Climate-Change Impacts on the Southernmost Mediterranean Arctic-Alpine Plant Populations

Human-induced climate- and land-use change have been affecting biogeographical and biodiversity patterns for the past two centuries all over the globe, resulting in increased extinction and biotic homogenization rates. High mountain ecosystems are more sensitive to these changes, which have led to physiological and phenological shifts, as well as to ecosystem processes’ deformation. Glacial relicts, such as arctic-alpine taxa, are sensitive indicators of the effects of global warming and their rear-edge populations could include warm-adapted genotypes that might prove—conservation-wise—useful in an era of unprecedented climate regimes. Despite the ongoing thermophilization in European and Mediterranean summits, it still remains unknown how past and future climate-change might affect the distributional patterns of the glacial relict, arctic-alpine taxa occurring in Greece, their European southernmost distributional limit. Using species distribution models, we investigated the impacts of past and future climate changes on the arctic-alpine taxa occurring in Greece and identified the areas comprising arctic-alpine biodiversity hotspots in Greece. Most of these species will be faced with severe range reductions in the near future, despite their innate resilience to a multitude of threats, while the species richness hotspots will experience both altitudinal and latitudinal shifts. Being long-lived perennials means that there might be an extinction-debt present in these taxa, and a prolonged stability phase could be masking the deleterious effects of climate change on them. Several ex situ conservation measures (e.g., seed collection, population augmentation) should be taken to preserve the southernmost populations of these rare arctic-alpine taxa and a better understanding of their population genetics is urgently needed.

Drought Trends in the Polish Carpathian Mts. in the Years 1991–2020

Mountains are highly sensitive to the effects of climate change, including extreme short- and long-term weather phenomena. Therefore, in spite of relatively high annual precipitation totals, mountains might become endangered by droughts. The paper presents drought trends in the Polish Carpathians located in Central Europe. Data from the period 1991–2020 from 12 meteorological stations located in various vertical climate zones of the mountains were used to define drought conditions using the following indices: Standardized Precipitation (SPI), Standardized Precipitation Evapotranspiration (SPEI), Relative Precipitation (RPI) and Sielianinov. Additionally, four forest drought indices were used in order to estimate the impact of drought on beech as a typical Carpathian tree species, i.e., the Ellenberg (EQ), Forestry Aridity (FAI), Mayr Tetratherm (MT) and De Martonne Aridity (AI) indices. Statistically significant but weak trends were obtained for the 6-month SPI for four stations (indicating an increase in seasonal to mid-term precipitation), for the 1-month SPEI for three stations, for the 3-month SPEI for four stations, and for MT for all stations (indicating an increase in drought intensity). The analysis of dry month frequency according to particular indices shows that at most of the stations during the last decade of the study period, the frequency of dry months was much higher than in previous decades, especially in the cold half-year. Two zones of the Polish Carpathians are the most prone to drought occurrence: the peak zone due to the shift in climatic vertical zones triggered by the air temperature increase, and the forelands and foothills, together with basins located about 200–400 m a.s.l., where the mean annual air temperature is the highest in all the vertical profile, the annual sums of precipitation are very diversified, and the conditions for beech are already unfavorable.