Leaf Traits and Aboveground Biomass Variability of Forest Understory Herbaceous Plant Species

Despite increasing use of trait-based approaches in community ecology, most studies do not account for intraspecific variability of functional traits. Although numerous studies investigated functional traits of species with high economic value, the intraspecific and interspecific (caused by species identity) trait variability of forest understory herbs is still poorly understood. We aimed to assess the variability of specific leaf area (SLA), total leaf area, aboveground biomass and leaf mass fraction among 167 forest understory plant species, and the level of variability explained by species identity and collection site. We hypothesized that the level of intraspecific variability of SLA is underestimated in commonly used trait databases and that the interspecific variability (caused by species identity) is greater than intraspecific variability (site-specific). Our study revealed higher interspecific than intraspecific variability of the traits studied. We also confirmed that level of intraspecific variability available in the LEDA database is underestimated. We confirmed that species identity was the main factor determining the values of all the traits studied, and site-specific random effects explained lower amounts of variation in traits. Use of trait values from databases not acknowledging intraspecific variability is biased by uncertainty about this variability. For that reason, our analysis used mean trait values to reduce uncertainty of the results in the study conducted to assess human impacts on ecosystems. Thus, our study might support the assumption that level of intraspecific variability of functional traits is lower than interspecific variability.