IOWDA – West Iberian Oak Woodland Distribution Abundance dataset

Summary The Iberian Oak Woodland Distribution and Abundance (IOWDA) dataset compiles and harmonizes geobotanical relevés of oak-dominated forests and scrublands across western Iberia, covering records from 1950 to 2024. The dataset includes floristic composition, standardized species nomenclature, syntaxonomic classification, and georeferenced coordinates. Each relevé was spatially validated using expert knowledge and modern tools, including Google Earth, MapCarta, and ArcGIS, resulting in 1227 georeferenced sites. To ensure taxonomic consistency and spatial precision, all data were digitized, filtered, and processed through custom Python scripts. Two matrices were generated: one with all relevés (1279) and another filtered by dominant Quercus species cover (988), both with 1460 species. This dataset fills a major gap in accessible, harmonized, fine-scale vegetation data in the Mediterranean Basin and supports studies on vegetation classification, biodiversity monitoring, climate change vulnerability, and forest restoration planning. IOWDA is an open-access resource for researchers, conservationists, and policymakers seeking to understand and protect Iberian oak ecosystems under changing environmental conditions. Dataset description The Iberian Oak Woodland Distribution and Abundance (IOWDA) dataset is a harmonised geobotanical database of oak-dominated forests and tall scrublands across western Iberia (Portugal and adjacent Spain), covering 1950–2024. It compiles floristic relevés from historical surveys and recent fieldwork, unifying them under a consistent taxonomic, spatial, and syntaxonomic framework. IOWDA provides: 1347 digitised geobotanical relevés, standardized and quality-checked 1314 georeferenced sites, validated using expert knowledge and tools such as Google Earth, MapCarta, and ArcGIS 1510 plant taxa, with harmonised nomenclature following current taxonomic standards Two analytical matrices: Complete Relevé Matrix (all inventories) Dominant Quercus Matrix (filtered to relevés where Quercus spp. are dominant) Syntaxonomic classification assigned or revised for each relevé Metadata fields including locality, coordinates, elevation, date, authorship, vegetation unit, and dominant species Open-access structure, fully documented and ready for reuse Use and applications Researchers, ecologists, conservation practitioners, forest managers, and policymakers interested in: Quercus woodlands Mediterranean and Atlantic vegetation Ecological gradients and biogeography Long-term vegetation dynamics Restoration ecology Methods Data Compilation The Iberian Oak Woodland Distribution and Abundance (IOWDA) dataset compiles 1279 phytosociological relevés of oak-dominated forests and scrublands across western Iberia, covering sources published between 1950 and 2024. Relevés were gathered from: Classical and modern phytosociological literature The SIVIM platform (Sistema de Información de la Vegetación Ibérica y Macaronésica), (http://sivim.info/sivi/), consultation period: 2024 to 2025 A total of 105 bibliographic references were reviewed, representing 51 Quercus-dominated associations. Each relevé includes the full floristic list, Braun–Blanquet cover values, and original locality information. Taxonomic and Nomenclatural Standardisation All species names (initially 2548 entries) were harmonised using: Expert botanical curation Cross-checking with the International Plant Names Index (IPNI) Consolidation of synonyms, outdated nomenclature, and typographic inconsistencies This reduced taxonomic inflation and yielded 1510 accepted taxa. All final matrices include only standardised, validated species names. Georeferencing Each relevé was spatially referenced and validated using a combination of: Author locality descriptions Google Earth, MapCarta, and ArcGIS Toponyms, elevation data, and Google Street View Expert knowledge on regional vegetation and geography Coordinates were standardised to UTM using the ETRS89 / UTM zone 29N (EPSG: 25829) coordinate reference system, typically at 10 × 10 km resolution, and refined to 1 × 1 km where possible.The final dataset includes 1314 unique georeferenced sites. Data Processing and Matrix Construction Custom Python (Pandas) workflows were developed to: Digitize and integrate all relevés into a unified database Standardize species names across all sources Merge relevés from different associations into consistent analytical grids Convert Braun–Blanquet cover values to numeric format Filter relevés based on dominance thresholds Two final matrices were generated: Full Matrix: 1347 relevés, 1510 species Dominant-Quercus Matrix: Filters sites where the dominant Quercus species has ≥ 37.5% cover (≥3 in Braun–Blanquet) 1082 relevés Both matrices include species composition, cover values Data availability The dataset is publicly available via the Zenodo repository under the Creative Commons Attribution 4.0 International (CC BY 4.0) license. Users are required to cite the dataset, the authors of the data mentioned in this page in any derived work or publication. In addition to the core matrices, the Zenodo repository includes a complementary “User Notes” Excel file providing extended metadata and documentation. This file contains the full list of relevé authors, publication years, bibliographic references, matrix legends, variable descriptions, and direct URLs to the complete and filtered matrices. The User Notes file is intended to facilitate correct interpretation, reuse, and citation of the dataset.