Traits as determinants of species abundance in a grassland community

Questions The patterns in abundances of plant species and the processes which determine these patterns have been intensively studied. While recent investigations have recognized plant functional traits as important determinants of species abundances, intraspecific trait variability as a driver of species abundance patterns has largely been ignored. The objective of this study was to quantify the effect of intraspecific trait variability and trait dissimilarity from mean community characteristics (community-weighted mean [CWM]) on the abundance of six widely distributed grassland species, while controlling for the possible influence of environmental conditions for three commonly used plant functional traits (Plant height - PH; specific leaf area - SLA; and leaf dry matter content - LDMC). Location Species-rich alvar grasslands in western Estonia. Methods We quantified the discrete effects of environmental conditions, intraspecific trait variability, and trait difference from CWM on species abundance and assessed individual contributions of both traits and environmental characteristics on species abundance patterns. Results We found a strong and consistent relationship between species' abundance and their intraspecific trait variability, where the biggest proportion of variation was explained by PH and SLA respectively. Local populations with larger PH and LDMC, and lower SLA were more abundant compared to populations having different values of these traits. Significant unimodal dependence of species abundance on CWM was detected for two species for which the optimum values of SLA and LDMC were close to the CWM values. For other species, the relationship between optimum trait values and CWM values was monotonous. The effect of measured environmental conditions (e.g., soil depth, above-ground biomass, and soil fertility) and trait difference from CWM on species abundance patterns was minor when compared to the effect of intraspecific trait variability. Conclusions Our study demonstrated a strong relationship between intraspecific trait variability and local performance of species within communities.

Automated summary

The study demonstrates a strong relationship between intraspecific trait variability and local species performance within communities, with plant height and specific leaf area explaining the biggest proportion of variation in species abundance. The impact of intraspecific trait variability on species abundance patterns is more significant compared to environmental conditions and trait differences from community-weighted mean values.