Andreas Mayr

Complex topography regulates near‐surface temperature above the treeline. It may thus sustain microrefugia for alpine plants and relax the need of shifting upward when the climate warms. The effectiveness of these microrefugia rests on the premise that plant distributions in alpine landscapes are mainly controlled by fine‐scale topographic variation. We tested this assumption by relating the distribution of 79 plant species and 10 community attributes across 900 1 m² plots in a landscape spanning 1677 m of elevation to 17 topographical descriptors at resolutions between 1 and 301 m. We found that the presence of most species and most community attributes were better explained by topographic variation at coarser scales (> 20 m). Fine‐scale topography is more clearly reflected in moisture than in temperature requirements of species. The elevational gradient rather than topographic variation at any scale, is the single most important driver of both species distributions and the variation in community attributes in the area studied. We hypothesise that our results reveal a hitherto underestimated influence of spatial mass effects on alpine plant distributions. These effects can override environmental filtering at fine scales and will thus impede the survival of cold‐adapted plants in small and fragmented refugia under climate warming.

The UN Decade on Ecosystem Restoration 2021–2030 has launched nature conservation, environmental protection, and ecosystem services' restoration on the global environmental policy agenda. However, particularly high mountain habitats being subject to erosion are up to now hardly restorable. Erosion with associated loss of vegetation, soil, and its fertility, is one of the most urgent environmental problems throughout the world. Consequently, we analyzed the soil seed bank of calcareous high‐mountain grassland in the European Alps to reveal the natural regeneration potential after shallow erosion events. We applied a chronosequence approach taking recently eroded grassland areas (<5 years) as well as areas with earlier erosion events (>5 up to 10 and >27 years) into account. Our results revealed that the vegetation of old eroded areas was not closely similar to the surrounding intact grasslands. However, it was well differentiated from the initial stages of young and intermediate eroded areas' vegetation and had higher plant cover and species richness. The old eroded areas' seed bank had higher seed density and species richness compared to younger areas. While typical mountain meadow species were present in the seedbank of eroded areas, the assessed indicator species of both, younger and older eroded areas did not resemble the ones of the aboveground vegetation. We conclude that the seed bank has important but limited potential for the restoration of the complete species range of calcareous eroded alpine grasslands. This implies that additional restoration measures are needed to reintroduce species absent from the seed bank.