Dynamics of the Czech flora over the last 60 years: Winners, losers and causes of changes

Over the past 60 years, natural habitats have been affected by various anthropogenic pressures. However, little is known about how these pressures have influenced the species composition of whole floras across large areas. We used a large database of the Czech flora to assess broad-scale temporal trends in temperate European flora over the last 60 years. We extracted over 4.6 million occurrence records of 1912 species collected over the past six decades and analysed the changes in species occurrence frequency over time using dynamic occupancy models within a Bayesian framework that accounted for various biases in the data. Five main patterns of temporal change were revealed. The increasing species were supported by different environmental changes that peaked at different periods. Competitively strong, nutrient-demanding generalist species that successfully colonize new and highly disturbed habitats supported by eutrophication and anthropogenic disturbances strongly increased in 1961–1980. Shade-tolerant species of less disturbed habitats increased between 1981 and 2000, indicating an effect of habitat abandonment, and thermophilous species began to spread in the last 20 years, reflecting rising temperatures. Competitively strong species of less frequently disturbed habitats with higher moisture and nutrient requirements and low light requirements increased gradually over the last six decades. In contrast, specialized species of nutrient-poor habitats with low colonization and competitive ability, associated with more frequent but less severe disturbances, steadily decreased due to the ongoing decline of habitat quality after the cessation of traditional management, and many of them have been included in the national Red List.