Variation in plant community functional traits is driven more by species composition than by intraspecific variation along a local elevation gradient

We analyzed changes in seven functional traits of dominant herbaceous vascular plant species in 14 plant communities across an elevation gradient at the Northern Urals: plant height (PH), leaf area (LA), leaf dry mass (LDM), leaf dry matter content (LDMC), specific leaf area (SLA), leaf nitrogen content (LNC) and leaf carbon content (LCC). The study plots were located at one catena with elevation range from 220 to 905 m above sea level, and covered three vegetation types: forest, open woodland and mountain tundra. The community-weighted means for PH, LA and SLA were found to decrease, while LDMC and LCC increased with elevation. This was due to an increase in the proportion of stress-tolerant plant species with small physical size and conservative strategy in the leaf economic spectrum in the most elevated mountain tundra communities. The variability of PH, LDMC, and SLA decreased with increasing elevation and deteriorating of ecological conditions, which is consistent with the stress-dominance hypothesis. The variability of the other traits did not show clear trends. Changes in species composition explained 57%-94% of the observed variability of functional traits for plant communities on the elevation gradient while intraspecific changes explained only 2% to 21% of the total variability. This provides a theoretical background for using functional traits derived from global databases and those measured in habitats with similar ecological characteristics in local-scale studies.