Spatial patterns of species richness in the Czech flora: effects of sampling intensity, environment and landscape history

Understanding the spatial patterns and drivers of species richness is crucial for biodiversity conservation. Using data from Pladias, a comprehensive botanical database of the Czech Republic, we mapped the richness of various plant species groups across grid cells in the country and examined the effects of current environmental conditions, current landscape structure, and historical landscape development.We also applied fivemethods to account for uneven sampling intensity and found that only rarefaction provided estimates of species richness independent of sampling intensity. Using spatial error models and a variation partitioning approach, we showed that plant richness at the country scale is predominantly driven by current environmental conditions. For overall species richness, as well as for native and threatened species richness, the most important factors were the proportion of carbonate bedrock and the level of climate moisture, while the heat sum in the growing season was crucial for naturalized alien species richness. Historical landscape development, especially the long-term continuity of forests and grasslands, significantly influenced the richness of all, native, and particularly threatened species. Human population density was positively related to all species groups, emerging as the most important variable for the richness of naturalized alien species. However, our study shows that uneven sampling intensity in the Pladias database may distort the effect of certain environmental factors, such as the heat sum in the growing season. These findings emphasise the importance of carefully considering the uneven intensity of sampling before analysing species richness and highlight the role of current environmental variables, current landscape structure, and historical landscape development in shaping plant species richness at the regional scale.