It is slightly modified, in the results of reviewers' comments, version of the "Vascular plant species richness in Poland version 1.0" dataset. The changes involve file names and their organization within the dataset. Poland has a long tradition of geobotanical studies. However, outputs of this research have never been used for mapping vascular plant species richness at a larger spatial scale. Here we presented the results of joining and harmonization data from distribution atlas of vascular plants in Poland (Zając and Zając 2001, 2019), and Polish Vegetation Database (Kącki and Śliwiński 2012) to obtain a comprehensive data set on vascular plant species richness in a 10 x 10 km square grid, covering the territory of entire Poland. The presented data set is based on the recent version of the both above-mentioned data sources, provided for harmonization in 2020. The species were classified according to their origin, conservation status, and frequency of occurrences. The 10x10 km spatial grid was prepared by Komsta (2016) and Verey (2017). We used the grid system downloaded from: https://worldbig.org/atpol, and clipped it to the study area extent. Kącki, Z. and Śliwiński, M., 2012. The Polish Vegetation Database: structure, resources and development. Acta societatis botanicorum Poloniae, 81(2). DOI: 10.5586/asbp.2012.014 Komsta, Ł., 2016. ATPOL geobotanical grid revisited-a proposal of coordinate conversion algorithms. Annales Universitatis Mariae Curie-Skłodowska. Sectio E, Agricultura, 71(1), pp.31-37. Verey, M (2017). Teoretyczna analiza i praktyczne konsekwencje przyjęcia modelowej siatki ATPOL jako odwzorowania stożkowego definiującego konwersję współrzędnych płaskich na elipsoidę WGS 84. Fragmenta Floristica et Geobotanica Polonica, 24(2), 469-488. Zając A. (1978) Atlas of distribution of vascular plants in Poland (ATPOL). Taxon, 481-484. https://doi.org/10.2307/1219899 Zając A., Zając, M. (2001) Atlas rozmieszczenia roślin naczyniowych w Polsce. Nakładem Pracowni Chorologii Komputerowej Instytutu Botaniki Uniwersytetu Jagiellońskiego, Kraków Zając, A., & Zając, M. (2019). Distribution atlas of vascular plants in Poland: appendix. Institute of Botany, Jagiellonian University.–Kraków. This dataset consists: Files_description - file with a description of the data stored. Taxa_list. The nomenclature according to Euro+Med PlantBase (Euro+Med.) and operational taxonomical units (OTUs) used for analysis and mapping in the project. For simplification, the taxonomical operational units are called ‘species’. Taxa_status. The species affinity to taxonomic units (family, genera), status in Polish flora (native, archeophytes, neophytes), conservation status (Red List species), and frequency of their distribution (rare, moderate and common). Species_richness. Statistics on species richness and frequency in species groups for 10 × 10 km ATPOL squares. The names of squares according to original names in the ATPOL project (Zając 1978). The sampling bias (SB) shows adequately sampled squares labelled with 1, while squares with 0 are those with low sampling effort. Cross-boundary squares (CBS) denoted by 1 are squares with more than 80% of the area within the terrestrial territory of Poland, while squares with CBS of 0 are those with 80% or less of the area within the terrestrial territory of Poland. The detail information about the particular columns is shown in ‘Files_description’ and ‘Taxa_status’ files. Map_data. A shapefile with squares geospatial locations, codes of their names, and data on species richness and frequency in species groups. The map is registered in WGS 84 coordinate reference system (EPSG code 4326). The abbreviations and square names used in ‘dbf’ file are the same as those used in ‘Species_richness’ file.

Funding information: National Science Centre, Poland, Grant/Award Number: 2019/35/B/NZ8/00273