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Susceptibility to landslides in mountain areas results from the interaction of various factors related to relief formation and soil development. The assessment of landslide susceptibility has generally taken into account individual events, or it has been aimed at establishing relationships between landslide-inventory maps and maps of environmental factors, without considering that such relationships can change in space and time. In this work, temporal and space changes in landslides were analysed in six different combinations of date and geomorphological conditions, including two different geological units, in a mountainous area in the northcentre of Venezuela, in northern South America. Landslide inventories from different years were compared with a number of environmental factors by means of logistic regression analysis. The resulting equations predicted landslide susceptibility from a range of geomorphometric parameters and a vegetation index, with diverse accuracy, in the study area. The variation of the obtained models and their prediction accuracy between geological units and dates suggests that the complexity of the landslide processes and their explanatory factors changed over space and time in the studied area. This calls into question the use of a single model to evaluate landslide susceptibility over large regions. [ABSTRACT FROM AUTHOR]

Land evaluation is a critical step in land-use planning. Although many methods have been developed since the formulation of the FAO framework for land evaluation, several of the more traditional approaches still remain in widespread use but have not been adequately evaluated. Contrary to more recent land evaluation systems, which need considerable data, these systems only require basic soil and landscape information to provide a general view of land suitability for major types of land use. As the FAO initially presented its qualitative framework for land-use planning, based on two previous methods developed in Iran and Brazil, in this study we assessed the reliability and accuracy of a traditional land evaluation method used in Iran, called land classification for irrigation ( LCI), comparing its results with several qualitative and quantitative methods and actual yield values. The results showed that, although simpler than more recently developed methods, LCI provided reliable land suitability classes and also showed good relationships both with other methods analysed and with actual yields. Comparisons between qualitative and quantitative methods produced similar results for common crops (a barley-alfalfa-wheat-fallow rotation). However, these methods performed differently for opportunist crops (such as alfalfa) that are more dependent on income and market conditions than on land characteristics. In this work, we also suggest that using the FAO method to indicate LCI subclasses could help users or managers to recognize limitations for land-use planning. [ABSTRACT FROM AUTHOR]

The aim of the present work was to evaluate the possibilities of using sub-basin data for calibration of the Soil and Water Assessment Tool (SWAT) model in a small (46 ha) ungauged basin (i.e. where the water flow is not systematically measured) and its response. This small basin was located in the viticultural Anoia-Penedès region (North-east Spain), which suffers severe soil erosion. The data sources were: daily weather data from an observatory located close to the basin; a detailed soil map of Catalonia; a 5-m resolution digital elevation model (DEM); a crop/land use map derived from orthophotos taken in 2010 and an additional detailed soil survey (40 points) within the basin, which included properties such as texture, soil organic carbon, electrical conductivity, bulk density and water retention capacity at −33 and −1500 kPa. A sensitivity analysis was performed to identify and rank the sensitive parameters that affect the hydrological response and sediment yield to changes of model input parameters. A 1-year calibration and 1-year validation were carried out on the basis of soil moisture measured at 0·20-m intervals from depths of 0·10 to 0·90 m in two selected sub-basins, and data related to estimations of runoff and sediment concentrations in runoff collected in the same sub-basins. The present paper shows a methodological approach for calibrating SWAT in small ungauged basins using soil water content measurements and runoff samples collected within the basin. The SWAT satisfactorily predicted the average soil water content, runoff and soil loss for moderate intensity events recorded during the study periods. However, it was not satisfactory for high-intensity events which would require exploring the possibilities of using sub-daily information as an input model parameter. [ABSTRACT FROM PUBLISHER]

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The article discusses a study which examined the spatial variability of runoff and erosion rates in vineyards of Northeastern Spain. The study examined plots with high disturbance (HD) and low disturbance (LD) of the soil profile and evaluated whether soil surface properties were conditioning runoff and erosion rates. It discusses soil and rainfall characteristics as well as runoff differences in the HD and LD plots and differences in sediment concentration.

Since the 1970s and 1980s, the vineyard areas in the Mediterranean region of north east Spain have undergone profound transformation to allow greater mechanization. This has involved land levelling, deep ploughing and the elimination of traditional soil conservation measures. Recently the EU Common Agricultural Policy encourages this through the vineyard restructuring and conversion plans (Commission Regulation EC No 1227/2000 of 31 May 2000) by subsidizing up to 50% of the cost of soil preparation such as soil movement and land levelling. A clear example of the problems that this causes is in the Penedès vineyard region (Catalonia, north east Spain), and the present research analyses the changes in soil properties caused by erosion, deep ploughing and land levelling. The study was carried out in an area of 30 000 ha for which a Soil Information System at a scale of 1:50 000 was developed based on 394 field observations (89 soil profiles and 251 auger hole samples down to 120 cm). The results show that 74% of the described soil profiles are disturbed with evidence of soil mixing and/or profile truncation due to erosion, deep ploughing and/or land levelling. The evidence from the topsoils is mainly the presence of fragments of calcic or petrocalcic horizons, marls and sandstones. Other important properties for crops such as organic matter (OM) content and soil depth show statistically significant differences between disturbed soils and undisturbed soils (22.3–33.3% OM content depletion and 35.1% soil depth reduction). These results confirm that the soils of the region are significantly altered by mechanical operations which also influence soil erosion and contribute to global warming effect through depletion of soil OM. [ABSTRACT FROM AUTHOR]

The article presents a study on the agricultural trajectories and farming systems in the Priorat region in Spain. In the Priorat region, as well as in the other mountain regions of Mediterranean European countries, the intensification of crops is said to be based on either land leveling or terracing, and the abandonment of usual land use management practices. One of the objectives of the study is to relate the coexisting farming systems in Priorat to the landscape impacts they involve. The researchers combined multivariate statistical techniques to understand the heterogeneity of farming systems on a local scale.

Automated mapping of land cover using black and white aerial photographs, as an alternative method to traditional photo-interpretation, requires using methods other than spectral analysis classification. To this end, textural measurements have been shown to be useful indicators of land cover. In this work, a neural network model is proposed and tested to map historical land use/land cover (LUC) from very detailed panchromatic aerial photographs (5 m resolution) using textural measurements. The method is used to identify different land use and management types (e.g. traditional versus mechanized vineyard systems). These have been tested with known ground reference data. The results show the potential of the methodology to obtain automatic, historic, and very detailed cartography information from a complex landscape such as the mountainous and Mediterranean region to which it is applied here, and the advantages that this method has over traditional methods. [ABSTRACT FROM AUTHOR]