Leaf Functional Traits and Ecological Strategies Are Important for the Formation of Subalpine Fens and Tall-Herb Plant Communities

Plant functional traits are important for the formation of plant communities and for the ability of plants to dominate there. The comparison of mean trait values of organisms within community with that for the random samples of the local biota allows estimating the importance of the trait for the formation of the community composition. The comparison of mean and community weighted mean values allow estimating their role for the dominance in any given community. We studied leaf functional traits (leaf area, mass, specific leaf area—SLA, leaf dry matter content—LDMC), as well as the contribution of Grime’s CSR strategy scores (competitors–stress-tolerators–ruderals) in two subalpine communities at the Teberda National Reserve (the Northwestern Caucasus, Russia). Many leaf functional traits and plant strategies differ significantly in the fens and tall-herb communities from the random set of the species belonging to the local high mountain flora. The tall-herb community species have larger size (area and mass) of leaves, higher SLA, and lower LDMC, as well as higher contribution of C and lower contribution of S and R strategies. The dominants of this community differ from the subordinate species by even larger leaf size, lower SLA, higher LDMC, and higher C strategy and lower R strategy scores. The plants of subalpine fens, in comparison with random set of species, have smaller leaf size, lower SLA and higher LDMC, higher contribution of stress tolerance (S), and lower contribution of C strategy and R strategy scores. In comparison with subordinate species, the dominants of subalpine fens have even lower SLA and higher LDMC and higher S strategy and lower R strategy scores. Thus, under the same climate conditions in depressions of mesorelief, but under different hydrological conditions, in the subalpine belt of mountains, there are plant communities with the contrasting functional structure. This underpins the important role of moisture conditions for the establishment of the spatial pattern of high mountain communities.