No abstract

No abstract

<p>The pressure plate method has been widely used for describing the soil water retention curve (SWRC). However, the simplified evaporation method (SEM) appears as an alternative because of its high resolution and automatization. On the other hand, the unimodal and bimodal van Genuchten models (VGM) have been used for describing the SWRC by computing the shape parameters. However, parametric pedotransfer functions (PTFs) have been developed based on the pressure plates method, focusing on the unimodal VGM. Therefore, the objectives of this study were: (1) to measure the SWRC with the simplified evaporation method (SEM) coupled to the dewpoint potentiometer (DP) in soils with different land use and soil texture, (2) to adjust and compare the VG unimodal and bimodal parameters, and (3) to estimate the VG unimodal and bimodal parameters through regression techniques including a linear approach and random forest. Thirty topsoils (disturbed and undisturbed cores) were sampled across a climate gradient and measured by duplicated. Preliminary results showed that the high resolution of the SWRC data obtained with the SEM + DP leads to a better fit when using the bimodal VGM.</p>

<p>Typical information in soil databases is the soil texture and particle size distribution. These properties are used for soil description or predicting other soil properties such as bulk density or hydraulic conductivity. Measuring particle size distribution with standards methods such as the pipette or hydrometer is time-consuming because of the sample pre-treatment used to remove organic matter or iron and the sample post-treatment. Nowadays, there are new methodologies for determining soil particle size distribution, such as the Integral Suspension Pressure (ISP) method, which measures the silt content in a semi-automatized process. Thus, the main objective of this study was to evaluate the suitability of the ISP method compared to standard techniques used in soil analysis and evaluate the effect of organic matter content in the ISP measurements. The main results showed that the ISP method is equivalent in accuracy to the pipette, especially for soils rich in silt or sand content. Also, the results demonstrate the convenience of removing the soil organic matter when using the ISP for soils with more than 1.5% organic matter.</p>

<p>Wildfires affect soil physical, chemical, and hydraulic properties, which in turn control many processes such as soil water availability, soil water balance, infiltration, and soil stability. Because of the multiple factors controlling the changes in soil properties and the nature of fire events, the number of predictive models for these effects is limited. Therefore, the objective of this study was to develop a soil-burning laboratory procedure to identify changes in physical and hydraulic soil properties across a fire temperature range. With this purpose, saturated hydraulic conductivity, pH, electric conductivity, soil texture, aggregate stability, repellency, and organic matter content (OM) were measured in soils burned at increasing temperatures. Six sandy loam soils were burned at four different temperatures (300ºC, 500ºC, 700ºC and 900ºC) and non-burned samples were used as a control to compute the change on each property. Additionally, three of these soils were sampled in a naturally burned area and used later to test the laboratory setup reliability to reproduce a natural fire. Preliminary results for soils burned in a muffle furnace (300ºC for two hours) showed that the changes in physical properties are more significant with soils rich in OM. On the other hand, properties such as water retention and hydraulic conductivity curves showed little variation at 300ºC.</p>