Introduction and objectives

This document reports the metadata and a figure of the pedogenon map for the Autonomous Community of the Basque Country, which was developed with the aim of delineating soil units according to the proposal for the Soil Monitoring and Resilience Law (Soil Monitoring Directive). The resolution from 10 April 2024 by the European Parliament on the the proposal for a directive of the European Parliament and of the Council on Soil Monitoring and Resilience Law (Soil Monitoring Law) (COM(2023)0416 – C9-0234/2023 – 2023/0232(COD)) proposes that Member States establish soil units for the monitoring and assessment of soil health across all their territory. These soil units should be defined seeking homogeneity in regard to soil type (IUSS Working Group WRB, 2022), climatic conditions, and land use or land cover Soil units are gathered under the governance of administrative districts, i.e., soil districts (European Commission, 2023; General Secretariat of the Council, 2024). “Soil districts should constitute the basic governance units to manage soils and to take measures to comply with the requirements laid down in this Directive, in particular with regard to the monitoring and assessment of soil health”(European Commission, 2023).

The main objective of SELVANS WP1 Pedogenon mapping in the context of long-term intensive land use was to adapt and improve the digital soil mapping (DSM) framework for pedogenon mapping of forest soils at regional and local scales, and specifically, to apply pedogenon mapping for delineating soil units for Euskadi. Pedogenon classes are a conceptual taxa that aim to define groups of homogeneous environmental variables. These groups are created applying unsupervised classification to a set of state variables, proxies of the soil-forming factors for a given reference time. The assumption is that the soil-forming processes within these classes (i.e., pedogenons) have been relatively similar over pedogenetic time and thus have developed soils with similar properties. Pedogenon classes can afterwards be divided into subclasses along a gradient from less (i.e., genosoils) to more anthropogenic pressure on soils (i.e., phenosoils), in an analogous way to the concept of genoform and phenoform (Rossiter and Bouma, 2018). The conceptualization and methodology for pedogenon mapping is explained with more detail in Román Dobarco et al. (2021).

The goals of pedogenon mapping are:

• Stratify the landscape into classes of homogeneous soil-forming factors (pedogenons) under the assumption that they delineate areas of similar pedogenesis up to a given reference time, that can be 
• Overlayed with information of forest management and land use change to define subclasses across a gradient of contemporary anthropogenic pressure, ranging from least affected and representative of natural and historic anthropedogenesis (i.e., genosoils) to variants by soil management that have seen modified their functions (i.e., phenosoils). In the context of the Basque Country, and example of genosoil would be a mixed broadleaved forest or a pasture that has resulted from the coevolution with human management. Examples of phenosoils could be oak or beech managed forests (relatively low pressure) or pine and eucalyptus commercial plantations (more intensive soil pressure).
•  The genosoils and phenosoils can be used to assess changes in soil condition in forest ecosystems.
•  The reference soils can be used to set targets for management.
•  The pedogenon classes are equivalent to soil units and used as strata for monitoring soil health in the context of the Soil Monitoring Law.

Overview of the product and metadata

The optimal number of soil units for Euskadi was nine, and the resulting pedogenon classes reflected the influence of climate, potential vegetation, relief and parent material. The choice of the optimal number of soil units was based on several criteria: minimum of three observations of the Basque forest soil monitoring network (BASONET) per soil district, maximising the compactness of the soil units in terms of the environmental variables used for k-means clustering (Calinski-Harabasz index), and minimising the ratio of within-district to between-district soil profile distances, using the BASONET data on clay, silt, and effective cation exchange capacity  from 0-20 cm and 20-40 cm depth as soil variables. The resulting map of soil units  designates a soil district with numbers from 1 to 9. 

• File name: smu_eus.tif
• Version: 1.0
• Description: Map of soil monitoring units for the Autonomous Community of the Basque Country.
• Process used to create the data: Digital Soil Mapping approach explained in detail in Román Dobarco et al. (2021) and a publication under review. Briefly, quantitative and spatially exhaustive variables representative of the soil-forming factors were sampled over a regular grid. The 90,000 pixels were used for unsupervised classification, applying k-means clustering (k = 9) to the decorrelated variables. The best of ten initializations (k-means ++ algorithm) was selected and used to map 9 soil units (see figure 2).
• Date of publication: 16/01/2025
• Reference period: 2024
• Date of creation: Thursday, ‎March ‎21, ‎2024
• Last modification: Thursday, ‎March ‎21, ‎2024
• Type of data: GeoTIFF file
• Pixel type: floating point (32 bit)
• No data value: nan
• Purpose of the data: Stratification of the Basque Country into soil monitoring units for the Soil Monitoring and Resilience Law.
• Lineage: First version. The sources of the input data will be described in the accompanied peer review publication and Deliverable 1.1.
• Resolution: 25 m
• Projected Coordinate system: ETRS 1989 UTM Zone 30N (EPSG: 25830)
• Geographic Coordinate system: ETRS 1989 (EPSG: 4258)
• Location details (geographic extent):
  •       North: 4,811,750 m
  •       South: 4,700,850 m
  •       West: 461,050 m
  •       East: 606,500 m
• Creator or author of the data: Mercedes Román Dobarco, Alex McBratney, Sophie Cornu, Jorge Curiel Yuste.
• Contact: Mercedes Román Dobarco (mercetadzio@gmail.com )
• Access and licensing information: These maps are available under the CC-BY 4.0 License.
• DOI: 10.5281/zenodo.14674358
• Associated publications / Conference presentation: Román Dobarco, M., McBratney, A., Cornu, S., Curiel Yuste, J. Soil. Monitoring the condition of forest soils in the Basque Country (Spain). An application of pedogenon mapping for policy implementation. Presented at the Centennial of the IUSS (May 19-21, 2024), Florence, Italy.
• Dataset citation: Román Dobarco, M., McBratney, A., Cornu, S., Curiel Yuste, J. 2025 Maps of soil monitoring units for the Basque Country (Spain). An application of pedogenon mapping for policy implementation. DOI: 10.5281/zenodo.14674358
• File size: 4.8 MB.
• Keywords: Pedogenon, digital soil mapping, soil monitoring, Soil Monitoring and Resilience Law, soil security.

References

European Commission, 2023. Proposal for a DIRECTIVE of the EUROPEAN PARLIAMENT and of the COUNCIL on Soil Monitoring and Resilience (Soil Monitoring Law) (No. COM(2023) 416 final). European Commission, Brussels.

General Secretariat of the Council, 2024. General approach on the Proposal for a DIRECTIVE of the EUROPEAN PARLIAMENT and of the COUNCIL on Soil Monitoring and Resilience (Soil Monitoring Law) (No. 2023/0232(COD)). Council of the European Union, Brussels.

IUSS Working Group WRB, 2022. World Reference Base for Soil Resources. International soil classification system for naming soils and creating legends for soil maps., 4th edition. ed. International Union of Soil Sciences, Vienna, Austria.

Román Dobarco, M., McBratney, A., Minasny, B., Malone, B., 2021. A modelling framework for pedogenon mapping. Geoderma, 393, p.115012. https://doi.org/10.1016/j.geoderma.2021.115012

Rossiter, D.G., Bouma, J. (2018). A new look at soil phenoforms–Definition, identification, mapping. Geoderma, 314, 113-121. https://doi.org/10.1016/j.geoderma.2017.11.002