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Background and aims Dolines are small-to large-sized bowl-shaped depressions of karst surfaces. They may constitute important microrefugia, as thermal inversion often maintains cooler conditions within them. This study aimed to identify the effects of large-(macroclimate) and small-scale (slope aspect and vegetation type) environmental factors on cool-adapted plants in karst dolines of East-Central Europe. We also evaluated the potential of these dolines to be microrefugia that mitigate the effects of climate change on cool-adapted plants in both forest and grassland ecosystems.Methods We compared surveys of plant species composition that were made between 2007 and 2015 in 21 dolines distributed across four mountain ranges (sites) in Hungary and Romania. We examined the effects of environmental factors on the distribution and number of cool-adapted plants on three scales: (1) regional (all sites); (2) within sites and; (3) within dolines. Generalized linear models and non-parametric tests were used for the analyses.Key Results Macroclimate, vegetation type and aspect were all significant predictors of the diversity of cooladapted plants. More cool-adapted plants were recorded in the coolest site, with only few found in the warmest site. At the warmest site, the distribution of cool-adapted plants was restricted to the deepest parts of dolines. Within sites of intermediate temperature and humidity, the effect of vegetation type and aspect on the diversity of cooladapted plants was often significant, with more taxa being found in grasslands (versus forests) and on north-facing slopes (versus south-facing slopes).Conclusions There is large variation in the number and spatial distribution of cool-adapted plants in karst dolines, which is related to large-and small-scale environmental factors. Both macro-and microrefugia are therefore likely to play important roles in facilitating the persistence of cool-adapted plants under global warming.

Questions Litter quantity in grasslands is highly affected by disturbance regime and influences seed recruitment of constituent species through different mechanisms. Does litter act as a mechanical barrier to burial of freshly shed seeds, and does seed morphology affect this? How is the fate and mobility of seeds affected by litter compared to that of seeds in the seed bank? Location Transylvanian Lowland, Romania. Methods We analysed the seed content of litter and underlying soil collected from six dry grassland sites having different disturbance histories, ranging from sites that are currently grazed to those that have been long abandoned. We related seed content of litter to the litter quantity, seed morphology and the seed content of soil, and the estimated seed production of the above‐ground vegetation. Results Grass litter represented a natural trap for seeds; we identified significant quantities of seeds of a large number of species (37) within litter samples, and there was a mass effect in the seed trapping by litter – higher litter quantities trapped more seeds. As a long‐term consequence, we expected that seed bank stores would be gradually depleted in abandoned grassland due to the elimination of seeds by litter, but this was not the case. The higher seed production of the above‐ground vegetation in undisturbed sites very probably compensated for seed losses through litter. Seeds retained in the litter were larger, more rounded and had appendages than those in soil. Especially for seeds meeting any of these criteria, litter represents a hazardous medium, since the seeds may fail or have delayed germination. Conclusions The role of litter as a seed trap is more relevant in grasslands that have not been disturbed for a long time, where litter seed entrapment can exert a selective pressure on certain species, and thus drive community assembly in grasslands.

Question: Do restoration measures involving yearly biomass removal over 9 yr have a beneficial effect on the structure and composition of long-term abandoned European steppe-like grassland? What is the effect of a single accidental fire event on this grassland community?Location: Continental dry steppe-like grassland, Suatu and Puini, Transylvania, Romania.Methods: In two long-term abandoned grassland sites, we experimentally carried out annual biomass removal by clipping and raking, and by raking alone over a period of 9 yr. We analysed the effect of the two planned treatments in both sites and that of an accidental fire in one of the sites on the structure and composition of vegetation. We applied a predominantly functional trait-based analysis, but the dominant species Stipa pulcherrima and Carex humilis were treated separately.Results: Annual biomass removal applied for 9 yr at one site favoured sub-dominant grasses and short-lived forbs over long-lived forbs and the two dominant species, and generated a successional shift to more open grassland. The clipping and raking treatment promoted plot-scale species richness when the grassland species pool was large enough. The number and abundance of Red-Listed species were not influenced by our treatments. The single accidental fire event at one of the sites negatively affected the two dominant species and promoted one of the sub-dominant grasses. In addition, burning in combination with abandonment and presence of stoloniferous grass species benefiting from fire decreased species richness. Variation in weather conditions, in particular the series of dry years during our experiment, caused significant changes in vegetation cover and the quantity of litter, and decreased the abundance of S. pulcherrima in both sites and that of long-lived forbs in one site.Conclusions: According to our results, biomass removal had a beneficial effect on vegetation structure and composition in long-term abandoned steppe-like grassland. Until further experimental data on the effect of burning on temperate dry grassland are available, traditional management practices should be favoured over alternative methods.

Studies addressing the question of how communities develop reported contrasting temporal patterns of species associations during succession. Several hypotheses were formulated about succession, but a general explanation of community assembly is missing. We analysed trends of species associations during old-field succession in two contrasting habitats: the first with chernozemic brown forest soil and temperate climate, and the second with sand soil and dryer climate. Significant pair-wise associations were calculated across a range of spatial scales. Comparing the two succession seres, one under harsh and the other under favourable environment, we attempted to make generalisations about species relation patterns. We found no trend but fluctuation in the level of community organization during succession. None of the existing succession models explained our results about changes in spatial structure of grassland communities during succession. Fluctuation in the number of significant associations was more intense and took longer under less favourable environmental conditions. Our results suggest that the stressed habitat type posed stronger constraints on species coexistence during succession than the favourable habitat did, but validating this hypothesis needs further investigations. Nomenclature: Flora Europaea