Sand and Dust Storms (SDS) are often considered as a natural phenomenon typical of the remote desert regions. It is becoming clear, however, that human activities also contribute to the increasing global impacts of SDS. The United Nations Convention to Combat Desertification has recently recognized the global relevance of the anthropogenic SDS sources. These are directly and/or indirectly linked to human activities that make the soils more susceptible to wind erosion, such as unsustainable agricultural practices, overgrazing, deforestation, and misuse of water resources: in other words, the drivers of land degradation. Human activities that contribute to climate change can also be considered as indirect drivers of SDS, as they affect SDS factors like drought patterns and wind regimes. Although the contribution of anthropogenic source areas to total global dust emissions is relatively limited as amount of dust emitted (19–25%), these sources are widespread in almost all environments including drylands, sub-humid and humid areas, and high latitudes. This article reviews the scientific evidence on the contribution of anthropogenic activities to SDS generation in a variety of SDS hotspots. The contexts considered in this study are associated with different levels of aridity (arid to humid) and with a wide range of land use systems and management practices, human drivers, and land health conditions. On one extreme, like in the Thar Desert of India, SDS are a manifestation of chronic and extensive historical land degradation in arid climatic conditions. On another extreme SDS are occasional events caused by a combination of exceptional weather conditions (e.g., drought spells, windstorms) and of factors increasing soil erodibility locally (e.g., bare fallow or soil disturbance after harvest) and in specific times of the year, as often observed in humid central Europe. Drivers linked to technological activities such as mining, industry, and military operations were also reviewed. Anthropogenic source areas are often of smaller size compared to the natural ones and marked by more scattered distribution patterns. SDS originated from these sources are in some cases occasional and relatively small but can have severe or cumulative impacts on local communities, local residential and transportation structures, and on downwind urban areas. The majority of SDS studies have mostly addressed large scale events and rarely addressed the distinction between natural and anthropogenic sources. The relationships between the observed impacts of the SDS events and the respective drivers have been poorly studied, as well as the interactions among the SDS drivers, also due to the lack of high resolution and field data on land use and land degradation conditions in the dust source areas. More in-depth research would be needed to understand to what extent the increasing frequency and severity of anthropogenic SDS can be considered as indicators of increasing desertification and reduced land resilience to climate change.

Sand and Dust Storms (SDS) are often considered as a natural phenomenon typical of the remote desert regions. It is becoming clear, however, that human activities also contribute to the increasing global impacts of SDS. The United Nations Convention to Combat Desertification has recently recognized the global relevance of the anthropogenic SDS sources. These are directly and/or indirectly linked to human activities that make the soils more susceptible to wind erosion, such as unsustainable agricultural practices, overgrazing, deforestation, and misuse of water resources: in other words, the drivers of land degradation. Human activities that contribute to climate change can also be considered as indirect drivers of SDS, as they affect SDS factors like drought patterns and wind regimes. Although the contribution of anthropogenic source areas to total global dust emissions is relatively limited as amount of dust emitted (19–25%), these sources are widespread in almost all environments including drylands, sub-humid and humid areas, and high latitudes. This article reviews the scientific evidence on the contribution of anthropogenic activities to SDS generation in a variety of SDS hotspots. The contexts considered in this study are associated with different levels of aridity (arid to humid) and with a wide range of land use systems and management practices, human drivers, and land health conditions. On one extreme, like in the Thar Desert of India, SDS are a manifestation of chronic and extensive historical land degradation in arid climatic conditions. On another extreme SDS are occasional events caused by a combination of exceptional weather conditions (e.g., drought spells, windstorms) and of factors increasing soil erodibility locally (e.g., bare fallow or soil disturbance after harvest) and in specific times of the year, as often observed in humid central Europe. Drivers linked to technological activities such as mining, industry, and military operations were also reviewed. Anthropogenic source areas are often of smaller size compared to the natural ones and marked by more scattered distribution patterns. SDS originated from these sources are in some cases occasional and relatively small but can have severe or cumulative impacts on local communities, local residential and transportation structures, and on downwind urban areas. The majority of SDS studies have mostly addressed large scale events and rarely addressed the distinction between natural and anthropogenic sources. The relationships between the observed impacts of the SDS events and the respective drivers have been poorly studied, as well as the interactions among the SDS drivers, also due to the lack of high resolution and field data on land use and land degradation conditions in the dust source areas. More in-depth research would be needed to understand to what extent the increasing frequency and severity of anthropogenic SDS can be considered as indicators of increasing desertification and reduced land resilience to climate change.

Topography-induced spatial heterogeneity influences soil organic carbon (SOC) stocks and microbial degradation (respiration) both in topsoil and subsoil compartments. However, the interaction between topographic position and soil horizons has rarely been assessed. This study aimed to investigate SOC dynamics in topsoil (5cm) and subsoil horizons (40 and 80cm) at shoulderslope and footslope positions in a toposequence in a Danish winter wheat field. In addition, SOC was quantified for 20-cm depth intervals to 100cm depths. Over a 1year period, gas samples for carbon dioxide (CO2) and oxygen (O2) analyses were collected from seven different soil depths (5 to 80cm) at the shoulder- and footslope positions. Soil surface CO2 fluxes were measured over a shorter period (January to June 2012). Soil samples from 5 and 40cm depths were incubated at 5 to 34°C to determine the temperature sensitivity (Q10) of soil respiration. Results showed that SOC stocks to a soil depth of 1m were larger at footslope (202MgCha−1) compared to shoulderslope (44MgCha−1) positions. Mean annual soil CO2 concentrations were higher at footslope positions, and increased with depth at both shoulder- and footslope positions. Temperature sensitivity of C turnover was similar in topsoil at shoulderslope (Q10=2.5) and footslope (Q10=2.6) positions; in subsoil (40cm), however, Q10 was lower at shoulderslope (Q10=2.0) than footslope (Q10=3.2) positions. Further, shoulderslope subsoil had less non-complexed organic C than footslope subsoil, suggesting that the shoulderslope subsoil was not C saturated and had higher potential for C stabilization. Despite the dissimilar subsoil characteristics at shoulder- and footslope positions, soil surface CO2 effluxes were similar, suggesting low contribution of subsoil C to short-term surface CO2 fluxes at footslope positions.

Many soil maps were drawn up after World War II with different soil classifications that have significantly evolved since. Updating such old maps with a new version or a new classification system is always complex: (i) we do not always possess all the original information; (ii) the criteria for determining references are often different, and (iii) on the most accurate scales, correlations come up against the complexity and specificities of each classification system. On Reunion, a volcanic tropical island in the Indian Ocean, we undertook a comprehensive overview of the old existing soil studies. This article describes (i) the procedure used to update the soil maps and the toposequence acquired with the old French Commission de Pédologie et de Cartographie des Sols (CPCS) classification system, without any new information, using the World Reference Base for soil resources (WRB); (ii) the construction of a new soil map drawn up with completely new information, and (iii) a comparison of these two approaches. At elevations below 350 m asl (above sea level), without any new pedological information, we updated Brown ferruginous soils, Reddish-brown ferrallitic soils, and Fersialitic soils into Haplic Nitisols (Humic, Eutric). The acquisition of new data showed that this update was incorrect because not all the diagnostic criteria of the Nitic horizons were met. The correct diagnostic horizons were a Mollic horizon when the thickness was 25 cm or more, or a Cambic horizon. Leptic Phaeozems and Leptic Cambisols were then the correct Reference Soil Group (RSG). At elevations from 350 to 900 m asl, without any new information, Brown and Reddish-brown ferrallitic soils, Andic ferrallitic soils, and Brown and Andic brown soils were updated into Haplic Nitisols (Humic, Dystric) and Andic Umbrisols (Humic). The acquisition of new data showed that this update was incorrect because Andic properties and the diagnostic criteria of the Nitic horizons were not met. Over 900 m asl, Poz

Many soil maps were drawn up after World War II with different soil classifications that have significantly evolved since. Updating such old maps with a new version or a new classification system is always complex: (i) we do not always possess all the original information; (ii) the criteria for determining references are often different, and (iii) on the most accurate scales, correlations come up against the complexity and specificities of each classification system. On Reunion, a volcanic tropical island in the Indian Ocean, we undertook a comprehensive overview of the old existing soil studies. This article describes (i) the procedure used to update the soil maps and the toposequence acquired with the old French Commission de Pédologie et de Cartographie des Sols (CPCS) classification system, without any new information, using the World Reference Base for soil resources (WRB); (ii) the construction of a new soil map drawn up with completely new information, and (iii) a comparison of these two approaches. At elevations below 350m asl (above sea level), without any new pedological information, we updated Brown ferruginous soils, Reddish-brown ferrallitic soils, and Fersialitic soils into Haplic Nitisols (Humic, Eutric). The acquisition of new data showed that this update was incorrect because not all the diagnostic criteria of the Nitic horizons were met. The correct diagnostic horizons were a Mollic horizon when the thickness was 25cm or more, or a Cambic horizon. Leptic Phaeozems and Leptic Cambisols were then the correct Reference Soil Group (RSG). At elevations from 350 to 900m asl, without any new information, Brown and Reddish-brown ferrallitic soils, Andic ferrallitic soils, and Brown and Andic brown soils were updated into Haplic Nitisols (Humic, Dystric) and Andic Umbrisols (Humic). The acquisition of new data showed that this update was incorrect because Andic properties and the diagnostic criteria of the Nitic horizons were not met. Over 900m asl, Pozols were correctly updated, as were the Andosols except from 900 to 1050m asl where not all the Andic properties were met. Without any new information, incorrect updates were observed for both the determination of RSG and the qualifiers. Despite the field descriptions, the lack of any analytical determinations on the old soil studies was a source of updating errors for the more developed soils formerly qualified as ferrallitic. In order to update limits for Andic properties and Andosols, the systematic use of analytical determinations has to be considered for updating old soil maps, as the diagnostic criteria are more restrictive than in the past.

Lateritic weathering of Miocene volcanic rocks from western Cameroon highlands formed duricrusted bauxitic profiles. Two weathering profiles on ca. 14 Ma basalt and ca. 16 Ma trachyte were studied using geochemical mass balance functions. Less mobile elements Ti and Zr were used as references to quantify volumetric change (strain, ε), element transfer rate (τ) and geochemical mass transfers during the bauxitization process of basalt and trachyte. Conversion of parent rocks to kaolinite and goethite rich saprolites evolved to Al-Fe rich bauxites, mostly composed of gibbsite and iron oxy-hydroxides (goethite and hematite). However, formation of Al-Fe bauxitic profiles required higher Si leaching on trachyte than on basalt. Our results document that chemical weathering of a larger thickness of trachyte than basalt has been required to form a unit meter of weathering profile, implying differential rates of rock chemical erosion and topographic decay of landscapes. Rates of chemical erosion and formation of lateritic weathering profiles in western Cameroon have been mostly controlled by drainage conditions and volcanic rocks composition (mostly SiO2 content differences), that also resulted in contrasted landscapes evolution during the Neogene.

Lateritic weathering of Miocene volcanic rocks from western Cameroon highlands formed duricrusted bauxitic profiles. Two weathering profiles on ca. 14 Ma basalt and ca. 16 Ma trachyte were studied using geochemical mass balance functions. Less mobile elements Ti and Zr were used as references to quantify volumetric change (strain, ε), element transfer rate (τ) and geochemical mass transfers during the bauxitization process of basalt and trachyte. Conversion of parent rocks to kaolinite and goethite rich saprolites evolved to Al-Fe rich bauxites, mostly composed of gibbsite and iron oxy-hydroxides (goethite and hematite). However, formation of Al-Fe bauxitic profiles required higher Si leaching on trachyte than on basalt. Our results document that chemical weathering of a larger thickness of trachyte than basalt has been required to form a unit meter of weathering profile, implying differential rates of rock chemical erosion and topographic decay of landscapes. Rates of chemical erosion and formation of lateritic weathering profiles in western Cameroon have been mostly controlled by drainage conditions and volcanic rocks composition (mostly SiO₂ content differences), that also resulted in contrasted landscapes evolution during the Neogene.

Many areas in the world suffer from relatively sparse soil data availability. This results in inefficient implementation of soil-related studies and inadequate recommendations for improving soil management strategies. Commonly, this problem is tackled by collecting new soil data to update legacy soil surveys. New soil data collection, however, is usually costly. In this paper, we demonstrate how to find homosoils with the objective of obtaining new soil data for a study area. Homosoils are soils that can be geographically distant but share similar soil-forming factors. We cluster the study area into homogenouse areas, and identify a homosoil to each area using distance metrics calculated in the character space spanned by the environmental covariates. In a case study in Mali, we found that large areas in India, Australia and America have similar soil-forming factors to the African Sahelian zone. We collected available soil data for these areas from the WoSIS database. Statistical analysis on the relationship between the homosoils corresponding to different areas of Mali and three soil properties (clay, sand, pH) displayed the unique variability captured by homosoils. The homosoils could explain 8% of the variation found in the soil datasets. There was a strong association between pH and homosoils corresponding to the semi-arid conditions and sedimentary parent material of Mali, whereas homosoils corresponding to other areas of Mali showed moderate association either with clay or sand. The location and spread of the group centroids were significantly different between depth-specific homosoils for the three soil properties. The approach developed in this paper shows the opportunity for identifying areas in the world with similar soils to populate areas with relatively low soil data density. The concept of homosoils is promising and we envision future applications such as transfer of soil models and agronomic experimental results between areas.

Many areas in the world suffer from relatively sparse soil data availability. This results in inefficient implementation of soil-related studies and inadequate recommendations for improving soil management strategies. Commonly, this problem is tackled by collecting new soil data which are used to update legacy soil surveys. New soil data collection, however, is usually costly. In this paper, we demonstrate how to find homosoils with the objective of obtaining new soil data for a study area. Homosoils are soils that can be geographically distant but share similar soil-forming factors. We cluster the study area into five areas, and identify a homosoil to each area using distance metrics calculated in the character space spanned by the environmental covariates. In a case study in Mali, we found that large areas in India, Australia and America have similar soil-forming factors to the African Sahelian zone. We collected available soil data for these areas from the WoSIS database. Statistical analysis on the relationship between the homosoils corresponding to different areas of Mali and tree soil properties (clay, sand, pH) displayed the unique variability captured by homosoils. The homosoils could explain 8% of the variation found in the soil datasets. There was a strong association between pH and homosoils corresponding to the semi-arid conditions and sedimentary parent material of Mali, whereas homosoils corresponding to other areas of Mali showed moderate association either with clay or sand. The location and spread of the group centroids were statistically significantly different between depth-specific homosoils for the three soil properties. The approach developed in this paper shows the opportunity for identifying areas in the world with similar soils to populate areas with relatively low soil data density. The concept of homosoils is promising and we envision future applications such as transfer of soil models and agronomic experimental results between areas.

We studied an improved slope form system using a fuzzy logic method to assess and map soil fertility of a mountain region in northern Vietnam that has strong relief conditions. The lack of good soil mapping techniques in Vietnam has brought about insufficient soil information, which often leads to false recommendations for land use and crop planning. The reviewed literature describes soil-mapping techniques using fuzzy logic method, but all of them are applied for mapping areas that have gentle relief conditions that are unlikely to be applicable to the mountainous soils in our study area. In this paper, we introduce a detailed slope form system that significantly describes the complexity of terrain characteristics of the area to be mapped, and provides more detail about the variability of the soil fertility of the area. Nine basic slopeforms were used to characterize for each of upper-, middle-, and foot slope positions, making the list 27 slopeforms. Together with crest and valley, the total unit number is 29. We investigated soils of the area and classified them into the major soil groups and calculated soil property indices for all of them. We identified four major environmental parameters affecting soil formation and soil quality: geology, elevation, slope inclination and land use. The findings indicated that soil fertility differs at slope positions. Soils located at upper slope positions, where agricultural activity only started recently, are more fertile than those found at middle slope positions. Soils located at foot slope positions, where eroded sediments accumulate, also have high levels of fertility compared to those on the middle slope. The improved slope form system then became an important additional environmental parameter for this soil mapping work. At a same comparable category, i.e. slope position, geology, soil group, elevation, slope gradient, straight slopeforms are an indicator for better soil fertility compared to convex and concave forms. Although the findings could not specify soil fertility variability for all 29 slopeforms, they did emphasize the major differences in soil fertility and soil formation based on three major forms of convex, straight and concave, with other factors taken into account, such as slope inclination, geology and elevation. We expect our results to be used by scientists and local authorities in deriving more effective land use and crop options for land use management strategies for the northern Vietnam's mountain regions.