Leaf functional traits are important for the formation of alpine plant communities' composition

The studies on the composition and structure of living organisms communities in terms of their functional traits became very popular the last decades. Functional approach is widespread, but is still rarely applied for solving two associated questions: 1) how species from the given community differ from random samples by mean values of functional traits (with the same number of species) of local flora; 2) how much mean values of functional traits in community species differ from community weighted means (by species abundance), or, in other words, how much higher or lower are these values in dominants in compare with other species. The aim of this study is to answer these questions, with the example of alpine communities of the north-western Caucasus. We studied leaf functional traits in four types of alpine communities, which cover maximum area in the alpine belt of the north-western Caucasus: alpine lichen heaths (ALH), Festuca varia grasslands (FVG), Geranium-Hedysarum meadows (GHM) and alpine snowbeds (SB). Water saturated leaves of ALH plants had significantly lower mass and specific leaf area (SLA), but higher dry matter content in compare with the samples of species from "random" communities. The dominants of this community had smaller leaves with higher dry matter content and lower SLA. Leaves of FVG plants had lower area and wet mass, but higher dry mass, while dominants had higher leaf dry mass and dry matter content, but lower leaf area and SLA. For the plants from more productive GHM, larger leaves and higher dry matter content are typical in compare with "random" species samples. Only three size traits (leaf area, wet mass, and dry mass) were significantly higher in the dominants of GHM in compare with other species of this community. Plants of alpine snowbeds, which grow under late snowmelt time and short growth season, had smaller leaves with high dry matter content and SLA. The dominants of these communities, in contrast, have larger leaves in compare with other species of SB. The results obtained confirm the delimiting role of stress-tolerance for establishment of communities in habitats with low snow cover and for dominance there (ALH, FVG), the significant role in competitive strategy of more large-leaved species in more productive GHM and comparatively high role of ruderality in formation of SB.