Methodology to standardize soil mapping in Portugal Metodologia para uniformizar a cartografia de solos em Portugal

Updated and harmonized soil information is essential for sustainable land use and the conservation of natural resources. In Portugal, however, soil maps vary significantly in scale, classification systems, and mapping and analytical methodologies. Standardizing these maps at a scale of 1:100,000 in the WRB system, utilizing digital tools and existing soil information, is crucial. In three pilot areas south of the Tagus River, factors influencing soil characteristics were categorized as follows: (i) lithology, in terms of rock origin, silica/carbonate content, and degree of consolidation; (ii) relief, considering slope, hypsometry, curvature, and landforms; and (iii) climate, based on thermal regime. By intersecting this information with the proportion of rocky outcrops, homogeneous zones were delineated, and soil-mapping units were subsequently defined using SROA/CNROA information (1:25,000). This process identified 23 lithological groupings, five relief classes, and seven climatic classes, resulting in 125 homogeneous zones with a minimum area of 30 ha. This standardized soil information aligns with the requirements of the EU INSPIRE directive, supporting the development of a harmonized land capability map for mainland Portugal.