Session

Due of the potential of species to determine ecosystem properties, it is important to understand why some species dominate the plant community and how the abundance of dominant species influences community assembly, biodiversity and ecosystem function. Using vegetation surveys (25 m2) on 35 extensively used dry meadows in north-east Slovenia, we defined dominant (8 species) and subordinate (61) species; they were compared on 14 plant traits to test for significant differences in community weighted mean (CWM) and functional diversity (FD). We found that the dominant and the subordinate species differed strongly in their functional traits. Dominants showed higher leaf dry matter content (LDMC), a more pronounced stress tolerant (S) strategy, they were all clonal with a large proportion of species with rhizomes and a rich bud bank in all layers, while other species had higher specific leaf area (SLA) values, a longer flowering period and more species classified as ruderal (R). For most traits, functional diversity was higher in subordinate species. Our results suggest that dominant species influence the structure of the studied grassland communities by limiting susceptibility to non-competitive processes. They support previous hypotheses that dominant species (which are constrained by the environment) may have a stronger positive effect on some subordinate species by mitigating environmental stressors that normally constrain subordinate species. Subordinate species are able to assemble together by being dissimilar and therefore use different fine-scale niches that are engineered and homogenised by dominant species. Our results show that there are fundamental differences in the relative importance of ecological processes between dominant and subordinate plants in species-rich dry grasslands, which is also important for their conservation and management.