Differences In Soil Hydraulic Properties Research Articles

Influence of gully erosion on hydraulic properties of black soil-based farmland

Gully erosion is a severe form of water erosion worldwide. However, the influence of gully vicinity on the soil hydraulic properties has been poorly studied, hindering the understanding of their effect on crop yields. Therefore, this study hypothesizes that gully vicinity influences farmlands and aims to determine the mechanism of their influence on soil hydraulic properties and crop characteristics. The soil properties from nine gullies in cultivated lands inclined at1%, 2%, and 3% in three latitudinal regions were determined at the gully edge (EG0) and 50 m further the edge into the farmlands (EG50) at the following gully units: head, mid-upper, mid, mid-lower, and tail. Soil hydraulic properties (bulk density, saturated hydraulic conductivity, and water retention), soil penetration resistance, and soil organic matter were analyzed. The study findings indicate that the gully existence affected the soil properties at diverse range of intensities. The total-available water content (θ30 - θ1500), the ratio of more-available water to total-available water content (θ30-θ330)/(θ30-θ1500), saturated hydraulic conductivity, and soil organic matter were lower, but the bulk density and soil penetration resistance were higher at EG0 compared with those at EG50. The (θ30-θ330)/(θ30-θ1500) ratio in the gully vicinity was considerably lower in our study than in previous studies, indicating gully erosion substantially deteriorated the hydraulic properties. The differences in soil hydraulic properties between EG0 and EG50 were more evident in higher latitudinal region and in steeper farmlands. In addition, the lower soil organic matter and higher bulk density probably led to a 3–11% decrease in crop yield at EG0 than at EG50. In summary, this study indicates that gully erosion affects farmland not only at its boundaries but also further into its surroundings. Accordingly, managements suited to the hydraulic properties of the gully-surrounded areas may be implemented to maximize the crop yield of farmlands.

Vegetation effects on soil pore structure and hydraulic properties in volcanic ash soils of the high Andes

AbstractSoil 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.

Do natural ecosystems differ in terms of some soil physical properties? Savanna vs native grassland

While numerous studies demonstrated the reduction effect of infiltration changes with natural vegetation conversion to croplands, few information is available examining inherent differences between natural ecosystems. We examined the steady state infiltration rate and other topsoil properties in two adjacent native ecosystem types (of the Brazilian tropical savanna) occurring under a similar soil type (oxisol), a native grassland and a savanna. We found a significantly higher steady state infiltration rate in the savanna (698 ± 521 mm h−1) compared to native grassland (413 ± 181 mm h−1). All soil properties were significantly different when comparing both ecosystem types indicating that higher topsoil permeability in the savanna is potentially related to higher organic matter content, lower bulk density, and lower penetration resistance. Previous studies have documented differences in soil hydraulic properties between natural and anthropogenic ecosystems under a similar soil type. Here we showed that such differences can also occur among natural ecosystems.

Determination of Soil Hydraulic Parameters and Evaluation of Water Dynamics and Nitrate Leaching in the Unsaturated Layered Zone: A Modeling Case Study in Central Croatia

Nitrate leaching through soil layers to groundwater may cause significant degradation of natural resources. The aims of this study were: (i) to estimate soil hydraulic properties (SHPs) of the similar soil type with same management on various locations; (ii) to determine annual water dynamics; and (iii) to estimate the impact of subsoil horizon properties on nitrate leaching. The final goal was to compare the influence of different SHPs and layering on water dynamics and nitrate leaching. The study was conducted in central Croatia (Zagreb), at four locations on Calcaric Phaeozem, Calcaric Regosol, and Calcaric Fluvic Phaeozem soil types. Soil hydraulic parameters were estimated using the HYPROP system and HYPROP-FIT software. Water dynamics and nitrate leaching were evaluated using HYDRUS 2D/3D during a period of 365 days. The amount of water in the soil under saturated conditions varied from 0.422 to 0.535 cm3 cm−3 while the hydraulic conductivity varied from 3 cm day−1 to 990.9 cm day−1. Even though all locations have the same land use and climatic conditions with similar physical properties, hydraulic parameters varied substantially. The amount and velocity of transported nitrate (HYDRUS 2D/3D) were affected by reduced hydraulic conductivity of the subsoil as nitrates are primarily transported via advective flux. Despite the large differences in SHPs of the topsoil layers, the deeper soil layers, having similar SHPs, imposed a buffering effect preventing faster nitrate downward transport. This contributed to a very similar distribution of nitrates through the soil profile at the end of simulation period. This case study indicated the importance of carefully selecting relevant parameters in multilayered soil systems when evaluating groundwater pollution risk.

Soil hydraulic properties and water source-sink relations affect plant rings’ formation and sizes under arid conditions

In semi-arid and arid environments, clonal plants occasionally appear in ring patterns. There is a general agreement that this pattern forms when ramets grow radially, leaving a dead centre where the parent plant once was. Nevertheless, there is still some controversy over the actual causes of this dieback and how water source–sink relations in and around the rings are involved in their formation. We studied Asphodelus ramosus rings in two sites with different soil textures (sand and loess) but comparable climate, in order to understand whether differences in soil hydraulic properties create different water source–sink relations and mechanisms that drive ring formation. We characterised soil hydraulic properties and dynamics, accompanied by measurements of soil texture and of belowground storage root biomass. We found that the nature of source–sink relations varies with soil texture and properties. In sandy soils, water supply to ring perimeters is mainly from their centres. In loessial soils, water supply to ring perimeters is mainly from the surrounding matrix. Consequently, rings are larger in sandy soils than in loessial soils. This suggests that rings in both sites are formed by different mechanisms: fine particle deposition in the centres of ring in the sandy soil but competition over water in rings in the loessial soil. Studying the formation of rings and other vegetation spatial patterns should consider local soil properties and the possibility that similar patterns may emerge through various processes.

Simulation of Soil Water and Heat Transfer under Subsurface Irrigation Considering Spatial Differences in Soil Hydraulic Properties

Simulation of Soil Water and Heat Transfer under Subsurface Irrigation Considering Spatial Differences in Soil Hydraulic Properties

Sources of inherent infiltration variability in postwildfire soils

AbstractAn automated disc infiltrometer was developed to improve the measurements of soil hydraulic properties (saturated hydraulic conductivity and sorptivity) of soils affected by wildfire. Guidelines are given for interpreting curves showing cumulative infiltration as a function of time measured by the autodisc. The autodisc was used to measure the variability of these soil hydraulic properties in three different sample sets: (a) a reference soil consisting of a nonrepellent, uniform, fine sand; (b) soils with the same soil textural classification derived from the same bedrock geology but having different initial burn severities; and (c) soils from different bedrock geology but having the same burn severity. The autodisc infiltrometer had greater sampling rates and volume resolution when compared with the visual minidisc infiltrometer from previous studies. There was no statistical difference in the mean values measured using the autodisc and visual minidisc, but the variability of the autodisc measurements was significantly less than the visual minidisc for a given set of samples. The greatest variability of soil hydraulic properties in reference samples with uniform particle size was attributed to different pore geometries (coefficient of variation [COV] = 0.28–0.34). Unburned field samples (same soil type) with heterogeneous particle sizes had greater variability (COV = 0.57–0.78) than the reference samples. However, this basic variability decreased or remained constant in these field samples as burn severity increased. Additional sources of variability (COV = 0.53–1.99) were attributed to multiple layers resulting from ash or sediment deposition. Results indicate that resolving differences in soil hydraulic properties from different sites requires more than the common 10 random samples because of the multiple sources of variability.

Seasonal Wetness, Soil Organic Carbon, and Fire Influence Soil Hydrological Properties and Water Repellency in a Sagebrush‐Steppe Ecosystem

AbstractPrescribed fire is an important tool for rangeland management in sage‐steppe ecosystems, yet the long‐term effects of this practice on soil hydraulic properties are not well known. We explore interactions among site geomorphology, soil organic carbon (SOC) soil N, soil water repellency (SWR), and plant community type on infiltration properties before fire and 8 years thereafter in a semiarid research watershed. The objective was to assess the sustainability of rangeland burning in sage‐steppe ecosystems. Many types of measurements were made in three plant communities to identify how differences in soil hydraulic properties are related to differences in plant cover and soil texture and to determine relationships among SOC, SWR, soil water contact angle, and infiltration properties. Measurements were made on transects in burned and unburned catchments. We found that severity and occurrence of surface SWR were substantially reduced 8 years after a fire within the area originally covered with mountain big sagebrush, where the fire intensity was greatest. Surface SWR was lowest in the sparsely vegetated low sagebrush, where SOC was also lowest. Unsaturated hydraulic conductivity (Kh) increased in each vegetation type over the 8‐year period after burning and was not directly related to SWR. Spatial variability in Kh was primarily controlled by soil texture, whereas differences in sorptivity (S) were controlled by SWR and aridity. SOC is not well correlated to soil surface SWR. The decadal scale changes in Kh and associations between S and site characteristics indicate forms of resilience to fire across a moisture gradient.

Previous Land Use Affects the Recovery of Soil Hydraulic Properties after Forest Restoration

Knowledge of soil hydraulic properties after forest restoration is essential for understanding the recovery of hydrological processes, such as water infiltration. An increase of forest cover may improve water infiltration and soil hydraulic properties, but little is known about the response and extent to which forest restoration can affect these properties. The purpose of this study was to investigate the effect of forest restoration on surface-saturated soil hydraulic conductivity (Ks), and to verify the Ks recovery to the pre-disturbance soil conditions. We sampled field Ks at the surface in Campinas municipality, Sao Paulo State, Brazil, at 18 plots under three land-cover types: (i) a pasture; (ii) a restored forest using a high-diversity mix of plantings (85 regional native species) of 9 years of age; and (iii) a remnant forest patch. We used the Beerkan method for soil hydraulic characterization. Bulk density (ρb), soil organic carbon content (OC), soil porosity and particle size data were also sampled. We found considerable differences in soil hydraulic properties between land-cover classes. The highest Ks were observed in remnant forest sites and the lowest Ks were associated with pasture sites. The Ks recovery differs markedly between restored forests. Our results strongly suggest that soil attributes and Ks recovery are influenced by the duration and intensity of land use prior to forest restoration. Attention needs to be given to management activities before, during and after forest restoration, especially where the soil is still compacted and Ks is low.

Influence of tree species and forest land use on soil hydraulic conductivity and implications for surface runoff generation

Forest planting is increasingly being incorporated into land management policies to mitigate diffuse pollution and localised flooding because forest soils are associated with enhanced hydraulic properties and lower surface runoff compared to soils under other vegetation types. Despite this, our understanding of the effects of different tree species and forest land use on soil hydraulic properties is limited. In this study we tested for the effects of two tree species, sycamore (Acer pseudoplatanus) and Scots pine (Pinus sylvestris), subject to contrasting land use systems, namely ungrazed forest and livestock grazed forest, on soil surface saturated hydraulic conductivity (Kfs) at a long term (23year) experimental site in Scotland. Additionally these forest land use systems were compared to grazed pasture. Kfs was found to be significantly higher under ungrazed Scots pine forest (1239mmhr−1) than under ungrazed sycamore forest (379mmhr−1) and under both of these forest types than under pasture (32mmhr−1). However, this measure did not differ significantly between the sycamore and Scots pine grazed forest and pasture. It was inferred, from comparison of measured Kfs values with estimated maximum rainfall intensities for various return periods at the site, that surface runoff, as infiltration excess overland flow, would be generated in pasture and grazed forest by storms with a return period of at least 1 in 2years, but that surface runoff is extremely rare in the ungrazed forests, regardless of tree species. We concluded that, although tree species with differing characteristics can create large differences in soil hydraulic properties, the influence of land use can mask the influence of trees. The choice of tree species may therefore be less important than forest land use for mitigating the effects of surface runoff.

Effect of soil hydraulic properties on water infiltration of containerised soil

The development of infrastructure in an urban city, such as road widening and building work, will inevitably result in the removal of trees. Therefore, innovative solutions such as containerised tree in the manner of increasing the portability of trees would be necessary to facilitate efficient transplanting in order to maintain a sustainable green urban environment. Differences in soil hydraulic properties between soil mixture and in situ soil naturally occur in tree planting, but this difference becomes more important in the use of container due to the limited tree root movement. The objective of this research was to examine the effects of soil hydraulic properties between the soils inside and outside of the container with focus being placed on moisture infiltration both in and out of the container. Field instrumentation and laboratory tests were carried out together with parametric study using numerical model. The results suggested that the higher the ratio between the saturated permeability of the soils inside and outside the container, the lower was the ability of water to flow in and out of the container.

Variation of soil hydraulic properties with alpine grassland degradation in the eastern Tibetan Plateau

Abstract. Ecosystems in alpine mountainous regions are vulnerable and easily disturbed by global environmental change. Alpine swamp meadow, a unique grassland type in the eastern Tibetan Plateau that provides important ecosystem services to the upstream and downstream regions of international rivers of Asia and other parts of the world, is undergoing severe degradation, which can dramatically alter soil hydraulic properties and water cycling processes. However, the effects of alpine swamp meadow degradation on soil hydraulic properties and the corresponding influencing mechanisms are still poorly understood. In this study, soil moisture content (SMC), field capacity (FC) and saturated hydraulic conductivity (Ks) together with several basic soil properties under lightly degraded (LD), moderately degraded (MD) and severely degraded (SD) alpine swamp meadow were investigated; the variations in SMC, FC and Ks with alpine swamp meadow degradation and their dominant influencing factors were analysed. The results showed that SMC and FC decreased consistently from LD to SD, while Ks decreased from LD to MD and then increased from MD to SD, following the order of LD > SD > MD. Significant differences in soil hydraulic properties between degradation degrees were found in the upper soil layers (0–20 cm), indicating that the influences of degradation were most pronounced in the topsoils. FC was positively correlated with capillary porosity, water-stable aggregates, soil organic carbon, and silt and clay content; Ks was positively correlated with non-capillary porosity (NCP). Relative to other soil properties, soil porosity is the dominant factor influencing FC and Ks. Capillary porosity explained 91.1 % of total variance in FC, and NCP explained 97.3 % of total variance in Ks. The combined effect of disappearing root activities and increasing sand content was responsible for the inconsistent patterns of NCP and Ks. Our findings suggest that alpine swamp meadow degradation would inevitably lead to reduced water holding capacity and rainfall infiltration. This study provides a more comprehensive understanding of the soil hydrological effects of vegetation degradation. Further hydrological modelling studies in the Tibetan Plateau and similar regions are recommended to understand the effects of degraded alpine swamp meadows on soil hydraulic properties.

Analysing the role of soil properties, initial biomass and ozone on observed plant growth variability in a lysimeter study

This simulation study is based on a lysimeter experiment with juvenile beech trees (Fagus sylvatica L.) which were grown under ambient or doubled ambient atmospheric ozone concentrations. The aim of the study was to analyze the role of differences in soil properties, differences in initial biomass and ozone impacts on observed plant growth variability at the eight lysimeters of this experiment. For this purpose, we established a new simulation model based on the model system Expert-N by coupling soil water and nitrogen transport models with the plant growth model PLATHO, which was already tested and applied for juvenile beech. In order to parameterize the soil model, for all lysimeters soil hydraulic parameters as well as carbon and nitrogen stocks were measured. Simulation results reveal that the observed decreased growth rates under elevated ozone are due to ozone impacts on plant growth, whereas the high plant growth variability between lysimeters is to a major part the consequence of differences in soil hydraulic properties. Differences in initial biomass are of minor importance to explain plant growth variability in this experiment.

Axle‐Load Impacts on Hydraulic Properties and Corn Yield in No‐Till Clay and Silt Loam

Wheel traffic‐induced compaction in no‐till (NT) farming can alter soil hydraulic properties and reduce crop yields, but specific information on the impacts of different levels of axle loads on the relationships between soil hydraulic properties and crop yields under long‐term NT systems is limited. Thus, this study set out to measure the differences in soil hydraulic properties including earthworm (Lumbricus terrestris) population and assess their relationships with corn (Zea mays L.) grain and stover yield in NT silt loam and clay loam in Ohio receiving three levels of axle loads for 20 yr. Imposition of three axle load treatments including control, 10 Mg, and 20 Mg affected water infiltration rates but not bulk density (ρb), saturated hydraulic conductivity (Ksat), soil water retention (SWR), plant available water (PAW), and pore‐size distribution in both soils. Imposition of axle loads reduced cumulative water infiltration by 6‐ to 20‐fold in the silt loam and by about sixfold in the clay loam. It decreased sorptivity by 10‐fold and steady state infiltration by fivefold. The reduction in water infiltration was related to the reductions in earthworm population. Application of 20 Mg axle load reduced earthworm numbers by 50% in the silt loam and by 70% in the clay loam. There were no significant differences in water infiltration parameters and earthworm population between 10 and 20 Mg axle loads. Application of axle loads reduced grain yield by 13% and stover yield by 23% on the clay loam but not on the silt loam. It reduced both grain and stover yields by 1.2 Mg ha−1. Cumulative infiltration explained 58% of the variability in grain yield and 53% in stover yield in the clay loam. Overall, axle load‐induced significant changes in water infiltration and earthworm population but changes in crop yields were soil specific.

Analysis of soil wetting and solute transport in subsurface trickle irrigation

The increased use of trickle or drip irrigation is seen as one way of helping to improve the sustainability of irrigation systems around the world. However, soil water and solute transport properties and soil profile characteristics are often not adequately incorporated in the design and management of trickle systems. In this paper, we describe results of a simulation study designed to highlight the impacts of soil properties on water and solute transport from buried trickle emitters. The analysis addresses the influence of soil hydraulic properties, soil layering, trickle discharge rate, irrigation frequency, and timing of nutrient application on wetting patterns and solute distribution. We show that (1) trickle irrigation can improve plant water availability in medium and low permeability fine-textured soils, providing that design and management are adapted to account for their soil hydraulic properties, (2) in highly permeable coarse-textured soils, water and nutrients move quickly downwards from the emitter, making it difficult to wet the near surface zone if emitters are buried too deep, and (3) changing the fertigation strategy for highly permeable coarse-textured soils to apply nutrients at the beginning of an irrigation cycle can maintain larger amounts of nutrient near to and above the emitter, thereby making them less susceptible to leaching losses. The results demonstrate the need to account for differences in soil hydraulic properties and solute transport when designing irrigation and fertigation management strategies. Failure to do this will result in inefficient systems and lost opportunities for reducing the negative environmental impacts of irrigation.

Tracer-based studies of soil water movement in semi-arid forests of New Mexico

The related issues of water movement and contaminant transport in arid and semi-arid environments have generated considerable interest and concern in the last few decades. Essential to understanding these issues is knowledge of how water moves through the soils that form the uppermost part of the vadose zone. The use of tracers, both natural and artificially introduced, is proving to be an effective method for gaining such knowledge in dry regions, where investigation by other means is difficult. In this study, natural stable-isotope and chloride tracers were used to investigate water movement in the soils of a piñon–juniper woodland and of a ponderosa pine forest on the Pajarito Plateau in northern New Mexico. The objectives were to (1) estimate and compare near-surface flux rates and evaluate the importance of evaporation in the two communities, and (2) determine to what extent differences in flux rates and evaporation are due to differences in plant cover and/or soil hydraulic properties. The results of this study will aid in evaluating the potential for contaminant mobility in semi-arid systems such as the Pajarito Plateau and, in addition, will increase understanding of nutrient distributions and plant water use in semi-arid environments. The stable-isotope data indicate a similarity between the piñon–juniper and ponderosa communities with respect to evaporation: in both, it is restricted mainly to the upper 10 cm of soil. Chloride profiles from the two communities, on the other hand, show a distinct difference with respect to downward fluxes: in the ponderosa pine forest, these fluxes (≈0.02 cm year −1) are an order of magnitude lower than those in the piñon–juniper woodland (≈0.2 cm year −1), even though total precipitation is about 4 cm year −1 higher in the ponderosa pine forest. This difference, however, appears to be related not to plant cover, but to differences in soil hydraulic properties. The soils of the ponderosa pine forest contain clay-rich B horizons that appear to restrict downward movement of water through the soil matrix, whereas the soils of the piñon–juniper community have B horizons much lower in clay content. The effect of differing soil properties on water movement suggests that contaminant distributions will vary across the Pajarito Plateau. The data on soil water ages support this hypothesis: they indicate that water (and, thus, contaminants) moves through the soil matrix in less than a decade in some areas, whereas in other areas, water takes hundreds of years to pass through the entire soil profile.