Data from: Disentangling the relative importance of species occurrence, abundance and intraspecific variability in community assembly: a trait-based approach at the whole-plant level in Mediterranean forests

Understanding which factors and rules govern the process of assembly in
communities constitutes one of the main challenges of plant community
ecology. The presence of certain functional strategies along broad
environmental gradients can help to understand the patterns observed in
community assembly and the filtering mechanisms that take place. We used a
trait-based approach, quantifying variations in aboveground (leaf and
stem) and belowground (root) functional traits along environmental
gradients in Mediterranean forest communities (south Spain). We proposed a
new practical method to quantify the relative importance of species
turnover (distinguishing between species occurrence and abundance) versus
intraspecific variation, which allowed us to better understand the
assemblage rules of these plant communities along environmental gradients.
Our results showed that the functional structure of the studied plant
communities was highly determined by soil environment. Results from our
modelling approach based on maximum likelihood estimators showed a
predominant influence of soil water storage on most of the community
functional traits. We found that changes in community functional structure
along environmental gradients were mainly promoted by species turnover
rather than by intraspecific variability. Specifically, our new method of
variance decomposition demonstrated that between-site trait variation was
the result of changes in species occurrence rather than in the abundance
of certain dominant species. In conclusion, this study showed that water
availability promoted the predominance of specific trait values (both in
above and belowground fractions) associated to a resource acquisition or
conservation strategy. In addition, we provided evidence that changes on
community functional structure along the environmental gradient were
mainly promoted by a process of species replacement, which represent a
crucial step towards a more general understanding of the relative
importance of intraspecific versus interspecific trait variation in these
woody Mediterranean communities.