- Geosciences, Vol. 10, Pages 85: The Effects of Slope Initialization on the Numerical Model Predictions of the Slope-Vegetation-Atmosphere Interaction
Deep slope movements and, eventually, slope failure, have been often interpreted to be due to slope-vegetation-atmosphere interaction on slopes formed of clayey materials in the Italian Southern-Eastern Apennines, as reported in the literature. Such slopes are generally formed of flysch, within which clay is the main lithotype. Such clays are characterized by a disturbed meso-fabric, as an effect of the intense tectonics. The paper presents the results of coupled hydromechanical numerical analyses of the slope-vegetation-atmosphere interaction for a clay slope representative for the geomechanical scenario where such climate-induced deep slope movements have been repeatedly recorded. In the analyses, different model initialization procedures and parameter values were adopted. The comparison of the numerical results with the site data is aimed at assessing the effects of the soil-vegetation-atmosphere interaction taking place in the top strata of the slope, on the stress-strain conditions across the whole slope, and on the slope stability. The comparison between the numerical results of the analyses carried out entailing different initialization stages are intended to evaluate the influence of such a stage on the model predictions. It is found that only when the slope model initialization accounts for the slope loading history, developed over geological time,the numerical predictions get close to the site observations. In such case, the numerical results confirm that deep movements consequent to progressive failure may take place in clay slopes due to the slope-vegetation-atmosphere interaction.
- Geosciences, Vol. 10, Pages 84: Late Quaternary Tectonic Activity of the Udine-Buttrio Thrust, Friulian Plain, NE Italy
The NW-SE trending Udine-Buttrio Thrust is a partly blind fault that affects the Friulian plain southeast of Udine in NE Italy. It is part of a wider fault system that accommodates the northward motion of the Adriatic plate. Although seismic reflection data and morphological evidence show that the fault was active during the Quaternary, comparably little is known about its tectonic activity. We used high-resolution digital elevation models to investigate the surface expression of the fault. Measured vertical surface offsets show significant changes along strike with uplift rates varying between 0 and 0.5 mm/yr. We then analyze a topographic scarp near the village of Manzano in more detail. Field mapping and geophysical prospections (Georadar and Electrical Resistivity Tomography) were used to image the subsurface geometry of the fault. We found vertical offsets of 1–3 m in Natisone River terraces younger than 20 ka. The geophysical data allowed the identification of deformation of the fluvial sediments, supporting the idea that the topographic scarp is a tectonic feature and that the terraces have been uplifted systematically over time. Our findings fit the long-term behaviour of the Udine-Buttrio Thrust. We estimate a post-glacial vertical uplift rate of 0.08–0.17 mm/yr recorded by the offset terraces. Our results shed light on the Late Quaternary behaviour of this thrust fault in the complicated regional tectonic setting and inform about its hitherto overlooked possible seismic hazard.
- Geosciences, Vol. 10, Pages 83: Morphotectonic Kinematic Indicators along the Vigan-Aggao Fault: The Western Deformation Front of the Philippine Fault Zone in Northern Luzon, the Philippines
The Vigan-Aggao Fault is a 140-km-long complex active fault system consisting of multiple traces in the westernmost part of the Philippine Fault Zone (PFZ) in northern Luzon, the Philippines. In this paper, its traces, segmentation, and oblique left-lateral strike-slip motion are determined from horizontal and vertical displacements measured from over a thousand piercing points pricked from displaced spurs and streams observed from Google Earth Pro satellite images. This work marks the first instance of the extensive use of Google Earth as a tool in mapping and determining the kinematics of active faults. Complete 3D image coverage of a major thoroughgoing active fault system is freely and easily accessible on the Google Earth Pro platform. It provides a great advantage to researchers collecting morphotectonic displacement data, especially where access to aerial photos covering the entire fault system is next to impossible. This tool has not been applied in the past due to apprehensions on the positional measurement accuracy (mainly of the vertical component). The new method outlined in this paper demonstrates the applicability of this tool in the detailed mapping of active fault traces through a neotectonic analysis of fault-zone features. From the sense of motion of the active faults in northern Luzon and of the major bounding faults in central Luzon, the nature of deformation in these regions can be inferred. An understanding of the kinematics is critical in appreciating the distribution and the preferred mode of accommodation of deformation by faulting in central and northern Luzon resulting from oblique convergence of the Sunda Plate and the Philippine Sea Plate. The location, extent, segmentation patterns, and sense of motion of active faults are critical in coming up with reasonable estimates of the hazards involved and identifying areas prone to these hazards. The magnitude of earthquakes is also partly dependent on the type and nature of fault movement. With a proper evaluation of these parameters, earthquake hazards and their effects in different tectonic settings worldwide can be estimated more accurately.
- Geosciences, Vol. 10, Pages 82: Design Strategies to Mitigate Slope Instabilities in Structurally Complex Formations
Stiff jointed clays (SJC) belong to so-called structurally complex formations in which the macroscale features of the deposit, that is the pattern of discontinuities affecting the soil mass, influence its response at the scale of engineering works. Such peculiar response was largely recognized during the excavation works carried out for the construction of two new road segments in southern Italy, where several structurally conditioned instability processes were triggered during excavation works. These phenomena mainly involved the Plio-Pleistocene marine clayey formation outcropping along the East coast of the Calabria region, where it constitutes most of the hills interested by construction works. Under a geotechnical perspective, the SJC-formation exhibits good mechanical characteristics at the scale of samples but, if considered as a whole, its behaviour is governed by the presence of discontinuities along which strength is typically at residual. Building on the author’s experience of some exemplary failure events, this paper aims at defining possible design strategies to minimize the risk of adverse and unexpected instability phenomena during construction in structurally complex formations. Design strategies oriented at reducing and possibly avoiding stress releases in the zone of influence were found to be most effective at preventing failures or restoring safety after the occurrence of a failure event.
- Geosciences, Vol. 10, Pages 81: Moroccan Groundwater Resources and Evolution with Global Climate Changes
In semi-arid areas, many ecosystems and activities depend essentially on water availability. In Morocco, the increase of water demands combined to climate change induced decrease of precipitation put a lot of pressure on groundwater. This paper reports the results of updating and evaluation of groundwater datasets with regards to climate scenarios and institutional choices. The continuous imbalance between groundwater extraction and recharge caused a dramatic decline in groundwater levels (20 to 65 m in the past 30 years). Additionally, Morocco suffers from the degradation in groundwater quality due to seawater intrusion, nitrate pollution and natural salinity changes. Climate data analysis and scenarios predict that temperatures will increase by 2 to 4 °C and precipitation will decrease by 53% in all catchments over this century. Consequently, surface water availability will drastically decrease, which will lead to more extensive use of groundwater. Without appropriate measures, this situation will jeopardize water security in Morocco. In this paper, we zoom on the case the Souss-Massa basin, where management plans (artificial recharge, seawater desalination, and wastewater reuse) have been adopted to restore groundwater imbalance or, at least, mitigate the recorded deficits. These plans may save water for future generations and sustain crop production.
- Variations in soil chemical and physical properties explain basin-wide Amazon forest soil carbon concentrations
Variations in soil chemical and physical properties explain basin-wide Amazon forest soil carbon concentrations Carlos Alberto Quesada, Claudia Paz, Erick Oblitas Mendoza, Oliver Lawrence Phillips, Gustavo Saiz, and Jon Lloyd SOIL, 6, 53–88, https://doi.org/10.5194/soil-6-53-2020, 2020 Amazon soils hold as much carbon (C) as is contained in the vegetation. In this work we sampled soils across 8 different Amazonian countries to try to understand which soil properties control current Amazonian soil C concentrations. We confirm previous knowledge that highly developed soils hold C through clay content interactions but also show a previously unreported mechanism of soil C stabilization in the younger Amazonian soil types which hold C through aluminium organic matter interactions.
- Multi-cooperation of soil biota in the plough layer is the key for conservation
tillage to improve N availability and crop yield
Multi-cooperation of soil biota in the plough layer is the key for conservation tillage to improve N availability and crop yield Shixiu Zhang, Liang Chang, Neil B. McLaughlin, Shuyan Cui, Haitao Wu, Donghui Wu, Wenju Liang, and Aizhen Liang SOIL Discuss., https//doi.org/10.5194/soil-2020-2,2020 Preprint under review for SOIL (discussion: open, 0 comments) Conservation tillage facilitates constructing a more heterogeneous distribution of soil organisms along the plough layer relative to conventional tillage (CT). The contribution of soil biota to soil N mineralization and their relationships with soybean yield were investigated under contrasting tillage practices. A stable supply of mineral N from soil to plant could be maintained by the either horizontal or vertical cooperation of soil biota in the plough layers.
- Machine learning and soil sciences: a review aided by machine learning tools
Machine learning and soil sciences: a review aided by machine learning tools José Padarian, Budiman Minasny, and Alex B. McBratney SOIL, 6, 35–52, https://doi.org/10.5194/soil-6-35-2020, 2020 The application of machine learning (ML) has shown an accelerated adoption in soil sciences. It is a difficult task to manually review all papers on the application of ML. This paper aims to provide a review of the application of ML aided by topic modelling in order to find patterns in a large collection of publications. The objective is to gain insight into the applications and to discuss research gaps. We found 12 main topics and that ML methods usually perform better than traditional ones.
- Monitoring soil salinity using time-lapse electromagnetic conductivity imaging
Monitoring soil salinity using time-lapse electromagnetic conductivity imaging Maria Catarina Paz, Mohammad Farzamian, Ana Marta Paz, Nádia Luísa Castanheira, Maria Conceição Gonçalves, and Fernando Monteiro Santos SOIL Discuss., https//doi.org/10.5194/soil-2019-99,2020 Preprint under review for SOIL (discussion: open, 1 comment) In this study electromagnetic induction (EMI) surveys and soil sampling were repeated over time to monitor soil salinity dynamics in an important agricultural area that faces risk of soil salinization. EMI data was converted to electromagnetic conductivity imaging through a mathematical inversion algorithm, and converted to 2D soil salinity maps until a depth of 1.35 m through a regional calibration. This is a non-invasive and cost-effective methodology that can be employed over large areas.
- Management-intensive Grazing Affects Soil Health
Management-intensive Grazing Affects Soil Health Casey Shawver, James A. Ippolito, Joe Brummer, Jason Ahola, and Ryan Rhoades SOIL Discuss., https//doi.org/10.5194/soil-2019-91,2020 Preprint under review for SOIL (discussion: open, 0 comments) Management-intensive Grazing (MiG) on irrigated, perennial pastures is steadily increasing due to numerous environmental pressures. However, many unknowns exist regarding MiG and its environmental impact, especially related to soil health. MiG improved biological soil health, but negatively impacted physical soil health due to grazing when soils were near saturation. If managed correctly, MiG systems have the potential for success with regards to supporting grazing and improving soil health.