Invasion by alien species (AS) is one of the most serious threats to ecosystems. In Europe, the Natura 2000 habitats network was established to protect habitats vital for the conservation of biodiversity and function of ecosystems. Therefore, the appearance of AS in Natura 2000 habitats is a warning signal that the most valuable European habitats may be endangered. However, quantitative studies encompassing a wide spectrum of habitats are lacking, and there is no insight into the differences in the level of invasion among habitats. Our survey is based on the State Monitoring of Natura 2000 data and aimed at an assessment of the level of invasion in natural habitat types in Poland. The percentage of invaded locations, number and frequency of alien plant species was assessed in 79 Natura 2000 habitats, both terrestrial and water, investigated on 5,941 locations. The most invaded habitats (with the highest percentage of invaded plots) were dunes with Hippophaë rhamnoides (habitat code 2160), rivers with muddy banks (habitat code 3270), and alpine rivers and herbaceous and ligneous vegetation along their banks (habitat codes: 3220, 3230, 3240). Grassland, forest and most of the bog, mire and fen habitats and also some habitats on a rock were invaded by a relatively large number of AS, but their frequency was comparatively low. In contrast, a high frequency of AS was found in the majority of dune and costal habitats and calaminarian grasslands. Compared with the period 2000–2010, the number of AS in some riparian, grassland and forest habitats rose noticeably. The occurrence of AS showed a negative correlation with conservation status of the habitats. This study has demonstrated that standard monitoring of Natura 2000 habitats provides the basis for the detection of AS, including invasive ones, in all types of habitats, and can be used for development rapid and effective response programs.

In recent decades, in the Polish Carpathians, agriculture has undergone major changes. Our goal was to investigate whether the former management (plowing or mowing and grazing) had an impact on the current species composition, diversity and conservation status of the vegetation of grazing areas. We carried out vegetation studies on 45 grazing sites with traditional methods of grazing (transhumant pastoralism). The survey covered both old (continuous) grasslands and grasslands on former arable land. The most widespread were Cynosurion pastures and mesic Arrhenatherion grasslands. Wet Calthion meadows occurred at more than a half of grazing sites, while nutrient-poor Nardetalia grasslands were only recorded at several grazing sites. For each grazing site, we used soil maps from the 1960s to read land use in the past. We mapped present grassland and arable land area. Compared with the 1960s, there was a significant decrease in the area of arable land and an increase in grasslands. Species diversity was greater in grazing sites where grasslands developed on former arable land. However, this diversity was associated mainly with the occurrence of common grassland species. Cynosurion pastures and wet Calthion meadows had the best conservation status, while nutrient-poor Nardetalia grasslands were the worst preserved. We concluded that the conservation status of mesic grasslands and pastures is dependent on the present diversity of land use within a grazing site, rather than the land use history 60 years ago. This is the first study of the natural, not economic, value of pasture vegetation in the Polish part of the Carpathians.

No abstract