Long-lasting Imprint of Former Glassworks on Vegetation Pattern in an Extremely Species-rich Grassland: A Battle of Species Pools on Mesic Soils

Increasing evidence suggests that past human activities have irreversibly changed soil properties and biodiversity patterns. In the White Carpathian Mts (Central-Eastern Europe), a mosaic of hyper-species-rich and species-rich patches have developed in a regularly mown dry grassland in the area of a glassworks abandoned in the eighteenth century. We tested whether and how anthropogenically changed soils affected the distribution of extraordinary species richness. Using magnetometry we detected former furnaces, workspace, waste deposit and unaffected surrounding grasslands and compared their vegetation and environmental conditions. Archaeological features, especially furnaces and waste deposits, showed a higher pH, higher soil concentrations of exchangeable phosphorus, manganese, lead and calcium, and higher productivity. Surrounding grassland showed higher iron and sodium concentrations in the soil, higher N:P ratio in the biomass and higher species richness. Moisture was uniformly lower in soils on archaeological features, where non-trivially a more ‘mesic’ vegetation in terms of European habitat classification occurred. Plant compositional variation was best explained by water-extractable phosphorus. Because nutrient-richer patches were not moister as common elsewhere, and because species richness was only poorly accounted for by productivity, the occurrence of a species-poor ‘mesic’ vegetation on archaeological features was evidently caused by a long-lasting phosphorus oversupply which favours a comparatively small species pool of rather recently arriving species. On the contrary, surrounding phosphorus-poorer grasslands still contain the ancient species pool whose extraordinary size determines the exceptional species richness of grasslands in the study region. Its maintenance or restoration demands a persistent phosphorus deficiency.