Abstract. Water resources and associated ecosystems are becoming highly endangered due to ongoing global environmental changes. Spatial ecological modelling is a promising toolbox for understanding the past, present and future distribution and diversity patterns in groundwater-dependent ecosystems, such as fens, springs, streams, reed beds or wet grasslands. Still, the lack of detailed water chemistry maps prevents the use of reasonable models to be applied on continental and global scales. Being major determinants of biological composition and diversity of groundwater-dependent ecosystems, groundwater pH and calcium are of utmost importance. Here we developed an up-to-date European map of groundwater pH and Ca, based on 7577 measurements of near-surface groundwater pH and calcium distributed across Europe. In comparison to the existing European groundwater maps, we included several times more sites, especially in the regions rich in spring and fen habitats, and filled the apparent gaps in eastern and southeastern Europe. We used random forest models and regression kriging to create continuous maps of water pH and calcium at the continental scale, which is freely available also as a raster map (Hájek et al., 2020b; https://doi.org/10.5281/zenodo.4139912). Lithology had a higher importance than climate for both pH and calcium. The previously recognised latitudinal and altitudinal gradients were rediscovered with much refined regional patterns, as associated with bedrock variation. For ecological models of distribution and diversity of many terrestrial ecosystems, our new map based on field groundwater measurements is more suitable than maps of soil pH, which mirror not only bedrock chemistry but also vegetation-dependent soil processes.

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Abstract. Water resources and associated ecosystems are becoming highly endangered due to ongoing global environmental changes. Spatial ecological modelling is a widely used tool for understanding the past, present and future distribution and diversity patterns in groundwater-dependent ecosystems, such as fens, springs, streams, reed beds or wet grasslands. Still, the lack of detailed water chemistry maps prevents their reasonable use on continental and global scales. Being major determinants of biological composition and diversity of groundwater-dependent ecosystems, groundwater pH and calcium are of utmost importance. Here we developed the up-to-date European map of groundwater pH and Ca, based on 7,577 measurements of near-surface groundwater pH and calcium distributed across Europe. In comparison to the existing European groundwater maps, we included a several times larger number of sites, especially in the regions rich in spring and fen habitats, and filled the apparent gaps in Eastern and Southeastern Europe. We used Random Forest models and regression kriging to create continuous maps of water pH and calcium at the continental scale, which is freely available also as a raster map (Hájek et al. 2020; https://doi.org/10.5281/zenodo.4139912). Lithology had higher importance than climate for both pH and calcium. The previously recognised latitudinal and altitudinal gradients were rediscovered with much refined regional patterns, as associated with bedrock variation. For ecological models of distribution and diversity of groundwater-dependent, but also other terrestrial, ecosystems, the new map is more suitable than previously used maps of soil pH, unlike which it mirrors bedrock chemistry more than vegetation-dependent soil processes.

This paper presents new records and noteworthy data on the following taxa in SE Europe and adjacent regions: the diatom alga Eunotia boreoalpina; the saprotrophic fungus Clitocybe truncicola; the liverwort Haplomitrium hookeri; the moss Leptodon smithii: the monocots Epipactis purpurata, Stipa tirsa, Typha laxmannii and T. shuttleworthii; and the dicots Krascheninnikovia ceratoides, Polygonum albanicum and Sorbus latifolia.

This paper presents new records and noteworthy data on the following taxa in SE Europe and adjacent regions: diatom alga Stauroneis neofossilis, parasitic fungus Anthracoidea arenariae, horsetail Equisetum hyemale, liverwort Harpanthus flotovianus, mosses Fissidens exilis and Rhizomnium punctatum, monocots Epipactis helleborine subsp. orbicularis, Himantoglossum calcaratum subsp. rumelicum and Schoenus nigricans and dicots Calluna vulgaris, Mahonia aquifolium and Willemetia stipitata subsp. albanica.