The conservation value of karst dolines for vascular plants in woodland habitats of Hungary: refugia and climate change

Limestone (karst) surfaces in Hungary are rich in dolines, in which many endangered vascular plant species occur. To date, the majority of studies dealing with doline vegetation have focused on the local rather than the landscape level, without using comparative data from other areas. However, in this study we aimed to compare the vegetation pattern and species composition of dolines under different climate regimes of Hungary with regard to regional species pools. The fieldwork was carried out between 2005 and 2012. Twenty dolines were selected in the Mecsek Mountains (southern Hungary) and nine dolines in the Aggtelek Karst area (northern Hungary). More than 900 vascular plants and more than 2000 plots were included in the study. The moving split window (MSW) technique, nestedness analysis and principal coordinates analysis (PCoA) were used to reveal the vegetation patterns in dolines. Although we found remarkable differences between the species composition of the two regions, dolines of both regions play a similar role in the preservation of different groups of species. Many plants, in particular mountain species, are restricted to the bottom of dolines where appropriate environmental conditions exist. In addition, depending on the doline geometry, many species of drier and warmer forests have colonized the upper slopes and rims. Thus, we can conclude that karst dolines of Hungary can be considered as reservoirs for many vascular plant species, therefore they are particularly important from a conservation point of view. Moreover, these dolines will likely become increasingly indispensable refugia for biodiversity under future global warming