Functional traits have globally consistent effects on plant competition

Georges Kunstler : Competition is a very important type of ecological interaction, especially in terrestrial vegetation where plants greatly modify the local environment for each other. Competitive interactions influence the growth and survival of individuals, and thereby change community composition over time into the future. However firm generalizations have yet to be established about outcomes of competition among species. Here we show that key species’ traits have consistent influences on growth and competition. Our analysis synthesize individuals tree growth data for more than 3-millions trees across a global set of forest-monitoring plots. Some traits have a strong effect on the growth rate of the species. Then traits in part determine the tolerance to competition and the impact of competitor’s on a focal tree. A notable generalization is that trait values that favour tolerance to competition also render species slow growing in absence of competition. There is also a small but detectable benefit in reducing competition from trait-dissimilarity between a focal plant and its competitors. The trait-based picture that emerges is
much simpler and more general than a quantification of competition coefficients between each pair of species, which is intractable at the global scale. Our results demonstrate that traits may be used to pre-dict competitive interactions in forests at a large scale.

Recent publications:
Kunstler, G., Courbaud, B., Lavergne, S., Thuiller, W., Vieilledent, G., Zimmerman, N.E., Kattage, J.;
Coomes, D.A. (2012) Competitive interactions between forest trees are driven by species’ trait hierarchy, not phylogenetic or functional similarity: implications for forest community assembly. Ecology Letters, 15, 831-840.