50–100 cm depth). Bypass flow induced by excessive precipitation and contributed the most to groundwater in FL. The observed rapid response of soil water and groundwater to extreme precipitation events is critical for soil and water management to mitigate problems such as nitrate leaching and groundwater contamination in headwater regions of semi-arid and sub-humid areas.

Soil water storage and movement are highly heterogeneous across landscapes and their response to spatiotemporal variations in meteorological forcing is complex. While different pools of soil water (including bound and mobile water) are observed, the mechanisms of soil water movement in semi-arid and sub-humid regions are not well understood due to high variation in soil water storage conditions. The Taihang Mountain is a headwater region that recharges both groundwater and surface water systems of the North China Plain, where groundwater levels have been declining and water storage loss is serious. Increasing land cultivation in the Taihang Mountain areas has increased evapotranspiration and reduced both surface runoff and groundwater recharge. Although extreme precipitation is critical for groundwater recharge in the headwater regions, the response mechanism of soil water movement and groundwater recharge remains unclear. In this study, soil water movement and groundwater recharge mechanisms in a cultivated farmland (FL) and land under natural vegetation (NV) were determined for a normal and an extreme precipitation year through the combined use of soil water content and stable isotopes of water (18O and 2H). Soil water got enriched in δ18O and δ2H (δ18O changed from −11.2 to −7.0‰ at NV and from −11.1 to −4.4‰ at FL; δ2H changed from −71 to −49‰ at NV and from −73 to −30% at FL) with increasing soil depth during the growing season suggesting that winter precipitation was generally transported via advection dispersion flow mechanism. However, this process was accompanied by the mixing of previously enriched soil water after large rain events (20–50 mm/day) during the rainy season in a normal precipitation year. Water movement changed from translatory flow to preferential flow after extreme precipitation in a wet precipitation year. Cultivation intensified water evaporation in the top soil layer (upper 10–20 cm), and induced preferential flow down to 50 cm soil depth under FL relative to land under NV. Thus, cropping significantly reduced groundwater recharge. Excessive storm during a wet year produced bypass flow after the first rainstorm, which rapidly recharged deep soil layers (50–100 cm depth). Bypass flow induced by excessive precipitation and contributed the most to groundwater in FL. The observed rapid response of soil water and groundwater to extreme precipitation events is critical for soil and water management to mitigate problems such as nitrate leaching and groundwater contamination in headwater regions of semi-arid and sub-humid areas.

Purpose: Inconsistent controlling factors of soil water content (SWC) spatial variation across regions and spatial scales have been acknowledged in previous studies. However, universal principles explaining these inconsistencies are still needed to be explored. The main aim of this study was to conclude the universal principles across regions and scales. Materials and methods: In this study, based on the surface (< 10-cm soil depth) SWC dataset from Meng et al. (2021) (https://doi.org/10.5194/essd-13-3239-2021) and the relevant environmental variables (climate including temperature and precipitation, topography including elevation and slope, soil including sand and clay contents, and vegetation including normalized difference vegetation index or NDVI) in a 1500 km × 1500 km study region in China, we calculated the correlations between them, and identified the controlling factors of surface SWC in different subregions and at different spatial scales. Results and discussion: Local factors like temperature, precipitation, and clay content that controling the vertical soil water replenishment and removal dominated the surface SWC spatial variation in this dry study region (mean SWC ≤ 0.10 m3 m−3). Nonlocal factors like topography (e.g., elevation and slope) and soil porosity (sand content) determining the lateral soil water redistribution had outweighed effects in the representative wet subregion. In addition, topography also exerted considerable effects on SWC in this study region due to its great spatial variability, especially when spatial scale < 800 km. As NDVI was complicatedly controlled by other environmental variables, its effect on SWC performed dramatic regional differentiation. In contrast, effect of slope on SWC was more associated with its spatial variability as it was independent from other environmental variables. Conclusions: This study emphasized that the inconsistencies of controlling factors of SWC spatial variation can be comprehensively explained by different regimes in the dry and wet conditions, spatial variability of environmental variables and the interactions among different environmental variables. These findings can deepen our understanding of the controls on SWC spatial variation across regions and scales. [ABSTRACT FROM AUTHOR]

Because tension infiltrometers apply water through a disk of finite size, the infiltrated water moves laterally as well as downward. Only the vertical component of this flow is indicative of the hydraulic conductivity K, so the algorithm for computing K must include a way of isolating that component from the total flow. Some commonly used formulas correct for the multidimensional effects by subtracting an estimate of the laterally spreading flow. For disks smaller than about 200 mm in diameter, however, lateral spreading constitutes so much of the total flow that these subtractive formulas lose considerable accuracy, and sometimes overcorrect so severely as to produce a negative number for K. Other methods rely on empiricisms that are not completely consistent with unsaturated‐flow theory and that require prior knowledge of certain soil properties. We developed a new formula that uses a multiplicative factor instead of a subtracted term to achieve the needed correction. For testing we conducted numerical experiments with synthetic data produced by solving the Richardson‐Richards equation using the code VS2DRTI, for diverse media and a range of disk sizes, including the widely used 45‐mm diameter. We compared K values calculated from our formula to the actual K used to generate the simulated data, as well as to results from other published formulas. This comparison shows that our method provides an algorithm based in unsaturated‐flow theory that produces more reliable values for small disks without requiring prior knowledge of soil properties. Plain Language Summary: Tension infiltrometers are much‐used devices for field measurement of the hydraulic conductivity of soil. Hydraulic conductivity is a measure of how easily water flows in the soil. If it is high, water at the soil surface can cause more infiltration and less runoff, and can move faster within the soil. Tension infiltrometers apply water over a circular area of the soil surface and measure the flow rate of the water being drawn into the soil. For small infiltrometers, a large fraction of the water spreads laterally within the soil, rather than straight down. Consequently, the amount of water flow measured by the infiltrometer is much greater than just the downward‐flowing portion needed to indicate hydraulic conductivity. This laterally flowing water must be corrected for in the formulas that calculate hydraulic conductivity from the measured data. If the diameter is less than about 200 mm, as it is for the great majority of infiltrometers, the needed correction is so large that large errors result from the approximate corrections applied by commonly used formulas. Our new method uses an estimate of the distance the water spreads laterally to give more accurate results. Key Points: Measurements from small diameter tension infiltrometers require a large correction to account for the lateral spreading of infiltrated waterThe use of a multiplicative, rather than subtractive, correction method provides greater accuracy when the correction is large, as needed for small disksOur proposed method provides a direct estimate of how much flow is going into lateral versus vertical components, thereby yielding additional information for interpretation as well as more accurate hydraulic conductivity results [ABSTRACT FROM AUTHOR]

To avoid flooding and erosion hazards, post-fire management actions are essential in Mediterranean forests after severe wildfires. In this regard, mulching is the most common action but some mulch materials, such as straw, may lead to adverse impacts in burned forests. The use of yellow mistletoe fruits (Loranthus europaeus Jacq., hereafter "LE") for the production of biodegradable mulch and its effectiveness in post-fire hydrology have never been studied. To fill this gap, this study has evaluated surface runoff and rainsplash erosion in a pine forest in Central Eastern Spain burned by a wildfire and mulched by a mixture of LE fruits and straw (with or without adding clay particles) using a portable rainfall simulator. Compared to untreated sites, runoff increased in burned and mulched soils (by 13.6% for the mixture without clay and by 17.2% when clay was added, in the latter case significantly). This increase was mainly due to the compact layer created by mulch application on the soil surface. However, the peak flow and the time to peak were lower in mulched soils (on average by 32.7% and 60.5%, significantly only for the mulch mixture without clay), thus indicating that, in these soils, peak runoff takes longer and its maximum value is lower compared to untreated sites. Soil erosion noticeably and significantly decreased (up to 97%) in mulched areas in comparison to untreated sites without significant differences between the two mixtures. Overall, this study indicates to land managers that soil mulching with a mixture of Loranthus europaeus Jacq. and straw is an effective post-fire management action to reduce the soil erosion risk after a wildfire. [ABSTRACT FROM AUTHOR]

Abstract The regulation of soil water retention by biochar amendment has been concerned especially in cropland ecosystem. However, the quantification of biochar's effects on soil hydrological properties and crop water use efficiency (WUE) is still limited, and the factors driving the biochar effect need to be investigated. Based on a database with 681 observations, meta‐analysis and structural equation model (SEM) were employed to reveal how biochar amendment affects water supply capacity and WUE. The results showed that biochar application increased available water content (AWC) and WUE by 26.8% and 4.7% on average, respectively. According to the SEM of AWC (R2 = 0.70–0.96), the increase of soil organic carbon (+36.1%) by biochar application can not only directly improve AWC but also indirectly improve AWC by affecting permanent wilting point (−1.0%) and mean weight diameter (+11.1%). The SEM of WUE (R2 = 0.74) indicated that soil moisture and porosity were increased by 10.8% and 7.0% under biochar amendment, which was the reason why biochar improved WUE. This study emphasized that biochar can improve soil hydrology and crop yield by increasing soil water supply conditions. And a rational rate of biochar is the precondition to obtaining the benefits of soil hydrology, otherwise, the excessive use of biochar may lead to the decline of WUE.

Water availability is an important driver of plant functional biogeography. Most studies focus on the effects of precipitation, and neglect the contribution of groundwater as a source when the water table depth (WTD) is accessible to roots. Previous studies suggested that shallow water tables select for acquisitive traits. These studies have mostly contrasted shallow vs. deep water tables, without considering a more fine-grained perspective within shallow water tables or the temporal WTD behavior. Here we tested whether the degree of variation in WTD translates into divergent modes of trait selection. We expect constantly shallow WTD leading to the selection of acquisitive traits, whilst high fluctuation of WTD would lead to tree communities with more conservative traits. We used community and trait data (wood density and leaf traits) from 25 1-ha forest monitoring plots spread over 600 km in central Amazonia, covering a gradient of shallow to intermediate (0–8 m deep) WTD along the Purus-Madeira interfluve. Wood density was measured directly in trunk cores (498 trees) and leaf traits (Specific Leaf Area, Leaf Dry Mass Content, Leaf Thickness) of >6,000 individuals were estimated with FT-NIR (Fourier-Transformed Near-Infrared Spectroscopy) spectral models calibrated with cross-Amazonian data. We observed a turnover of families, genera, and species along the gradient of temporal WTD fluctuation range. This taxonomic turnover was accompanied by a change in wood traits, with higher wood density associated to higher WTD fluctuation and higher climatic water deficit. Leaf traits, however, varied in the opposite direction than initially hypothesized, i.e., trees had more acquisitive traits toward intermediate WTD with higher fluctuation. Based on those results, we propose that the effect of WTD selection should be conceptualized in a quadratic form, going from water excess in very shallow WTD (5 m, limiting condition, with conservative traits again).

Most of the uncovered slope surfaces in tropical climates are highly susceptible to shallow, rainfallinduced soil erosion. The practice of re-vegetation is known to hold promise for a sustainable and longterm solution. Hence this study aimed to evaluate slope hydrological performance associated with vegetation and identify correlations among the parameters. Three experimental plots were set up comprising three density treatments; control (C; without the addition of plants), less dense (LD; 0.7 plant/m2), and dense (D; 1 plant/m²). The vegetated plots were grown with potential pioneers, namely Lantana camara, Melastoma malabathricum, and Bauhinia pupurea in a mixed species composition. A significant decrease in soil bulk density and an increase in soil total porosity, hydraulic conductivity, moisture content, organic matter, and organic carbon were found in D plot. These positive changes boosted plant growth, resulting in higher community-plants aboveground biomass and root length density resulting in the erosion rate being alleviated in LD and D plots by 50.1% and 74.04%, respectively. Soil infiltration capacity, soil structural dynamics, and soil water retention capacity explained the first three components of the principal component analysis (PCA). Thus, we suggest that the promising observations could improve our understanding of differential plant density responses to cut slope restoration performance, particularly for the eroded cut slopes in the tropics. [ABSTRACT FROM AUTHOR]

Real-time in situ measurements are increasingly being used to improve the estimations of simulation models via data assimilation techniques such as particle filter. However, models that describe complex processes such as water flow contain a large number of parameters while the data available are typically very limited. In such situations, applying particle filter to a large, fixed set of parameters chosen a priori can lead to unstable behavior, i.e., inconsistent adjustment of some of the parameters that have only limited impact on the states that are being measured. To prevent this, in this study correlation-based variable selection is embedded in the particle filter, so that at each step only a subset of the most influential parameters is adjusted. The particle filter used in this study includes genetic algorithm operators and Monte Carlo Markov Chain for alleviating filter degeneracy and sample impoverishment. The proposed method was applied to a water flow model (Hydrus-1D) in which soil water content at various depths and soil hydraulic parameters were updated. Two case studies are presented. Overall, the proposed method yielded parameters and states estimates that were more accurate and more consistent than those obtained when adjusting all the parameters. Furthermore, the results show that the higher the influence of a parameter on the model output under the current conditions, the better the estimation of this parameter is. [ABSTRACT FROM AUTHOR]

Soil hydraulic properties control the provision of hydrological services. Vegetation and topography influence these properties by altering soil structure and porosity. The underlying mechanisms are not yet fully understood for the high Andean region. In this study, we examined how vegetation and topographic attributes are related to soil hydraulic properties and soil pore structure in young volcanic ash soils, and further correlated them to soil texture, organic carbon, and root characteristics to explain these relationships. In a 0.7 km2 study site located in the Andean páramo of northern Ecuador, we measured soil water retention, saturated hydraulic conductivity, bulk density (BD), and pore size distribution parameters on eight soil profiles with contrasting vegetation types (cushion‐forming plants vs. tussock grasses) and topographic positions (summit vs. hillslope). We observed significant differences in soil hydraulic properties and soil pore structure in the uppermost horizons by vegetation type, whereas topography had a minor effect. In the A horizons, we found higher water retention at saturation and field capacity (10%–14%), higher total available water (8%–15%), and higher saturated hydraulic conductivity (4–12 times) under cushion‐forming plants compared to tussock grasses. The elevated values under cushion plants were attributed to the presence of larger pores, lower soil BD, and higher soil organic carbon content as a result of coarser root systems. Total available water was generally high (0.34–0.40 cm3 cm−3), and locally not associated with any soil property. The higher water retention in soils under cushion vegetation can enhance soil water storage for plants and the regulation of water flows during prolonged rainfall events. The saturated hydraulic conductivity of the surface horizons is high compared to rainfall intensities resulting in high infiltration capacity; whilst its decline with depth reveals the potential for generation of subsurface stormflow, especially below cushion‐forming plants. Our findings highlight that soil hydraulic properties differ among vegetation types, and show the significance of vegetation types for soil hydrology. [ABSTRACT FROM AUTHOR]

Knowing soil indicators during forest restoration is essentially better for understanding the recovery of ecosystem functions for water conservation. The aim of this study is to assess seasonal changes in hydrological properties of sandy soils subjected to passive restoration over 8 (F8), 11 (F11), and 46 (F46) years in the Cerrado. The soils assessed herein have the same land use history and climate conditions. Soil density (SD), moisture (SM), organic matter (SOM), resistance to penetration (SRP), infiltration rate (IR), and soil conductivity (K) were measured for 12 months, and a repellency index (RI) was obtained in the dry season. Some annual soil hydrological property differences based on passive restoration sites were observed, but differences in other properties were only noticed through seasonal analyses. Higher SM, IR, and K values were recorded in the rainy season, and higher SRP values were observed in the dry season. IR was approximately fourfold higher in F8 and threefold higher in F11 and F46 in the rainy season than in the dry season. IR was higher in the oldest restoration site and lower (by over 60%) in the youngest restoration site, which also showed higher RI. Thus, significant differences in several hydrological soil properties and forest restoration soils subjected to the assessed chrono-sequence helped to confirm the study hypothesis, namely: these properties are influenced by forest age and are a warning against deforestation and climate change scenarios. The recovery of hydrological properties can be a slow process, much slower than deforestation, and this can have severe implications because soil water inflow is related to groundwater maintenance. Therefore, improvement of hydrological properties can help to develop sustainable land management and better and more efficient soil conservation strategies for sites undergoing passive restoration such as the Cerrado.