scholarly journals The characteristics of gravelly soil physical properties and their effects on permafrost dynamics: A case study on the central Qinghai-Tibetan Plateau

2018 ◽  
Author(s):  
Shuhua Yi ◽  
Yujie He ◽  
Xinlei Guo ◽  
Jianjun Chen ◽  
Qingbai Wu ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Tibetan Plateau ◽  
Physical Properties ◽  
Active Layer ◽  
Saturated Hydraulic Conductivity ◽  
Soil Porosity ◽  
Silty Clay ◽  
Model Errors ◽  
Matric Potential ◽  
Gravelly Soil

Abstract. Soils on the Qinghai-Tibetan Plateau (QTP) have distinct physical properties from agricultural soils due to weak weathering and strong erosion. These properties might affect permafrost dynamics. However, few studies have investigated both quantitatively. In this study, we selected a permafrost site on the central region of the QTP and excavated soil samples from 20 cm to 200 cm. We measured soil porosity, thermal conductivity, saturated hydraulic conductivity and matric potential in the laboratory. Finally, we ran a simulation model replacing default sand or silty clay parameters with different combinations of these measured parameters. Results showed that gravel content (diameter > 2 mm) was ~ 55 % on average in soil profile; soil porosity was less than 0.3; saturated hydraulic conductivity ranged from 0.004–0.03 mm s−1; saturated matric potential ranged from −14 to −604 mm. When default sand or silty clay parameters were substituted with these measured values, the model errors of soil temperature, soil liquid water content, active layer depth and permafrost lower boundary were reduced. The root mean squared errors of active layer depths simulated using measured parameters, and the default sand and silty clay parameters were about 0.28, 1.06, 1.83 m, respectively. Among these measured parameters, porosities, which were much smaller than soil textures used in land surface models, played a dominant role in reducing model errors. We also demonstrated that soil water dynamic processes should be considered, rather than using static properties under frozen and unfrozen soil states as in most permafrost models. We concluded that it is necessary to consider the distinct physical properties of soil and water dynamics on the QTP when simulating dynamics of permafrost in this region. It is important to develop methods for systematic measuring physical properties of gravelly soil and to develop a spatial dataset for porosity because of its importance in simulating permafrost dynamics in this region.

scholarly journals The physical properties of coarse-fragment soils and their effects on permafrost dynamics: a case study on the central Qinghai–Tibetan Plateau

2018 ◽  
Vol 12 (9) ◽  
pp. 3067-3083 ◽  
Author(s):  
Shuhua Yi ◽  
Yujie He ◽  
Xinlei Guo ◽  
Jianjun Chen ◽  
Qingbai Wu ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Tibetan Plateau ◽  
Physical Properties ◽  
Active Layer ◽  
Soil Samples ◽  
Saturated Hydraulic Conductivity ◽  
Soil Porosity ◽  
Matric Potential ◽  
Data Set ◽  
Mean Square Errors

Abstract. Soils on the Qinghai–Tibetan Plateau (QTP) have distinct physical properties from agricultural soils due to weak weathering and strong erosion. These properties might affect permafrost dynamics. However, few studies have investigated both quantitatively. In this study, we selected a permafrost site on the central region of the QTP and excavated soil samples down to 200 cm. We measured soil porosity, thermal conductivity, saturated hydraulic conductivity, and matric potential in the laboratory. Finally, we ran a simulation model replacing default sand or loam parameters with different combinations of these measured parameters. Our results showed that the mass of coarse fragments in the soil samples (diameter >2 mm) was ∼55 % on average, soil porosity was less than 0.3 m3 m−3, saturated hydraulic conductivity ranged from 0.004 to 0.03 mm s−1, and saturated matric potential ranged from −14 to −604 mm. When default sand or loam parameters in the model were substituted with these measured values, the errors of soil temperature, soil liquid water content, active layer depth, and permafrost lower boundary depth were reduced (e.g., the root mean square errors of active layer depths simulated using measured parameters versus the default sand or loam parameters were about 0.28, 1.06, and 1.83 m). Among the measured parameters, porosity played a dominant role in reducing model errors and was typically much smaller than for soil textures used in land surface models. We also demonstrated that soil water dynamic processes should be considered, rather than using static properties under frozen and unfrozen soil states as in most permafrost models. We conclude that it is necessary to consider the distinct physical properties of coarse-fragment soils and water dynamics when simulating permafrost dynamics of the QTP. Thus it is important to develop methods for systematic measurement of physical properties of coarse-fragment soils and to develop a related spatial data set for porosity.

The ability of Distichlis spicata to grow sustainably within a saline discharge zone while improving the soil chemical and physical properties

Soil Research ◽  
2008 ◽  
Vol 46 (1) ◽  
pp. 37 ◽  
Author(s):  
M. R. Sargeant ◽  
C. Tang ◽  
P. W. G. Sale
Keyword(s):  
Electrical Conductivity ◽  
Hydraulic Conductivity ◽  
Physical Properties ◽  
Soil Nitrogen ◽  
Fold Increase ◽  
Dry Weight ◽  
Saturated Hydraulic Conductivity ◽  
Distichlis Spicata ◽  
Discharge Zone ◽  
Spatial And Temporal Variation

Landholder observations indicate that the growth of Distichlis spicata in saline discharge sites improves the soil condition. An extensive soil sampling survey was conducted at the Wickepin field site in Western Australia, where D. spicata had been growing for 8 years, to test the hypothesis that this halophytic grass will make improvements in chemical and physical properties of the soil. Soil measurements included saturated hydraulic conductivity, water-stable aggregates, root length and dry weight, electrical conductivity, pH, and soil nitrogen and carbon. Results confirm that marked differences in soil properties occurred under D. spicata. For example, a 12-fold increase in saturated hydraulic conductivity occurred where D. spicata had been growing for 8 years, compared to adjacent control soil where no grass had been growing. There were also improvements in aggregate stability, with the most notable improvements in the top 0.10 m of soil, again with the greatest improvements occurring where 8 years of growth had occurred. Soil nitrogen and carbon increased under the sward, with the biggest increases occurring in the top 0.10 m of soil. Electrical conductivity measurements were more variable, mostly due to the large spatial and temporal variation encountered. However, the findings generally support the proposition that the growth of D. spicata does not lead to an accumulation of salt within the rooting zone.

Spatial relationship between soil hydraulic and soil physical properties in a farm field

2009 ◽  
Vol 89 (4) ◽  
pp. 473-488 ◽  
Author(s):  
A Biswas ◽  
B C Si
Keyword(s):  
Hydraulic Conductivity ◽  
Physical Properties ◽  
Soil Properties ◽  
Shape Parameter ◽  
Spatial Relationship ◽  
Soil Physical Properties ◽  
Saturated Hydraulic Conductivity ◽  
Hydraulic Parameters ◽  
Curve Shape ◽  
Scaling Parameter

The relationship between soil properties may vary with their spatial separation. Understanding this relationship is important in predicting hydraulic parameters from other soil physical properties. The objective of this study was to identify spatially dependent relationships between hydraulic parameters and soil physical properties. Regularly spaced (3-m) undisturbed soil samples were collected along a 384 m transect from a farm field at Smeaton, Saskatchewan. Saturated hydraulic conductivity, the soil water retention curve, and soil physical properties were measured. The scaling parameter, van Genuchten scaling parameter α (VGα), and curve shape parameter, van Genuchten curve shape parameter n (VGn), were obtained by fitting the van Genuchten model to measured soil moisture retention data. Results showed that the semivariograms of soil properties exhibited two different spatial structures at spatial separations of 20 and 120 m, respectively. A strong spatial structure was observed in organic carbon, saturated hydraulic conductivity (Ks), sand, and silt; whereas a weak structure was found for VGα and VGn. Correlation circle analysis showed strong spatially dependent relationships of Ks and VGα; with soil physical properties, but weak relationships of θs and VGn with soil physical properties. The spatially dependent relationships between soil physical and soil hydraulic parameters should be taken into consideration when developing pedotransfer functions. Key words: Spatial relationship, geostatistics, linear coregionalization model, principal component analysis, pedotransfer function

MONOLITH COLUMNS FOR STUDYING ORGANIC SOIL PROFILES

1986 ◽  
Vol 66 (4) ◽  
pp. 737-742
Author(s):  
J. A. MILLETTE ◽  
R. S. BROUGHTON
Keyword(s):  
Hydraulic Conductivity ◽  
Physical Properties ◽  
Bulk Density ◽  
Organic Soil ◽  
Saturated Hydraulic Conductivity ◽  
Fiber Content ◽  
Organic Soils ◽  
Soil Profiles ◽  
Sampling Procedures ◽  
Monolith Columns

Monolith column construction and sampling procedures were described for organic soil profiles and used to measure the variation with depth of saturated hydraulic conductivity, bulk density and fiber content. The top 0.30 m of the organic soil was more permeable, had a greater bulk density and had a greater fiber content than the soil layer between 0.60 and 0.90 m from the soil surface. These columns can be used for correlations studies between physical properties and studies of the dynamic nature of the physical properties of organic soils. Key words: Saturated hydraulic conductivity, bulk density, fiber content, organic soil, monolith columns

Soil Physical and Hydrological Changes Associated with Logging a Wet Pine Flat with Wide-Tired Skidders

1993 ◽  
Vol 17 (1) ◽  
pp. 22-25 ◽  
Author(s):  
W. M. Aust ◽  
T. W. Reisinger ◽  
J. A. Burger ◽  
B. J. Stokes
Keyword(s):  
South Carolina ◽  
Hydraulic Conductivity ◽  
Physical Properties ◽  
Coastal Plain ◽  
Soil Physical Properties ◽  
Soil Porosity ◽  
Hydrological Changes ◽  
Disturbed Areas ◽  
Before And After ◽  
Traffic Disturbance

Abstract A wet pine flat in the coastal plain of South Carolina was harvested with a rubber-tired skidder equipped with 68-in.-wide tires. Soil physical properties were measured immediately before and after a salvage harvest to document changes associated with traffic disturbance. Paired t-tests indicate that the wide-tired operation significantly increased soil volumetric water content, bulk density, and soil strength, and decreased saturated hydraulic conductivity, soil porosity, and depth to the water table. Changes were greatest for the more disturbed areas, and rutting that occurred in the skid trails apparently interrupted subsurface drainage. South. J. Appl. For. 17(1):22-25.

scholarly journals Prediction of biopore- and matrix-dominated flow from X-ray CT-derived macropore network characteristics

2016 ◽  
Vol 20 (10) ◽  
pp. 4017-4030 ◽  
Author(s):  
Muhammad Naveed ◽  
Per Moldrup ◽  
Marcel G. Schaap ◽  
Markus Tuller ◽  
Ramaprasad Kulkarni ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Preferential Flow ◽  
Air Permeability ◽  
Saturated Hydraulic Conductivity ◽  
Soil Columns ◽  
Macropore Flow ◽  
Matric Potential ◽  
X Ray ◽  
Network Characteristics ◽  
Gas Diffusivity

Abstract. Prediction and modeling of localized flow processes in macropores is of crucial importance for sustaining both soil and water quality. However, currently there are no reliable means to predict preferential flow due to its inherently large spatial variability. The aim of this study was to investigate the predictive performance of previously developed empirical models for both water and air flow and to explore the potential applicability of X-ray computed tomography (CT)-derived macropore network characteristics. For this purpose, 65 cylindrical soil columns (6 cm diameter and 3.5 cm height) were extracted from the topsoil (5 cm to 8.5 cm depth) in a 15 m  ×  15 m grid from an agricultural field located in Silstrup, Denmark. All soil columns were scanned with an industrial X-ray CT scanner (129 µm resolution) and later employed for measurement of saturated hydraulic conductivity, air permeability at −30 and −100 cm matric potential, and gas diffusivity at −30 and −100 cm matric potential. Distribution maps for saturated hydraulic conductivity, air permeability, and gas diffusivity reflected no autocorrelation irrespective of soil texture and organic matter content. Existing empirical predictive models for saturated hydraulic conductivity and air permeability showed poor performance, as they were not able to realistically capture macropore flow. The tested empirical model for gas diffusivity predicted measurements at −100 cm matric potential reasonably well, but failed at −30 cm matric potential, particularly for soil columns with biopore-dominated flow. X-ray CT-derived macroporosity matched the measured air-filled porosity at −30 cm matric potential well. Many of the CT-derived macropore network characteristics were strongly interrelated. Most of the macropore network characteristics were also significantly correlated with saturated hydraulic conductivity, air permeability, and gas diffusivity. The predictive Ahuja et al. (1984) model for saturated hydraulic conductivity, air permeability, and gas diffusivity performed reasonably well when parameterized with novel, X-ray CT-derived parameters such as effective percolating macroporosity for biopore-dominated flow and total macroporosity for matrix-dominated flow. The obtained results further indicate that it is crucially important to discern between matrix-dominated and biopore-dominated flow for accurate prediction of macropore flow from X-ray CT-derived macropore network characteristics.

Development of a Homogeneous Model Municipal Solid Waste

2013 ◽  
Vol 831 ◽  
pp. 331-335 ◽  
Author(s):  
Ren Peng ◽  
Yu Jing Hou ◽  
Xue Dong Zhang ◽  
Qing Lei Sun
Keyword(s):  
Shear Strength ◽  
Hydraulic Conductivity ◽  
Physical Properties ◽  
Municipal Solid Waste ◽  
Solid Waste ◽  
Homogeneous Model ◽  
Saturated Hydraulic Conductivity ◽  
Unit Weight ◽  
The Real ◽  
Compression Factor

A model waste mixing with kaolin, sand, and peat was developed. The physical properties of the waste were compared with the real municipal solid waste (MSW). The influence of unit weight on compression factor, shear strength, and saturated hydraulic conductivity was acquired. In addition, the homogeneous of the soil model was detected using the IWHR 450g-ton centrifuge and the newly developed centrifuge-robot.

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