The assembly of plants into communities is one of the central topics in plant community ecology. The objective of this study was to investigate how plant functional trait diversity and environmental factors influence community assembly in two different grassland communities, and if variation in these factors could explain the difference in species assembly between these communities.
Six grazed ex-arable fields and eight semi-natural grasslands in southeast Sweden.
We estimated species abundance and measured soil attributes at each site. For each species within each site we measured specific leaf area (SLA), leaf dry matter content (LDMC) and seed mass. We analysed the data both for abundance-weighted species values and species occurrence.
Trait gradient analysis indicated random distribution of species among sites, while CCA analysis indicated that both soil phosphorus and moisture were related to species assembly at a site. Correlations and fourth-corner analysis also revealed a relationship between measured species traits and soil phosphorus and moisture. There was a lower average seed mass and higher SLA of species in ex-arable fields compared to species in semi-natural grasslands.
Even though trait gradient analysis indicated that plant community assembly in the studied grasslands was random, other results implied that species occurrence and abundance was influenced both by environmental factors and species traits. Higher species richness in semi-natural grasslands was associated with more large-seeded species found there compared to ex-arable fields, indicating that large-seeded species establish in grasslands later than small-seeded species.