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In 1991, at the launch of a national symposium devoted to soil structure, the Australian Society of Soil Science invited Professor John Letey to deliver a keynote address, which was later published in the society's journal. In his lecture, he shared the outcome of his reflexion about what the assessment of soil structure should amount to, in order to produce useful insight into the functioning of soils. His viewpoint was that the focus should be put on the openings present in the structure, rather than on the chunks of material resulting from its mechanical dismantlement. In the present article, we provide some historical background for Letey's analysis, and try to explain why it took a number of years for the paradigm shift that he advocated to begin to occur. Over the last decade, his perspective that soil structure needs to be characterised via nondestructive methods appears to have gained significant momentum, which is likely to increase further in the near future, as we take advantage of recent technological advances. Other valuable lessons that one can derive from Letey's pioneering article relate to the extreme value for everyone, even neophytes, to constantly ask questions about where research on given topics is heading, what its goals are, and whether the methods that are used at a certain time are optimal. Keywords: aggregate stability, computed tomography, earthworms, micromorphology, soil fauna, soil functions, soil image analysis, soil microorganisms, soil measuring, soil organic matter., Introduction From the 1950s to the 1980s, the topic of soil structure attracted considerable attention among soil scientists in Australia, and the scientific literature contains many frequently-cited contributions on the [...]

As the consequences of climate change are looming large, agricultural soil carbon credits have emerged as an increasingly advocated lever to incentivize the reduction of greenhouse gas emissions and promote carbon storing farming practices. These credits are exchanged on self‐regulated voluntary carbon markets, each of them using distinct protocols to assess the changes in soil carbon stocks and convert them into carbon credits. Although serious discrepancies between protocols have already been noted regarding general carbon credit accounting principles, an in‐depth evaluation of how changes in soil organic carbon stocks are calculated is still lacking. In this context, the primary objective of our study was to investigate how changes in soil organic carbon stock are estimated by the major carbon credit protocols worldwide. We evaluated the requirements of each protocol regarding the estimation of the initial SOC stock as well as the modelling and/or measurement of changes in stock with time. We found that existing protocols vary greatly in their scientific rigour. We showed in particular that some protocols do not require in situ soil analyses to estimate initial soil carbon stocks but rely on regional values, leading them to potentially overestimate these stocks by up to 2.5 times. Our study also found that the protocols relying on models require different farming practices and different levels of information for each practice to estimate SOC stock changes. The protocols relying, at least partly, on soil sampling also displayed different requirements for the sampling design, sampling tools, SOC analysis methods and SOC stock calculation methods. On this basis, we suggest reforms designed to improve and standardize the quantification of carbon stock changes in soils and to improve the reliability of soil carbon credits. [ABSTRACT FROM AUTHOR]

This study investigates the colloid systems and interfaces stability of cerium oxide nanoparticles in aqueous environments as a function of pH, monovalent cations (Na+) and divalent cations (Ca2+), and humic substances (humic acid (HA) and fulvic acid (FA)). Results show that the solution chemistry affected the colloidal stability and aggregation kinetics of CeO2 NPs. The pH point of zero charge (pHPZC) of CeO2 NPs was measured at pH 10.2 with diameter of CeO2 NPs aggregates of ∼1,700 nm. The effects of Na+ and Ca2+ and HA and FA on the magnitudes and rates of aggregation were pH-dependent. In addition, when salts were present in the aqueous systems, although the CeO2 NPs were stable at pH < pHPZC (expect for 1 mM of NaCl/CaCl2) and pH > pHPZC (except for 0.5 mM CaCl2), the aggregation was enhanced at pH = pHPZC, with the diameter of CeO2 NPs in the ∼1,300–3,600 nm range. HA also stabilized CeO2 NPs under pH > pHPZC with an enhanced aggregation of pH = pHPZC with the diameter of CeO2 NPs in the ∼1,500–1,900 nm range, and in the presence of 0 and 1 mM of NaCl/CaCl2 at pH < pHPZC. At three pH levels (8.2, 10.2, and 12.2) and under all different electrolyte concentrations (0–1 mM of NaCl or CaCl2), FA (0.14 mg/L) exhibited a greater degree of efficiency in stabilizing CeO2 NPs than HA (5 mg/L), with CeO2 NPs aggregates growing at low rates and resulting in diameter of ∼95–115 nm. [ABSTRACT FROM AUTHOR]

Multidisciplinary courses are being developed at a number of US colleges and universities to highlight the connections between the rise or fall of world civilizations and the sustainable or unsustainable uses of soil and water resources. The content presented in these courses is complex because it includes concepts from disciplines as varied as geology, soil science, politics, economics, history, and anthropology. The learning goals for the courses include developing skills in the critical analysis of complex "real-world" problems for which there is often no simple or correct solution. Didactic materials for such courses are limited. Field trips to sites around the world that present some of the issues covered in the course would be ideal, but are logistically challenging. We considered that a series of virtual field trips (VFTs) to sites around the world would allow us to present students with complicated real-world situations, with which to practice critical analysis skills. The VFTs envisaged are neither tutorials nor field/lab exercises. Rather, they are meant to be complex, multi-faceted representations of a past or current civilization and how it affects or is affected by its environment. We expect that the students will use the VFTs to explore the relationships between physical geography and culture and how the decisions or actions of a civilization impact natural resources and the environment and thus affect its fate. A goal of the VFTs is that through consideration of their experiences, students arrive at novel associations that lead to dynamic in-class dialogue about the material presented and a deeper understanding of the intricacies of the situation in the field. This article describes the process of assembling a VFT, and analyzes the technological and didactic choices the process requires. Our experience with a pilot VFT suggests that no single medium (i.e., video clips, interactive maps, animation sequences, etc.) is comprehensive enough to meet the course learning goals. Thus, a web-based, open architecture format was selected for the VFTs because of its simplicity, flexibility and extensibility. Each medium was selected for its ability to support the course learning goals. The learning process was mediated by the VFT text, questions for thought, and in-class discussions. Preliminary results with the pilot VFT are encouraging. (Contains 7 figures.)

Over the last decade, the ecosystem services (ESs) framework has been increasingly used to support mapping and assessment studies for sustainable land management purposes. Previous analysis of practical applications has revealed the significance of the spatial scale at which input data are obtained. This issue is particularly problematic with soil data that are often unavailable or available only at coarse scales or resolutions in various part of the world. In this context, four soil‐based ecosystem services, namely biomass provision, water provision, global climate regulation, and water quality regulation, are assessed using three conventional soil maps at the 1:1,000,000, 1:250,000 and 1:50,000 scales. The resulting individual and joint ES maps are then compared to examine the effects of changing the spatial scale of soil data on the ES levels and spatial patterns. ES levels are finally aggregated to landforms, land use, or administrative levels in order to try to identify the determinants of the sensitivity of ES levels to change in the scale of input soil data. Whereas the three soil maps turn out to be equally useful whenever ESs levels averaged over the whole 100 km2 territory are needed, the maps at the 1:1,000,000 and 1:250,000 induced biases in the assessment of ESs levels over spatial units smaller than 100 and 10 km2, respectively. The simplification of the diversity and spatial distribution of soils at the two coarsest scales indeed resulted in local differences in ES levels ranging from several 10 to several 100%. Identification of the optimal representation of soil diversity and distribution to obtain a reliable representation of ESs spatial distribution is not straightforward. The ESs sensitivity to scale effect is indeed context‐specific, variable among individual ESs, and not directly or simply linked with the soil typological diversity represented in soil maps. Forested and natural lands in the study area appear particularly sensitive to soil data scales as they occupy marginal soils showing very specific ESs signatures. [ABSTRACT FROM AUTHOR]

Over the last two decades, there has been a documented decline in public trust toward science. This evolution has often been attributed to the fast expansion of Internet, making it very easy to spread alternate viewpoints. In the present perspective piece, it is argued that the unethical behavior of some researchers also has fueled the public distrust toward science. In this context, a solution could come from creating publicly accessible registries that would provide all the information needed by the public to determine whether a given researcher could safely be presumed to be an 'honest broker', i.e. to act in a disinterested manner about particular issues being debated. In the development of such registries, academies would be particularly suited to provide oversight, since some of their senior members, by virtue of their retirement from active duty, meet many of the conditions to effectively be honest brokers. [ABSTRACT FROM AUTHOR]